tag:theconversation.com,2011:/global/topics/sexual-reproduction-1552/articlesSexual reproduction – The Conversation2024-03-13T15:03:15Ztag:theconversation.com,2011:article/2255962024-03-13T15:03:15Z2024-03-13T15:03:15ZIt’s a myth that male animals are usually larger than females – new study<p>Males are bigger than females, right? Generally, this is true of humans – imagine the extremes of Dwayne “The Rock” Johnson and singer Kylie Minogue. It is also true of other familiar mammals including pets, such as cats and dogs, and livestock such as sheep and cows.</p>
<p>But <a href="https://www.nature.com/articles/s41467-024-45739-5">a new study</a> by US scientist Kaia Tombak and colleagues found that, in many mammal species, males are not larger than females. In fact, in a comparison of 429 species in the wild, 50% of species including rodents and some bats – which make up <a href="https://news.mongabay.com/2022/04/of-rats-and-bats-hundreds-of-mammal-species-still-unidentified-study-says/">a large proportion</a> of all mammal species – showed no difference in body size between the sexes. Male-biased size dimorphism (where males are larger than females) was found in only 28% of mammal species.</p>
<p>So, why do a lot of people have a misconception that males are normally larger than females? </p>
<p><a href="https://www.nature.com/scitable/students-page/160/">Anisogamy</a> is the term used to describe the difference in sex cells – small, numerous, sperm, compared to relatively large eggs. Males can produce sperm throughout most of their lifespan, whereas females are born with a finite number of eggs. Therefore, females (or rather, their eggs), are a scare resource for which males compete for access. Generally, in species where females are a limited resource that males need to fight over, males are larger than females.</p>
<p>In terms of evolution, most males have been shaped to be larger, bolder, heavier, more adorned and have more weaponry than females. This is due to males fighting to acquire females – a larger stag with bigger antlers would do much better in a fight, <a href="https://www.discoverwildlife.com/animal-%20facts/mammals/understand-the-british-deer-rut">known as a rut</a>, than a small stag with tiny antlers. So, bigger usually wins.</p>
<p>This includes species such as lions and baboons, where size is an advantage when competing physically for mates. Male northern elephant seals, who fight for access to harems of females, show the largest male-biased size dimorphism, being over 3.2 times heavier than females. These are the animals that tend to attract research</p>
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<h2>The strange world of fish</h2>
<p>But, what happens in species where males don’t fight for access to females? Generally, females are larger than males. This is because larger females usually produce more offspring. Indeed, Tombak’s study noted that larger female rabbits usually have multiple litters each mating season. Being a larger female is much more advantageous in terms of reproductive success. But more so when offspring do not need extended parental care and when gestation periods are short.</p>
<p>The most extreme sexual size dimorphism is found outside of mammals. Cichlid fish (<em>Lamprologus callipterus</em>) males are up to 60 times larger than females. The males protect empty snail shells for the females to breed in. <a href="https://link.springer.com/article/10.1007/s12038-010-0030-6">Larger females</a> can produce more offspring but they need larger shells and therefore a larger male to defend those shells.</p>
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<p>In mammals, the largest female-biased size dimorphism is found in peninsular tube-nosed bats, where females are 1.4 times the size of males. However, more dimorphism in body size is seen in fish, reptiles and insects. For example, the female orb-weaving spider (<em>Nephila plumipes</em>) has a much larger body size than the male, reaching up to ten times his size. Size dimorphism also shows a correlation with cannibalism, where larger females are more likely to eat their male partner.</p>
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<span class="caption">A female golden orb weaving spider and the smaller male.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/close-photograph-female-golden-orb-weaving-1692871246">Cassandra Madsen/Shutterstock</a></span>
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<p>Anglerfish that typically live at the bottom of oceans, are an example of extreme sexual dimorphism in body size. While the females look like typical fish, the males are tiny, basic organisms. In order to survive, the male needs to fuse with a female, tapping into her nutrients to produce enough sperm to fertilise her. Female deep-sea anglerfish (<em>Ceratias
holboelli</em>) are <a href="https://www.livescience.com/49330-animal-sex-anglerfish.html">60 times longer</a> and half a million times heavier than males.</p>
<p>But, the most extreme sexual size dimorphism is found in rhizocephala, types of barnacle where the male looks like a larvae. Once a male finds a mate, he <a href="https://www.wired.com/2015/07/absurd-creature-of-the-week-rhizocephalan/">inserts himself into the females</a>, transforming into nothing more than a mass of cells.</p>
<h2>What about mammals?</h2>
<p>So, why isn’t sexual size dimorphism seen in more mammals? Mammals tend to have fewer offspring than other species such as fish or spiders. They only have a few offspring at a time, and often have long gestation periods or extended periods of parental care. In addition, the majority of mammals are monogamous, so there is less need for males to fight over females. That’s why species such as lemurs, golden moles, horses, zebra and tenrecs, usually have similar sized males and females.</p>
<p>It is thought that biases in the scientific literature may have led to the misconception that males are normally bigger as research historically focused on <a href="https://wwf.panda.org/discover/our_focus/wildlife_practice/flagship_keystone_indicator_definition/">species considered “charismatic”</a>, such as primates and carnivores, that attract funding. These are some of the few mammalian species where males compete for mates, and so gain an evolutionary advantage if they are larger. </p>
<p>There was also a bias of <a href="https://www.nationalgeographic.co.uk/science-and-technology/2019/10/once-most-famous-scientists-were-men-thats-changing">male scientists</a> conducting research. And, although a study in 1977 <a href="https://www.journals.uchicago.edu/doi/epdf/10.1086/283223">by a female scientist</a> found that species with little sexual size dimorphism were frequent in mammals, the research was drowned out by studies on charismatic species with a bias towards large males. Perhaps if there had been more female scientists at the time, we might have had a different preconception about body size in the animal kingdom.</p><img src="https://counter.theconversation.com/content/225596/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Louise Gentle works for Nottingham Trent University. </span></em></p>Does size matter? In the animal kingdom, yes.Louise Gentle, Principal Lecturer in Wildlife Conservation, Nottingham Trent UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2146902023-10-23T12:25:17Z2023-10-23T12:25:17ZBiological sex is far from binary − this college course examines the science of sex diversity in people, fungi and across the animal kingdom<figure><img src="https://images.theconversation.com/files/554094/original/file-20231016-21-1wrv5k.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C2169%2C1382&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Biological sex comes in many more forms than just male or female.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/watercolour-illustration-of-male-and-female-symbols-royalty-free-image/1209433697">Yifei Fang/Moment via Getty Images</a></span></figcaption></figure><figure class="align-right ">
<img alt="Text saying: Uncommon Courses, from The Conversation" src="https://images.theconversation.com/files/499014/original/file-20221205-17-kcwec8.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/499014/original/file-20221205-17-kcwec8.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=375&fit=crop&dpr=1 600w, https://images.theconversation.com/files/499014/original/file-20221205-17-kcwec8.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=375&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/499014/original/file-20221205-17-kcwec8.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=375&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/499014/original/file-20221205-17-kcwec8.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=471&fit=crop&dpr=1 754w, https://images.theconversation.com/files/499014/original/file-20221205-17-kcwec8.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=471&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/499014/original/file-20221205-17-kcwec8.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=471&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><em><a href="https://theconversation.com/topics/uncommon-courses-130908">Uncommon Courses</a> is an occasional series from The Conversation U.S. highlighting unconventional approaches to teaching.</em> </p>
<h2>Title of course:</h2>
<p>Diversity of Biological Sex Characteristics</p>
<h2>What prompted the idea for the course?</h2>
<p>Most people view biological sex, or the physical features related to reproduction, as <a href="https://www.pewresearch.org/social-trends/2022/06/28/americans-complex-views-on-gender-identity-and-transgender-issues/">simple and binary</a> – either male or female. Even those who recognize that gender – referring to cultural norms around biological sex, or a person’s internal feeling of being masculine, feminine or both – can be complex and nuanced don’t see biological sex in the same way. Many also regard variability in sex and gender as exclusive to people – not found in nonhuman animals.</p>
<p>I am a <a href="https://scholar.google.com/citations?user=OaEmJXAAAAAJ&hl=en">behavioral neurobiologist</a> who has been teaching human physiology since 1998. Over the past several years, I have <a href="https://theconversation.com/brain-scientists-havent-been-able-to-find-major-differences-between-womens-and-mens-brains-despite-over-a-century-of-searching-143516">focused my reading and writing</a> <a href="https://www.psychologytoday.com/us/blog/governing-behavior">on the biology of sex</a>. It struck me that many of my students had misguided assumptions about sex characteristics, including that all people are physically either 100% male or 100% female. </p>
<p>A <a href="https://ari.oucreate.com/4873-5873_syllabus.pdf">course on biological sexual diversity</a> in both nonhuman animals and people could challenge these assumptions.</p>
<h2>What does the course explore?</h2>
<p>First, we examine <a href="https://doi.org/10.1002/dvg.1020150303">why sexual reproduction evolved</a> in any species. This question is <a href="https://theconversation.com/why-did-sex-evolve-researchers-edge-closer-to-solving-longstanding-mystery-55407">still hotly debated among biologists</a> because sex is inefficient. It requires time and energy to find a suitable mate and unite your sex cells, plus it allows you to pass on only half your genes to your offspring.</p>
<p>In comparison, <a href="https://openstax.org/books/biology-2e/pages/32-3-asexual-reproduction">asexual reproduction</a> – essentially cloning yourself – is much more efficient. You don’t have to find a mate, and everyone can produce offspring themselves because there are no males. In biology, “male” refers to an individual that makes small sex cells like sperm, and “female” refers to an individual that makes large sex cells like eggs.</p>
<p>Next, we explore <a href="https://www.ucpress.edu/book/9780520280458/evolutions-rainbow">nonhuman sexual diversity</a>, including fungi that have <a href="https://doi.org/10.1016/j.fbr.2015.08.002">thousands of sexes</a> and aphids that <a href="https://doi.org/10.1016/S0169-5347(01)02331-X">reproduce asexually most of the year</a> but sexually once each fall. Among many others, we also learn about fish that are male or female at <a href="https://doi.org/10.1016/B978-0-12-800049-6.00160-8">different times of their lives</a>; <a href="https://doi.org/10.1016/j.isci.2020.101652">intersex crayfish</a>; and <a href="https://doi.org/10.1016/j.yhbeh.2005.07.013">female spotted hyenas</a> that have a penis.</p>
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<figcaption><span class="caption">Sex characteristics manifest in different ways across the animal kingdom.</span></figcaption>
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<p>We then transition from nonhuman animals to people, via the brain. We learn about <a href="https://doi.org/10.1177/1073858419867298">a few small</a> <a href="https://doi.org/10.1007/s00359-019-01376-8">brain structures in vertebrates</a> that likely have reproductive functions and are differently sized in females versus males on average. We also learn that most people have some brain structures that are more typically male, others that are more typically female and still others that are intermediate – in other words, <a href="https://doi.org/10.1073/pnas.1509654112">most people are mosaics</a> of female-typical and male-typical brain sex characteristics.</p>
<p>Finally, we focus on the biological sex characteristics of <a href="https://doi.org/10.1038/518288a">intersex people</a>. The <a href="https://doi.org/10.1038/nrendo.2014.130">chromosomes and reproductive organs</a> of intersex people have <a href="https://www.ted.com/talks/emily_quinn_the_way_we_think_about_biological_sex_is_wrong#t-781094">some typically female and some typically male characteristics</a> or are intermediate between them.</p>
<p>Students then build on their knowledge of the diversity of biological sex characteristics to discuss whether intersex infants should have <a href="https://aeon.co/essays/people-born-intersex-have-a-right-to-genital-integrity">surgery to “correct” their genitals</a>, as well as <a href="https://www.nytimes.com/2016/07/03/magazine/the-humiliating-practice-of-sex-testing-female-athletes.html">who should be allowed</a> <a href="https://doi.org/10.1080/15265161.2012.680533">to compete in</a> <a href="https://theconversation.com/striking-a-balance-between-fairness-in-competition-and-the-rights-of-transgender-athletes-159685">girls and women’s athletics</a>.</p>
<h2>Why is this course relevant now?</h2>
<p>Perhaps more than ever, there is a debate about how to treat people who do not fit neatly into a female or a male box. Many assume that biological sex is binary and regard transgender and nonbinary people as mistaken or confused. In addition, for many decades, <a href="https://theconversation.com/gender-affirming-care-has-a-long-history-in-the-us-and-not-just-for-transgender-people-201752">intersex infants</a> have undergone surgical procedures to make them appear more typically male or female. Even those who support transgender, nonbinary and intersex people often assume that biological sex is binary. But this assumption is not anchored in evidence.</p>
<h2>What will the course prepare students to do?</h2>
<p>Students often say that before they took this course, they had no idea biological sex characteristics could be so diverse, despite having taken several biology courses. </p>
<p>An improved awareness of the complexity of biological sex may help shape the research and teaching of future biologists. This will help them design experiments that take account of the diversity of their subjects and be more <a href="https://theconversation.com/trans-students-benefit-from-gender-inclusive-classrooms-research-shows-and-so-do-the-other-students-and-science-itself-204777">inclusive in their teaching</a>. It may also help all students ask better questions and make better judgments about social and political issues related to sex and gender.</p><img src="https://counter.theconversation.com/content/214690/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ari Berkowitz receives funding from the Oklahoma Center for the Advancement of Science and Technology and has received funding from the National Science Foundation and the National Institutes of Health.</span></em></p>Spanning evolutionary biology, genetics, development, neurobiology, endocrinology and psychology, as well as current events and sports, students explore the complexities of the biology of sex.Ari Berkowitz, Presidential Professor and Director of Graduate Studies, Biology; Director, Cellular & Behavioral Neurobiology Graduate Program, University of OklahomaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2128492023-09-20T21:09:33Z2023-09-20T21:09:33ZSex life discovery raises IVF hope for endangered purple cauliflower soft coral<figure><img src="https://images.theconversation.com/files/549271/original/file-20230920-25-omlgkz.jpg?ixlib=rb-1.1.0&rect=7%2C27%2C1650%2C2293&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">David Harasti</span></span></figcaption></figure><p>Vital coastal habitat was destroyed in the devastating floods that hit New South Wales in 2021 and 2022. </p>
<p>The purple cauliflower soft coral <em>Dendronephthya australis</em>, now listed as an endangered species, was almost completely wiped out in the Port Stephens estuary and along the coast. That’s a tragedy because this coral shelters young snapper and the endangered White’s seahorse. </p>
<p>Unfortunately, a lack of knowledge hampered recovery efforts – until now. </p>
<p>In <a href="https://doi.org/10.1007/s00227-023-04298-x">our new research</a> we discovered how the coral reproduces. We used IVF (in-vitro fertilisation) to create baby coral in the lab. And we successfully transplanted the coral into the wild. This offers new hope for the survival of the species. </p>
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<figcaption><span class="caption">Understanding the sex life of purple cauliflower soft coral offers hope for the species.</span></figcaption>
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Read more:
<a href="https://theconversation.com/beautiful-rare-purple-cauliflower-coral-off-nsw-coast-may-be-extinct-within-10-years-160184">Beautiful, rare 'purple cauliflower' coral off NSW coast may be extinct within 10 years</a>
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<h2>Variety is the spice of life</h2>
<p>Corals have a complicated sex life. There’s more than one way to “do it”. And gender varies too. </p>
<p>Corals can reproduce asexually, meaning they create genetic copies of themselves. This process often entails shedding polyps that can attach to reefs to form new colonies. </p>
<p>Using this process is a common approach for coral restoration. It’s a bit like propagating plants. Cuttings or fragments are removed from adult colonies, briefly maintained in the lab, and then new corals are transplanted into the wild. This isn’t a simple process for soft corals, though we have been exploring <a href="https://doi.org/10.1002/aqc.3895">ways to make this work</a> for <em>Dendronephthya australis</em>.</p>
<p>Many corals are hermaphrodites, which means they have both male and female reproductive organs. Others form colonies that are entirely male or female. And some mix or swap sexes. </p>
<p>Spawning is the release of eggs and sperm. Again, corals can use various techniques. Broadcast spawning is where eggs and sperm are released into the water column. Brooding is where eggs are fertilised within colonies and later released as larvae. </p>
<p>But until sexual reproduction of an individual species is observed, their sex life remains a private matter.</p>
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<a href="https://images.theconversation.com/files/548615/original/file-20230916-27-tj4s7a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Graphic illustrating the life cycle of the purple cauliflower coral, which begins with an egg being fertilised by sperm, to embryo cell division within 2-4 hours, to fully grown larvae by day 5, to metamorphosis to polyp from 8 days of age." src="https://images.theconversation.com/files/548615/original/file-20230916-27-tj4s7a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/548615/original/file-20230916-27-tj4s7a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=337&fit=crop&dpr=1 600w, https://images.theconversation.com/files/548615/original/file-20230916-27-tj4s7a.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=337&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/548615/original/file-20230916-27-tj4s7a.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=337&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/548615/original/file-20230916-27-tj4s7a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/548615/original/file-20230916-27-tj4s7a.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/548615/original/file-20230916-27-tj4s7a.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">The life cycle of the purple cauliflower coral <em>Dendronephthya australis</em> begins with an egg being fertilised by sperm, proceeds to embryo cell division within 2-4 hours, to fully grown larvae by day 5, to metamorphosis to polyp from 8 days of age.</span>
<span class="attribution"><span class="source">Meryl Larkin</span></span>
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<h2>A chance discovery in the lab</h2>
<p>We were growing coral in the lab, raising asexual clones from fragments, when we noticed something unusual. </p>
<p>There were small orange dots inside some of the corals. These were much larger than the grains of dry orange “coral food” we fed them. So they had to be something else. </p>
<p>We soon realised the orange dots were unfertilised eggs. Half of the fragments in our care contained eggs. As sperm is much smaller, we had to sacrifice small portions of the remaining coral fragments for closer inspection of their contents (under a microscope). In doing this, we discovered the other half were sperm-bearing. </p>
<p>As fate would have it, we had collected fragments from two donor colonies – one female and one male. By chance, we discovered <em>Dendronephthya australis</em> is “gonochoric” (meaning colonies are either male or female). </p>
<p>We watched the corals carefully over the following weeks and made more discoveries. Females spawned (released their eggs) around the “neap tide” (when the moon appears half full) during the summer months. </p>
<p>Maybe the coral evolved to spawn when tidal currents are slowest, to maximise the chance of fertilisation. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/548616/original/file-20230916-27-8l7r3c.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A closeup photo of a soft coral fragment containing unfertilised eggs (orange dots)" src="https://images.theconversation.com/files/548616/original/file-20230916-27-8l7r3c.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/548616/original/file-20230916-27-8l7r3c.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=470&fit=crop&dpr=1 600w, https://images.theconversation.com/files/548616/original/file-20230916-27-8l7r3c.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=470&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/548616/original/file-20230916-27-8l7r3c.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=470&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/548616/original/file-20230916-27-8l7r3c.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=591&fit=crop&dpr=1 754w, https://images.theconversation.com/files/548616/original/file-20230916-27-8l7r3c.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=591&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/548616/original/file-20230916-27-8l7r3c.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=591&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Unfertilised eggs (orange dots) were observed in <em>Dendronephthya australis</em> fragments for the first time.</span>
<span class="attribution"><span class="source">Meryl Larkin</span></span>
</figcaption>
</figure>
<h2>Coral IVF for making babies</h2>
<p>We used IVF techniques to fertilise harvested eggs. Cell division occurred within hours. Mobile larvae grew over the following week. </p>
<p>From eight days of age, the larvae started to transform into polyps; we were the first people to witness these tiny cauliflower coral babies (as single polyps).</p>
<p>Within just a few weeks, we had produced 280 babies from just a few coral fragments. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/548617/original/file-20230916-29-f94gns.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A closeup photo showing baby single coral polyps after metamorphosis from the larval stage" src="https://images.theconversation.com/files/548617/original/file-20230916-29-f94gns.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/548617/original/file-20230916-29-f94gns.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=429&fit=crop&dpr=1 600w, https://images.theconversation.com/files/548617/original/file-20230916-29-f94gns.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=429&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/548617/original/file-20230916-29-f94gns.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=429&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/548617/original/file-20230916-29-f94gns.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=539&fit=crop&dpr=1 754w, https://images.theconversation.com/files/548617/original/file-20230916-29-f94gns.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=539&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/548617/original/file-20230916-29-f94gns.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=539&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Researchers achieved larval settlement, witnessing the change to the single polyp stage of the soft coral.</span>
<span class="attribution"><span class="source">David Harasti</span></span>
</figcaption>
</figure>
<p>Understanding how the purple cauliflower coral reproduces is important for several reasons:</p>
<ul>
<li><p>maintaining genetic diversity: if the sex ratio becomes unbalanced, the effective population size will be lower than the total number of remaining individuals</p></li>
<li><p>achieving fertilisation: broadcast spawning in corals is density-dependent. That means if more colonies are lost, the chance of natural sexual reproduction decreases </p></li>
<li><p>restoring gender balance: any attempt to grow more coral from fragments will need to ensure both male and female colonies are represented </p></li>
<li><p>scaling up production: sexual reproduction provides an opportunity to raise more baby corals while maintaining genetic diversity in the population. </p></li>
</ul>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/548618/original/file-20230916-29-ebwo29.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A photo of a Four-month-old juvenile coral transplanted in Port Stephens" src="https://images.theconversation.com/files/548618/original/file-20230916-29-ebwo29.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/548618/original/file-20230916-29-ebwo29.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=475&fit=crop&dpr=1 600w, https://images.theconversation.com/files/548618/original/file-20230916-29-ebwo29.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=475&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/548618/original/file-20230916-29-ebwo29.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=475&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/548618/original/file-20230916-29-ebwo29.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=597&fit=crop&dpr=1 754w, https://images.theconversation.com/files/548618/original/file-20230916-29-ebwo29.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=597&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/548618/original/file-20230916-29-ebwo29.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=597&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Four-month-old juvenile coral transplanted in Port Stephens.</span>
<span class="attribution"><span class="source">Meryl Larkin</span></span>
</figcaption>
</figure>
<h2>Ongoing restoration work</h2>
<p>Since this discovery, we have successfully repeated these IVF techniques. We transplanted hundreds of coral babies and released thousands of larvae back into Port Stephens. </p>
<p>Early results suggest some IVF babies survived at least the first 18 months and performed better than the asexual fragments.</p>
<p>We plan to implement the IVF program annually. We’re optimistic that we can boost the population of this endangered coral in ways never thought possible.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/coral-meet-coral-how-selective-breeding-may-help-the-worlds-reefs-survive-ocean-heating-166412">Coral, meet coral: how selective breeding may help the world's reefs survive ocean heating</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/212849/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Meryl Larkin receives funding from the NSW Department of Primary Industries, Southern Cross University’s National Marine Science Centre and Marine Ecology Research Centre, and the Australian Government Research Training Program. Ongoing work (subsequent to Meryl Larkin's PhD project) has been supported with funding from the NSW Environmental Trust. </span></em></p><p class="fine-print"><em><span>David Harasti received funding from the NSW Environmental Trust to implement recovery actions for the endangered soft coral.</span></em></p><p class="fine-print"><em><span>Kirsten Benkendorff, Stephen D. A. Smith, and Tom R Davis do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>After a chance discovery in the lab, this team used IVF to make hundreds of coral babies for restoration projects in New South Wales. So far the IVF babies are doing well in the wild.Meryl Larkin, PhD Candidate, Southern Cross UniversityDavid Harasti, Adjunct assistant professor, Southern Cross UniversityKirsten Benkendorff, Professor, Southern Cross UniversityStephen D. A. Smith, Professor of Marine Science, National Marine Science Centre, Southern Cross UniversityTom R Davis, Research Scientist - Marine Climate Change, Hunter New England Local Health DistrictLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2106472023-08-02T19:59:26Z2023-08-02T19:59:26ZIf the world were coming to an end, what would be the most ethical way to rebuild humanity ‘off planet’?<figure><img src="https://images.theconversation.com/files/540634/original/file-20230802-25-uh2308.jpg?ixlib=rb-1.1.0&rect=14%2C0%2C4977%2C3330&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">NASA/AP</span></span></figcaption></figure><p>Last week, scientists announced that for the first time on record, Antarctic ice has failed to “substantially recover” over winter, in a “once in 7.5-million-year event”. Climate change is the <a href="https://theconversation.com/antarctica-is-missing-a-chunk-of-sea-ice-bigger-than-greenland-whats-going-on-210665">most likely culprit</a>. </p>
<p>Petra Heil, a sea ice physicist from the Australian Antarctic Division, <a href="https://www.abc.net.au/news/2023-07-24/antarctic-sea-ice-levels-nosedive-five-sigma-event/102635204">told the ABC</a> it could tip the world into a new state. “That would be quite concerning to the sustainability of human conditions on Earth, I suspect.”</p>
<p>And in March, a senior United Nations disarmament official <a href="https://press.un.org/en/2023/sc15250.doc.htm">told the Security Council</a> the risk of nuclear weapons being used today is higher than at any time since the end of the Cold War.</p>
<p>Both warnings speak to concerns about Earth’s security. Will our planet be able to support human life in the future? And if not, will humanity have another chance at survival in space? </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/this-is-the-way-the-world-ends-nevil-shutes-on-the-beach-warned-us-of-nuclear-annihilation-its-still-a-hot-button-issue-209243">'This is the way the world ends': Nevil Shute's On the Beach warned us of nuclear annihilation. It's still a hot-button issue</a>
</strong>
</em>
</p>
<hr>
<h2>‘Billionauts’ and how to choose who goes</h2>
<p>Over the past few years, we’ve witnessed the rise of the “billionaut”. The ultra-wealthy are engaged in a <a href="https://theconversation.com/billionaire-space-race-the-ultimate-symbol-of-capitalisms-flawed-obsession-with-growth-164511">private space race</a> costing billions of dollars, while <a href="https://www.forbes.com/sites/oliverwilliams1/2021/12/21/billionaire-space-race-turns-into-a-publicity-disaster/?sh=79056f7e5e4d">regular citizens often condemn</a> the wasted resources and contribution to global carbon emissions. </p>
<p>Space – described in the <a href="https://www.unoosa.org/oosa/en/ourwork/spacelaw/treaties/introouterspacetreaty.html">Outer Space Treaty</a> as being the “province of all mankind” – risks instead becoming the playground of the elite few, as they try to escape the consequences of environmental destruction. </p>
<p>But if we have to select humans to send into space for a species survival mission, how do we choose who gets to go? </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/540631/original/file-20230802-29-z9e4e7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/540631/original/file-20230802-29-z9e4e7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/540631/original/file-20230802-29-z9e4e7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/540631/original/file-20230802-29-z9e4e7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/540631/original/file-20230802-29-z9e4e7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/540631/original/file-20230802-29-z9e4e7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/540631/original/file-20230802-29-z9e4e7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/540631/original/file-20230802-29-z9e4e7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">How should we choose who we include in a species survival mission?</span>
<span class="attribution"><span class="source">Mikhail Nilov/Pexels</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>In Montreal last month, the <a href="https://irg.space/irg-2023/">Interstellar Research Group</a> explored the question: how would you select a crew for the first interstellar mission? </p>
<p>A panel led by <a href="https://www.erikanesvold.com/">Erika Nesvold</a>, a co-editor of the new book <a href="https://global.oup.com/academic/product/reclaiming-space-9780197604793?cc=au&lang=en&#">Reclaiming Space</a>, discussed the perspectives of gender minorities, people with disabilities and First Nations groups regarding the ideal composition for an off-world crew. </p>
<p>I was on the panel to discuss my contribution to the book, which explores how we can promote procreation in our new off-world society, without diminishing the reproductive liberty of survivors.</p>
<h2>The ultra-wealthy and reproductive slavery</h2>
<p>The first step in deciding how to allocate limited spaces on our “lifeboat” is identifying and rejecting options that are practically or ethically unacceptable. </p>
<p>The first option I rejected was a user-pay system, whereby the wealthy can purchase a seat on the lifeboat. A 2022 Oxfam report showed the investments of just 125 billionaires collectively contribute 393 million tonnes of carbon dioxide equivalent per year: <a href="https://www.oxfam.org/en/press-releases/billionaire-emits-million-times-more-greenhouse-gases-average-person#:%7E:text=Recent%20data%20from%20Oxfam's%20research,%C2%B0C%20goal%20of%20the">a million times more</a> than the average for most global citizens.</p>
<p>If the ultra-wealthy are the only ones to survive an environmental apocalypse, there’s a risk they would just create another one, on another planet. This would undermine the species survival project.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/540627/original/file-20230802-19-o2s08v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/540627/original/file-20230802-19-o2s08v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/540627/original/file-20230802-19-o2s08v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/540627/original/file-20230802-19-o2s08v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/540627/original/file-20230802-19-o2s08v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/540627/original/file-20230802-19-o2s08v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/540627/original/file-20230802-19-o2s08v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/540627/original/file-20230802-19-o2s08v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Jeff Bezos (second from left), founder of Amazon and space tourism company Blue Origin.</span>
<span class="attribution"><span class="source">Tony Guitierrez/AP</span></span>
</figcaption>
</figure>
<p>The second option I rejected was allowing a reproductive slave class to develop, with some survivors compelled to populate the new community. This would disproportionately impact cis-gender women of reproductive capacity, demanding their gestational labour in exchange for a chance at survival. </p>
<p>Neither a user-pay system nor reproductive slave labour would achieve the goal of “saving humanity” in any meaningful way. </p>
<p>Many would argue preserving human values - including equality, reproductive liberty, and respect for diversity - is more important than saving human biology. If we lose what makes us unique as a species, that would be a kind of extinction anyway. </p>
<p>But if we want humanity to survive, we still need to build our population in our new home. So what other options do we have?</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/doomsday-bunkers-mars-and-the-mindset-the-tech-bros-trying-to-outsmart-the-end-of-the-world-188661">Doomsday bunkers, Mars and 'The Mindset': the tech bros trying to outsmart the end of the world</a>
</strong>
</em>
</p>
<hr>
<h2>Reproduction and diversity</h2>
<p>How can we avoid discrimination on the basis of reproductive capacity – including age, sexuality, <a href="https://theconversation.com/infertility-through-the-ages-and-how-ivf-changed-the-way-we-think-about-it-87128">fertility status</a> or personal preference? </p>
<p>We could avoid any questions about family planning when selecting our crew. This would align with <a href="https://www.seek.com.au/career-advice/article/illegal-interview-questions-what-employers-have-no-right-to-ask">equal opportunity policies</a> in other areas, like employment. But we would then have to hope enough candidates selected on other merits happen to be willing and able to procreate. </p>
<p>Alternatively, we could reserve a certain number of places for those who agree to contribute to population growth. Fertility would then become an inherent job requirement. This might be similar to taking on a role as a <a href="https://theconversation.com/surrogacy-laws-why-a-global-approach-is-needed-to-stop-exploitation-of-women-98966">surrogate</a>, in which reproductive capacity is essential. </p>
<p>But what if, after accepting such a position on the mission, someone changed their mind about wanting children? Would they be expected to provide some sort of compensation? Would they be vulnerable to retaliation? </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/540635/original/file-20230802-10044-kwy7jj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/540635/original/file-20230802-10044-kwy7jj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/540635/original/file-20230802-10044-kwy7jj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/540635/original/file-20230802-10044-kwy7jj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/540635/original/file-20230802-10044-kwy7jj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/540635/original/file-20230802-10044-kwy7jj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/540635/original/file-20230802-10044-kwy7jj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/540635/original/file-20230802-10044-kwy7jj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Fertility could potentially be a ‘job requirement’ for some space colonisers.</span>
<span class="attribution"><span class="source">Oleksandr Canary Islands/Pexels</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>The more we focus on procreation, the less diversity we will preserve in the species as a whole – especially if we deliberately select against diverse sexualities, disabilities and older people. </p>
<p>A lack of diversity would also threaten the long-term viability of the new society. For example, even if we exclude all physiologically or socially infertile people from the initial crew, these traits will reappear in future generations.</p>
<p>The difference is: these children would be born into a less accepting community. Cooperation will be essential for the new human society – so promoting hostility would be counterproductive. </p>
<p>So, what options are left? Using a random global sample to select travellers might alleviate concerns about equity and fairness. But the ability of a random sample to maximise our survival as a species would depend on how large the sample can be. </p>
<p>A global sample would minimise bias. But there’s a risk it might yield a crew without doctors, engineers, farmers or other essential personnel. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/venus-the-trouble-with-sending-people-there-191534">Venus: the trouble with sending people there</a>
</strong>
</em>
</p>
<hr>
<h2>Random selection versus a points-based system</h2>
<p>The best balance between competing needs might be a stratified random sampling method, involving randomly selecting survivors from predetermined categories. Reproductive potential might be one category. Others might focus on other elements of practical usefulness or contribution to human diversity.</p>
<p>Another option is a points-based system, whereby different skills and characteristics are ranked in terms of their desirability. In this system, an elderly person who speaks multiple languages may score higher than a physiologically fertile young person, due to their ability to substantially contribute to language preservation and education. </p>
<p>This does not entirely eliminate the potential for discrimination, of course. Someone would need to decide which traits are most desirable and valuable to the new human society.</p>
<p>However we determine our lifeboat candidates, it should be carefully considered. In our attempt to “save humanity”, we must avoid sacrificing the very things that make us human. </p>
<hr>
<p><em>Evie Kendal is a contributor to <a href="https://global.oup.com/academic/product/reclaiming-space-9780197604793?cc=au&lang=en&#">Reclaiming Space: Progressive and Multicultural Visions of Space Exploration</a> (Oxford University Press)</em></p><img src="https://counter.theconversation.com/content/210647/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Evie Kendal does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Climate change and the nuclear threat are raising concerns about our planet’s future ability to support human life. If we launch a species survival mission, who should go?Evie Kendal, Senior lecturer of health promotion, Swinburne University of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1842412022-06-02T20:18:46Z2022-06-02T20:18:46ZThis Australian grasshopper gave up sex 250,000 years ago and it’s doing fine<figure><img src="https://images.theconversation.com/files/466494/original/file-20220601-49050-8arffe.jpeg?ixlib=rb-1.1.0&rect=7%2C7%2C5168%2C3437&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Michael Kearney</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Most animals on Earth have two sexes, male and female, that combine and mix their genes when they reproduce. We are so accustomed to this state of affairs that the existence of all-female species that don’t have sex, but instead reproduce by cloning, comes as a great surprise.</p>
<p>The beautiful green grasshopper <em>Warramaba virgo</em> is one of these rare “parthenogenetic” species, in which an egg can develop into an embryo without being fertilised by a sperm. It lives in the southern parts of the Australian arid zone, where it feeds on mulga trees and other shrubs and bushes in the summertime.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/466495/original/file-20220601-48567-e5l8xx.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A full-body photo of a Warramaba virgo grasshopper against a white background." src="https://images.theconversation.com/files/466495/original/file-20220601-48567-e5l8xx.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/466495/original/file-20220601-48567-e5l8xx.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/466495/original/file-20220601-48567-e5l8xx.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/466495/original/file-20220601-48567-e5l8xx.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/466495/original/file-20220601-48567-e5l8xx.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/466495/original/file-20220601-48567-e5l8xx.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/466495/original/file-20220601-48567-e5l8xx.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The grasshopper <em>Warramaba virgo</em> reproduces asexually.</span>
<span class="attribution"><span class="source">Michael Kearney</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>We have studied these grasshoppers for the past 18 years to understand how they developed asexual reproduction, and how the change has affected their ability to survive and reproduce.</p>
<p>Our <a href="https://doi.org/10.1126/science.abm1072">new research published in Science</a> shows <em>W. virgo</em> arose about 250,000 years ago from a cross between two different sexually reproducing species of grasshopper, and giving up sex appears to have had no negative repercussions for them whatsoever.</p>
<h2>The puzzle of parthenogenesis</h2>
<p>Biologists studying evolution have often considered the rarity of parthenogenetic species like <em>W. virgo</em> as a major puzzle. </p>
<p>This is because sex imposes big costs on animal reproduction. First, there is the “two-fold cost of sex”: half a creature’s offspring (the males) are unable to produce their own offspring alone, so they are often seen as “evolutionary wastage”. </p>
<p>Moreover, finding a mate takes energy and mating animals are often at greater risk of attack by predators. Doing away with males also removes these drawbacks.</p>
<figure class="align-center ">
<img alt="A photograph showing a low bushy green tree in a landscape of red dirt" src="https://images.theconversation.com/files/466496/original/file-20220601-49336-m39kx3.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/466496/original/file-20220601-49336-m39kx3.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/466496/original/file-20220601-49336-m39kx3.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/466496/original/file-20220601-49336-m39kx3.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/466496/original/file-20220601-49336-m39kx3.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/466496/original/file-20220601-49336-m39kx3.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/466496/original/file-20220601-49336-m39kx3.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"><em>Warramaba virgo</em> feeds on mulga trees (many of which also reproduce asexually).</span>
<span class="attribution"><span class="source">Michael Kearney</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>So why does sex exist at all? The main reason, biologists think, relates to the mixing or “recombination” of genes as a consequence of sex. This can speed up the rate of adaptation by bringing favourable combinations of genes together and also helps to purge a population of combinations of bad mutations. </p>
<p>Parthenogenetic species don’t have these processes: instead, all members of the species have virtually identical genes. This means they might be less able to adapt when the environment changes. What’s more, parthenogens could accumulate bad mutations that reduce their fitness.</p>
<p>But are these costs real? Do they result in the rapid extinction of any parthenogens that happen to form? </p>
<h2>What’s the secret of W. virgo?</h2>
<p>Over the past 18 years we have been investigating these questions in <em>W. virgo</em>. </p>
<p>This grasshopper was first studied in 1962 by the eminent evolutionary biologist and geneticist <a href="https://www.science.org.au/fellowship/fellows/biographical-memoirs/michael-james-denham-white-1910-1983">Michael White</a>. White’s young son Nicholas first discovered them near the New South Wales town of Hillston, when he noted that only females of a particular species could be found. </p>
<p>White then went on to show that the same species was present 2,000 km away in Western Australia, along with a sexual species (recently named <em>W. whitei</em>). </p>
<p><em>W. virgo</em> turned out to have a hybrid origin: a cross between <em>W. whitei</em> and another species, <em>W. flavolineata</em>, many thousands of years in the past.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/466497/original/file-20220601-48861-vp3ro2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A triptych of three face-on photographs of different grasshoppers." src="https://images.theconversation.com/files/466497/original/file-20220601-48861-vp3ro2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/466497/original/file-20220601-48861-vp3ro2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=132&fit=crop&dpr=1 600w, https://images.theconversation.com/files/466497/original/file-20220601-48861-vp3ro2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=132&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/466497/original/file-20220601-48861-vp3ro2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=132&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/466497/original/file-20220601-48861-vp3ro2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=166&fit=crop&dpr=1 754w, https://images.theconversation.com/files/466497/original/file-20220601-48861-vp3ro2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=166&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/466497/original/file-20220601-48861-vp3ro2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=166&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"><em>Warramaba virgo</em> (middle) and its ‘parent species’, <em>W. flavolineata</em> (left) and <em>W. whitei</em> (right)</span>
<span class="attribution"><span class="source">Michael Kearney</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>A parthenogenetic species might have an advantage if its genetic diversity is boosted by repeated hybridisations between the two parent species, producing an army of different clones. Combining the genomes of the two species might also make the parthenogens more vigorous.</p>
<p>Such “hybrid vigour” does occur in some animals, such as mules (crosses between a horse and a donkey). The mule has much greater strength and endurance than its parent species. </p>
<p>Could it be that the hybrid origins of <em>W. virgo</em> generated a diverse clone army with special abilities compared to its sexual relatives, or a hybrid with high level of vigour?</p>
<h2>Few benefits to giving up sex, but also no drawbacks</h2>
<p>The answers to these questions were a resounding “No”! </p>
<p>We examined more than 1,500 genetic markers in <em>W. virgo</em> and found almost no variation in the parthenogens compared with the parent species. </p>
<p>This showed clearly that only one hybrid mating between <em>W. whitei</em> and <em>W. flavolineata</em> was responsible for producing <em>W. virgo</em> in the first place. Based on the number and nature of mutations that have occurred in <em>W. virgo</em>, we estimate the mating occurred some 250,000 years ago.</p>
<p>We also showed that the parthenogen had no advantage over its parent species in a range of physiological traits including tolerance to heat and cold, rate of metabolism, how many eggs they lay, the size of their eggs, how long they take to mature and how long they live.</p>
<p>Meanwhile, <em>W. virgo</em> naturally produced twice as many female offspring as the sexual species. It retained its two-fold advantage over sexual species despite 250,000 years for low fitness mutations to accumulate in this species. </p>
<p>The conclusion from our research then is that <em>W. virgo</em> has become parthenogenic but without costs. It has also successfully spread all the way from the west side of the country to the east side, unlike its parent species.</p>
<h2>Why don’t more species give up on sex?</h2>
<p>So why then do we see sexual species everywhere despite their two-fold reproductive cost? We suspect it must be very difficult to develop parthenogenesis in the first place. </p>
<p>Indeed, we have tried experimentally crossing the same sexual species that gave rise to <em>W. virgo</em> and only created a few hybrids, none of which were able to produce offspring. The hybrid state may disturb the normal processes of egg development sufficiently to make parthenogenesis an extremely uncommon phenomenon in animals more generally.</p>
<figure class="align-center ">
<img alt="A photograph of a grasshopper sitting on a leaf." src="https://images.theconversation.com/files/466734/original/file-20220602-20-bpwey2.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/466734/original/file-20220602-20-bpwey2.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=228&fit=crop&dpr=1 600w, https://images.theconversation.com/files/466734/original/file-20220602-20-bpwey2.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=228&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/466734/original/file-20220602-20-bpwey2.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=228&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/466734/original/file-20220602-20-bpwey2.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=286&fit=crop&dpr=1 754w, https://images.theconversation.com/files/466734/original/file-20220602-20-bpwey2.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=286&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/466734/original/file-20220602-20-bpwey2.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=286&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A lab-made cross of W. whitei and W. flavolineata. She produced few eggs, none of which hatched.</span>
<span class="attribution"><span class="source">Michael Kearney</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>We think future research into the paradox of sexual reproduction should focus on barriers that prevent sex from being lost, rather than only focusing on the advantages of sex.</p><img src="https://counter.theconversation.com/content/184241/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ary Hoffmann receives funding from the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Michael Kearney does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Few animals have babies without sex, so biologists assumed asexual reproduction must have evolutionary drawbacks. But a self-cloning Australian grasshopper shows things might be more complicated.Michael Kearney, Professor in Ecophysiology and Evolutionary Biology, The University of MelbourneAry Hoffmann, Professor, School of BioSciences and Bio21 Institute, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1709652021-11-04T05:21:21Z2021-11-04T05:21:21ZThe endangered condor surprised researchers by producing fatherless chicks. Could ‘virgin birth’ rescue the species?<figure><img src="https://images.theconversation.com/files/430146/original/file-20211104-24-1oafxjd.jpeg?ixlib=rb-1.1.0&rect=85%2C54%2C5090%2C3391&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Virgin birth – which involves the development of an unfertilised egg – has preoccupied humans for aeons. And although it can’t <a href="http://theconversation.com/is-virgin-birth-possible-yes-unless-you-are-a-mammal-52379">happen in mammals</a>, it does seem to be possible in other animals with backbones (vertebrates), such as birds and lizards. </p>
<p>A <a href="https://academic.oup.com/jhered/advance-article/doi/10.1093/jhered/esab052/6412509">recent paper</a> led by researchers from San Diego Zoo in the United States reports two fatherless male chicks raised in a program to save the Californian condor from extinction. Could the species be restored by a single surviving female?</p>
<p>Sexual reproduction is fundamental in all vertebrates. Normally it requires an egg from a female to be fertilised by a sperm from a male, so each parent contributes one copy of the genome. </p>
<p>Violation of this rule, as for the fatherless condor chicks, tells us a lot about why sexual reproduction is such a good biological strategy – as well as how sex works in all animals, including humans.</p>
<h2>How the fatherless chicks were identified</h2>
<p>The magnificent California condor, a type of vulture, is the largest flying bird in North America. In 1982 the species declined to a population of just <a href="https://academic.oup.com/jhered/advance-article/doi/10.1093/jhered/esab052/6412509">22 individuals</a>, sparking an ambitious captive breeding program led by San Diego Zoo which has seen numbers start to grow.</p>
<p>With so few birds, the team had to be careful not to choose parents that were closely related, as a lack of genetic variation would produce less vigorous offspring and steepen the slide to extinction. </p>
<p>The researchers conducted a detailed genetic study of the birds to avoid this, using DNA markers that were specific for condors and which varied between individual birds. They collected feathers, blood and eggshells from nearly 1,000 birds over 30 years. </p>
<p>By analysing these data, they established parentage, confirming that half the DNA markers in each chick came from a female and half from a male, as you’d expect. They continued to follow the fates of hundreds of captive-bred chicks in the colony, and after releasing them into the wild.</p>
<p>But there was something unusual about two male chicks, as detailed in the recent paper. These chicks, which hatched several years apart from eggs laid by different females, had DNA markers that all came from the female parent. There was no trace of markers from the male she’d been paired with. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/430151/original/file-20211104-27-h9x77u.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A condor chick" src="https://images.theconversation.com/files/430151/original/file-20211104-27-h9x77u.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/430151/original/file-20211104-27-h9x77u.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/430151/original/file-20211104-27-h9x77u.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/430151/original/file-20211104-27-h9x77u.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/430151/original/file-20211104-27-h9x77u.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/430151/original/file-20211104-27-h9x77u.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/430151/original/file-20211104-27-h9x77u.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">There are currently about 500 living condors in the world.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Virgin birth</h2>
<p>The development of unfertilised eggs is called “parthenogenesis” (from Greek words that literally mean “virgin creation”). It’s quite common in <a href="https://www.nationalgeographic.com/animals/article/parthenogenesis-how-animals-have-virgin-births">insects and other invertebrates</a> like aphids and starfish, and can be accomplished by several different mechanisms. But it’s very <a href="https://pubmed.ncbi.nlm.nih.gov/29559496/">rare in vertebrates</a>.</p>
<p>There have been reports of parthenogenesis in fish and reptiles that were housed without males. In Tennessee, a lonely female Komodo dragon held in captivity for many years gave up on finding a mate and <a href="https://www.scientificamerican.com/article/strange-but-true-komodo-d/">produced three viable</a> offspring on her own. So did a <a href="https://www.nationalgeographic.com/animals/article/141023-virgin-birth-pythons-snakes-animals-science">female python and a boa</a>, although these parthenogenic offspring all died early.</p>
<p>Some lizards, however, have adopted parthenogenesis as a way of life. There are <a href="https://www.scientificamerican.com/article/asexual-lizards/">female-only species</a> in Australia and the US in which females lay eggs carrying only combinations of their own genes.</p>
<p>Parthenogenesis also happens in domesticated chickens and turkeys raised in the absence of a male, but the embryo usually dies. There are only a few reports of fatherless male turkeys that made it to adulthood, and just one or two that produced sperm.</p>
<h2>How does it happen?</h2>
<p>In birds, parthenogenisis always results from an egg cell carrying a single copy of the genome (haploid). Eggs are made in the ovary of a female by a special sort of cell division called meiosis, which shuffles up the genome and also halves the chromosome number. Sperm cells are made by the same process in the testis of a male.</p>
<p>Normally an egg cell and a sperm cell fuse (fertilisation), incorporating both parents genomes and restoring the usual (diploid) number of chromosomes. </p>
<p>But in parthenogenesis, the egg cell is not fertilised. Instead, it achieves a diploid state either by fusing with another cell from the same division — which is normally jettisoned — or by replicating its genome without the cell being divided.</p>
<p>So rather than getting one genome from the mother and a different one from the father, the resulting egg only has a subset of the mother’s genes in a double dose. </p>
<h2>Fatherless birds will always be male</h2>
<p>Condors, like other birds, determine sex by Z and W sex chromosomes. These work in the opposite way to the human XX (female) and XY (male) system, in which the SRY gene on the Y chromosome <a href="http://theconversation.com/what-makes-you-a-man-or-a-woman-geneticist-jenny-graves-explains-102983">determines maleness</a>.</p>
<p>However, in birds males are ZZ and females are ZW. Sex is determined by the dosage of a gene (DMRT1) on the Z chromosome. The ZZ combination has two copies of the DMRT1 gene and makes a male, whereas the ZW combination has only one copy and makes a female. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-birds-become-male-or-female-and-occasionally-both-112061">How birds become male or female, and occasionally both</a>
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<p>Haploid egg cells receive either a Z or a W from the ZW mother. Their diploid derivatives will therefore be ZZ (normal male) or WW (dead). The reason WW embryos can’t develop is because the W chromosome contains hardly any genes, whereas the Z chromosome has 900 genes which are vital for development.</p>
<p>Fatherless chicks must therefore be ZZ males, as was observed.</p>
<h2>Why virgin birth fails</h2>
<p>Is it possible an endangered bird species such as the condor could be resuscitated from a lone female survivor, by hatching a fatherless male chick and breeding with it? </p>
<p>Well not quite. It turns out parthenogens (fatherless animals) don’t do so well. Neither of the two fatherless condors produced offspring of their own. One died before reaching sexual maturity and the other was weak and submissive – making it a poor prospect for fatherhood. </p>
<p>In chickens and turkeys, parthenogenesis produces either dead embryos or weak hatchlings. Even female-only lizard species, though they seem robust, are generally the product of a recent blending of two species which messed up meiosis and left them no other option. These species don’t seem to last long.</p>
<p>Why do parthenogens do so poorly? The answer goes to the core of a fundamental biological question. That is: why do we have sex at all? You’d think it would be more efficient for the mother’s genome to be simply handed down to her clonal offspring without bothering about meiosis.</p>
<h2>Variation is key</h2>
<p>But the evidence says it’s not healthy to have a genome consisting entirely of the mother’s genes. Genetic variation is all-important in the health of an individual and its species. Mixing the gene variants from male and female parents is vital.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/these-sex-starved-creatures-scavenge-new-genes-from-other-pondlife-56913">These sex-starved creatures scavenge new genes from other pondlife</a>
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<hr>
<p>In diploid offspring with two parental genomes, good variants can cover for mutants. Individuals that inherit genes only from the mother may have two copies of a maternal mutant gene that weakens them – without a healthy version from a male parent to compensate.</p>
<p>Variation also helps protect populations from deadly viruses, bacteria and parasites. Meiosis and fertilisation provide many rearrangements of different gene variants, which can baffle pathogens. Without this added protection, pathogens could run amok in a population of clones, and a genetically similar population would not contain resistant animals.</p>
<p>So the ability of condor females to hatch chicks without a father is unlikely to save the species. On the bright side, human efforts have now led to hundreds of females – and males – flying the Californian skies.</p><img src="https://counter.theconversation.com/content/170965/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jenny Graves receives funding from the Australian Research Council</span></em></p>Researchers were surprised to find two female condors had managed to hatch chicks that had no fathers. But virgin birth does not seem to produce healthy birds that could strengthen the population.Jenny Graves, Distinguished Professor of Genetics and Vice Chancellor's Fellow, La Trobe UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1526702021-05-18T12:24:54Z2021-05-18T12:24:54ZEngineers and economists prize efficiency, but nature favors resilience – lessons from Texas, COVID-19 and the 737 Max<figure><img src="https://images.theconversation.com/files/400844/original/file-20210514-19-jy5kl9.jpg?ixlib=rb-1.1.0&rect=0%2C12%2C8409%2C5576&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The power grid in Texas provides a stark lesson in the balance between efficiency and resilience.</span> <span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/TexasBlackoutsInmates/b71dd8075a6a4c80bbad12d50dd93d8d/photo?boardId=6576eeb175bb4623a6e17828de4a73e8&st=boards&mediaType=audio,photo,video,graphic&sortBy=&dateRange=Anytime&totalCount=9&currentItemNo=0">AP Photo/David J. Phillip</a></span></figcaption></figure><p><strong>Takeaways:</strong></p>
<ul>
<li><p><strong>The damage from Winter Storm Uri, the economic devastation from the COVID-19 pandemic and the fatal Boeing 737 Max accidents show the price society pays for a relentless pursuit of efficiency.</strong></p></li>
<li><p><strong>Modern society has prioritized free-market economics and efficient computer systems to the detriment of other priorities.</strong></p></li>
<li><p><strong>Studies of algorithms show that efficiency can come at a high cost.</strong></p></li>
<li><p><strong>Sexual reproduction and car insurance highlight the benefits of resilience.</strong></p></li>
</ul>
<hr>
<p>There is a trade-off between efficiency and resilience. Efficiency requires optimal adaptation to an existing environment, while resilience is an <a href="https://www.wsj.com/articles/efficiency-isnt-the-only-economic-virtue-11583873155">ability to adapt to large or sudden changes in the environment</a>. Society’s <a href="https://www.project-syndicate.org/commentary/economic-thought-efficiency-versus-sustainability-by-robert-skidelsky-2020-12?barrier=accesspay">emphasis on short-term gains</a> has long tipped the balance in favor of efficiency.</p>
<p>However, the relentless pursuit of efficiency removes hurdles to the speed and reach of transactions, hurdles that also serve as <a href="https://www.nytimes.com/2020/05/30/opinion/sunday/coronavirus-globalization.html">buffers against shocks</a>. Buffers provide resilience in the face of ecological, geopolitical and financial crises.</p>
<p>As a <a href="https://scholar.google.com/citations?user=DQaARsgAAAAJ&hl=en">computer scientist</a>, I look at how algorithms provide a way to test assumptions about resilience, even as the field of computing itself shares the bias toward efficiency. Three recent crises – the 2021 winter storm in Texas, the COVID-19 pandemic and the Boeing 737 Max software failure – highlight the cost of valuing efficiency over resilience and provide lessons for bringing society into balance. </p>
<h2>Economists and engineers ❤️ efficiency</h2>
<p>Economics has long been <a href="https://www.project-syndicate.org/commentary/economic-thought-efficiency-versus-sustainability-by-robert-skidelsky-2020-12">obsessed with efficiency</a>. <a href="https://www.investopedia.com/terms/e/economic_efficiency.asp">Economic efficiency</a> means that goods and production are distributed or allocated to their most valuable uses and waste is eliminated or minimized. </p>
<p>Free-market advocates argue that through individual <a href="https://www.investopedia.com/terms/i/invisiblehand.asp">self-interest and freedom of production and consumption</a>, economic efficiency is achieved and the best interests of society, as a whole, are fulfilled. But this conflates efficiency with the best outcome.</p>
<p>The intense focus on efficiency at the expense of resilience plagues not only business and economics but also technology. Society has educated generations of computer scientists that analyzing algorithms, the step-by-step instructions at the heart of computer software, boils down to measuring their computational efficiency. </p>
<p><a href="https://www-cs-faculty.stanford.edu/%7Eknuth/taocp.html">“The Art of Computer Programming,”</a> one of the founding texts of computer science, is dedicated to the analysis of algorithms, which is the process of figuring out the amount of time, storage or other resources needed to execute them. In other words, efficiency is the sole concern in the design of algorithms, according to this guide.</p>
<p>But what about resilience? Designing resilient algorithms requires computer scientists to consider in advance what can go wrong and build effective countermeasures into their algorithms. Without designing for resilience, you get efficient but brittle algorithms.</p>
<h2>A storm, a plague and some bad software</h2>
<p>Brittle systems are more likely than resilient systems to break down when crises strike. Cold temperatures and blackouts during <a href="https://www.pbs.org/wgbh/nova/article/texas-winter-storm-uri/">Winter Storm Uri</a> killed <a href="https://www.houstonchronicle.com/news/houston-texas/houston/article/texas-cold-storm-200-died-analysis-winter-freeze-16070470.php">nearly 200 people</a> in February 2021 in Texas. The storm damaged the power grid and water systems, which lacked the weatherproofing features common to utility infrastructure in much of the rest of the country. </p>
<p>The harsh economic consequences of failing to prepare for a pandemic, despite many <a href="https://www.aging.senate.gov/imo/media/doc/hr157ml.pdf">early warnings</a>, provoke questions about whether the obsessive pursuit of efficiency, which has dominated standard business orthodoxy for decades, has <a href="https://www.wsj.com/articles/efficiency-isnt-the-only-economic-virtue-11583873155">made the global economic system more vulnerable</a> to disruptive changes. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/400846/original/file-20210514-23-5shuna.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A twin-engine jetliner with its landing gear partway down and the name Boeing on the side descends through the air" src="https://images.theconversation.com/files/400846/original/file-20210514-23-5shuna.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/400846/original/file-20210514-23-5shuna.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/400846/original/file-20210514-23-5shuna.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/400846/original/file-20210514-23-5shuna.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/400846/original/file-20210514-23-5shuna.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/400846/original/file-20210514-23-5shuna.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/400846/original/file-20210514-23-5shuna.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The Boeing 737 Max fiasco resulted from engineering and business decisions that put efficiency ahead of resilience.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/FAABoeing/9ca52000db8d439e8daf2ec17450cb6f/photo?boardId=6576eeb175bb4623a6e17828de4a73e8&st=boards&mediaType=audio,photo,video,graphic&sortBy=&dateRange=Anytime&totalCount=5&currentItemNo=0">AP Photo/Elaine Thompson</a></span>
</figcaption>
</figure>
<p>A stark example of a system designed for efficiency and not resilience is the flight-control algorithm for the Boeing 737 Max. Boeing retrofitted the 737, a passenger aircraft first produced more than half a century ago, with more efficient engines. This retrofitting caused some <a href="https://www.forbes.com/sites/petercohan/2019/04/02/mit-expert-highlights-divergent-condition-caused-by-737-max-engine-placement/?sh=a0aa1140aabe">flight instability</a>, which the flight-control algorithm was designed to overcome. </p>
<p>But the algorithm <a href="https://www.cnn.com/2019/04/30/politics/boeing-sensor-737-max-faa/index.html">relied on data from a single sensor</a>, and when the sensor failed, the algorithm incorrectly determined that the plane was stalling. In response, the algorithm caused the plane to dive as an emergency measure to recover from a stall that wasn’t happening.</p>
<p>The result was two horrific crashes and hundreds of the aircraft being <a href="https://www.flightradar24.com/blog/the-boeing-737-max-grounding/">grounded for nearly two years</a>. In retrospect, the engineers overly optimized for fuel economy and time to market <a href="https://www.nytimes.com/2020/11/24/sunday-review/boeing-737-max.html">at the expense of safety</a>.</p>
<h2>The price of anarchy</h2>
<p>If brittle systems are prone to disasters, why is society filled with them? One explanation is that, short of disasters, systems that emphasize efficiency can achieve a kind of stability. A fundamental theorem in economics states that under certain assumptions a market will tend toward a competitive balance point, known as the <a href="https://www.britannica.com/topic/Pareto-optimality">Pareto-optimal equilibrium</a>, in which economic efficiency is achieved. </p>
<p>But how well does such an equilibrium serve the best interests of society? A team of computer scientists studied <a href="https://doi.org/10.1016/j.cosrev.2009.04.003">how beneficial or detrimental equilibria can be</a> from a computational perspective. The researchers studied systems in which uncooperative agents share a common resource, the mathematical equivalent of roadways or fisheries. </p>
<p>They came up with a ratio between the worst possible equilibrium – traffic congestion or overfishing – and the social optimum, a ratio dubbed the “<a href="http://www.ams.org/publicoutreach/feature-column/fcarc-anarchy">Price of Anarchy</a>” because it measures how far from optimal such uncooperative systems can be. They showed that this ratio can be very high. In other words, economic efficiency does not guarantee that the best interests of society are fulfilled. </p>
<p>Another team of researchers asked <a href="https://doi.org/10.1137/070699652">how long it takes until economic agents converge to an equilibrium</a>. By studying the <a href="http://www.esi2.us.es/%7Embilbao/complexi.htm">computational complexity</a> of computing such equilibria, the researchers showed that there are systems that take an exceedingly long time to converge to an equilibrium. </p>
<p>The implication is that economic systems are very unlikely ever to be in an equilibrium, because the underlying variables – such as prices, supply and demand – are very likely to change while the systems are making their slow way toward convergence. In other words, <a href="https://www.investopedia.com/terms/e/economic-equilibrium.asp">economic equilibrium</a>, a central concept in economic theory, is a mythical rather than a real phenomenon. This is not an argument against free markets, but it does require a pragmatic view of them.</p>
<figure class="align-center ">
<img alt="an older man holding a large cloth bundle under his arm walks along the sidewalk in front of the metal grate of a closed pawn shop" src="https://images.theconversation.com/files/400845/original/file-20210514-17-ei6956.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/400845/original/file-20210514-17-ei6956.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/400845/original/file-20210514-17-ei6956.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/400845/original/file-20210514-17-ei6956.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/400845/original/file-20210514-17-ei6956.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/400845/original/file-20210514-17-ei6956.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/400845/original/file-20210514-17-ei6956.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Free markets can be efficient and at the same time bad for society as a whole.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/EconomyJobsReport/79fc99505312438584edfad8b2e42448/photo?boardId=6576eeb175bb4623a6e17828de4a73e8&st=boards&mediaType=audio,photo,video,graphic&sortBy=&dateRange=Anytime&totalCount=8&currentItemNo=1">AP Photo/Lynne Sladky</a></span>
</figcaption>
</figure>
<h2>When sex is best</h2>
<p>It is interesting to consider how nature deals with the trade-off between efficiency and resilience. This issue was addressed in a computer science paper titled “<a href="http://dx.doi.org/10.1145/2934662">Sex as an Algorithm</a>.” Computer scientists know that search techniques <a href="https://mathworld.wolfram.com/SimulatedAnnealing.html">allowing individual steps that are less than optimal but could lead to an overall better solution</a> are, in general, <a href="https://doi.org/10.1023/A:1018538202952">computationally superior</a> to search techniques that mimic <a href="https://evolution.berkeley.edu/evolibrary/article/evo_25">natural selection</a> by creating “offspring” of previous solutions and adding random mutations.</p>
<p>[<em><a href="https://theconversation.com/us/newsletters/science-editors-picks-71/?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=science-corona-important">The Conversation’s most important coronavirus headlines, weekly in a science newsletter</a></em>]</p>
<p>Why, then, has nature chosen sexual reproduction as the almost exclusive reproduction mechanism in animals? The answer is that sex as an algorithm <a href="http://dx.doi.org/10.1145/2934662">offers advantages</a> other than good performance. </p>
<p>In particular, natural selection favors genes that work well with a greater diversity of other genes, and this makes the species more adaptable to disruptive environmental changes – that is to say, more resilient. Thus, in the interest of long-term survival, nature prioritized resilience over efficiency.</p>
<h2>Car insurance and climate change</h2>
<p>The bottom line is that resilience is a fundamental but underappreciated societal need. But both computing and economics have underemphasized resilience. In general, markets and people are quite bad at <a href="https://www.amazon.com/Black-Swan-Improbable-Robustness-Fragility/dp/081297381X">preparing for very low-probability or very long-term events</a>. </p>
<p>For example, people have to be forced to buy car insurance, because buying insurance is not efficient. After all, in the aggregate, the insurance business is profitable for the insurers, not for the insured. The purpose of insurance is increased resilience. This example shows that ensuring resilience requires societal action and cannot be left to markets. </p>
<p>The economic impact of the pandemic shows the cost of society’s failure to act. And COVID-19 may be just the <a href="https://www.scmp.com/comment/opinion/article/3114641/covid-19-only-dress-rehearsal-transformations-coming-climate-change">warmup act</a> for the much bigger impending climate crisis, so focusing on resilience is becoming more and more important. </p>
<p>There seems to be a broad recognition that the incalculable suffering and trauma of COVID-19 <a href="https://www.washingtonpost.com/opinions/2020/10/06/fareed-zakaria-lessons-post-pandemic-world/">offers societies</a> ways to <a href="https://www.wired.com/story/who-will-we-be-when-the-pandemic-is-over/">change for the better</a>. Similar lessons can be drawn from Winter Storm Uri and the Boeing 737 Max. </p>
<p>Focusing on resilience is a way for societies to change for the better. In the meantime, the steady flow of news events – like a pipeline company that <a href="https://www.washingtonpost.com/business/2021/05/15/energy-cost-cutting-price/">appears to have underinvested in security</a> – continues to underscore the cost of prizing efficiency over resilience.</p><img src="https://counter.theconversation.com/content/152670/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Moshe Y. Vardi is affiliated with the Baker Institute for Public Policy.</span></em></p>Disasters highlight the cost of society’s love of efficiency. Nature, in contrast, favors resilience. Being more like nature offers benefits for society, especially in the face of the climate crisis.Moshe Y. Vardi, Professor of Computer Science, Rice UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1504962020-12-15T13:20:28Z2020-12-15T13:20:28ZVirgin births from parthenogenesis: How females from some species can reproduce without males<figure><img src="https://images.theconversation.com/files/374837/original/file-20201214-17-2nde3j.png?ixlib=rb-1.1.0&rect=0%2C0%2C5463%2C3006&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Getting the job done. A female Asian water dragon (Physignathus cocincinus) produced a daughter (left) without the assistance of a male. </span> <span class="attribution"><a class="source" href="https://nationalzoo.si.edu/news/scientists-confirm-facultative-parthenogenesis-smithsonians-national-zoos-asian-water-dragon">Skip Brown/Smithsonian’s National Zoo</a></span></figcaption></figure><p>An Asian water dragon hatched from an egg at the Smithsonian National Zoo, and her keepers were shocked. Why? Her mother had never been with a male water dragon. Through genetic testing, zoo scientists discovered the newly hatched female, born on Aug. 24, 2016, had been produced through a <a href="https://doi.org/10.1371/journal.pone.0217489">reproductive mode called parthenogenesis</a>.</p>
<p>Parthenogenesis is a Greek word meaning “virgin creation,” but specifically refers to female asexual reproduction. While many people may assume this behavior is the domain of science fiction or religious texts, parthenogenesis is <a href="https://doi.org/10.1038/sdata.2014.15">surprisingly common throughout the tree of life</a> and is found in a variety of organisms, including plants, insects, fish, reptiles and even birds. Because mammals, including human beings, require certain genes to come from sperm, <a href="https://doi.org/10.1159/000090812">mammals are incapable of parthenogenesis</a>.</p>
<h2>Creating offspring without sperm</h2>
<p>Sexual reproduction involves a female and a male, each contributing genetic material in the form of eggs or sperm, to create a unique offspring. The vast majority of animal species reproduce sexually, but females of some species are able to produce eggs <a href="https://www.britannica.com/science/parthenogenesis">containing all the genetic material required for reproduction</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/373966/original/file-20201209-19-1x4523.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A microscopic view of a translucent water flea show four round eggs inside." src="https://images.theconversation.com/files/373966/original/file-20201209-19-1x4523.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/373966/original/file-20201209-19-1x4523.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=418&fit=crop&dpr=1 600w, https://images.theconversation.com/files/373966/original/file-20201209-19-1x4523.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=418&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/373966/original/file-20201209-19-1x4523.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=418&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/373966/original/file-20201209-19-1x4523.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=526&fit=crop&dpr=1 754w, https://images.theconversation.com/files/373966/original/file-20201209-19-1x4523.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=526&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/373966/original/file-20201209-19-1x4523.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=526&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A female freshwater water flea (<em>Daphnia magna</em>) carrying parthenogenetic eggs.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/microscopic-view-of-freshwater-water-flea-royalty-free-image/841300586">buccaneership/iStock via Getty Images Plus</a></span>
</figcaption>
</figure>
<p>Females of these species, which include <a href="https://doi.org/10.1002/evl3.30">some wasps</a>, <a href="https://doi.org/10.1086/283761">crustaceans</a> and <a href="https://www.scientificamerican.com/article/asexual-lizards/">lizards</a>, reproduce only through parthenogenesis and are called obligate parthenogens.</p>
<p>A larger number of species experience spontaneous parthenogenesis, best documented in animals kept in zoo settings, like the Asian water dragon at the National Zoo or a <a href="https://doi.org/10.1111/j.1095-8649.2008.02018.x">blacktip shark at the Virginia Aquarium</a>. Spontaneous parthenogens typically reproduce sexually, but may have occasional cycles that produce developmentally ready eggs.</p>
<p>Scientists have learned <a href="https://doi.org/10.1098/rspb.2009.2113">spontaneous parthenogenesis may be a heritable trait</a>, meaning females that suddenly experience parthenogenesis might be more likely to have daughters that can do the same.</p>
<h2>How can females fertilize their own eggs?</h2>
<p>For parthenogenesis to happen, <a href="https://doi.org/10.1534/g3.112.005421">a chain of cellular events must successfully unfold</a>. First, females must be able to create egg cells (oogenesis) without stimulation from sperm or mating. Second, the eggs produced by females need to begin to develop on their own, forming an early stage embryo. Finally, the eggs must successfully hatch. </p>
<p>Each step of this process can easily fail, particularly step two, which requires the chromosomes of DNA inside the egg to double, ensuring a full complement of genes for the developing offspring. Alternatively, the egg can be “faux fertilized” by leftover cells from the egg production process known as <a href="https://doi.org/10.1002/mrd.21266">polar bodies</a>. Whichever method kicks off the development of the embryo <a href="https://doi.org/10.1525/bio.2009.59.7.3">will ultimately determine the level of genetic similarity</a> between the mother and her offspring.</p>
<p>The events that trigger parthenogenesis are not fully understood, but appear to include environmental change. In species that are capable of both sexual reproduction and parthenogenesis, such as <a href="https://doi.org/10.1371/journal.pone.0115099">aphids</a>, stressors like <a href="https://doi.org/10.1111/een.12080">crowding and predation</a> may cause females to switch from parthenogenesis to sexual reproduction, but not the other way around. In at least one <a href="https://doi.org/10.1007/978-90-481-2770-2_15">type of freshwater plankton</a>, <a href="https://doi.org/10.5762/KAIS.2016.17.4.692">high salinity</a> appears to cause the switch.</p>
<h2>Advantages of self-reproduction</h2>
<p>Though spontaneous parthenogenesis appears to be rare, it does provide some benefits to the female who can achieve it. In some cases, it can allow females to generate their own mating partners. </p>
<p>The sex of parthenogenetic offspring is determined by the same method sex is determined in the species itself. For organisms where sex is determined by chromosomes, like the XX female and XY male chromosomes in some insects, fish and reptiles, a parthenogenetic female can produce offspring only with the sex chromosomes she has at hand – which means she will always produce XX female offspring. But for organisms where females have ZW sex chromosomes (such as in snakes and birds), all living offspring produced will either be ZZ, and therefore male, or <a href="https://doi.org/10.1098/rsbl.2010.0793">much more rarely, WW, and female</a>.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"976632933531316224"}"></div></p>
<p>Between 1997 and 1999, <a href="https://doi.org/10.1111/j.1095-8312.2012.01954.x">a checkered gartersnake kept at the Phoenix Zoo</a> gave birth to two male offspring that ultimately survived to adulthood. If a female mated with her parthenogenetically produced son, it would constitute inbreeding. While inbreeding can result in a host of genetic problems, from an evolutionary perspective it’s better than having no offspring at all. The ability of females to produce male offspring through parthenogenesis also suggests that asexual reproduction in nature may be more common than scientists ever realized before. </p>
<p>Biologists have observed, over long periods of time, that <a href="https://doi.org/10.1016/0022-5193(71)90058-0">species that are obligate parthenogens frequently die out</a> from <a href="https://doi.org/10.1038/s41514-018-0025-3">disease</a>, <a href="https://doi.org/10.1073/pnas.87.9.3566">parasitism</a> or <a href="https://doi.org/10.1002/evl3.30">changes in habitat</a>. The inbreeding inherent in parthenogenetic species appears to contribute to their short evolutionary timelines. </p>
<p>Current research on parthenogenesis seeks to understand why some species are capable of both sex and parthenogenesis, and whether occasional sexual reproduction might be enough for a species to survive.</p><img src="https://counter.theconversation.com/content/150496/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mercedes Burns has previously received funding from the National Science Foundation. </span></em></p>Parthenogenesis, a form of reproduction in which an egg develops into an embryo without being fertilized by sperm, might be more common than you realized.Mercedes Burns, Assistant Professor of Biological Sciences, University of Maryland, Baltimore CountyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1437762020-08-18T14:39:06Z2020-08-18T14:39:06ZCoral sex: how reproducing species in the lab could be key to restoring reefs in the wild<figure><img src="https://images.theconversation.com/files/353421/original/file-20200818-14-z0jebp.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C3539%2C2654&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/acropora-coral-spawning-on-magnetic-island-1556924156">Coral Brunner/Shutterstock</a></span></figcaption></figure><p>Coral reefs host <a href="https://www.frontiersin.org/articles/10.3389/fmars.2017.00158/full">a quarter of all sea species</a>, but climate change, overfishing, and pollution could drive these ecosystems to extinction within a matter of decades. </p>
<p>Marine biologists have been racing to restore degraded reefs by collecting corals from the wild and breaking them into fragments. This encourages them to grow fast and quickly produces hundreds of smaller corals which can be raised in nurseries and eventually transplanted back onto the reef. </p>
<p>But if each fragment is an identical copy with one common parent, any resulting colony is likely to be genetically identical to the rest of the population. This matters – having a diverse range of genetically conferred traits can help insure reefs against disease and a rapidly changing environment.</p>
<p>So what if scientists could use sexual reproduction in coral restoration projects? In the wild, the stony coral species that compose the bulk of the world’s tropical reefs cast their sperm and eggs into the water column to reproduce. Corals often synchronise these mass spawning events with full moons, when tides are exceptionally high. This ensures powerful water currents disperse the eggs far and wide, so that they’re fertilised by sperm of distant colonies.</p>
<figure class="align-center ">
<img alt="A light shines on a tropical coral at night, illuminating sperm and egg cells in the water." src="https://images.theconversation.com/files/351952/original/file-20200810-18-6h7axy.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/351952/original/file-20200810-18-6h7axy.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/351952/original/file-20200810-18-6h7axy.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/351952/original/file-20200810-18-6h7axy.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/351952/original/file-20200810-18-6h7axy.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/351952/original/file-20200810-18-6h7axy.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/351952/original/file-20200810-18-6h7axy.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Corals often broadcast their sperm and eggs during the full moon.</span>
<span class="attribution"><span class="source">Jenny Mallon</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Sexually produced offspring have a unique combination of genes from distinct parents, and this helps keep coral populations genetically diverse. Reefs restored with corals created by sexual reproduction are likely to be more resilient, though managing this process hasn’t been easy for scientists to do. But by working on one project in Mexico, I saw what is possible, and learned how to do it myself.</p>
<h2>Coral sex in the lab</h2>
<p>Coral reefs are so enormous they’re visible from space. But watching them spawn is surprisingly tricky. They only do it on a handful of nights each year and the exact date and time is determined by environmental factors that scientists are still working to fully understand. </p>
<p>Climate change is causing reefs with known spawning patterns to shift their timing too, <a href="https://science.sciencemag.org/content/365/6457/987.full%5D">making these events less frequent and predictable</a>. This makes it difficult for different colonies to synchronise spawning, reducing their chances of successful fertilisation in the wild. </p>
<p>The CORALIUM Laboratory of the National Autonomous University of Mexico is part of a <a href="https://www.secore.org">Caribbean-wide network</a> of dedicated coral spawning experts. Scientists here collect coral sperm and eggs from multiple Caribbean reefs in order to fertilise them in the lab. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/z9h-xyLlpro?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Javier Iturrieta, Akumal Dive Center & Thomas Vogt.</span></figcaption>
</figure>
<p>The team wait for the full moon to signal when corals are likely to spawn. Coral sperm and eggs are collected with floating nets and plastic containers, and divers take extreme care to avoid damaging the reef. The millions of sperm and eggs collected are rushed back to the lab where they’re cleaned and monitored all night as they undergo assisted fertilisation to begin life as free swimming larvae. These larvae are very sensitive to water quality, temperature and pathogens, so they need constant care. </p>
<p>Eventually, the larvae settle on hard surfaces where they change into polyps – the initial building blocks of a coral colony. In the ocean, these surfaces are often dead coral skeletons. In the lab, they are <a href="http://www.secore.org/site/our-work/detail/engineering-restoration.60.html">seeding units</a> – 3-D shapes designed by scientists at the conservation organisation <a href="http://www.secore.org/site/home.html">SECORE</a> to resemble coral rubble that can float on ocean currents before resting on reefs.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/352314/original/file-20200811-14-mntl05.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A selection of pieces of artificial coral rubble." src="https://images.theconversation.com/files/352314/original/file-20200811-14-mntl05.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/352314/original/file-20200811-14-mntl05.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/352314/original/file-20200811-14-mntl05.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/352314/original/file-20200811-14-mntl05.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/352314/original/file-20200811-14-mntl05.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/352314/original/file-20200811-14-mntl05.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/352314/original/file-20200811-14-mntl05.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Seeding units are designed to be carried naturally on currents and to right themselves on reefs.</span>
<span class="attribution"><span class="source">SECORE International/Amanda Baye</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Each juvenile produced this way carries a unique mix of genes which they will pass on to a new generation of corals. The resulting population has a stronger gene pool that can help it withstand new diseases and other threats. This long-term strategy also ensures sexual reproduction can continue on restored reefs, which would not be possible for a population composed of identical clones. </p>
<h2>Restoring Caribbean reefs</h2>
<p>The Caribbean may have lost as much as <a href="https://science.sciencemag.org/content/301/5635/958">80% of its coral cover since the mid-1970s</a>. The colonies that remain are now relatively isolated, reducing the chances of them being able to crossbreed. But in the controlled conditions of the lab, fertilisation rates of over 80% are common and larval survival is high. That means thousands of juvenile corals are reared until they’re ready for the reef after just a few weeks of incubation.</p>
<p>But with late night dives by experts, specialised materials for collecting spawn and a lab where fertilisation is carefully controlled, this work is often too expensive for smaller restoration projects. So scientists here have developed low-cost methods for lab spawning and are training teams from across the Caribbean to do it.</p>
<p>I took their course in 2016, and one year later, found myself setting up a new spawning site in Akumal, one hour south of the CORALIUM lab near Cancun. Coral spawning had never been observed here, but I trained volunteers from a local dive centre on how to spot the signs. On our fifth consecutive night dive, we saw the synchronised spawning of multiple colonies of Elkorn corals.</p>
<p>We set up a hotel room as a temporary lab with sterilised plastic larvae tanks and filtered seawater and produced thousands of coral babies for restoration sites. In 2018, we built a beachside coral spawning laboratory on a shoestring budget. Positioned under a tree, the breeze block structure has mosquito netting walls that allow the cool sea breeze to keep the tanks at a constant 28-29°C.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/352366/original/file-20200811-17-14brkl2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A laboratory interior with water-filled crates and a microscope." src="https://images.theconversation.com/files/352366/original/file-20200811-17-14brkl2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/352366/original/file-20200811-17-14brkl2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/352366/original/file-20200811-17-14brkl2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/352366/original/file-20200811-17-14brkl2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/352366/original/file-20200811-17-14brkl2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/352366/original/file-20200811-17-14brkl2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/352366/original/file-20200811-17-14brkl2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Larval rearing bins and a microscope are set up and ready for coral spawning.</span>
<span class="attribution"><span class="source">Jenny Mallon</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The lab was just about up and running in time for that year’s lunar eclipse. We hadn’t anticipated a mass spawn of so many colonies, so the lab inauguration was a chaos of colour coded collection cups from different sites and parent colonies.</p>
<p>Running a coral spawning site has been the most rewarding experience of my career so far. It is everything that research should be: cutting edge, dynamic and challenging. It’s what I signed up for when I became a marine scientist.</p><img src="https://counter.theconversation.com/content/143776/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jenny Mallon receives funding from the Coral Conservation Society. The work described here was completed in partnership with CORALIUM, SECORE International, Ridge to Reefs, Hotel Akumal Caribe and the Akumal Dive Center.</span></em></p>Sexual reproduction helps keep coral colonies diverse and resilient. Now, scientists are doing it in a lab to restock flagging reefs.Jennifer Mallon, PhD Candidate in Coral Reef Biogeochemistry, University of GlasgowLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1282842019-12-11T12:44:19Z2019-12-11T12:44:19ZLeopard slugs mate in the most beautifully bizarre way – and nobody knows why<figure><img src="https://images.theconversation.com/files/306088/original/file-20191210-95125-sj2zwu.jpg?ixlib=rb-1.1.0&rect=0%2C7%2C4710%2C2987&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Beautifully bizarre.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/mating-leopard-slugs-limax-maximus-australia-1435271348">Ken Griffiths/Shutterstock</a></span></figcaption></figure><p>Under the cover of night, two large leopard slugs begin to court, circling each other, before climbing single-file up a tree or onto a rock. They lower themselves on a mucus rope, while entwining their bodies in a strictly anti-clockwise fashion.</p>
<p>Both slugs then push out and entwine two overly-sized penises from openings on the side of their head, before exchanging sperm that may later fertilise each of their eggs. Or, perhaps be eaten. Eventually, one slug crawls off and the other follows, eating the mucus trapeze as it goes.</p>
<p>The astonishing sex lives of leopard slugs, or <em>Limax maximus</em>, have long been recognised by naturalists and frequently feature in <a href="https://youtu.be/wG9qpZ89qzc">wildlife documentaries</a>. But while their carnal dance has mesmerised millions, nobody knows why they mate in this most bizarre way.</p>
<p>This is because slug sex science has rarely attracted anything other than observational study. Fortunately for our curiosity, there are a few <a href="http://www.scholarpedia.org/article/Gastropod_reproductive_behavior">noble individuals</a> who have taken time to understand the mating habits of snails and slugs, and <a href="http://www.joriskoene.com/">whose research</a> can give us some valuable clues.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/Zxow0-hZia4?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>It’s well known that leopard slugs, like the majority of land-based snails and slugs, are hermaphrodites – meaning that both sexual organs are contained in the same individual. Yet, self-fertilisation is generally not the <a href="https://zslpublications.onlinelibrary.wiley.com/doi/abs/10.1017/S0952836905007648">preferred option</a>. This is likely because natural selection favours mating with another individual to avoid the loss of health, fertility and fitness associated with <a href="https://www.sciencedirect.com/science/article/pii/S0169534716301586">inbreeding</a>.</p>
<p>Even though they can choose whether to mate as male or female, most slugs and snails mate as male and female at the same time. They can also <a href="http://www.scholarpedia.org/article/Gastropod_reproductive_behavior">store sperm</a> for months and even years, and so don’t always need to receive sperm if they have previously mated with a better partner. They can have the best of both worlds by choosing to eat and digest most of the sperm, while retaining just enough to fertilise their eggs.</p>
<p>We also know why leopard slugs turn anti-clockwise when mating. Just like human hearts are <a href="https://www.theguardian.com/science/blog/2016/sep/08/situs-inversus-and-my-through-the-looking-glass-body">nearly always</a> to the left hand side in our bodies, a slug’s body is also asymmetric. This is most obvious during mating, when the genitals emerge from the right side of the head. This asymmetry makes leopard slugs turn anti-clockwise in synchrony during courting and mating – and is also what made rare left-coiling snail Jeremy <a href="https://web.archive.org/web/20171020222103/http://www.bbc.co.uk/bbcthree/item/249e54d9-7c5c-451e-940c-7826f6dd2a14">a media sensation</a> in his/her <a href="https://www.npr.org/sections/thetwo-way/2017/05/17/528796939/tragic-love-triangle-is-sad-for-lonely-rare-snail-still-good-for-science">search for love</a>.</p>
<h2>The rest is mystery</h2>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/306207/original/file-20191210-95138-q0ny8k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/306207/original/file-20191210-95138-q0ny8k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=903&fit=crop&dpr=1 600w, https://images.theconversation.com/files/306207/original/file-20191210-95138-q0ny8k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=903&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/306207/original/file-20191210-95138-q0ny8k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=903&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/306207/original/file-20191210-95138-q0ny8k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1135&fit=crop&dpr=1 754w, https://images.theconversation.com/files/306207/original/file-20191210-95138-q0ny8k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1135&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/306207/original/file-20191210-95138-q0ny8k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1135&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">It’s a long way up from there.</span>
<span class="attribution"><a class="source" href="https://flickr.com/photos/kongniffe/48904576193/">Inge Knoff/flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span>
</figcaption>
</figure>
<p>The rest of their elaborate mating behaviour is less well understood. It might be that that <a href="https://www.youtube.com/watch?v=UOcLaI44TXA">communication and cooperation</a> are important aspects of sexual behaviour in the mollusc world, beginning with the head-to-tail <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/brv.12023">trail-following</a>. The long mucus trapeze could be an example of sexual evolution going into overdrive to signify commitment to what’s to come, making sure that any mating efforts won’t be wasted. The spiral entwinement between mating slugs may also facilitate close physical contact and commitment, minimising the risk of sudden withdrawal.</p>
<p>But this behaviour is also more sinister than it first appears. Some slugs and snails engage in hormone warfare or sexual conflict to increase their chances of fertilising their mate. For example, as artistically interpreted by <a href="https://www.youtube.com/watch?v=BckqviVaWl0">Isabella Rossellini</a>, many snails (including the common garden variety) <a href="https://bmcevolbiol.biomedcentral.com/articles/10.1186/1471-2148-5-25">stab each</a> with <a href="https://en.wikipedia.org/wiki/Love_dart">love-darts</a>, transferring hormones to improve the chances that sperm are used for fertilisation. The field slug <em>Deroceras</em>, seen below, <a href="https://youtu.be/b70CGCdeP3I?t=180">flicks and strokes</a> its partner with what looks like a <a href="https://bioone.org/journals/american-malacological-bulletin/volume-23/issue-1/0740-2783-23.1.137/A-review-of-mating-behavior-in-slugs-of-the-genus/10.4003/0740-2783-23.1.137.short">sticky slug blanket</a> for the same reason.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/b70CGCdeP3I?wmode=transparent&start=210" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>The leopard slug’s beautiful entwinement could be another manifestation of this sexual coercion, maximising surface area for hormone transfer. The long penises – which can be <a href="http://www.scholarpedia.org/article/Gastropod_reproductive_behavior">60 to 90cm</a> long in one <a href="http://www.scholarpedia.org/article/File:Limax_Long_Penes.jpg">Italian version</a> of the leopard slug – may also be another extreme result of an evolutionary arms race to improve the prospects of fertilisation.</p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/306350/original/file-20191211-95159-bxkp7.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/306350/original/file-20191211-95159-bxkp7.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1067&fit=crop&dpr=1 600w, https://images.theconversation.com/files/306350/original/file-20191211-95159-bxkp7.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1067&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/306350/original/file-20191211-95159-bxkp7.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1067&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/306350/original/file-20191211-95159-bxkp7.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1341&fit=crop&dpr=1 754w, https://images.theconversation.com/files/306350/original/file-20191211-95159-bxkp7.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1341&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/306350/original/file-20191211-95159-bxkp7.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1341&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Yes, that’s all penis.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Accoppiamento_fra_lumache_2.JPG">Viktor Volkov/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Why they intertwine so intricately is another matter. It could be that the beautiful complexity makes it more difficult for one slug to “cheat” by giving sperm and then not receiving some in return.</p>
<p>In the absence of direct study, the above explanations can only be considered speculation. The truth is that science doesn’t yet have a firm handle on the fascinating sex rituals of leopard slugs.</p>
<h2>More than voyeurism</h2>
<p>Scientists are not just being voyeuristic when we say we’d like to unravel the mysteries of slug sex. Aside from just understanding the wonder and beauty of the behaviour, there are potential benefits.</p>
<p>Some species of slugs are <a href="https://www.rhs.org.uk/advice/profile?pid=228">farm and garden pests</a>, eating holes in leaves, stems, flowers, tubers and bulbs and causing particular damage to new growth. With the pending ban of key pesticides for agricultural use in some countries, including the active ingredient in <a href="https://www.gardenorganic.org.uk/news/metaldehyde-slug-pellets-ban-overturned">slug pellets</a>, there is growing pressure to find other ways to control their spread. One way could be to identify otherwise harmless chemicals that interfere with their sex lives. A contraceptive sheath for slugs, so to speak.</p>
<p>Another approach could be to question why some of the slugs that cause the most agricultural nuisance forgo sex completely, especially in northern latitudes. Lack of sex reduces genetic variation, which causes crops such as potatoes and bananas to suffer from disease outbreaks. Studying the self-contained reproductive habits of slugs may reveal a similar vulnerability that could be exploited to control their numbers.</p>
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<p>There may of course also be benefits which we can’t anticipate. So just as people champion trees, bees and butterflies, we need more slug enthusiasts of <a href="https://www.bbc.co.uk/news/entertainment-arts-46399187">all kinds</a> to help unravel their mucosal mysteries, including backyard explorers who can contribute to <a href="https://www.rhs.org.uk/slugssurvey">citizen science</a> studies. </p>
<p>Of course, if you are already a convert, then how about a leopard slug sex ornament for the <a href="http://www.furaffinity.net/view/25744884/">Christmas tree</a>?</p><img src="https://counter.theconversation.com/content/128284/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Angus Davison received funding from the Biotechnology and Biological Sciences Research Council</span></em></p>Scientists don’t just want to unravel the mysteries of slug sex for voyeurism.Angus Davison, Associate Professor and Reader in Evolutionary Genetics, University of NottinghamLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/996752018-07-18T19:32:00Z2018-07-18T19:32:00ZThe origins of those sexual organs: a fishy tale much more primitive than we thought<figure><img src="https://images.theconversation.com/files/227938/original/file-20180717-44103-10wjj9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">_Euphanerops_, a primitive jawless fish from the World Heritage site at Miguasha, Quebec, which has now been found to have paired hind limb structures and copulatory sex organs.</span> <span class="attribution"><span class="source">François Miville-Deschênes with permission</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Fossil discoveries from the <a href="https://www.livescience.com/43596-devonian-period.html">Devonian</a> rocks of Scotland and Australia first revealed that the earliest jawed fishes, the <a href="http://www.ucmp.berkeley.edu/vertebrates/basalfish/placodermi.html">placoderms</a>, <a href="https://theconversation.com/copulate-to-populate-ancient-scottish-fish-did-it-sideways-30910">reproduced using copulation</a> in much the same way as sharks and rays do today.</p>
<p>They also had the first paired pelvic skeletons, the precursor to the hind paired fins – and legs – of all animals. Their paired reproductive organs, called “claspers”, probably <a href="https://theconversation.com/the-first-vertebrate-sexual-organs-evolved-as-an-extra-pair-of-legs-27578">developed in the same way as limbs</a>.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/the-first-vertebrate-sexual-organs-evolved-as-an-extra-pair-of-legs-27578">The first vertebrate sexual organs evolved as an extra pair of legs</a>
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<p>The <a href="https://theconversation.com/chew-on-this-we-finally-know-how-our-jaws-evolved-64559">appearance of jaws</a> and teeth in the first vertebrates was thus intimately linked to the origin of paired hind limbs (pelvic girdles) and an advanced kind of sexual reproduction.</p>
<h2>Before jaws</h2>
<p>But a new discovery from the Miguasha site, in Quebec, eastern Canada, dated at around 380 million years old, rewrites this view of sexual evolution. </p>
<iframe src="https://www.google.com/maps/embed?pb=!1m18!1m12!1m3!1d10913011.102158058!2d-75.31303489087323!3d48.1042678792208!2m3!1f0!2f0!3f0!3m2!1i1024!2i768!4f13.1!3m3!1m2!1s0x4c9831f2ecb3a20f%3A0xe94e1f17cce791e7!2sMiguasha+National+Park!5e0!3m2!1sen!2sau!4v1531807712317" width="100%" height="400" frameborder="0" style="border:0" allowfullscreen=""></iframe>
<p>Our new paper, published recently in <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/pala.12379">Palaeontology</a>, shows that a Devonian jawless fish, named <em>Euphanerops</em> (pictured top), had paired hind limb structures called pelvic discs and paired slender male reproductive organs.</p>
<p>This is remarkable as these structures, once thought to be unique to jawed fishes (gnathostmes), are now seen to first appear further down the evolutionary tree, in jawless fishes.</p>
<p>This is the first account of such structures in any jawless fish, and suggests that the evolutionary mechanisms necessary for limb and clasper development were in place well before jaws and teeth arose.</p>
<p><em>Euphanerops</em> is an eel-like fish with simple paired fins along the midline of the body. It was first described from Miguasha in 1900 by Arthur Smith Woodward of the British Museum.</p>
<p>It was <a href="http://www.miguasha.ca/mig-en/euphanerops.php">originally thought to belong</a> to a group of extinct jawless fishes called anaspids, but this was disputed in recent years. Anaspids were abundant in older Late Silurian and early Devonian times rocks, about 427 million to 400 million years ago.</p>
<p>Our new paper includes a new phylogenetic analysis that also resolves the evolutionary position of <em>Euphanerops</em> as being a true anaspid, showing that the group is monophyletic, or forming a natural clade (or branch in an evolutionary tree). <em>Euphanerops</em> is thus seen to be a late-surviving relict of this once flourishing group. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/226897/original/file-20180710-70039-st9h63.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/226897/original/file-20180710-70039-st9h63.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/226897/original/file-20180710-70039-st9h63.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=528&fit=crop&dpr=1 600w, https://images.theconversation.com/files/226897/original/file-20180710-70039-st9h63.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=528&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/226897/original/file-20180710-70039-st9h63.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=528&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/226897/original/file-20180710-70039-st9h63.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=664&fit=crop&dpr=1 754w, https://images.theconversation.com/files/226897/original/file-20180710-70039-st9h63.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=664&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/226897/original/file-20180710-70039-st9h63.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=664&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Fossil of <em>Euphanerops</em> showing pelvic bone structures and paired sex organs (labelled as ‘intromittent organs’). Scale on top right figure is 1mm.</span>
<span class="attribution"><span class="source">Marion Chevrinais, Universite du Quebec a Rimouski</span></span>
</figcaption>
</figure>
<h2>Getting some backbone</h2>
<p>Most significantly, this fossil jawless fish shows that the backbone has specialised regions that differ from each other, thus the axial skeleton can be said to be regionalised, or specialised into different kinds of vertebral and rib-like bones along its length.</p>
<p>This is the first time such an advanced feature has been identified in any fish without jaws. Very few of these ancient jawless fishes have the internal skeleton well enough preserved to study it properly. </p>
<p>The specimens of <em>Euphanerops</em> are exceptional because they were preserved in fine-grained sediments laid down in an ancient estuary. Each tiny element of its skeleton is clearly preserved. </p>
<p>The high diversity and excellent preservation of fishes and plant fossils found at Miguasha are the reason why this site was designated as a <a href="https://www.pc.gc.ca/en/culture/spm-whs/sites-canada/sec02m">UNESCO World Heritage site in 1999.</a></p>
<p>Work on the living jawless lamprey, <a href="http://animaldiversity.org/accounts/Petromyzon_marinus/"><em>Petromyzon</em></a>, was then initiated by our team to see if there was any corresponding regionalisation in its skeleton. To our surprise we found that certain variations along the backbone indicated a similar style of regionalisation was also present. </p>
<p>This is significant as the specialised type of backbone land animals have is not usually seen in fishes. Some fossilised ray-finned fishes, such as <a href="http://rspb.royalsocietypublishing.org/content/279/1741/3264.short"><em>Tarrasius</em></a>, show the regionalised spine had evolved by Carboniferous times, but this is an exception, not the regular condition. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/227709/original/file-20180715-27036-112h3a4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/227709/original/file-20180715-27036-112h3a4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/227709/original/file-20180715-27036-112h3a4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=410&fit=crop&dpr=1 600w, https://images.theconversation.com/files/227709/original/file-20180715-27036-112h3a4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=410&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/227709/original/file-20180715-27036-112h3a4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=410&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/227709/original/file-20180715-27036-112h3a4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=515&fit=crop&dpr=1 754w, https://images.theconversation.com/files/227709/original/file-20180715-27036-112h3a4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=515&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/227709/original/file-20180715-27036-112h3a4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=515&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The evolutionary sequence of intromittent sex organs. The new discovery made in <em>Euphanerops</em> pushes back the origin of advanced sexual reproduction using copulation to early jawless fishes.</span>
<span class="attribution"><span class="source">Brian Choo, Flinders University</span></span>
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</figure>
<h2>Old fossils, new finds</h2>
<p>The new discovery shows that old fossils of <em>Euphanerops</em>, known for a long time in museum collections, and that had been studied multiple times in the past, could still yield exciting new information when new technological approaches are applied.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/its-less-than-2cm-long-but-this-400-million-year-old-fossil-fish-changes-our-view-of-vertebrate-evolution-96419">It's less than 2cm long, but this 400 million year old fossil fish changes our view of vertebrate evolution</a>
</strong>
</em>
</p>
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<p>The detailed study of the cartilage structure in <em>Euphanerops</em> was critical to identifying skeletal elements (cartilage derived) in the pelvic region, and finding the paired male reproductive organs. The fossils also pointed us to find new information about the axial skeleton in living lampreys.</p>
<p>It seem likely that the next big steps to understanding the early evolution of the first jawed vertebrates will be found by studying more well-preserved early jawless fishes. These kinds of fossils hold the key to when and how more advanced structures found in jawed vertebrates first developed.</p><img src="https://counter.theconversation.com/content/99675/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>John Long receives funding from The Australian Research Council </span></em></p><p class="fine-print"><em><span>Marion Chevrinais does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Sexual organs similar to what we see in sharks and rays today appeared many millions of years ago in much more primitive ancient fishes than was previously thought.John Long, Strategic Professor in Palaeontology, Flinders UniversityMarion Chevrinais, PhD, Evolutionary Biology, Université de NantesLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/907642018-02-14T13:13:45Z2018-02-14T13:13:45ZKamikaze sperm and four-headed penises – the hidden ways animals win the mating game<figure><img src="https://images.theconversation.com/files/206154/original/file-20180213-44651-1j0cpnw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The echidna has a four-headed penis.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/download/success?src=5Mt7Ua1T_g5mVPXvneA1VA-1-1">Shutterstock</a></span></figcaption></figure><p>We all know that individuals fight over potential love interests. Just think of Daniel Cleaver (Hugh Grant) and Mark Darcy (Colin Firth) scuffling – rather impotently – <a href="https://www.youtube.com/watch?v=iapVomK4eFA">over Bridget Jones in a fountain</a>. But you might be surprised to hear that the fierce rivalry continues behind the scenes – in the form of <a href="https://www.youtube.com/watch?v=WnxuCiwVc-4">sperm competition</a>. This is when the sperm of two or more males compete inside the reproductive tract of a female, to fertilise the eggs, something that is widespread in the animal kingdom. </p>
<p>It is generally assumed that the sperm in a female’s reproductive tract around the time of fertilisation will belong to one male. But <a href="http://onlinelibrary.wiley.com/doi/10.1046/j.1365-294X.2002.01613.x/full">DNA fingerprinting</a> has revealed that even “monogamous” bird species that form exclusive pair bonds are not as exclusive as was once thought.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/206155/original/file-20180213-44627-a8hy6b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/206155/original/file-20180213-44627-a8hy6b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=484&fit=crop&dpr=1 600w, https://images.theconversation.com/files/206155/original/file-20180213-44627-a8hy6b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=484&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/206155/original/file-20180213-44627-a8hy6b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=484&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/206155/original/file-20180213-44627-a8hy6b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=608&fit=crop&dpr=1 754w, https://images.theconversation.com/files/206155/original/file-20180213-44627-a8hy6b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=608&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/206155/original/file-20180213-44627-a8hy6b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=608&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">‘Are you sure they’re all mine?’</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/download/success?src=fx_yzW7nlC1MYKZ-_nhGLQ-1-12">Shutterstock</a></span>
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<p>In fact, extra-pair young (those fathered by another male) are found in around 90% of bird species, and extra-pair copulations (matings with a different male) result typically in 11% of all young. In fact, the percentage of extra-pair young can be as high as 76% in species such as the <a href="https://changingtheclimateblog.wordpress.com/2017/04/07/the-promiscuous-life-of-the-superb-fairy-wren/">superb fairy wren</a>.</p>
<p>Fertilising an egg is often likened to winning a lottery – the more tickets you possess, the higher your chances of winning. Consequently, the more sperm a male manages to get to the egg, the greater his chances of fathering offspring. This has led to huge variation in copulatory behaviour and sperm morphology.</p>
<p>Here are five elaborate methods that have evolved to increase the chance that an individual male’s sperm is the winner:</p>
<h2>1. When big is best</h2>
<p>The obvious way to increase the chance of fertilising an egg is to increase the number of sperm that are produced. Males have been found to make the most sperm in species where individuals
are most promiscuous. For example, the <a href="https://www.nature.com/articles/293055a0">testes</a> of gorillas – a monogamous species – are 30g, whereas testes of chimpanzees – <a href="https://theconversation.com/why-did-humans-evolve-big-penises-but-small-testicles-71652">a promiscuous species with multiple mates</a> – are a whopping 120g. To put this in context, human testes are around 50g, and chimps are around two thirds our body size, making chimp testes, relatively speaking, almost four times the size of human ones.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/206156/original/file-20180213-44647-1d35qfc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/206156/original/file-20180213-44647-1d35qfc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/206156/original/file-20180213-44647-1d35qfc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/206156/original/file-20180213-44647-1d35qfc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/206156/original/file-20180213-44647-1d35qfc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/206156/original/file-20180213-44647-1d35qfc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/206156/original/file-20180213-44647-1d35qfc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Chimps have big testes. Relative to body size, they are four times bigger than humans’.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/download/success?src=fx_yzW7nlC1MYKZ-_nhGLQ-1-12">Shutterstock</a></span>
</figcaption>
</figure>
<h2>2. Sperm ‘trains’</h2>
<p>In general, larger sperm (specifically, those that are longer) are more successful because they have a greater swimming velocity. So, sperm length is longer in more promiscuous species. One species that has truly taken advantage of this is the <a href="http://www.nature.com/news/2002/020711/full/news020708-10.html">wood mouse</a>, where the sperm possess hooks to attach to each other. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/206157/original/file-20180213-44636-skmaks.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/206157/original/file-20180213-44636-skmaks.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/206157/original/file-20180213-44636-skmaks.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/206157/original/file-20180213-44636-skmaks.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/206157/original/file-20180213-44636-skmaks.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/206157/original/file-20180213-44636-skmaks.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/206157/original/file-20180213-44636-skmaks.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The wood mouse: a canny mater.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/download/confirm/306247235?src=A6OuqlgE5HWoqaj3XmnT1w-1-1&size=medium_jpg">Shutterstock</a></span>
</figcaption>
</figure>
<p>This means they can form aggregations, or mobile “trains”, of hundreds or thousands of sperm cells, greatly increasing sperm motility.</p>
<h2>3. Kamikaze sperm</h2>
<p>Around 20% of sperm are abnormal – possessing two heads, no heads or two tails, for example. These <a href="https://www.psychologytoday.com/blog/how-we-do-it/201310/kamikaze-sperms-or-flawed-products">“kamikaze” sperm </a> are incapable of fertilising eggs but it is thought that they might be able to prevent sperm from rival males reaching the egg, either by killing them with enzymes or simply by blocking them. Although there is little evidence of kamikaze sperm in non-humans, some <a href="https://www.sciencedirect.com/science/article/pii/S0968432897000644?via%3Dihub">snails</a> possess abnormal sperm that contain enzymes capable of degrading sperm.</p>
<h2>4. Preventative behaviour</h2>
<p>Many males cement up the genital opening of the female with a copulatory plug, producing an obstacle to prevent other males from further copulations. For example, male <a href="http://www.nature.com/news/spider-mating-plugs-become-better-with-age-1.15407">European dwarf spiders</a> produce a plug which starts as a liquid secreted by a specialised gland and then hardens to become an obstacle. What’s more, the longer the copulation, the larger the plug left behind. Smaller, fresher plugs are relatively easy for other males to remove. But males are unlikely to try to remove larger plugs, benefiting those that have invested more time in the female.</p>
<h2>5. Brushes and whips</h2>
<p>If females mate with multiple males, each suitor generally will father more offspring than the previous one. Therefore, males compete by trying to ensure their sperm is the one to fertilise the egg. </p>
<p>This has led to the evolution of some bizarre penises. The <a href="http://news.softpedia.com/news/Why-Do-Echidnas-Have-Four-Headed-Penises-69334.shtml">echidna</a> (a spiny, egg-laying mammal) for example, has a four-headed penis – although only two heads ejaculate at once. </p>
<p>In some species, penises are specifically shaped to pack sperm tightly into the corners of the female reproductive tract, whereas others are armed with spines, brushes, barbs or hooks to scrape out the sperm of previous males, or stimulate the females to release sperm. The most <a href="http://www.sciencephoto.com/media/368301/view">elaborate</a> are the <a href="http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.567.2582&rep=rep1&type=pdf">penises of odonata</a>, insects such as dragonflies. Some even possess whip-like flagella to remove rival sperm. </p>
<p>These removal methods are quite successful as even the <a href="http://news.bbc.co.uk/1/hi/health/3128753.stm">human penis</a> is able to remove 90% of sperm from a reproductive tract.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/206158/original/file-20180213-44639-h93isn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/206158/original/file-20180213-44639-h93isn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/206158/original/file-20180213-44639-h93isn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/206158/original/file-20180213-44639-h93isn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/206158/original/file-20180213-44639-h93isn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=425&fit=crop&dpr=1 754w, https://images.theconversation.com/files/206158/original/file-20180213-44639-h93isn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=425&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/206158/original/file-20180213-44639-h93isn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=425&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">‘Are you looking at my claspers?’</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/download/confirm/306247235?src=A6OuqlgE5HWoqaj3XmnT1w-1-1&size=medium_jpg">Shutterstock</a></span>
</figcaption>
</figure>
<p>Many reptiles, rays and sharks actually possess two “penises”. In <a href="http://www.arkive.org/epaulette-shark/hemiscyllium-ocellatum/image-G116530.html">sharks</a> these are known as <a href="https://www.youtube.com/watch?v=JHUm6cgLbYY">claspers</a>, and either one can be used to inseminate the female. These claspers not only possess small hooks to anchor them in place, but they are also linked to siphon sacs filled with seawater that spray the sperm into the female reproductive tract under pressure. It has even been theorised that one of the claspers could act as a “<a href="http://www.science.fau.edu/sharklab/courses/elasmobiology/readings/whitney%20et%20al.pdf">jet wash</a>”, cleaning out the sperm of previous males, although there is little evidence for this as shark matings are rarely observed.</p>
<p>Whatever the reason, it is clear that animals have evolved some extraordinary ways of ensuring that they win the competition for fertilisation.</p><img src="https://counter.theconversation.com/content/90764/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Louise Gentle works for Nottingham Trent University</span></em></p>The competition to father young is often most intense behind the scenes.Louise Gentle, Senior Lecturer in Behavioural Ecology, Nottingham Trent UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/841792017-10-31T16:07:36Z2017-10-31T16:07:36ZSynthetic sex in yeast promises safer medicines for people<figure><img src="https://images.theconversation.com/files/192654/original/file-20171031-18720-13bi7tz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">What can mating yeast tell us about new drugs?</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/conchur/13316830914">Conor Lawless</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>Our old friend <em>Saccharomyces cerevisiae</em> – the yeast that’s helped people bake bread and brew beer <a href="https://doi.org/10.1073/pnas.0407921102">for millennia</a> – has just had its sex life upgraded.</p>
<p>Bioengineers at the University of Washington have <a href="https://doi.org/10.1073/pnas.1705867114">reprogrammed the mating habits</a> of this single-celled organism, letting the fungus get it on like never before. The result? A sexual revolution that could lead scientists to safer future medicines.</p>
<h2>Yeast as lab guinea pig</h2>
<p>We already rely on yeast for a lot more than just fermented food. Much of our modern understanding of genetics and cell biology has come from careful study and manipulation of the fungus.</p>
<p>Scientists and drug designers love <a href="http://doi.org/10.1038/nrc1372">working with yeast</a> because of its rapid cell cycle (a new generation is born every 90 minutes) and the relative ease with which its genes can be tweaked. Even human genes and genes encoding protein-based drugs can be spliced in, allowing researchers to study them in the lab in detail. Anti-cancer drugs <a href="http://dx.doi.org/10.1038/nri1837">have been optimized</a> this way. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/186279/original/file-20170917-8076-cg1xmj.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/186279/original/file-20170917-8076-cg1xmj.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/186279/original/file-20170917-8076-cg1xmj.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=408&fit=crop&dpr=1 600w, https://images.theconversation.com/files/186279/original/file-20170917-8076-cg1xmj.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=408&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/186279/original/file-20170917-8076-cg1xmj.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=408&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/186279/original/file-20170917-8076-cg1xmj.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=512&fit=crop&dpr=1 754w, https://images.theconversation.com/files/186279/original/file-20170917-8076-cg1xmj.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=512&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/186279/original/file-20170917-8076-cg1xmj.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=512&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Our species’ relationship with yeast predates our use of gold, horses and writing.</span>
<span class="attribution"><span class="source">Ian Haydon</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>One of the most popular techniques for this type of biomolecular research is known as <a href="https://doi.org/10.1038/nbt0697-553">yeast surface display</a>. Using this method, a gene can be added to yeast and the protein that results will appear on the easily accessible outer surface of the cell. With a new protein displayed on the surface, researchers can easily determine what other biomolecules the protein interacts with.</p>
<p>This method, pioneered in the laboratory of <a href="http://kdw-lab.mit.edu/">Dane Wittrup</a>, exploits aspects of the fungus’ sexual machinery.</p>
<p>Yes, even single-cell microbes can have sex. But as is often the case outside the animal kingdom, the way DNA gets swapped can seem unusual to human observers.</p>
<h2>Fungal fornication</h2>
<p>The terms “male” and “female” don’t really apply to budding yeast. Instead of forming sperm or eggs, the sex cells of yeast all look the same – like tiny, single-cell blobs. What makes two yeast blobs able to sexually reproduce are their so-called mating types.</p>
<p>The proteins that decorate the outside of a yeast sex cell, or gamete, determine that cell’s mating type. Put on copies of one protein and you’re one mating type; swap them out for a different protein and you’re the other. Agglutination (the unsexy term for yeast sex) only happens when the surface proteins of yeast gametes from opposite mating types interact.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/186262/original/file-20170916-8121-vevpb8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/186262/original/file-20170916-8121-vevpb8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/186262/original/file-20170916-8121-vevpb8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=387&fit=crop&dpr=1 600w, https://images.theconversation.com/files/186262/original/file-20170916-8121-vevpb8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=387&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/186262/original/file-20170916-8121-vevpb8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=387&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/186262/original/file-20170916-8121-vevpb8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=487&fit=crop&dpr=1 754w, https://images.theconversation.com/files/186262/original/file-20170916-8121-vevpb8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=487&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/186262/original/file-20170916-8121-vevpb8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=487&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Single-celled yeast as seen under a scanning electron microscope.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Saccharomyces_cerevisiae_SEM.jpg">Mogana Das Murtey and Patchamuthu Ramasamy</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Inspired by this molecular precision, a team of synthetic biologists led by University of Washington graduate student David Younger realized they could convert the natural yeast mating system into a new tool that would let them precisely measure molecular interactions at a much larger scale. </p>
<p>Though tiny and difficult to measure, molecular interactions are a big deal in drug design. Virtually every drug works via specific interactions with its target, and drugs that bind where they shouldn’t can be lethal.</p>
<p>Some experts blame off-target interactions for last year’s failed phase III clinical trial of Alnylam Pharmaceuticals’ revusiran, an RNA drug designed to treat a rare heart disease. <a href="https://doi.org/10.1038/nbt1216-1213">Nineteen people died</a> before the trial was called off, and the company’s stock took a <a href="https://www.businessinsider.com.au/alnylam-stock-down-after-drug-trial-discontinued-2016-10">US$3 billion hit</a>.</p>
<p>Figuring out whether a new drug binds what it’s supposed to is relatively easy; figuring out whether it binds anything else in our cells is tough. Established laboratory techniques like yeast surface display have helped scientists screen new drugs for potentially dangerous off-target interactions before they make it to clinical trials, but that technique lets you look for off-target interactions only one at a time. Younger’s team envisioned a way to test hundreds of drugs against thousands of potential targets, all by redesigning yeast sex.</p>
<h2>Redesigning yeast sex with multiple mating types</h2>
<p>To start, Younger needed a way to precisely measure mating efficiency in lab-grown yeast. Perfect efficiency would mean every cell that could fuse would do so. The more efficient the mating, the better matched the two mating types.</p>
<p>The team linked genetically encoded fluorescent markers – one blue, one red – to each of the natural yeast mating types. That made it simple to measure mating efficiency for a whole yeast population: They could just count the cells that stayed blue or red (unmated) versus those that turned purple (mated). It turns out for typical yeast grown in the lab, mating efficiency is around 60 percent.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/192653/original/file-20171031-18730-17dpxn9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/192653/original/file-20171031-18730-17dpxn9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/192653/original/file-20171031-18730-17dpxn9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/192653/original/file-20171031-18730-17dpxn9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/192653/original/file-20171031-18730-17dpxn9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/192653/original/file-20171031-18730-17dpxn9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/192653/original/file-20171031-18730-17dpxn9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/192653/original/file-20171031-18730-17dpxn9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Example of fluorescent-tagged yeast, in this case red and green. Together the markers look yellow.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Yeast_membrane_proteins.jpg">Masur</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>The team then deleted the natural agglutination proteins and replaced them with a pair of foreign proteins known to interact weakly. The mating efficiency dropped tenfold to 5.7 percent. They swapped in another pair and saw it rise to 19 percent. When they tried a third pair of proteins known to interact with much higher affinity, mating efficiency rose to 51.6 percent – close to what was seen in natural agglutination.</p>
<p>Just by tracking mating efficiency, the team could tell how strongly any two protein molecules interact. When they checked a pair of proteins that shouldn’t interact at all, mating efficiency was a meager 0.2 percent.</p>
<p>Now, instead of just the two natural mating types, <a href="https://doi.org/10.1073/pnas.1705867114">scientists can quickly engineer thousands of “sexes”</a> by coaxing individual yeast to decorate the outside of their cells with new, human-specified proteins. If a pair of new mating types are sexually compatible – meaning the proteins decorating their cell surfaces interact – their offspring will rise in number. By tallying up each genetically distinct offspring in a tube not much bigger than a thimble, thousands of potential molecular interactions can be quantified.</p>
<h2>Improving drug safety</h2>
<p>To show that their new tool could aid in drug development, the team generated 1,400 distinct variants of an emerging anti-cancer drug known as <a href="https://doi.org/10.7554/eLife.20352">XCDP07</a>. The drug is supposed to disrupt the unrestrained growth of cancer cells by binding specific cellular targets, but as with every drug, significant off-target interactions could render it useless. By mixing yeast displaying different versions of the drug with other yeast displaying human proteins, the team was able to identify versions of XCDP07 which only bound to the intended target.</p>
<p>Younger is working to get his new tool into the hands of more scientists. He’s already gifted his engineered yeast strains to eager researchers at Stanford, Yale, UCSD and beyond. Concerns over the cost and safety of emerging drugs have motivated him to start a company – funded by scientific grants, not investors – to turn his results into the next generation of medicines. Younger says the goal is to provide “comprehensive preclinical drug screening, rather than the current practice of screening a very small subset of possible off-target interactions.”</p>
<p>The next blockbuster drugs may owe a debt to yeast and their mating practices. Who says you can’t teach an old fungus new tricks?</p><img src="https://counter.theconversation.com/content/84179/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ian Haydon is a researcher at the Institute for Protein Design at the University of Washington.</span></em></p>By exploiting the way yeast cells mate, researchers have figured out a quicker, easier way to identify on- and off-target drug interactions.Ian Haydon, Doctoral Student in Biochemistry, University of WashingtonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/852812017-10-18T11:15:13Z2017-10-18T11:15:13ZThe menopause: dreaded, derided and seldom discussed<figure><img src="https://images.theconversation.com/files/190611/original/file-20171017-30436-7ngg97.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Sign of caution – or celebration?</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/caution-sign-sky-background-menopause-ahead-635264690?src=PKOavMeFTtvkhox3XHVarA-1-4">Shutterstock</a></span></figcaption></figure><p>Women experience the menopause between the ages of around 45 and 55, but their experiences of this significant stage of life are diverse. Each woman’s menopause is unique. </p>
<p>Common themes run through women’s stories, however. From <a href="http://www.bris.ac.uk/social-community-medicine/people/isabel-o-de-salis/pub/124277454">our research</a> talking with women in midlife, we found that they often talk about menopause as a normal, inevitable and natural process, which of course, it is. Seeing menopause in this way allows women to minimise symptoms and behave stoically. “It’s no big deal,” one woman told us. “You just get on with it.” </p>
<p>But this positive approach can also be a rebuttal of a <a href="http://www.charis.wlc.edu/publications/symposium_spring02/fecteau.pdf">common perception in society</a> of the menopause as a negative event – a view which leads to denigrating women who react differently to the menopause. </p>
<p>Because for some, menopause is considered a loss, a struggle. Bodily sensations such as mood swings or hot flushes can be overwhelming and embarrassing. The negative images many often associate with menopause can be distressing – a barren land signalling the end of fertility, youthfulness and sexuality. Women may mourn the passing of a phase of life when their biological usefulness is over – menopause is seen as “a marker of getting old”. </p>
<p>One told us: </p>
<blockquote>
<p>I feel like my life’s over. It marks the end of being young and attractive and fertile.</p>
</blockquote>
<p>Some of those with no close female network and who worked in predominantly male environments, felt unable to share their experience. Women often felt foolish asking for help – that they would be wasting their GP’s time or admitting incompetence to a boss. </p>
<p>The stigma of menopause, with its <a href="https://www.ncbi.nlm.nih.gov/pubmed/20693828">associations of hysteria and incompetence</a>, the shame of ageing, and the taboo about revealing menopausal symptoms, compounds the distress and struggle. Stigma can become internalised so that beliefs about other people’s reactions to menopausal symptoms such as hot flushes <a href="https://www.ncbi.nlm.nih.gov/pubmed/21339056">can be unduly negative</a>. </p>
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<p>Less commonly, menopause is treated as a positive marker of “moving on” to the next stage – a time of “new beginnings” and renewed libido. For these women, menopause is a “rite of passage” involving both social and psychic transformation whereby a sense of self emerges anew from loss, grief and shame. Another different experience occurs when bodily sensations like hot flushes are actually welcomed. Some described the physical side of menopause as feeling “nice and toasty”, and “helping me move on to another stage in life”. </p>
<p>So although menopause is frequently perceived negatively, as something to be ignored or dreaded, we heard positive perceptions. This is important. One woman commented: </p>
<blockquote>
<p>It’s kind of a gateway isn’t it, in to the next stage of your life? It sets a point in the sand about how long you’ve been on the earth.</p>
</blockquote>
<p>Women with more negative attitudes towards menopause report more symptoms <a href="https://www.ncbi.nlm.nih.gov/pubmed/19954900">during the transition</a>, and we know from <a href="https://www.ncbi.nlm.nih.gov/pubmed/11400220">cross-cultural research</a> that experiences of menopause are socio-culturally shaped and not universal. </p>
<p>The most <a href="http://www.annualreviews.org/doi/abs/10.1146/annurev-anthro-081309-145641">common reported symptom among Japanese women</a>, for example, is not hot flushes or night sweats, but chilliness. Menopause can be experienced particularly negatively where fertility status is highly valued <a href="https://www.ncbi.nlm.nih.gov/pubmed/14559382">as in rural Iran</a>. But where post-reproductive status is seen as positively transforming, as <a href="https://www.ncbi.nlm.nih.gov/pubmed/11833972">among Taureg women</a> in the Sahara desert, or <a href="http://www.sciencedirect.com/science/journal/03785122/4/3?sdc=1">Rajput women</a> in India, it is welcomed. </p>
<p>Contrasting lifestyles, physiology, diet, genetics, reproductive history and physical environment all contribute to the variety of experiences worldwide. But we need also to acknowledge how important are the expectations and meanings of menopause, and the attitudes towards fertility loss and ageing. </p>
<h2>Reclaiming the menopause</h2>
<p>Many women want and need more support going through menopause. They want reliable information. There is now more discussion about <a href="https://theconversation.com/three-reasons-employers-need-to-recognise-the-menopause-at-work-82543">what can be done in the workplace</a> to support women through menopause, especially if they have difficult symptoms. </p>
<p>A <a href="https://www2.le.ac.uk/offices/press/press-releases/2017/august/workplace-menopause-study-finds-2018women-feel-they-need-to-cope-alone2019">recent report</a> from the University of Leicester acknowledged that gendered ageism is a significant concern for women at work. The <a href="https://www.nice.org.uk/guidance/ng23">official guidelines on menopause</a> may enable the health sector to address women’s health matters seriously. </p>
<p>Can we reclaim the menopause as a powerful and positive process in women’s lives? It is difficult to experience menopause as transformative when it is primarily considered as degeneration and decline, and the <a href="https://books.google.co.uk/books?id=dfBHoWeU9bcC&pg=PT21&lpg=PT21&dq=the+left+hand+of+the+goddess:+the+silencing&source=bl&ots=0GONJu1QsZ&sig=_ur-ybuCgGvn-Vzh6FDHeZUOC8M&hl=en&sa=X&ved=0ahUKEwjj5pHHsffWAhVJBsAKHfpdCEMQ6AEILTAB#v=onepage&q=the%20left%20hand%20of%20the%20goddess%3A%20the%20silencing&f=false">multiple meanings of menopause are hidden</a>. As part of our research at the University of Bristol, we are <a href="https://www.eventbrite.co.uk/e/our-menopauses-the-great-menopause-event-tickets-38138665776">inviting women</a> to share their experiences with us. </p>
<p>Menopause is a political issue that is rarely discussed. Imagine, for example, a society that accepts women having hot flushes in the boardroom or in which post-reproductive status is valued. Perhaps even a society which allows for women to welcome the menopause. </p>
<p>Fundamentally, we need to value all women’s diverse menopausal experiences without assuming they are hysterical, incompetent, or “past it”. We need to end the silence that surrounds a stage of life that half of humanity go through.</p><img src="https://counter.theconversation.com/content/85281/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dr Isabel de Salis receives funding for this project from the UK Medical Research Council, Economic and Social Research Council, Biotechnology and Biological Sciences Research Council and the Arts Research Council.</span></em></p>What if the menopause was something we thought positively about or were able to discuss openly without fear of derision?Isabel de Salis, Research Fellow in Medical Anthropology, University of BristolLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/618902016-07-14T12:01:08Z2016-07-14T12:01:08ZDo women’s periods really synch when they spend time together?<figure><img src="https://images.theconversation.com/files/130417/original/image-20160713-12362-puzh67.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">That's when I had PMT remember?</span> <span class="attribution"><a class="source" href="http://www.shutterstock.com/pic-384195502/stock-photo-diverse-people-electronic-devices-concept.html?src=w9O9a5dAE93Bj1GvDlD5LA-1-6">Shutterstock</a></span></figcaption></figure><p>It is a popular belief that women who live together synchronise their menstrual cycles, and that it’s mediated by their pheromones – the airborne molecules that enable members of the same species to communicate non-verbally. </p>
<p>The idea originated in a study <a href="http://www.nature.com/nature/journal/v229/n5282/abs/229244a0.html">published in Nature in 1971</a>, which recorded data on the onset of menstruation for 135 American college students living in a dormitory. The dorm had four corridors each with around 25 girls living in single and double rooms. Based on the analysis of around eight cycles per woman, the study reported an increase in synchronisation (a decrease in the difference between onset dates) for room mates and among closest friends, but not among random pairings in the dormitory. The author hypothesised that this was driven by the amount of time that women spent together, as this would allow for pheromone communication.</p>
<p>Since then, so-called “socially mediated synchrony” has been intensely studied in various groups of women, such as <a href="http://www.sciencedirect.com/science/article/pii/0031938495001426">room mates</a>, <a href="http://www.sciencedirect.com/science/article/pii/S0306453098000924">co-workers</a>, <a href="http://www.sciencedirect.com/science/article/pii/030645309390017F">lesbian couples</a> and women from <a href="http://sites.lsa.umich.edu/bis/wp-content/uploads/sites/171/2014/10/Strassmann-1997-Current-Anthropology-38-123-129.pdf">high fertility populations</a> – and in a number of animal species, including <a href="http://www.sciencedirect.com/science/article/pii/0018506X78900715">rats</a>, <a href="http://beheco.oxfordjournals.org/content/23/3/573.full.pdf">baboons</a> and <a href="http://www.ncbi.nlm.nih.gov/pubmed/15940707">chimpanzees</a>. The theory goes that synchronisation leads to females becoming sexually receptive at the same time.</p>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/130420/original/image-20160713-12389-11e755x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/130420/original/image-20160713-12389-11e755x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=392&fit=crop&dpr=1 600w, https://images.theconversation.com/files/130420/original/image-20160713-12389-11e755x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=392&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/130420/original/image-20160713-12389-11e755x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=392&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/130420/original/image-20160713-12389-11e755x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=492&fit=crop&dpr=1 754w, https://images.theconversation.com/files/130420/original/image-20160713-12389-11e755x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=492&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/130420/original/image-20160713-12389-11e755x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=492&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">How evolutionary theorists might explain it.</span>
<span class="attribution"><a class="source" href="http://www.shutterstock.com/pic-119942749/stock-photo-woman-standing-in-front-of-men-making-a-heart-shape-sign-on-gray-background.html?src=SdKfNuRziFxntVfbi9ZkOA-1-25">Shutterstock</a></span>
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<p>There have been many evolutionary arguments for why females would synchronise the timing of sexual receptivity. These theories – <a href="http://www.sciencedirect.com/science/article/pii/0169534790902183">reviewed here</a> – assume that synchrony would serve to maximise the reproductive success of females (and also sometimes males). The most popular one is that it enables females to minimise the risk of being monopolised by a single dominant male, and thus make it easier to engage in polyandry. </p>
<p>It is true that in multi-male, multi-female groups in which both males and females mate with multiple partners, if all females are sexually receptive at the same time then it is difficult for a male to control the sexual access to a particular female at all times. In this vein, <a href="http://www.ncbi.nlm.nih.gov/pubmed/19018288">a meta-analysis of 19 primate species</a> found that the degree to which a dominant male would father all offspring was inversely related to the degree to which the females synchronised their cycles. In other words, a dominant male had less control over reproduction if all females were receptive at the same time.</p>
<h2>Casting serious doubts</h2>
<p>However, there is now accumulating evidence that casts serious doubt on the existence of the phenomenon. First, the original 1971 study was criticised <a href="https://labs.psych.ucsb.edu/roney/james/other%20pdf%20readings/reserve%20readings/wilson.pdf">on methodological grounds</a>. Second, a number of studies with both human groups and non-human species <a href="https://smartsite.ucdavis.edu/access/content/group/05df5a0c-16e3-4d15-8626-76c7c012163b/Readings/Yang-Schank2006.pdf">failed to replicate the initial findings</a>, with at least as many studies reporting <a href="http://www.sciencedirect.com/science/article/pii/003193849390273I">positive results</a> as studies reporting <a href="https://sites.oxy.edu/clint/physio/article/MenstrualsynchronyFactorartifact.pdf">negative ones</a>. </p>
<p><a href="http://beheco.oxfordjournals.org/content/early/2012/01/20/beheco.arr230.full.pdf">Mathematical analyses</a> have also revealed that some degree of synchrony is to be expected given the shifts in female reproductive condition over time, and that no adaptive process needs to be invoked to explain what is observed. In other words, synchrony or the overlap of cycles between females is best explained by chance. </p>
<p>A number of critics have pointed out constraints on the very idea of the evolution of synchrony – for instance, studies have documented the significant variability in cycle length among and within women, which can make the evolution of synchronisation a “<a href="http://www.sciencedirect.com/science/article/pii/S0306453000000299">mathematical impossibility</a>”. One <a href="http://sites.lsa.umich.edu/bis/wp-content/uploads/sites/171/2014/10/Strassmann-1997-Current-Anthropology-38-123-129.pdf">in-depth analysis</a> that looked at the distribution of menstrual cycles of women living in a pre-industrial society revealed that much of the variability in the onset and length of menstrual cycles instead depended on the idiosyncracies of women’s lives, such as the timing of failed pregnancy, energy balance and psychological stress.</p>
<p>The hypothesis that synchronisation of menstrual or oestrus (being “on heat” in the case of many non-human primates) cycles is an adaptive process can be appealing as it suggests that evolution favoured females who cooperated in the face of male sexual domination. However, as disappointing as it may be, it seems that there is now overwhelming evidence to suggest that menstrual synchrony in humans is no more than a methodological artefact from one study that has since turned into an urban myth.</p><img src="https://counter.theconversation.com/content/61890/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alexandra Alvergne consults for the Clue app by BioWink.</span></em></p>Women often say their periods begin at the same time as their friends’.Alexandra Alvergne, Associate Professor in Biocultural Anthropology, University of OxfordLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/569132016-04-14T20:01:08Z2016-04-14T20:01:08ZThese sex-starved creatures scavenge new genes from other pondlife<figure><img src="https://images.theconversation.com/files/118507/original/image-20160413-18093-1jdics8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The tiny rotifer has thrived for millions of years without sex.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/28594931@N03/15987678953/in/photostream/">Flickr/Specious Reasons</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span></figcaption></figure><p>Sexual reproduction is thought to be essential for mixing up genes and holding your own in the race for survival. A major embarrassment to this theory are microscopic animals called <a href="http://www.microscopy-uk.org.uk/mag/artnov99/rotih.html">rotifers</a>, one class of which has reproduced without sex for millions of years.</p>
<p>Theory says they should be extinct, but clearly they aren’t. So how have they done it? </p>
<p>DNA sequencing now shows that they make up for their lack of sex by incorporating genes from other rotifers of the same or different species, or even from fungi and bacteria.</p>
<p>You’ll find rotifers in ponds or puddles. Under the microscope they’re incredibly cute little (smaller than 1mm) multicelled invertebrates, motoring around like tiny paddle-steamers.</p>
<p>This is an illusion from the circle of whirling cilia around their heads that drives them forward and wafts tasty algae and decaying scum through their tough little jaws.</p>
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<p>When their puddle dries up, rotifers shrink into dehydrated specks that look like crinkly barrels. They can stay that way for years and blow around to new pools. They rehydrate in just a few hours, and can efficiently patch up their DNA, broken in many places during desiccation.</p>
<p>This insignificant little creature poses a big problem for understanding one of biology’s oldest mysteries: why do animals have sex?</p>
<h2>Why sex?</h2>
<p>Sex is spectacularly inefficient. Animals waste a lot of time and energy courting and keeping a mate. Worse, half the population have no offspring. </p>
<p>The “why sex?” question was first asked by Charles Darwin 150 years ago. Ever since, evolutionary geneticists have wondered <a href="http://www.pbs.org/wgbh/evolution/sex/">why sex</a> seems always to win the evolutionary race over asexual reproduction. </p>
<p>Many theories have been put forward and debated over decades. The most accepted is that sex is useful for shuffling new gene combinations by recombining parent genomes. </p>
<p>This enables animals to adapt to changed environments and colonise new ecological niches. Importantly, all these new combinations of genes help animals to keep pathogens at bay by giving them a “moving target”. </p>
<h2>Sex in animals</h2>
<p>In mammals, sexual reproduction is obligatory – we can’t do <a href="http://theconversation.com/is-virgin-birth-possible-yes-unless-you-are-a-mammal-52379">virgin birth</a>. A few reptile and frog species reproduce by <a href="http://www.britannica.com/science/parthenogenesis">parthenogenesis</a>, in which the female makes diploid eggs from combinations of her own genes. But offspring developed from unfertilised eggs are less fit than their sexual sisters. So asexual species don’t last long.</p>
<p>Many invertebrates can reproduce both sexually and asexually, and some (such as aphids) indulge in sex only sporadically, in response to environmental cues. But there are none that never have sex – except for bdelloid rotifers. </p>
<p>In the hundreds of years since the Dutch scientist <a href="http://www.britannica.com/biography/Antonie-van-Leeuwenhoek">Antonie van Leeuwenhoek</a> first saw bdelloid rotifers under his newly invented microscope, no-one has ever spotted a male.</p>
<p>Females lay eggs but there is no meiosis (the reduction division that produces sperm or eggs), so her eggs all contain genomes identical to hers.</p>
<p>Genomes of bdelloid rotifers are weird. There are two copies of each gene as you expect of a diploid, but they are very different. This suggests that they originated as a hybrid between two species whose <a href="http://science.sciencemag.org/content/288/5469/1211">genes and genomes diverged 60 million years ago</a>. </p>
<p>Their homologous chromosomes have been differently rearranged so they can’t pair at meiosis. The conclusion is that bdelloid rotifers have eschewed sex for 60 million years. </p>
<h2>New DNA for rotifers</h2>
<p>Sequencing a bdelloid rotifer genome produced a big surprise, as about 8% of the genes <a href="http://www.nature.com/nature/journal/v500/n7463/full/nature12326.html">looked foreign</a>. Some genes were typical of fungi or bacteria, and endowed the rotifer with handy new properties such as breaking down toxins or <a href="http://dx.doi.org/10.1371/journal.pgen.1003035">using new foodstuffs</a>. This “<a href="http://www.britannica.com/science/horizontal-gene-transfer">horizontal transfer</a>” between rotifers and other organisms is <a href="http://bmcbiol.biomedcentral.com/articles/10.1186/s12915-015-0202-9">ancient and ongoing</a>.</p>
<p>Foreign DNA is spread all over the rotifer genome. So how did it get there? It seems that dehydration makes holes in cell membranes that <a href="http://www.ncbi.nlm.nih.gov/pubmed/20421328">can suck up DNA</a>. The rotifers’ efficient mechanism for repairing double stranded DNA breaks in dehydrated animals is perfect for incorporating foreign DNA into the genome.</p>
<p>More extraordinary still is what happens to DNA from other rotifer individuals or species. It isn’t incorporated just anywhere in the genome, but lines up with the <a href="http://dx.doi.org/10.1016/j.cub.2016.01.031">appropriate DNA sequence and recombines</a>. This means that a new version of a particular gene may replace the old. Just like sex.</p>
<h2>Bacteria can do it</h2>
<p>This ability to take up and use DNA from the environment isn’t unique to rotifers. </p>
<p>Bacteria reproduce by fission to make clones of genetically identical cells. But they can <a href="http://www.ncbi.nlm.nih.gov/pubmed/7968924">take up DNA from another bacterial strain</a>, swap it for the resident gene, and express a variant protein in the wild. This “DNA transformation” provided the first evidence that genes are made from DNA.</p>
<p>DNA transformation is only one of several tricks that bacteria use to scavenge variant and novel genes. Bacteria can also receive little packages of foreign bacterial genes by way of a virus.</p>
<p>Some bacteria can exchange long DNA molecules – even the whole genome – through tube-like structures. This conjugation looks most like what we would consider sex. </p>
<p>In throwing up a great variety of genotypes, sexual reproduction still seems to be the best bet in the long run – for vertebrates and invertebrates.</p>
<p>In its absence, organisms such as the tiny rotifers have had to find other ways to boost their gene pool.</p>
<p>Far from falsifying the theory that genetic variation is essential for evolutionary success, rotifers brilliantly confirm it.</p><img src="https://counter.theconversation.com/content/56913/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jenny Graves has received funding from the Australian research Council and the National Health and Medical research Council. </span></em></p>Rotifers are tiny creatures found in ponds or puddles and can reproduce without sex. The theory says they should not have survived so how have they done it?Jenny Graves, Distinguished Professor of Genetics, La Trobe UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/561642016-03-12T09:22:53Z2016-03-12T09:22:53ZExplainer: how can twins have different fathers?<figure><img src="https://images.theconversation.com/files/114852/original/image-20160311-11288-eybiic.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>The recent report from northern Hòa Bình province in Vietnam of twins born to two different fathers has been making headlines around the world. The father of the twins took the infants for DNA tests where it was revealed he was the biological father to just one of them - the other twin was <a href="http://www.bbc.co.uk/news/world-asia-35761281">fathered by another man</a>. How could a set of twins have different fathers?</p>
<p>This is an extremely rare occurrence in humans and is known as heteropaternal superfecundation. We don’t know exactly how often this occurs and cases only arise when suspicious family members request DNA testing. But one study estimated that it might occur in as many as <a href="http://www.ncbi.nlm.nih.gov/pubmed/7871943?dopt=Abstract&holding=npg">one in 400</a> (0.25%) twin births in the US. Another study reported that among non-identical twins whose parents had been involved in paternity suits <a href="http://www.ncbi.nlm.nih.gov/pubmed/1488855">the frequency was 2.4%</a>. </p>
<h2>Conception challenge</h2>
<p>For heteropaternal superfecundation to occur, the mother’s body must release two eggs during ovulation that are then fertilised by two sperm cells from two different men. The odds of one sperm fertilising an egg during one instance of intercourse are actually rather small. So the chances of two sperm cells from different males being successful are even smaller, relying on a culmination of timing and superb reproductive biology. A rare event indeed.</p>
<p>From the millions of sperm deposited during intercourse, only a few hundred or less reach the eggs. The sperm’s journey through the female reproductive tract is an arduous process and they they must circumnavigate the cervix, uterus and fallopian tubes to reach the eggs. At the same time they have to survive the harsh environment of the female reproductive tract and avoid the woman’s immune response, which sees white blood cells target sperm cells as invaders.</p>
<p>Fertilisation is also a matter of timing. The ovulated egg is available for a short window (12-24 hours) and so the sperm must be present in the fallopian tube during that time for fertilisation to occur. In the case reported from Vietnam, the woman would have had to have intercourse with two different men over a short period - within at least a day before or after ovulation - for both eggs to be fertilised. </p>
<p>Almost <a href="bit.ly/1RbM2by">one in 100 births</a> in the UK and US are to non-identical or “dizygotic” twins, although the global frequency varies widely with factors such as genetics, nutrition statue and BMI all playing a role. Rates also increase considerably with maternal age, probably because of changes in reproductive hormone levels. Women aged 35-39 are <a href="https://www.ncbi.nlm.nih.gov/pubmed/10336022">four times as likely</a> to have dizygotic twins than those aged 15-35.</p>
<h2>Copulation competition</h2>
<p>Although heteropaternal superfecundation is rare in humans, it is <a href="http://www.ncbi.nlm.nih.gov/pubmed/20394608">not uncommon in nature</a> and has been reported in many animal species including dogs, cats, cows, mink and rodents. What’s more, in many species that have multi-pair copulations, the males have developed a variety of strategies to ensure their sperm reach the egg.</p>
<p>This can include evolving strange penile structures to scoop out rival sperm (<a href="http://www.nytimes.com/2011/10/18/science/18dragonfly.html?_r=0">as in dragonflies</a> and damselflies), or damage the female, thus preventing subsequent mating (referred to as <a href="https://theconversation.com/invertebrates-inject-a-bit-of-romance-during-sex-by-stabbing-each-other-24154">traumatic insemination</a>. This phenomenon is referred to as “<a href="http://www.sciencedirect.com/science/article/pii/S0960982204000284">sperm competition</a>”. It has even been suggested that the shape of the human penis evolved to function as a displacement device to remove any semen <a href="http://www.sciencedirect.com/science/article/pii/S1090513803000163">deposited by a previous male</a>.</p><img src="https://counter.theconversation.com/content/56164/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michael Carroll does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>A set of twins in Vietnam have been found to have different fathers.Michael Carroll, Senior Lecturer in Reproductive Science, Manchester Metropolitan UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/488362015-10-13T04:22:23Z2015-10-13T04:22:23ZHow understanding evolution might help solve problems that bedevil society<figure><img src="https://images.theconversation.com/files/98088/original/image-20151012-17858-qkwnx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Understanding how evolution affects behaviour can help address societal problems. </span> <span class="attribution"><span class="source">Reuters/Mike Hutchings </span></span></figcaption></figure><p>Evolution has drawn more criticism from non-scientists than any other scientific theory, probably because it speaks to the origins of humanity. </p>
<p>Much is therefore at stake. And despite the mountains of evidence in support of evolution, there is still much opposition to it. Opposition stems largely from evolution’s unintended consequence of removing humanity from the pedestal of special <a href="http://creation.com/">creation</a>. </p>
<p>Such opposition is fuelled by a misunderstanding of how evolution works and the claims it makes. For example, it is often alleged that evolution claims that humans have <a href="http://www.inquisitr.com/2425614/homo-naledi-find-starts-bizarre-racism-row-in-south-africa/">evolved</a> from baboons. But all that evolution claims is that humans and other non-human primates share a common ancestor – a very different claim. </p>
<p>Evolution also does not claim that extant non-human primates, including monkeys, baboons, chimpanzees and gorillas, if given enough time, will evolve into humans. </p>
<p>The truth is we cannot predict with any degree of certainty what form the descendants of any living organism will evolve into 10,000 or one million years from now. There are just too many variables to consider and the process of evolution includes a component of randomness. </p>
<p>But a better understanding of how humans evolved and how that affects human behaviour can unlock alternative and workable solutions to societal problems.</p>
<h2>How evolution works</h2>
<p>Life propagates through the duplication of DNA and transference of that DNA from parent to offspring. Offspring are not exact copies of each other or of their parents as a result of <a href="http://learn.genetics.utah.edu/content/variation/mutation/">mutation</a> and <a href="http://learn.genetics.utah.edu/content/variation/reproduction/">sexual reproduction</a>. This results in differences among individuals in the traits they possess, including size, shape, colour and behaviour. </p>
<p>Such differences are a fundamental characteristic of all natural populations and the generation of such differences is entirely random. We cannot predict which differences are likely to arise in any population. </p>
<p>Life plays out in time and space – in some kind of habitat or environment. Differences among traits of individuals will translate into differences in how long individuals live or how many offspring they produce. </p>
<p>Differences in survival and reproduction result in a change in the relative proportions of individuals in subsequent generations. This is evolution.</p>
<p>Although the generation of individual differences is random, which individuals survive and reproduce is not. Individuals with traits more suited to their particular environment will survive and reproduce. Those with traits less suited to their environment will be eliminated from the population. This is <a href="http://darwin200.christs.cam.ac.uk/pages/index.php?page_id=d3">natural selection</a> and it is not random. The environment selects which traits are transmitted to the next generation. </p>
<h2>Competition for resources</h2>
<p>Resources are finite and natural selection occurs because individuals have to compete for the resources they need to survive and reproduce. These include sexual partners, food and living space. In species with separate sexes, the costs of reproduction are different for males and females. </p>
<p>For example, reproduction in female <a href="http://www.arkive.org/mammals/">mammals</a> involves energetically expensive eggs, which provide the nutrition needed by the developing <a href="http://www.merriam-webster.com/dictionary/zygote">zygote</a>, a lengthy pregnancy, and energy-rich milk for the baby. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/98081/original/image-20151012-17811-p3yl22.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/98081/original/image-20151012-17811-p3yl22.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/98081/original/image-20151012-17811-p3yl22.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/98081/original/image-20151012-17811-p3yl22.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/98081/original/image-20151012-17811-p3yl22.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/98081/original/image-20151012-17811-p3yl22.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/98081/original/image-20151012-17811-p3yl22.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">South Africa’s Deputy President Cyril Ramaphosa kisses the skull of a newly discovered Homo naledi.</span>
<span class="attribution"><span class="source">Reuters/Siphiwe Sibeko</span></span>
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<p>In contrast, male reproduction involves sperm that has relatively little investment of energy. Over the span of their lives males produce millions of sperm. Their reproductive potential is never tied up by pregnancy or milk production. This gives males the potential to impregnate hundreds of females. </p>
<p>Reproduction for males is limited only by access to females. In contrast, female reproduction is limited by resources. But males can gain access to females by providing them with the resources they need to reproduce. This generates much competition among males for resources. Such <a href="http://link.springer.com/article/10.1007/BF00166344">competition increases</a> when resources are scarce.</p>
<p>In <a href="http://global.britannica.com/topic/animal-social-behaviour">social animals</a>, males may form alliances that improve their access to resources and therefore to females. The differential costs of reproduction and the male alliances that such costs promote has the potential to explain many phenomena observed in human and non-human animal societies.</p>
<h2>Evolution shaping behaviour</h2>
<p>For example, it might explain not only why xenophobic and gang violence occurs in human societies but also why these behaviours are largely restricted to impoverished communities and perpetrated almost exclusively by <a href="http://children.pan.org.za/node/8263">young males</a> in the prime of their reproductive potential. </p>
<p>Male alliances are evolved strategies that allow males greater access to females. Groups of males can compete more effectively than individual males for resources and females. A potential solution to some societal problems may be to reduce competition among males for females. This can be done by reducing poverty through a more equitable distribution of resources so that competition is reduced. </p>
<p>Another way is to improve access to resources by females through equality of education, opportunity, and employment equity. This may reduce competition among males because controlling resources would no longer be important for access to females. In short, patriarchy must fall. </p>
<p>Competent delivery of key socioeconomic services by governments is crucial for tackling many of the ills associated with competition for scarce resources. This includes the recent xenophobic attacks in South Africa, which have been blamed on the fierce competition for scarce jobs between locals and foreign nationals.</p>
<p>We accept that there are sets of human behaviours which are similar despite differences in race, culture and gender. We call this human nature. Fossils provide us with evidence that our physical form has evolved. The existence of human nature is evidence that our behaviours have evolved. Evolution therefore provides us with a tool to scientifically investigate the causes of human behaviour.</p>
<hr>
<p><em>Parts of this article were taken from the author’s forthcoming book, <a href="http://jutaacademic.co.za/media/filestore/2015/09/2015-6_UCT_FOR_PRINT-3_WEBSITE.pdf">Evolution’s Chimera: Amazing Adaptations in Bats</a>, to be published by University of Cape Town Press.</em></p><img src="https://counter.theconversation.com/content/48836/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>David Jacobs receives funding from the South African Research Chair Initiative of the Department of Science and Technology administered by the National Research Foundations, from Incentive Funding for Rated Researchers from the National Research Foundation and from the University Research Committee of the University of Cape Town. </span></em></p>Evolution also does not claim humans evolved from primates. Neither does it say non-human primates, including monkeys, baboons, chimpanzees and gorillas, will evolve into humans with time.David Jacobs, Professor of Animal Evolution & Systematics, University of Cape TownLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/461882015-08-17T19:52:04Z2015-08-17T19:52:04ZFossils suggest an aquatic plant that bloomed underwater was among first flowering plants<figure><img src="https://images.theconversation.com/files/92097/original/image-20150817-5127-hqpl6d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Compression of the long-leaf form of _Montsechia_.</span> <span class="attribution"><span class="source">David Dilcher</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Photosynthesis – the ability to convert energy from the sun into fuel – first appeared on Earth in single-celled organisms, which eventually evolved into algae, then mosses, then ferns. Flowering plants, now such a familiar part of our landscape, didn’t evolve until the Jurassic period, after dinosaurs and mammals had already hit the scene. At this time, insects were diversifying, and the evolving plants used the emerging bugs to carry their own genetic material from plant to plant. Flowering plants, also known as angiosperms, are a product of this early version of sex and its exchange of genetic material – so important in evolution.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/92168/original/image-20150817-5103-15xv0kx.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/92168/original/image-20150817-5103-15xv0kx.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/92168/original/image-20150817-5103-15xv0kx.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=449&fit=crop&dpr=1 600w, https://images.theconversation.com/files/92168/original/image-20150817-5103-15xv0kx.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=449&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/92168/original/image-20150817-5103-15xv0kx.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=449&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/92168/original/image-20150817-5103-15xv0kx.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=564&fit=crop&dpr=1 754w, https://images.theconversation.com/files/92168/original/image-20150817-5103-15xv0kx.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=564&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/92168/original/image-20150817-5103-15xv0kx.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=564&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Evolution of plant diversity.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Plant_Diversity_(2).svg">Laurenprue216</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>A recent discovery and analysis of fossilized plants has opened up the discussion of the nature and relationships of these early plants. First found in the lithographic limestone being mined in the Pyrenees Mountains over 100 years ago, these fossils, with their strange sprawling stems, were little understood. Some thought they were mosses, some considered them to be conifers, but few recognized the fossils as flowering plants.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/92187/original/image-20150817-5110-oph9xs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/92187/original/image-20150817-5110-oph9xs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/92187/original/image-20150817-5110-oph9xs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=443&fit=crop&dpr=1 600w, https://images.theconversation.com/files/92187/original/image-20150817-5110-oph9xs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=443&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/92187/original/image-20150817-5110-oph9xs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=443&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/92187/original/image-20150817-5110-oph9xs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=557&fit=crop&dpr=1 754w, https://images.theconversation.com/files/92187/original/image-20150817-5110-oph9xs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=557&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/92187/original/image-20150817-5110-oph9xs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=557&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Fossils collected in mountainous areas around El Montsec and Las Hoyas in Spain.</span>
<span class="attribution"><span class="source">PNAS 10.1073/pnas.1509241112</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Now my colleagues and I, on a team of paleobotantists led by Bernard Gomez of Lyon, France, <a href="http://www.pnas.org/cgi/doi/10.1073/pnas.1509241112">have presented evidence</a> that this fossil, <em>Montsechia</em>, which lived as long ago as 130 million years, is the earliest known example of a fully submerged aquatic flowering plant. After careful analysis of hundreds of well-preserved newly collected fossils from northeastern Spain, we believe <em>Montsechia</em> flowered underwater and was pollinated underwater, living in a similar fashion to the plant <em>Ceratophyllum</em> that’s found around the world today.</p>
<p>Flowers are all about sex and getting new genetic material into the breeding line. <em>Montsechia</em> is an example of a very early line of evolution that solved this challenge in a new and novel way – relying on water to disperse its pollen, not the wind or animal pollinators. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/92098/original/image-20150817-5098-1dcevs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/92098/original/image-20150817-5098-1dcevs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/92098/original/image-20150817-5098-1dcevs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/92098/original/image-20150817-5098-1dcevs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/92098/original/image-20150817-5098-1dcevs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/92098/original/image-20150817-5098-1dcevs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/92098/original/image-20150817-5098-1dcevs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/92098/original/image-20150817-5098-1dcevs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Typical fragment of the short-leaf form of <em>Montsechia</em>.</span>
<span class="attribution"><span class="source">David Dilcher</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>The plant we see in these new old fossils</h2>
<p>Based on the many fossil examples we examined, <em>Montsechia</em> floated in freshwater lakes and was submerged in the water. It had a spreading growth, branching freely. This flowering plant didn’t display any of the showy blossoms we tend to associate with flowers. But because it contains seeds enclosed in a fruit, the basic characteristic of angiosperms, it is classified as a flowering plant.</p>
<p>We’ve found two forms of this fossil: one form has leaves that are small and closely pressed to the stem. On this form, we frequently saw mature fruits.</p>
<p>The other form has leaves that extend out from the stems and only rarely are mature seeds found attached. We saw the two leaf types associated together at the same fossil localities.</p>
<p>Today, many flowers are made up of petals and then male stamens (with filaments and anthers that produce pollen) and female carpels (which mature into fruits and contain the seeds, like peas in a pod). We didn’t identify any male flowers or remains of where they were borne on the stems in <em>Montsechia</em>. It appears they had separate flowers to contain pollen organs and carpels.</p>
<h2>Fishing around for the first flower</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/92151/original/image-20150817-5098-1ajya5s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/92151/original/image-20150817-5098-1ajya5s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/92151/original/image-20150817-5098-1ajya5s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/92151/original/image-20150817-5098-1ajya5s.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/92151/original/image-20150817-5098-1ajya5s.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/92151/original/image-20150817-5098-1ajya5s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/92151/original/image-20150817-5098-1ajya5s.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/92151/original/image-20150817-5098-1ajya5s.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Magnolia flower.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/kevineddy/2491579148">Kevin Eddy</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<p>When asking the question of what the first flower in the world was like, 30 years ago some botanists said that magnolias were the typical form. Later, others suggested that perhaps water lily flowers may be a better choice.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/92145/original/image-20150817-5095-ug5afb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/92145/original/image-20150817-5095-ug5afb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/92145/original/image-20150817-5095-ug5afb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=668&fit=crop&dpr=1 600w, https://images.theconversation.com/files/92145/original/image-20150817-5095-ug5afb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=668&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/92145/original/image-20150817-5095-ug5afb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=668&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/92145/original/image-20150817-5095-ug5afb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=839&fit=crop&dpr=1 754w, https://images.theconversation.com/files/92145/original/image-20150817-5095-ug5afb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=839&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/92145/original/image-20150817-5095-ug5afb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=839&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"><em>Amborella trichopoda</em>, previous contender for earliest angiosperm.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/pennstatelive/5609235215">Penn State</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span>
</figcaption>
</figure>
<p>Then the tools of molecular systematics allowed botanists to use DNA and RNA from the nuclei and chloroplasts of plant cells to puzzle out relationships based on molecular characteristics. That’s when a genus called <em>Amborella</em>, found living today only in New Caledonia, gained favor as a possible first flowering plant.</p>
<p>Another contender, <em>Ceratophyllum</em>, was also once thought to be basal to all flowering plants before being displaced by <em>Amborella</em>, and its position in the angiosperms has been uncertain since. <em>Montsechia</em>, at 130 million years old – among the oldest megafossil remains known of any flowering plant – is in the lineage of <em>Ceratophyllum</em>. This makes this lineage of flowering plants one of the oldest known and suggests that underwater <em>Ceratophyllum</em> is back in the running to be the original flowering plant. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/92141/original/image-20150817-5127-wjz6sy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/92141/original/image-20150817-5127-wjz6sy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/92141/original/image-20150817-5127-wjz6sy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/92141/original/image-20150817-5127-wjz6sy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/92141/original/image-20150817-5127-wjz6sy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/92141/original/image-20150817-5127-wjz6sy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/92141/original/image-20150817-5127-wjz6sy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/92141/original/image-20150817-5127-wjz6sy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"><em>Ceratophyllum submersum</em> are the modern version of the fossilized plant.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Ceratophyllum_submersum.jpg">Totodilefan</a></span>
</figcaption>
</figure>
<h2><em>Ceratophyllum</em>, modern descendent of first flower</h2>
<p><em>Ceratophyllum</em> consists of six species found around the world today in the single genus in its own order, Ceratophyllales. These plants, known as foxtails, live in freshwater lakes on all continents of the world today, save Antarctica.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/92143/original/image-20150817-5110-1tjmadi.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/92143/original/image-20150817-5110-1tjmadi.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/92143/original/image-20150817-5110-1tjmadi.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=690&fit=crop&dpr=1 600w, https://images.theconversation.com/files/92143/original/image-20150817-5110-1tjmadi.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=690&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/92143/original/image-20150817-5110-1tjmadi.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=690&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/92143/original/image-20150817-5110-1tjmadi.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=868&fit=crop&dpr=1 754w, https://images.theconversation.com/files/92143/original/image-20150817-5110-1tjmadi.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=868&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/92143/original/image-20150817-5110-1tjmadi.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=868&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Life cycle of a flowering plant.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Angiosperm_life_cycle_diagram-en.svg">LadyofHats Mariana Ruiz</a></span>
</figcaption>
</figure>
<p>These modern-day descendents of <em>Montsechia</em> have separate male and female flowers with no sepals or petals, just simple reproductive organs, like stamens and carpels. When they reproduce, the stamens release the anthers that contain the pollen to float up to the water’s surface. Then the pollen is released and begins to slowly sink through the water column. As it descends, being moved by water currents, a branched pollen tube grows out. When the pollen tube makes it into the vicinity of a female, a branch will find a small hole enter and pollinate. This is how the plant fertilizes and creates a seed. </p>
<p>Because of the water dispersal of the pollen there is genetic mixing or outcrossing, just as if an insect had carried the pollen.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/92152/original/image-20150817-5110-1tp9p9x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/92152/original/image-20150817-5110-1tp9p9x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/92152/original/image-20150817-5110-1tp9p9x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=801&fit=crop&dpr=1 600w, https://images.theconversation.com/files/92152/original/image-20150817-5110-1tp9p9x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=801&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/92152/original/image-20150817-5110-1tp9p9x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=801&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/92152/original/image-20150817-5110-1tp9p9x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1006&fit=crop&dpr=1 754w, https://images.theconversation.com/files/92152/original/image-20150817-5110-1tp9p9x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1006&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/92152/original/image-20150817-5110-1tp9p9x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1006&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"><em>Ceratophyllum demersum</em>.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Ceratophyllum_demersum.jpg">Totodilefan</a></span>
</figcaption>
</figure>
<p>The fossil fruits of <em>Montsechia</em> also have a similar small pore in the fruit wall, and the seed is positioned similarly as those of <em>Ceratophyllum</em> today. This suggests that these very ancient flowers flowered underwater, were very simple in nature (no beautiful petals yet) and were pollinated underwater. This very early and inventive way for flowering plants to manage their reproduction so early in their evolution is impressive.</p>
<p><em>Montsechia</em> places the <em>Ceratophyllum</em> lineage as one of the oldest of all the flowering plants and suggests that we need to reevaluate the nature of the evolution of the original angiosperm again.</p><img src="https://counter.theconversation.com/content/46188/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>David Dilcher does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The fossilized plant Montsechia relied on water to disseminate its genetic material and may rewrite the book on when and how the first flowering plants evolved.David Dilcher, Emeritus Professor of Geological Sciences and Paleobotany, Indiana UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/437512015-06-25T12:11:26Z2015-06-25T12:11:26ZAre plastics making men infertile?<figure><img src="https://images.theconversation.com/files/86368/original/image-20150625-12990-1pwdna7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Gird your loins</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p><a href="http://www.thetimes.co.uk/tto/health/news/article4473064.ece">Recent research</a> has reignited concerns that exposure to chemicals from plastics might be to blame for low sperm counts in young men. I share the concerns about the high prevalence of low sperm counts <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2605.2005.00635.x/abstract">(one in six young men)</a> – and <a href="http://embor.embopress.org/content/13/5/398.long">my research</a> is directed at trying to identify what causes it. But whether plastics are to blame isn’t a simple matter.</p>
<p>Plastics are part of the fabric of our everyday lives and perform many essential functions. Without their thousands of uses, many of which are not obvious to us, our modern world could not function as it is. Plastics bring everyday benefits whether through children’s toys, the insulation around electrical wiring, their utility in food containers/wraps or their widespread use in medical products from blood bags, gloves and syringes, to the coating of some tablets and capsules. </p>
<p>But are there hidden dangers of plastics to human health, especially to male fertility? This is a surprisingly difficult question to answer, not least because everyone is exposed to chemicals that derive from plastics. This means we don’t really have an unexposed group (“control”) against which to compare. </p>
<p>Most people probably don’t understand how we are exposed to chemicals from plastics. After all, we don’t eat the plastic wraps around food or chew electric wiring. Plasticisers are chemicals used to make plastic (which is naturally hard and brittle) bendy and resistant to breaking, so prolonging its useful life. As a guide, the more flexible the plastic, the more plasticiser it will contain. The most widely used plasticisers are called <a href="http://toxtown.nlm.nih.gov/text_version/chemicals.php?id=24">phthalates</a>, which come in different forms with different uses.</p>
<p>Plasticisers leach out of the plastic over time and will contaminate any food, drink or other material with which they have contact. This was the primary reason why phthalate plasticisers were removed from use in water bottles many years ago and replaced by polyethylene terephthalate, which has different properties. Nevertheless our main route of exposure to the most commonly used phthalate <a href="http://www.ncbi.nlm.nih.gov/pubmed/23333758">is still via</a> our food/diets, even if we do not fully understand how this contamination occurs.</p>
<p>What ignited concerns about phthalate effects on fertility were <a href="http://humrep.oxfordjournals.org/content/18/7/1383.long">studies in laboratory rats</a>. These showed that exposure in pregnancy to certain phthalates caused reproductive disorders in the male offspring, including reduced sperm counts and fertility. As pregnant women (and thus the male fetuses in their wombs) are exposed to the same phthalates, could this be the cause of reproductive disorders in men?</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/86379/original/image-20150625-13016-1u6t4cw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/86379/original/image-20150625-13016-1u6t4cw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=375&fit=crop&dpr=1 600w, https://images.theconversation.com/files/86379/original/image-20150625-13016-1u6t4cw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=375&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/86379/original/image-20150625-13016-1u6t4cw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=375&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/86379/original/image-20150625-13016-1u6t4cw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=471&fit=crop&dpr=1 754w, https://images.theconversation.com/files/86379/original/image-20150625-13016-1u6t4cw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=471&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/86379/original/image-20150625-13016-1u6t4cw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=471&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">One is all you need.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Conflicting evidence</h2>
<p>The seemingly direct way to answer this question is to measure phthalate exposure of pregnant women and see if high exposure is associated with reproductive disorders in their sons. Some, but not all, <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1280349/">such studies</a> have shown an association between male reproductive disorders and phthalate exposure of the mother. The problem is that this approach can never prove that the exposure caused the disorder. More importantly, <a href="http://press.endocrine.org/doi/10.1210/jc.2011-2411?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%3dpubmed">other evidence</a> points in the completely <a href="http://www.greenbiz.com/news/2010/05/24/science-behind-phthalates-ban">opposite direction</a>.</p>
<p>Phthalates cause male reproductive disorders in rats by reducing production of the male sex hormone – testosterone – by the testes of the male fetus. To induce this effect, pregnant rats have to be exposed to phthalate levels 50,000 times higher than pregnant women are exposed to. Exposure of human fetal testes (obtained with ethical permission from legal pregnancy terminations) to the same high phthalate levels as in rats has no effect on their testosterone production. Nor do reproductive disorders occur in male monkeys after their mothers are exposed to equally high phthalate levels during pregnancy. </p>
<p>In research it is common to be faced with problems such as this, where different types of data simply do not agree. But what should we do in the face of this uncertainty? One reaction is to assume the worst, accept the association studies and ignore the studies that don’t agree with them. In which case, the next step would be to ban or restrict phthalate use, resulting in numerous changes to our modern society that will affect everyone. Some argue that this is the <a href="https://chemicalwatch.com/20622/us-panel-wants-five-phthalates-banned-in-childrens-products">safest route</a> to take.</p>
<p>While I am 100% in favour of safety, I know that in science one cannot simply choose to ignore evidence that does not fit a particular point of view, at least not when that evidence is known to be robust. It is not an evidence-led approach and is, by any standards, nonsensical.</p>
<p>This does not mean that I am fully convinced that plastics are 100% safe, but neither does the available evidence convince me that they are a major factor in male reproductive disorders. I am convinced that something in our environment or lifestyles is causing low sperm counts. I just wish I knew what.</p>
<p><em>Note: this piece was changed on August 6 2015 to be clear that there is no suggestion plastic drinking bottles still contain phthalate plasticisers.</em></p><img src="https://counter.theconversation.com/content/43751/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Richard Sharpe receives funding from the UK Medical research Council.</span></em></p>Recent research into the health effects of the plastic-making chemicals phthalates has reignited concerns about low sperm counts. But the evidence is far from conclusive.Richard Sharpe, Group leader, male reproductive health, The University of EdinburghLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/275782014-06-08T21:09:01Z2014-06-08T21:09:01ZThe first vertebrate sexual organs evolved as an extra pair of legs<figure><img src="https://images.theconversation.com/files/50436/original/m4gq5qx3-1402022055.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A bull male _Eastmanosteus_ placoderm. Placoderms were the first creatures to evolve paired reproductive organs with a bony skeleton called claspers.</span> <span class="attribution"><span class="source">Brian Choo &amp; John Long, Flinders University.</span></span></figcaption></figure><p>We humans use the euphemism for sex that “we like to get a leg over” but the first jawed vertebrates – the <a href="http://www.ucmp.berkeley.edu/vertebrates/basalfish/placodermi.html">placoderms</a> – they liked to get a leg in.</p>
<p>They were the first back-boned creatures to evolve male genital organs, or claspers, supported by a bony internal skeleton.</p>
<p>What’s even more peculiar is that, unlike the cartilaginous claspers of modern <a href="http://marinelife.about.com/od/glossary/g/Clasper.htm">sharks</a>, which are a modified part of the pelvic fin, our <a href="http://onlinelibrary.wiley.com/doi/10.1111/brv.12118/abstract">new research</a> has shown that in placoderms they were basically a separate set of paired appendages.</p>
<h2>The reign of the placoderms</h2>
<p>Placoderms had thick bony plates enveloping the head and trunk regions. They ruled the seas, rivers and lakes of the world for 70 million years, becoming extinct around 360 million years ago.</p>
<p>Placoderms were the world’s first megapredators, with ancient behemoths such as <a href="http://dinosaurs.wikia.com/wiki/Dunkleosteus"><em>Dunkleosteus</em></a> reaching the same size as today’s <a href="http://animals.nationalgeographic.com.au/animals/fish/great-white-shark/">Great White Shark</a>.</p>
<p>They were also the first vertebrate animals on Earth to have a complex form of sexual reproduction – copulation – where males fertilised the females internally rather than just spawning in water.</p>
<p>To achieve this, the males bore bony paired structures – the claspers – which were previously thought to be similar to the cartilaginous claspers of modern sharks.</p>
<p>For many years placoderms were thought of as “shark-like fishes” and so their anatomy was routinely interpreted using sharks as a model. This approach has shadowed the secret of their true evolutionary significance for almost the past century.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/50437/original/3nkrt48x-1402022332.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/50437/original/3nkrt48x-1402022332.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/50437/original/3nkrt48x-1402022332.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=188&fit=crop&dpr=1 600w, https://images.theconversation.com/files/50437/original/3nkrt48x-1402022332.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=188&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/50437/original/3nkrt48x-1402022332.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=188&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/50437/original/3nkrt48x-1402022332.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=237&fit=crop&dpr=1 754w, https://images.theconversation.com/files/50437/original/3nkrt48x-1402022332.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=237&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/50437/original/3nkrt48x-1402022332.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=237&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The skeleton of placoderm <em>Coccosteus</em>, showing the bony claspers situated well behind the pelvic fins.</span>
<span class="attribution"><span class="source">John Long, Flinders University.</span></span>
</figcaption>
</figure>
<h2>Hints of hidden genitals</h2>
<p>The first hint that placoderm fishes were sexually dimorphic (meaning males look different to females) was seen in the different pelvic fins by English palaeontologist <a href="http://en.wikipedia.org/wiki/D._M._S._Watson">David M.S. Watson</a> in the 1930s. He studied a placoderm fish called <em>Rhamphodopsis</em> that lived around 390 million years ago in Scotland.</p>
<p>In the 1960s Norwegian palaeontologist Tor Ørvig studied a similar kind of placoderm (a ptyctodontid) named <em>Ctenurella</em> and went one step further. He identified the strange structures near the pelvic fins as claspers, implying they were intromittent or insertable organs.</p>
<p>Nonetheless, just identifying these structures doesn’t mean the fishes actually used them to internally fertilise the females. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/50214/original/jv6sk7d8-1401858488.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/50214/original/jv6sk7d8-1401858488.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/50214/original/jv6sk7d8-1401858488.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=223&fit=crop&dpr=1 600w, https://images.theconversation.com/files/50214/original/jv6sk7d8-1401858488.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=223&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/50214/original/jv6sk7d8-1401858488.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=223&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/50214/original/jv6sk7d8-1401858488.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=281&fit=crop&dpr=1 754w, https://images.theconversation.com/files/50214/original/jv6sk7d8-1401858488.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=281&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/50214/original/jv6sk7d8-1401858488.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=281&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A male placoderm, <em>Rhamphodopsis</em>, head towards the left, showing the bony claspers well behind the position of the pelvic girdle and fin.</span>
<span class="attribution"><span class="source">John Long, Flinders University.</span></span>
</figcaption>
</figure>
<p>The first hard evidence that placoderms really did copulate was when our team announced in 2008 that we had found <a href="http://www.nature.com/nature/journal/v453/n7195/full/nature06966.html">complete embryos</a> in perfectly preserved fossil specimens from the Gogo Formation of Western Australia.</p>
<p>These were found in just one group of placoderms called <a href="http://en.wikipedia.org/wiki/Ptyctodontida">ptyctodontids</a>, which showed sexual differences in the pelvic region.</p>
<p>We found further embryos in the largest group of placoderms – the arthrodires – <a href="http://www.nature.com/nature/journal/v457/n7233/full/nature07732.html">in 2009</a> and later that same year identified the first male copulatory organs <a href="http://www.nature.com/nature/journal/v460/n7257/full/nature08176.html">in this group</a>.</p>
<h2>Evidence there all the time</h2>
<p>Our new study shows that many other common species of placoderm also had similar complex reproductive organs. The evidence was sitting in museum collections around the world but not noticed until one of us (Kate Trinajstic) went searching for and found them.</p>
<p>Our research has shown that the mating organs of the ancient placoderms were rather complex. The review of the reproductive structures in placoderms produced many new examples which showed an unusual pattern emerging.</p>
<p>One specimen even showed an unborn embryo with a tiny clasper developed, so we could tell it was a male.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/50241/original/4c2dyg3v-1401862753.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/50241/original/4c2dyg3v-1401862753.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/50241/original/4c2dyg3v-1401862753.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/50241/original/4c2dyg3v-1401862753.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/50241/original/4c2dyg3v-1401862753.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/50241/original/4c2dyg3v-1401862753.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/50241/original/4c2dyg3v-1401862753.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/50241/original/4c2dyg3v-1401862753.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A tiny clasper (white rod, centre bottom) from an unborn (embryonic) baby boy placoderm, <em>Incisoscutum</em>, from the Gogo site, Western Australia.</span>
<span class="attribution"><span class="source">Zerina Johanson, Natural History Museum, London.</span></span>
</figcaption>
</figure>
<p>Unlike the claspers of modern sharks and rays that are a part of the paired pelvic fins, the claspers and female basal plates in placoderms were not at all connected to that fin.</p>
<p>Instead they developed as an extra pair of limbs further down the body.</p>
<p>This discovery implies that the first vertebrates did not conform to the typical <a href="http://www.ucmp.berkeley.edu/vertebrates/tetrapods/tetramm.html">tetrapod</a>-like pattern of having just two pairs of paired limbs (arms, or pectoral fins, and legs, or pelvic fins) that typifies the basic jawed vertebrate body pattern from fishes through to mammals. </p>
<p>The implications of this study mean that the similar looking male claspers in placoderms and sharks are actually not the same structures, but most likely evolved independently.</p>
<p>As the bony placoderm claspers were not rigidly fixed to the pelvic fin, they would have been able to rotate forwards, so the earliest sexual mating position was likely to have been a missionary one.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/50461/original/mvygnz9f-1402030310.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/50461/original/mvygnz9f-1402030310.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/50461/original/mvygnz9f-1402030310.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=348&fit=crop&dpr=1 600w, https://images.theconversation.com/files/50461/original/mvygnz9f-1402030310.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=348&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/50461/original/mvygnz9f-1402030310.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=348&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/50461/original/mvygnz9f-1402030310.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=437&fit=crop&dpr=1 754w, https://images.theconversation.com/files/50461/original/mvygnz9f-1402030310.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=437&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/50461/original/mvygnz9f-1402030310.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=437&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">How placoderms such as <em>Incisoscutum</em> probably mated.</span>
<span class="attribution"><span class="source">John Long, Flinders University.</span></span>
</figcaption>
</figure>
<p>The claspers in placoderms can now be regarded as a <a href="http://evolutionwiki.org/wiki/Serial_homology">serial homologue</a> or gradual development of the other paired appendages - an extra pair of legs, so to speak.</p>
<p>The mechanism for how this happens is clear. Certain homeobox (<a href="http://en.wikipedia.org/wiki/Hox_gene">hox</a>) genes control the repetition of structures such as limbs (as in the <a href="http://en.wikipedia.org/wiki/Sonic_hedgehog">sonic hedgehog gene</a>) and the position of them on the body axis (the hox genes <a href="http://en.wikipedia.org/wiki/T-box">tbx4, tbx5</a>).</p>
<p>In the case of placoderms, the zone of competence to form paired appendages was much enlarged compared to modern vertebrates, and extended beyond the pelvic fins, enabling an extra pair of structures to develop.</p>
<p>In sharks the pelvic fins became elongated and <a href="http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0000754">modified as claspers</a> using a different set of hox genes (hoxd13) .</p>
<p>This new discovery implies that the so-called primitive way of vertebrate reproduction – spawning in water – changed dramatically to copulation almost as soon as vertebrates had the right tools for the job.</p>
<p><a href="http://www.nature.com/nature/journal/v491/n7426/full/nature11555.html">Jaws</a> appeared around the same time as claspers in placoderms, and so might also have been connected to this early reproductive behaviour in some way.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/JHUm6cgLbYY?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Grey Reef Sharks Mating. Dracon Mounier.</span></figcaption>
</figure>
<p>In addition to aiding in the capture of prey, feeding and ventilation, jaws may also have been utilised for holding on to a partner whilst mating, as many sharks do today (video, above).</p>
<p>Clearly we don’t know the full story yet. There is still a lot more to discover about this fascinating group of ancient extinct fishes.</p><img src="https://counter.theconversation.com/content/27578/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>John Long receives funding from the Australian Research Council.</span></em></p><p class="fine-print"><em><span>Kate Trinajstic receives funding from Australian Research Council. </span></em></p>We humans use the euphemism for sex that “we like to get a leg over” but the first jawed vertebrates – the placoderms – they liked to get a leg in. They were the first back-boned creatures to evolve male…John Long, Strategic Professor in Palaeontology, Flinders UniversityKate Trinajstic, Associate Professor, Department of Chemistry, Curtin UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/218722014-01-15T13:19:19Z2014-01-15T13:19:19ZCaught in the act: microbes do have sex<figure><img src="https://images.theconversation.com/files/38946/original/h7cyn9cp-1389608612.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Trypanosomes in the blood.</span> <span class="attribution"><span class="source">Wendy Gibson</span></span></figcaption></figure><p>There is no denying that humans think sex is important, but it also matters for microbes. Sex allows genes from two parents to be mixed, leading to new combinations of genes in the offspring. </p>
<p>In the past, many disease-causing protozoa were thought to reproduce by splitting in half with no genetic exchange, which is the common way that most microbes reproduce. But new results show they also use sex to swap genes between strains. Research into the sex lives of pathogens helps scientists understand how new strains of disease-causing microbes arise.</p>
<p>In the case of disease-causing pathogens, like the yeast <em>Candida</em> or the malaria parasite <em>Plasmodium</em>, sex can lead to several harmful genes being combined in one new daughter cell. For example, it is through sex that genes for drug resistance can spread among different pathogen strains faster than it would through asexual methods. Mixing up the genes may also give rise to new pathogen strains that the human population has less resistance to. </p>
<h2>Tsetse and sex</h2>
<p>Trypanosomes are the single-celled parasites that cause <a href="http://www.who.int/mediacentre/factsheets/fs259/en/">sleeping sickness</a> in Africa and <a href="http://www.who.int/topics/chagas_disease/en/">Chagas disease</a> in Latin America. At the University of Bristol, my research group works on African trypanosomes, which are found in the blood and central nervous system of those afflicted with sleeping sickness and are carried by bloodsucking <a href="http://www.un.org/apps/news/story.asp?NewsID=46905&Cr=FAO&Cr1=">tsetse flies</a>. These trypanosomes also cause the disease <a href="http://www.ncbi.nlm.nih.gov/pubmed/7501369">Nagana</a> in African livestock.</p>
<p>Although we have known for a long time that trypanosomes have sex, we’ve never yet managed to catch them in the act – until now. The stumbling block has been that these microbes only have sex inside the tsetse fly and that has made it difficult to see what’s going on. </p>
<p>We developed a method to use fluorescent markers to tag individual trypanosomes, making them light up like tiny light bulbs. To tell the two parents apart, each is tagged with a different colour, red or green. This has the advantage that hybrid offspring have both colours, and look yellow.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/38888/original/2st3b8g5-1389552031.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/38888/original/2st3b8g5-1389552031.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/38888/original/2st3b8g5-1389552031.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=412&fit=crop&dpr=1 600w, https://images.theconversation.com/files/38888/original/2st3b8g5-1389552031.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=412&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/38888/original/2st3b8g5-1389552031.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=412&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/38888/original/2st3b8g5-1389552031.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=518&fit=crop&dpr=1 754w, https://images.theconversation.com/files/38888/original/2st3b8g5-1389552031.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=518&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/38888/original/2st3b8g5-1389552031.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=518&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Tsetse fly salivary gland packed full of red and green fluorescent trypanosomes.</span>
<span class="attribution"><span class="source">Wendy Gibson</span></span>
</figcaption>
</figure>
<p>We used this approach to see what the trypanosomes were getting up to inside the tsetse fly – and we found, as reported in <a href="http://www.cell.com/current-biology/fulltext/S0960-9822(13)01499-1">Current Biology</a>, a previously unknown type of cell that looked a bit like a sperm cell, swimming about by means of a long flagellum. Just like typical gametes (sperm or egg), these cells contained only half the normal amount of DNA. </p>
<h2>Sex in colour</h2>
<p>Trypanosome gametes look and behave the same, rather than being totally different like sperm and eggs. They were seen intertwining their long flagella and gyrating together. We think this behaviour is the prelude to cell fusion, since we also found yellow hybrid trypanosomes with them.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/38889/original/vrg3dg96-1389552255.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/38889/original/vrg3dg96-1389552255.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/38889/original/vrg3dg96-1389552255.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=253&fit=crop&dpr=1 600w, https://images.theconversation.com/files/38889/original/vrg3dg96-1389552255.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=253&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/38889/original/vrg3dg96-1389552255.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=253&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/38889/original/vrg3dg96-1389552255.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=319&fit=crop&dpr=1 754w, https://images.theconversation.com/files/38889/original/vrg3dg96-1389552255.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=319&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/38889/original/vrg3dg96-1389552255.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=319&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Trypanosome gamete with long flagellum. Series of images of one of these sperm-like cells swimming.</span>
<span class="attribution"><span class="source">Wendy Gibson</span></span>
</figcaption>
</figure>
<p>Our new results not only revealed the previously unseen details of trypanosome mating, but also suggested that sex is not an optional or rare part of this protozoan’s lifecycle and probably occurs quite frequently. This has implications for the ability of these trypanosomes to swap genes around. </p>
<p>For example, we know that just a single gene – the <em>SRA</em> gene – helps trypanosomes in East Africa to infect humans rather than other animals. This means that sex can generate new strains of human infective trypanosomes by transferring the <em>SRA</em> gene to a different genetic background. </p>
<p>Trypanosomes mate inside the tsetse fly, but having sex in the insect carrier of disease isn’t unique to them. For the malaria parasite <a href="http://www.plospathogens.org/article/info%3Adoi%2F10.1371%2Fjournal.ppat.1002404"><em>Plasmodium</em></a>, for example, sex happens every time the parasite gets carried from person to person by a bloodsucking mosquito and is part of the microorganism’s life cycle. </p>
<p>For the trypanosome though, there is a twist. Tsetse flies feed on our blood, which goes straight into their gut. But to reach the human host, any trypanosomes present in the bloodmeal have to reach the insect’s salivary glands, so they can be squirted into the next victim along with the anti-coagulant saliva. For a tiny microbe, this is a long and tortuous journey through the body of the fly, and few survive it. </p>
<p>Those that do are arguably the fittest, and it is these trypanosomes that get the chance to have sex inside the salivary glands. It may be months or years before trypanosomes in the bloodstream of a human suffering from sleeping sickness get picked up by a tsetse fly, so maybe this is nature’s way of ensuring that only the trypanosomes that are still capable of reaching the salivary glands get to have sex.</p><img src="https://counter.theconversation.com/content/21872/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Wendy Gibson received funding from The Wellcome Trust to carry out this research.</span></em></p>There is no denying that humans think sex is important, but it also matters for microbes. Sex allows genes from two parents to be mixed, leading to new combinations of genes in the offspring. In the past…Wendy Gibson, Professor of Protozoology, University of BristolLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/137442013-06-17T04:41:25Z2013-06-17T04:41:25ZExplainer: why do women menstruate?<figure><img src="https://images.theconversation.com/files/25637/original/hn7m7c9x-1371430887.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Only a handful of mammals aside from us – primates, some bat species and the elephant shrew – get their period.</span> <span class="attribution"><span class="source">Image from shutterstock.com</span></span></figcaption></figure><p>For half the population, it comes three to five days each month, 12 months each year, for 40 years of our lives. Menstruation can be debilitating, relieving, disappointing, or simply an inconvenient fact of life.</p>
<p>But why do humans menstruate, when most animals don’t? When you shake the tree of life, you find that only a handful of mammals aside from us – primates, a small number of bat species, and the elephant shrew – have opted for the monthly bleed. </p>
<p>Each month the uterus prepares a thick and luxurious lining in preparation for the arrival of a fertilised egg – an embryo that will develop into a fetus and after nine months, a full-term baby. If no embryo arrives, there will be no pregnancy and menstruation sheds the thickened lining. </p>
<p>Evolution is often viewed in terms of a cost-benefit ledger: if something is costly, it must have some benefit. Women lose over half a standard glass of wine’s worth in iron-rich blood and tissue – about 90 millilitres – each time they menstruate, so the process does seem quite costly. And in the predator-filled environs of our early ancestors, leaving a trail of blood was presumably not advantageous.</p>
<p>So how did menstruation arise? Over recent decades, evolutionary biologists have come up with three key theories to explain human menstruation. </p>
<h2>Cleansing mechanism</h2>
<p>One controversial theory, <a href="http://www.jstor.org/stable/2831191">proposed in the 1990s by self-taught biologist Margie Profet</a>, suggested menstruation was a cleansing mechanism. Being the amorous species that we are, human females require a mechanism to regularly flush out the infection-laden sperm that gathers from our sexual conquests.</p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/25638/original/hn7hgzdw-1371431070.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/25638/original/hn7hgzdw-1371431070.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=688&fit=crop&dpr=1 600w, https://images.theconversation.com/files/25638/original/hn7hgzdw-1371431070.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=688&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/25638/original/hn7hgzdw-1371431070.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=688&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/25638/original/hn7hgzdw-1371431070.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=865&fit=crop&dpr=1 754w, https://images.theconversation.com/files/25638/original/hn7hgzdw-1371431070.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=865&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/25638/original/hn7hgzdw-1371431070.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=865&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Most women go through 450 to 480 menstrual cycles in their lifetime.</span>
<span class="attribution"><span class="source">Image from shutterstock.com</span></span>
</figcaption>
</figure>
<p>This argument was soon found to have more than a few flaws. For a start, women are more susceptible, not less, to infections such as chlamydia and gonorrhoea during menstruation, as the cervical mucus thins out. </p>
<p>The iron-rich blood also serves as an attractive food source for <a href="http://www.betterhealth.vic.gov.au/bhcv2/bhcarticles.nsf/pages/Staphylococcus_aureus_golden_staph">Staphylococcus aureus</a>, of tampon-associated <a href="http://www.betterhealth.vic.gov.au/bhcv2/bhcarticles.nsf/pages/Toxic_shock_syndrome">toxic shock syndrome</a> notoriety. </p>
<p>And there is no correlation between level of promiscuity in us and our close primate relatives and heaviness of bleeding, as the theory predicts.</p>
<h2>Invasive embryos</h2>
<p>A more plausible explanation for menstruation is that it <a href="http://www.ncbi.nlm.nih.gov/pubmed/9618925">evolved to accommodate</a> the peculiar way in which human embryos embed into the lining of the uterus – the endometrium – during pregnancy. </p>
<p>In some mammals with a placenta, a fertilised embryo attaches to the endometrium only superficially. In humans and other menstruating species, implantation is deep and invasive, and requires an especially luxurious lining to develop in preparation for implantation. </p>
<p>While other mammals are able to reabsorb the lining that adorns their fertile womb, the volume of tissue in humans is too great, so if no pregnancy ensues, it is expelled instead. </p>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/25635/original/p6x6thnh-1371430305.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/25635/original/p6x6thnh-1371430305.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=468&fit=crop&dpr=1 600w, https://images.theconversation.com/files/25635/original/p6x6thnh-1371430305.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=468&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/25635/original/p6x6thnh-1371430305.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=468&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/25635/original/p6x6thnh-1371430305.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=588&fit=crop&dpr=1 754w, https://images.theconversation.com/files/25635/original/p6x6thnh-1371430305.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=588&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/25635/original/p6x6thnh-1371430305.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=588&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The lining of the uterus, or endometrium, thickens in preparation for pregnancy.</span>
<span class="attribution"><span class="source">National Cancer Institute" zoomable</span></span>
</figcaption>
</figure>
<p>In the evolutionary cost-benefit analysis, building up the lining only when a pregnancy is on the cards – only when we ovulate once a month – could be less costly than maintaining this expensive lining indefinitely.</p>
<p>Another key difference between menstruators and non-menstruators is in the impetus for uterine thickening. In non-menstruating mammals, the final thickening of the endometrium (a process called decidualisation) only occurs once the lining senses the bleating signals from the embryo saying, “I’m here, now make my bed!”</p>
<p>Somewhere along the human evolutionary path, the dialogue between embryo and uterus shifted, so that the signals causing the endometrium to thicken came not from the embryo, but from the mother herself. Instead of being linked to the presence of the embryo, uterine thickening became linked to ovulation and the choreographed hormonal up-and-down that each woman cycles through on a monthly basis.</p>
<h2>Maternal self-defence</h2>
<p>But what’s with all this pre-emptive pampering? Not all mammals prepare for pregnancy so hopefully each month. Rabbits, for example, only ovulate and thicken their endometrium when they copulate. </p>
<p>American evolutionary biologists Deena Emera, Roberto Romero and Günter Wagner <a href="http://dx.doi.org/10.1002/bies.201100099">argue</a> that the spontaneous thickening of the uterine lining is in fact a defence mechanism. Except the defence is against our own parasitic offspring, rather than sperm-borne infection. </p>
<p>Since mother and child do not share identical genes, their purposes are at odds. From the embryo’s perspective, the maximum benefit is gained from squeezing as many resources from its mother as possible. It even dampens its mother’s response to insulin, ensuring that a greater slice of the circulating sugar pie is placenta-bound during its nine-month residence. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/25636/original/5wbn6ny3-1371430576.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/25636/original/5wbn6ny3-1371430576.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/25636/original/5wbn6ny3-1371430576.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=906&fit=crop&dpr=1 600w, https://images.theconversation.com/files/25636/original/5wbn6ny3-1371430576.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=906&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/25636/original/5wbn6ny3-1371430576.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=906&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/25636/original/5wbn6ny3-1371430576.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1139&fit=crop&dpr=1 754w, https://images.theconversation.com/files/25636/original/5wbn6ny3-1371430576.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1139&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/25636/original/5wbn6ny3-1371430576.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1139&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The embryo tries to squeeze as many resources from its mother as possible.</span>
<span class="attribution"><span class="source">Image from shutterstock.com</span></span>
</figcaption>
</figure>
<p>The mother, meanwhile, prefers to be frugal with her resources, so that she can survive this pregnancy and go on to populate the next generation with additional children endowed with her unique genetic contribution.</p>
<p>There are two reasons that this maternal–fetal tug of war could have resulted in spontaneous thickening of the uterus. First, with implantation already invasive in humans and other menstruating species, the pre-thickened lining could be an evolutionary push-back to prevent the embryo from burrowing even deeper into the uterine wall.</p>
<p>The second reason is to protect the mother from expending valuable resources on faulty fetuses. The thickened lining could be an efficient way to sense – and if necessary, jettison – any tainted, and therefore unwanted, embryos. Around <a href="http://dx.doi.org/10.1002/bies.201300022">30% to 60% of all human embryos are unceremoniously discarded in this way</a>, before any signs of pregnancy occur. </p>
<p>While its evolutionary origins are firmly rooted in what takes place during pregnancy, the reality is that for most menstrual cycles, no embryo arrives. The decidual cells that have thickened the uterine lining pack up shop, the extracellular matrix keeping them all together breaks down, and the lining becomes as deciduous as the autumn leaves. </p>
<p>For Western most women who bear few children, this menstrual cycle is repeated 450 to 480 times over.</p><img src="https://counter.theconversation.com/content/13744/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dyani Lewis receives funding from the Department of Health and Ageing.</span></em></p>For half the population, it comes three to five days each month, 12 months each year, for 40 years of our lives. Menstruation can be debilitating, relieving, disappointing, or simply an inconvenient fact…Dyani Lewis, Sexual health researcher, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/117142013-02-01T03:32:48Z2013-02-01T03:32:48ZPMS is real and denying its existence harms women<figure><img src="https://images.theconversation.com/files/19729/original/dpbczfwm-1359591101.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">We no longer have to take the view that women’s biology, including their hormone profiles, are unimportant.</span> <span class="attribution"><span class="source">Susan/Flickr</span></span></figcaption></figure><p>A recent <a href="http://www.smh.com.au/opinion/society-and-culture/pms-may-be-gone-but-women-are-in-no-mood-to-lose-anger-20130114-2cpnd.html">opinion piece</a> in the Fairfax papers – based on a <a href="http://theconversation.com/the-myth-of-premenstrual-moodiness-10289">Conversation article</a> – discussed “the theory that (PMS) is all in women’s minds as opposed to their endocrinology …” Why is this debate from the 1970s about whether or not PMS is “just an excuse” that women use for their anger resurfacing now? </p>
<p>Premenstrual syndrome (PMS) is a broad term used to describe the physical and psychological symptoms experienced by some women prior to menstruation. The term was first coined by British doctor Katharina Dalton in 1957, and her clinic successfully treated many women over 40 years. </p>
<p>The issue has resurfaced because of a <a href="http://www.sciencedirect.com/science/article/pii/S1550857912001349#">recent study</a> conducted by researchers at the University of Toronto. The authors did a meta-analysis of 41 studies, concluding</p>
<blockquote>
<p>Taken together, these studies failed to provide clear evidence in support of the existence of a specific premenstrual negative mood syndrome in the general population. This puzzlingly widespread belief needs challenging, as it perpetuates negative concepts linking female reproduction with negative emotionality.</p>
</blockquote>
<p>So, why has this study taken us all the way back to a debate that should have finished ages ago? </p>
<p>There are two main reasons. First, many opinions about the existence of PMS are fuelled by personal philosophy and politics, rather than by reason and good research.</p>
<p>Over the centuries, women have had to cope with dismissive views about their anger, depression or capabilities, and being labelled as “irrational” during “that time of the month”. In the 1970s, feminists fought hard against the concept of hormone influences on women’s behaviour in their struggle to achieve equality for women. It was important back then to dismiss women’s biology as the only determining factor of her life. </p>
<p>Today, we don’t have to take the view that women’s biology, including their hormone profiles, are unimportant. We can reclaim biology and integrate it with the psychological plus social contexts to see that PMS does exist and does cause real suffering for many women. </p>
<p>Second, a vast body of neuroscience work is being ignored. The evidence (from many studies) about the <a href="http://www.ncbi.nlm.nih.gov/pubmed/8818400">integration of hormones with mental processes</a> is now well established. </p>
<p>Recent brain research has demonstrated the <a href="http://www.ncbi.nlm.nih.gov/pubmed/11040417">powerful influence</a> that hormones such as <a href="http://www.ncbi.nlm.nih.gov/pubmed/18678800">estrogen</a>, progesterone and testosterone have on brain chemistry, which underpins emotion, mood and behaviour. It is uninformed to write off these potent brain hormones as only “reproductive”, since they have <a href="http://www.ncbi.nlm.nih.gov/pubmed/9396940">many roles</a> in brain development and ongoing mental function. </p>
<p>The Canadian study assumes that all women universally respond to cyclical hormone changes in the same way, and at the same time of each cycle. There are vast differences in individuals’ mental health changes in response to shifts in the complex array of hormones. Some women are very mentally sensitive to hormone changes, while others are not.</p>
<p>Some women suffer from physical and mental disorders that become worse cyclically – migraines and epilepsy are well-accepted examples. Every disorder has a biological, psychological and social context. It is just that with many physical illnesses, there’s the capacity to actually see the tissue damage, or measure markers of the illness, while mental disorders are difficult to measure or visualise in the same way.</p>
<p>This leaves debates about the existence of certain conditions, such as PMS, open to ideologically-motivated opinions rather than evidence-based realities. </p>
<p>In addition to a lack of neuroscientific understanding, the current PMS debate is defined by a lack of consideration for social context. The argument by <a href="http://theconversation.com/the-myth-of-premenstrual-moodiness-10289">Jane Ussher</a> in this publication in her article about the study (and quoted in the Fairfax opinion piece) that PMS is a “Western” woman’s disorder fails to take into account that mental health disorders are not given a priority in some cultures where there are many other battles to contend with. </p>
<p>The recent spate of stories about the difficulties in reporting rape in India is testimony to the level of gender inequality in certain parts of the world. So it’s not surprising that non-life-threatening conditions, such as PMS, are given little consideration in some non-Western countries. </p>
<p>Rejecting the existence of PMS leads to increased hardship for women. Added to her burden of distressing symptoms is the frustration and pain of invalidation, and pejorative comments of disbelief about her cyclical mood or other symptoms. Women with severe PMS want and deserve validation and understanding of their condition. </p>
<p>One argument put up by those wishing to deny the existence of PMS is that medicalising PMS leads to harm and stigma. This erroneous belief is based on the supposition that medicalisation means that (male) doctors will force harmful, ineffective treatments upon passive, uninformed, powerless women. </p>
<p>Patient empowerment through knowledge is a major part of health care, and there are many sources of information about PMS available to women. There are also many different treatments, including combinations of hormone treatments (both natural and synthetic types), healthy lifestyle approaches and psychological interventions. Good PMS management involves comprehensive collaboration between the woman and her doctor, and an integrated treatment approach. </p>
<p>Happily, we are approaching an era of individualised medicine, where each person’s biological, psychological and social context can be taken into consideration. With rapidly accumulating scientific knowledge about the role of hormones in the brain and on behaviour, we are in a better place to listen to and discuss their concerns and issues with women, while taking the role of cyclical hormone changes into account. </p>
<p>Let’s leave the tired old debates of the 1970s in the past and aim for better integration of biology with psychology and the social context. Because that’s where real help and hope lies for many women.</p><img src="https://counter.theconversation.com/content/11714/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jayashri Kulkarni is the Director of the Monash Alfred Psychiatry research centre and receives research funding from the
NHMRC, ARC, The Stanley Medical Research Institute ,Washington,Jansen Cilag, Astra Zeneca,Roche.</span></em></p>A recent opinion piece in the Fairfax papers – based on a Conversation article – discussed “the theory that (PMS) is all in women’s minds as opposed to their endocrinology …” Why is this debate from the…Jayashri Kulkarni, Professor of Psychiatry, Monash UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/115202013-01-10T19:26:37Z2013-01-10T19:26:37ZBirds and boasting: honest when mating, dishonest when dating<figure><img src="https://images.theconversation.com/files/19107/original/9ky9n3nn-1357780942.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A female zebra finch finds herself surrounded by male suitors - but who to listen to?</span> <span class="attribution"><span class="source">Simon Griffith</span></span></figcaption></figure><p>A <a href="http://www.ncbi.nlm.nih.gov/pubmed/23256191">new study</a> has revealed what many people possibly already suspect – males are more honest when displaying their “quality” to a partner than to an unfamiliar female.</p>
<p>These findings, from a study of a socially monogamous bird, are likely to apply to any animal that forms long-term partnerships, including humans. </p>
<p>What do we mean by “quality” here? Well, in evolutionary terms, “quality” refers to the variation in an individual’s health, strength, size, and ability to provide resources.</p>
<p>In socially monogamous animals it makes sense for females to try and identify all the qualities of a male that will help her to produce lots of offspring. Males often hold territories, and provide food to the offspring, as well as providing sperm that help to create the offspring in the first place.</p>
<h2>The long haul</h2>
<p>Because of the prolonged association between partners, it is very difficult for a male to keep deceiving a partner about his quality in the long term. Why? It’s all about the cost.</p>
<p>In birds, singing is costly to males in terms of:</p>
<ul>
<li>the energy required to produce song</li>
<li>the time invested in singing at the expense of other activities (such as foraging), and</li>
<li>the cost of exposing oneself to predators.</li>
</ul>
<p>As a result, only males in good condition can maintain high levels of singing for an extended period. </p>
<p>When initially encountering an unknown female for the first time, it makes sense for all males to “display” at a similarly high rate, in an attempt to attract a female’s attention and make a good first impression.</p>
<p>For displays that are energetically expensive, such as singing, even lower-quality males are able to perform at a similar level to their rivals for that important but short first encounter. After a short period, lower-quality males are unable to sustain the effort, but if the female has already moved on it doesn’t matter.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/19115/original/dfsdnzgb-1357793185.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/19115/original/dfsdnzgb-1357793185.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=424&fit=crop&dpr=1 600w, https://images.theconversation.com/files/19115/original/dfsdnzgb-1357793185.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=424&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/19115/original/dfsdnzgb-1357793185.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=424&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/19115/original/dfsdnzgb-1357793185.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=533&fit=crop&dpr=1 754w, https://images.theconversation.com/files/19115/original/dfsdnzgb-1357793185.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=533&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/19115/original/dfsdnzgb-1357793185.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=533&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">bartolomeo/Flickr</span></span>
</figcaption>
</figure>
<h2>Speed-dating</h2>
<p>In their new study, Morgan David and colleagues at the University of Bergundy in France placed male <a href="http://en.wikipedia.org/wiki/Zebra_Finch">zebra finches</a> in a cage with an unknown female for either five minutes or one hour. The researchers found that all males took the opportunity to court the female with their song.</p>
<p>In these “speed-dating” trials, the amount of song produced by different males was unrelated to the underlying quality of those males.</p>
<p>(In this study quality was measured by looking at individual body mass. High quality birds typically carry a little more weight than those in lower condition, and this measure of condition is a great predictor of long-term survival and how many offspring a male produces over its life.)</p>
<p>By contrast, when the researchers examined song rates in males that had already established partnerships, and that were singing to a “steady” female partner, they found that call rate was a very reliable predictor of underlying quality.</p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/19117/original/2mj6n8wf-1357793359.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/19117/original/2mj6n8wf-1357793359.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1012&fit=crop&dpr=1 600w, https://images.theconversation.com/files/19117/original/2mj6n8wf-1357793359.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1012&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/19117/original/2mj6n8wf-1357793359.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1012&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/19117/original/2mj6n8wf-1357793359.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1272&fit=crop&dpr=1 754w, https://images.theconversation.com/files/19117/original/2mj6n8wf-1357793359.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1272&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/19117/original/2mj6n8wf-1357793359.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1272&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">Peripitus/Wikimedia Commons</span></span>
</figcaption>
</figure>
<p>That is, only males in the best condition produced song at a high rate.</p>
<p>This is probably because males of lower quality were unable to sustain this costly activity for as long, or may have depleted their reserves more quickly and had to break off from their displaying to feed, or rest and recover.</p>
<h2>The long game</h2>
<p>In the short-term, low quality males can potentially bluff and perhaps dig deeper into their reserves. But when there is a true cost to a signal, it is increasingly difficult to maintain such bluff over the long-term, and it might cause long-term damage (if the male chooses singing over foraging, for example).</p>
<p>A good reason for the honesty with which an individual signals its quality to a partner is the nature of the partnership itself. Given partnerships are ultimately about reproduction (in animals at least), socially monogamous partners have a shared interest in being honest with one another about their quality.</p>
<p>It makes sense for a male to signal to his partner about his condition and qualities, because that information is useful to a female in deciding when, and how many offspring to produce. As mentioned above, it may be detrimental to a male to falsely signal his quality to his partner.</p>
<p>If the female tailors her reproduction to his signal, and the number of young she believes he is capable of feeding, then they may end up with too many offspring, none of which will get enough food to ensure healthy development. The male and the female will therefore both lose out in the long-run.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/XNCYAZcDuGQ?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<h2>Not just birds</h2>
<p>While this study was conducted on small birds native to the harsh conditions of the Australian outback, there are <a href="https://theconversation.com/australias-first-supermodel-no-not-that-one-2469">lessons about ourselves</a> that can be taken from such studies.</p>
<p>An individual’s evolutionary interests change over time and vary with their status in the mating game. Single, young-blooded males are prone to displays of wealth, status and prowess, the reliability of which is not necessarily easy for a potential partner to assess. Having one good suit or hiring a Porsche for the weekend are good examples of ways individuals can create a false impression of status.</p>
<p>But having a wardrobe full of Italian suits and owning a Porsche outright is more difficult to achieve, and it’s a more honest signal of underlying wealth. </p>
<p>The obvious implication here is to be wary of first impressions – they can be deceptive. The secret to getting an honest appraisal of an individual is through long-term acquaintance. In that sense, a second date is probably far more useful than the first date!</p>
<p>The stronger a bond becomes between a couple and the more intimate they become the better they know and understand the quality and current condition of their partner.</p>
<p>This makes sense because, they are now working as a team and looking out for each other and trying to plan for the future accordingly.</p>
<p>Decisions about where to live, when and if and how many children to have are all very important and are best optimised with a good understanding of each other’s position. </p>
<p>The nice thing about this recent work is that it demonstrates the complexity with which animal signals are used and abused. As well as listening to the song, we need to also consider who is singing, and what his agenda is likely to be.</p><img src="https://counter.theconversation.com/content/11520/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Simon Griffith receives funding from the Australian Research Council.</span></em></p>A new study has revealed what many people possibly already suspect – males are more honest when displaying their “quality” to a partner than to an unfamiliar female. These findings, from a study of a socially…Simon Griffith, Associate Professor of Avian Behavioural Ecology, Macquarie UniversityLicensed as Creative Commons – attribution, no derivatives.