tag:theconversation.com,2011:/au/topics/evolutionary-theory-23399/articlesEvolutionary theory – The Conversation2023-10-10T12:33:29Ztag:theconversation.com,2011:article/2127382023-10-10T12:33:29Z2023-10-10T12:33:29ZCancer in kids is different from cancer in grown-ups – figuring out how could lead to better pediatric treatments<figure><img src="https://images.theconversation.com/files/552398/original/file-20231005-24-z0nr4r.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C2120%2C1415&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Cancer in children is often more invasive and aggressive than that of adults.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/doctor-with-arm-around-young-cancer-patient-royalty-free-image/1263102729">FatCamera/E+ via Getty Images</a></span></figcaption></figure><p>Cancer arises when cells accumulate enough damage to change their normal behavior. The likelihood of accruing damage <a href="https://www.cancer.gov/about-cancer/causes-prevention/risk/age">increases with age</a> because the safeguards in your genetic code that ensure cells function for the greater good of the body weaken over time. </p>
<p>Why, then, do children who haven’t had sufficient time to accumulate damage develop cancer?</p>
<p>I am a <a href="https://orcid.org/0000-0002-5045-9333">doctoral student</a> who is exploring the evolutionary origins of cancer. Viewed through an evolutionary lens, cancer develops from the <a href="https://theconversation.com/microbes-in-your-food-can-help-or-hinder-your-bodys-defenses-against-cancer-how-diet-influences-the-conflict-between-cell-cooperators-and-cheaters-195810">breakdown of the cellular collaboration</a> that initially enabled cells to come together and function as one organism. </p>
<p>Cells in children are still learning how to collaborate. Pediatric cancer develops when rogue cells that defy cooperation emerge and grow at the body’s expense.</p>
<h2>Adult versus pediatric cancer</h2>
<p>The cells in your body adhere to a set of instructions defined by their <a href="https://www.genome.gov/genetics-glossary/Genetic-Code">genetic makeup</a> – a unique code that carries all the information that cells need to perform their specific function. When cells divide, the genetic code is copied and passed from one cell to another. Copying errors can occur in this process and contribute to the development of cancer. </p>
<p>In adults, cancer evolves through a gradual accrual of errors and damages in the genetic code. Although there are <a href="https://www.khanacademy.org/science/ap-biology/cell-communication-and-cell-cycle/regulation-of-cell-cycle/a/cancer">safeguards against uncontrolled cell growth</a> and <a href="https://www.khanacademy.org/science/biology/dna-as-the-genetic-material/dna-replication/a/dna-proofreading-and-repair">repair mechanisms</a> to fix genetic errors, aging, exposure to environmental toxins and unhealthy lifestyle can weaken these protections and lead to the breakdown of tissues. The most common types of adult cancers, such as <a href="https://www.cancer.org/cancer/types/breast-cancer/risk-and-prevention/lifestyle-related-breast-cancer-risk-factors.html">breast cancer</a> and <a href="https://www.cdc.gov/cancer/lung/basic_info/risk_factors.htm">lung cancer</a>, often result from such accumulated damage.</p>
<p>In children, whose tissues are still developing, there is a dual dynamic between growth and cancer prevention. On one hand, rapidly dividing cells are organizing themselves into tissues in an environment with <a href="https://doi.org/10.1172%2FJCI31405">limited immune surveillance</a> – an ideal setting for cancer development. On the other hand, children have robust safeguards and tightly regulated mechanisms that act as counterforces against cancer and make it a rare occurrence.</p>
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<a href="https://images.theconversation.com/files/552401/original/file-20231005-19-f2nwmn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Father carrying child with cancer wearing a bandana and holding a stuffed animal, talking to a health care provider" src="https://images.theconversation.com/files/552401/original/file-20231005-19-f2nwmn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/552401/original/file-20231005-19-f2nwmn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/552401/original/file-20231005-19-f2nwmn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/552401/original/file-20231005-19-f2nwmn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/552401/original/file-20231005-19-f2nwmn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/552401/original/file-20231005-19-f2nwmn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/552401/original/file-20231005-19-f2nwmn.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>
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<span class="caption">Although pediatric cancer is rare, it is a leading cause of death for children under 15 in the U.S.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/child-with-leukemia-visits-the-doctor-with-her-royalty-free-image/1162646816">FatCamera/E+ via Getty Images</a></span>
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<p>Children seldom accumulate errors in their genetic code, and pediatric cancer patients have a much <a href="https://blog.dana-farber.org/insight/2018/09/difference-cancer-adults-cancer-children/">lower incidence of genetic errors</a> than adult cancer patients. However, <a href="https://www.cancer.gov/news-events/cancer-currents-blog/2015/pediatric-germline">nearly 10%</a> <a href="https://www.healthychildren.org/English/health-issues/conditions/cancer/Pages/When-You-Have-a-Family-History-of-Childhood-Cancer.aspx">of pediatric cancer</a> cases in the U.S. are due to inherited genetic mutations. The most common heritable cancers arise from genetic errors that influence cell fate – that is, what a cell becomes – during the developmental stages before birth. Mistakes in embryonic cells accumulate in all subsequent cells after birth and can ultimately manifest as cancer.</p>
<p>Pediatric cancers can also spontaneously arise while children are growing. These are driven by genetic alterations distinct from those common in adults. Unlike in adults, where damage typically accumulates as small errors during cell division, pediatric cancers often result from <a href="https://doi.org/10.1016/j.omtn.2017.01.005">large-scale rearrangements</a> of the genetic code. Different regions of the genetic code swap places, disrupting the cell’s instructions beyond repair. </p>
<p>Such changes frequently occur in tissues with constant turnover, such as the <a href="https://www.cancer.gov/news-events/cancer-currents-blog/2016/gene-fusion-pediatric-glioma">brain</a>, <a href="https://doi.org/10.1002%2Fgcc.22335">muscles</a> and <a href="https://doi.org/10.3390%2Fncrna7010010">blood</a>. Unsurprisingly, the <a href="https://www.cancer.org/cancer/types/cancer-in-children/types-of-childhood-cancers.html">most prevalent</a> pediatric cancers often emerge from these tissues.</p>
<p>Genetic alterations are not a prerequisite for pediatric cancers. In certain pediatric brain cancers, the region of the genetic code responsible for cell specialization becomes <a href="https://doi.org/10.1172%2FJCI9462">permanently silenced</a>. Although there is no error in the genetic code itself, the cell is unable to read it. Consequently, these cells become trapped in an uncontrolled state of division, ultimately leading to cancer.</p>
<h2>Tailoring treatments for pediatric cancer</h2>
<p>Cells in children typically exhibit greater growth, mobility and flexibility. This means that pediatric cancer is often <a href="https://www.acco.org/types-of-childhood-cancer/">more invasive and aggressive</a> than that of adults, and can severely affect development even after successful therapy due to long-term damage. Because the cancer trajectories in children and adults are markedly different, treatment approaches should also be different for each. </p>
<p>Standard cancer therapy includes radiotherapy or chemotherapy, which affect both cancerous and healthy, actively dividing cells. If the patient becomes unresponsive to these treatments, oncologists try a different drug.</p>
<p>In children, the side effects of certain treatments <a href="https://www.cancer.org/cancer/survivorship/children-with-cancer/late-effects-of-cancer-treatment.html">are amplified</a> since their cells are actively growing. Unlike adult cancers, where different drugs can target different genetic errors, pediatric cancers have <a href="https://doi.org/10.1158%2F2159-8290.CD-20-0779">fewer of these targets</a>. The rarity of pediatric cancer also makes it challenging to test new therapies in large-scale clinical trials.</p>
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<figcaption><span class="caption">Standard cancer treatments can lead to lifelong effects for pediatric patients.</span></figcaption>
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<p>A common reason for treatment failure is when cancer cells adapt to evade treatment and become <a href="https://www.cancer.gov/about-cancer/treatment/research/drug-combo-resistance">drug resistant</a>. Applying principles from evolutionary biology to cancer treatment can help tackle this. </p>
<p>For example, <a href="https://doi.org/10.1002/cncr.32777">extinction therapy</a> is an approach to treatment inspired by natural mass extinction events. The goal of this therapy is to eradicate all cancer cells before they can evolve. It does this by applying a “first strike” drug that kills most cancer cells. The remaining few cancer cells are then targeted through focused, smaller-scale interventions. </p>
<p>If complete extinction is not possible, the goal turns to preventing treatment resistance and keeping the tumor from progressing. This can be achieved with <a href="https://isemph.org/Adaptive-Therapy">adaptive therapy</a>, which takes advantage of the competition for survival among cancer cells. Treatment is dynamically turned “on” and “off” to keep the tumor stable while allowing cells that are sensitive to the therapy to out-compete and suppress resistant cells. This approach <a href="https://doi.org/10.1007/s10555-019-09836-y">preserves the tissue</a> and improves survival.</p>
<p>Although pediatric cancer patients have a better prognosis than adults do after treatment, cancer remains the <a href="https://www.cancer.net/cancer-types/childhood-cancer/statistics">second-leading cause of death</a> in children under 15 in the U.S. Recognizing the developmental differences between pediatric and adult cancers and using <a href="https://theconversation.com/cancers-are-in-an-evolutionary-battle-with-treatments-evolutionary-game-theory-could-tip-the-advantage-to-medicine-170175">evolutionary theory</a> to “<a href="https://doi.org/10.1001/jamaoncol.2018.3395">anticipate and steer</a>” the cancer’s trajectory can enhance outcomes for children. This could ultimately improve young patients’ chances for a brighter, cancer-free future.</p><img src="https://counter.theconversation.com/content/212738/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ranjini Bhattacharya 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>Children typically haven’t accumulated enough cellular damage to develop cancer. Because their bodies are still developing, pediatric cancers differ from adult cancers in key ways.Ranjini Bhattacharya, Ph.D. Candidate in Integrated Mathematical Oncology, University of South FloridaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2086532023-07-03T03:05:31Z2023-07-03T03:05:31Z4 reasons not teaching evolution in schools is immoral<figure><img src="https://images.theconversation.com/files/535184/original/file-20230703-182282-gjldng.jpeg?ixlib=rb-1.1.0&rect=0%2C35%2C3000%2C1958&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>Educators involved in curriculum design know one hard truth: you can’t fit in everything. Whatever the finished product, there will always be someone who thinks something important has been missed or something unnecessary has been included. </p>
<p>This is what happened in the recent redesign of the Australian Curriculum, for example, where the emphasis on Western civilisation <a href="https://theconversation.com/the-national-history-curriculum-should-not-be-used-and-abused-as-an-election-issue-176783">became politicised</a>.</p>
<p>When it comes to science curriculums, the amount of potential content that can be included is staggering. </p>
<p>In the case of physics in primary or middle schools, we may or may not see the inclusion of topics such as wave theory, acoustics, electronics or relativity. Some may lament these exclusions, but most agree physics at this level can be taught without them. </p>
<p>Similarly, there are areas of biology that may be considered optional at this level, such as botany, entomology or marine ecosystems. Evolution, however, is a concept that underpins and integrates all facets of biological study.</p>
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Read more:
<a href="https://theconversation.com/what-exactly-is-the-scientific-method-and-why-do-so-many-people-get-it-wrong-65117">What exactly is the scientific method and why do so many people get it wrong?</a>
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<h2>The central role of evolution in biology</h2>
<p>As evolutionary biologist Theodosius Zobzansky noted in the title of his <a href="https://www.pbs.org/wgbh/evolution/library/10/2/text_pop/l_102_01.html">seminal essay</a>, Nothing in Biology Makes Sense Except in the Light of Evolution. </p>
<p>Without evolution, the living world is a kaleidoscope of disconnected form and colour. With evolution, it is breathtakingly coherent. In terms of its simplicity and explanatory power, the theory of evolution by natural selection is arguably one of our most successful scientific achievements.</p>
<p>Because of evolution’s centrality to biology, its omission in any substantive course seems a matter of serious neglect. </p>
<p>Today many countries in the world, predominantly Islamic ones, do not teach evolution, as it is <a href="https://www.nature.com/articles/s41562-019-0771-7#">said to contradict</a> religious teachings.</p>
<p>Recently, <a href="https://www.science.org/content/article/scientists-india-protest-move-drop-darwinian-evolution-textbooks">India</a> also removed evolution from the formal education of students up to Year 10. This decision was supposedly related to its right-wing government’s commitment to <a href="https://www.aljazeera.com/news/2023/4/14/mughals-rss-evolution-outrage-as-india-edits-school-textbooks">promoting Hindu-nationalist</a> perspectives.</p>
<p>These examples do not represent simple oversight. They are serious attempts to restrict people thinking about evolution and, ultimately, to delegitimise science for ideological gain. </p>
<h2>Excluding evolution is a moral concern</h2>
<p>Omitting evolution from educational curriculums isn’t just educationally fraught, it’s also a serious moral issue.</p>
<p>Morally speaking, at least four related points present themselves in favour of the inclusion of evolution in any biology curriculum.</p>
<p><strong>1. Equality of opportunity</strong></p>
<p><a href="https://plato.stanford.edu/entries/rawls/">John Rawls</a>, one of the most influential political philosophers of the 20th century, set <a href="https://edeq.stanford.edu/sections/section-2-conceptions-equality-opportunity/fair-equality-opportunity">equality of opportunity</a> as a key social justice principle. </p>
<p>Many scientists have been inspired towards their work by understanding the grand narrative of evolution, which provides a coherent and effective framework to understand biological systems and their relationships. </p>
<p>Depriving students of this educational experience means they could be disadvantaged in further study or work. Or, worse, they might be dissuaded from it. </p>
<p><strong>2. Free inquiry</strong></p>
<p>Deliberate attempts to exclude serious rational inquiry are anathema to most philosophical schools of thought. Philosopher and scientist <a href="https://digitalcommons.montclair.edu/cgi/viewcontent.cgi?article=1120&context=educ-fdns-facpubs#:%7E:text=Peirce%20argued%20that%20even%20though,is%20%27self%2Dcorrective%27.">C.S. Peirce</a> expressed this powerfully:</p>
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<p>Upon this first, and in one sense this sole, rule of reason, that in order to learn you must desire to learn, and in so desiring not be satisfied with what you already incline to think, there follows one corollary which itself deserves to be inscribed upon every wall of the city of philosophy: do not block the way of inquiry.</p>
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<p>To stifle inquiry is also to inhibit the development of important traits in students – especially curiosity, one of our most powerful tools for knowledge creation. </p>
<p><strong>3. Fairness and public reasoning</strong></p>
<p>Philosopher Immanuel Kant, expressing the essence of the <a href="https://www.nypl.org/sites/default/files/kant_whatisenlightenment.pdf">Enlightenment</a> as he saw it, set public reasoning through an individual commitment to rational inquiry as its cornerstone. </p>
<p>If we value the freedom to inquire and freedom of religious belief, it follows that no particular ideology should have unquestioned authority over others. </p>
<p>It’s naive to think science is a value-free arena. Yet it represents the most effective means of rational inquiry into the world we currently possess. </p>
<p>We can certainly allow for (and indeed need) explanations that the methodologies of science can’t provide. But rational inquiry needs to be accommodated, rather than usurped, by religious or political ideologies.</p>
<p>As the late author and journalist <a href="https://www.nytimes.com/2011/12/16/arts/christopher-hitchens-is-dead-at-62-obituary.html">Christopher Hitchens</a> elegantly stated:</p>
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<p>We do not rely solely upon science and reason, because these are necessary rather than sufficient factors, but we distrust anything that contradicts science or outrages reason.</p>
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<p><strong>4. Intellectual honesty, integrity and a commitment to scientific truths</strong></p>
<p>An extended biology course that doesn’t contain evolution represents a promise made and broken. </p>
<p>To present something as scientific means it should embrace the methodologies and dispositions of scientific inquiry, including open-mindedness, scepticism and fallibility. </p>
<p>Ideologically driven censorship is therefore intellectually dishonest and, in these cases, results in a misrepresentation of science.</p>
<h2>The bottom line</h2>
<p>A moral stance is not something simply held dogmatically. It is one that can be reasoned in a way that’s rationally accessible to others. </p>
<p>Education in a cosmopolitan world – in as much as it is social, collaborative and cooperative – should be characterised by morality and rationality. Excising our best ideas from curriculums is both immoral and irrational.</p>
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Read more:
<a href="https://theconversation.com/guide-to-the-classics-darwins-on-the-origin-of-species-96533">Guide to the classics: Darwin's On the Origin of Species</a>
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<p class="fine-print"><em><span>Peter Ellerton is affiliated with the Rationalist Society of Australia.</span></em></p>There are areas of biology that may be considered optional at younger year levels, such as botany, entomology and marine ecosystems. Evolution is not one of these.Peter Ellerton, Senior Lecturer in Philosophy and Education; Curriculum Director, UQ Critical Thinking Project, The University of QueenslandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2006102023-03-07T06:14:01Z2023-03-07T06:14:01ZBlue ticks: what evolutionary theory tells us about the turmoil around social media verification<figure><img src="https://images.theconversation.com/files/513158/original/file-20230302-16-deh1mm.jpg?ixlib=rb-1.1.0&rect=0%2C9%2C5979%2C3359&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Paid-for verification can disrupt our expectations about the reliability of profiles on social media</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/businessman-using-laptop-verification-account-blue-2266705077">Shutterstock / Poca Wander Stock</a></span></figcaption></figure><p>“Integrity,” “Professionalism”, “Creativity” — three of many words I used to see around one of the offices I worked in in New York. </p>
<p>Like other aspects of corporate culture, these annoyed me. It’s easy to write words in big font on the glass doors of meeting rooms. But it’s something else to embody the qualities they suggest.</p>
<p>I didn’t realise it at the time, but what irritated me about these words related to a larger question in the <a href="https://en.wikipedia.org/wiki/Signalling_theory">theory of signalling</a>, which deals with the ways different species communicate at a fundamental level.</p>
<p>Signals are used by animals to advertise their desirable qualities to a potential mate, such as when <a href="https://www.jstor.org/stable/4533969">red deer roar</a> to signal their size. Meanwhile, the bright colours sported by poisonous frogs are used to ward off predators. Research around signalling theory can help to explain how signals <a href="https://www.britannica.com/science/animal-communication/Evolution-of-signals">gain</a> and <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/jeb.13416">lose</a> meaning.</p>
<p>Today, we’re seeing this plainly in the way that major tech companies allow users to pay for verification — what’s widely known as having a “blue tick”. This system may be thought of as a form of legitimacy in the social media world. </p>
<p>But the notion of legitimacy is now being undermined, and this is entirely because the signals, much like those words on the walls of so many offices, are becoming meaningless.</p>
<h2>Unreliable signals</h2>
<p>Since the 1990s, researchers in the evolutionary sciences have looked to signals to explain many otherwise unexplainable human behaviours. From warfare and sports to religion and political movements, we adopt signals to tell others something about ourselves. For example, some people <a href="https://pubmed.ncbi.nlm.nih.gov/26190055/">believe</a> that following religious ritual is a signal of commitment to a person’s social group.</p>
<p>This is an ancient process, and despite its ubiquity among people, has its roots in the most basic forms of life. Signals <a href="https://onlinelibrary.wiley.com/doi/10.1111/j.1420-9101.2006.01258.x">evolve among animals</a> because of the effects they have on those who perceive them, what we call the “receivers.” They may, but don’t always, represent some underlying quality of the signaller. </p>
<p>For example, <a href="https://global.oup.com/academic/product/animal-signals-9780198526858?cc=gb&lang=en&">some flies</a> and spiders bring parcels of food to potential mates to signal that they are good hunters. This information is used by the receiver, the potential mate, to decide whether to take up the offer.</p>
<p>Except — as with everything in evolution — there’s a catch. Some flies, and <a href="https://blogs.scientificamerican.com/not-bad-science/fake-jewels-male-spiders-give-worthless-gifts-to-entice-females/">some spiders</a>, bring empty parcels. The gift bags are empty, and the desired mates might be basing their decisions on false information. </p>
<p>In the language of evolutionary theory, we’d say that the signal is a fake one, because the signaller hasn’t paid the costs — in this case, the time and energy to find and catch prey — to make it honest.</p>
<h2>Layers of complexity</h2>
<p>With humans, the picture is more complicated still. We have complex cultures, languages, and rituals that are all nonetheless built on the same foundations as mating signals used by insects and arachnids. </p>
<p>With every layer of complexity, there’s an opportunity to fake signals. But many aspects of human culture evolve that send out signals that are costly — energetically, economically, or socially — and therefore harder to fake. </p>
<p>In hunter-gatherer cultures (which reflect the circumstances we evolved living in) hunting of course provides food but can also be a signal about fitness. </p>
<p>In fact, <a href="https://pubmed.ncbi.nlm.nih.gov/26189411/">anthropological data suggest</a> that good hunters don’t necessarily eat more than others. Instead, they appear to mate and marry earlier, and frequently have more mates than others who don’t hunt as well. </p>
<p><a href="https://academic.oup.com/beheco/article/14/1/116/209182">A landmark study</a> in the early 2000s showed this trend convincingly among the Meriam people, who have traditionally hunted turtles in the waters of Australia’s Torres Strait. It isn’t really possible to fake being a good turtle hunter: the way humans gossip makes falsifying this signal extremely difficult.</p>
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<img alt="Sea turtle" src="https://images.theconversation.com/files/513201/original/file-20230302-19-cr9ht6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/513201/original/file-20230302-19-cr9ht6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/513201/original/file-20230302-19-cr9ht6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/513201/original/file-20230302-19-cr9ht6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/513201/original/file-20230302-19-cr9ht6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/513201/original/file-20230302-19-cr9ht6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/513201/original/file-20230302-19-cr9ht6.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">Green sea turtles are prized by Meriam hunters.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/hawaiian-green-sea-turtle-cruising-warm-353816774">Shutterstock/Shane Myers Photography</a></span>
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<p>Flash forward to modern culture. Like hunter-gatherers, we use signals all the time to convey to others key qualities about ourselves. </p>
<p>Some people spend their careers building a profile in their industry and are consequently awarded legitimacy by their peers. This may manifest as awards, certifications, degrees or, in the case of social media, verification.</p>
<p>Blue ticks evolved, culturally speaking, from the idea that important figures in different areas — journalists, politicians, musicians, and so forth — require a signal of legitimacy and prestige. </p>
<p>We also need to know, as receivers, whether the person posting to Twitter and Instagram is the public figure they purport to be.</p>
<h2>Undermining the system</h2>
<p>Verification solves this issue, but as with any signalling system it presents problems of its own. With Twitter, it wasn’t always clear why some people had blue ticks or whether the verification system lent more legitimacy to some journalistic outlets than others. </p>
<p>But there was a kind of shared belief that if someone had a blue tick, they were more likely to be a legitimate figure. With paid-for verification, however, tech companies have <a href="https://www.theguardian.com/technology/2022/nov/01/musk-charging-twitter-verified-accounts">undermined that signalling system</a>.</p>
<p>When Twitter introduced subscription-based blue ticks, many fake accounts for politicians <a href="https://www.bbc.co.uk/news/technology-63599553">popped up</a> and spread disinformation. Some of this was done for fun, some wasn’t. </p>
<p>To its credit, <a href="https://www.washingtonpost.com/technology/2022/11/11/twitter-fake-verified-accounts/">Twitter quickly dealt with that issue</a>, but disinformation on the platform is now an <a href="https://www.science.org/content/article/fake-news-spreads-faster-true-news-twitter-thanks-people-not-bots">increasingly potent issue</a>. To use an analogy, if having a PhD were reduced to spending $15 (£12) a month in a subscription to a university, we wouldn’t take it seriously. </p>
<p>Much as it doesn’t give a corporation integrity if it pays a few hundred dollars to paint the word around the office, Twitter or Instagram users don’t automatically gain legitimacy by paying for a blue tick.</p>
<p>The difference is that most employees are highly sceptical when their companies use cheap signals to promote desirable qualities. Social media users aren’t, at least not yet. But the effects of undermining the signalling system are likely to be far-reaching. </p>
<p>Going forward, it would be smart to question posts by verified accounts as much as any others. The signal, much like the fly’s empty offer to a potential mate, may be meaningless.</p><img src="https://counter.theconversation.com/content/200610/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jonathan R Goodman 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>Signalling theory tells us lots about the way paid-for verification has disrupted the blue tick system.Jonathan R Goodman, Researcher, Human Evolutionary Studies, University of CambridgeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1987672023-02-08T19:09:18Z2023-02-08T19:09:18ZNew bird brain study shows evolving a big brain depends on having ‘good’ parents<figure><img src="https://images.theconversation.com/files/508037/original/file-20230203-24-uvmpl6.jpg?ixlib=rb-1.1.0&rect=33%2C16%2C5506%2C3715&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A hyacinth macaw (Anodorhynchus hyacinthinus).</span> <span class="attribution"><span class="source">Tristan Barrington/Shutterstock</span></span></figcaption></figure><p>As owners of some of the biggest brains in the animal kingdom, we humans often assume cognitive performance, task solving and social interactions were the basic ingredients that promoted the evolution of our complex brains.</p>
<p>Our <a href="https://www.pnas.org/doi/10.1073/pnas.2121467120">new study</a>, recently published in the Proceedings of the National Academy of Sciences, challenges this intuitive assumption.</p>
<p>Taken together with other biological and ecological factors, cognitive and social factors lose their leading role in driving increased brain sizes. Instead, it is the amount of parental care the offspring receives that supports a larger brain.</p>
<h2>Brains are expensive</h2>
<p>The brain is one of the most <a href="https://www.sciencedirect.com/science/article/abs/pii/S0960982222007357">costly organs</a> in an animal’s body – neural activity requires large amounts of energy. The bigger the brain is, the more energy it needs to sustain itself.</p>
<p>Biologists have long assumed this large cost has to come with some solid benefits provided by being large-brained. Some of the proposed advantages were cognitive skills, the ability to solve difficult problems and engage in complex social interactions.</p>
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Read more:
<a href="https://theconversation.com/what-is-it-about-the-human-brain-that-makes-us-smarter-than-other-animals-new-research-gives-intriguing-answer-183848">What is it about the human brain that makes us smarter than other animals? New research gives intriguing answer</a>
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<p>Looking at humans, great apes and other primates seemed to confirm this assumption: our large brains are routinely used in situations requiring <a href="https://www.pnas.org/doi/10.1073/pnas.1505913113">creative solutions</a>, and to <a href="https://www.scientificamerican.com/article/social-network-size-linked-brain-size/">maintain social integrity in large groups</a>.</p>
<p>There is one problem with this reasoning. Large brains take a long time to grow and while they do so, they still need substantial amounts of fuel (even <a href="https://onlinelibrary.wiley.com/doi/abs/10.1002/evan.21831">more</a> than in adulthood). They are also significantly less powerful before they reach their final size and complexity. Growing animals would therefore have to “pay” for growing brains, but would not be able to use the brains’ power for a considerable time.</p>
<h2>Bird brain investigations</h2>
<p>To solve this apparent paradox, we decided to look away from mammals, which are traditionally used in brain research – but also have almost exclusively been studied in the context of cognition. Instead, we dived into the bird world. Birds are amazing models in many evolutionary studies: they are extremely diverse, have a wide range of lifestyles, and live in nearly <a href="https://www.nature.com/articles/s41467-020-18779-w">all wild habitats on Earth</a>.</p>
<p>Bird brain sizes are also hugely variable, ranging from relatively small-brained chickens and ostriches to some of the smartest large-brained species such as parrots and corvids. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/508776/original/file-20230208-29-1s2l0s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Three ostriches" src="https://images.theconversation.com/files/508776/original/file-20230208-29-1s2l0s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/508776/original/file-20230208-29-1s2l0s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=415&fit=crop&dpr=1 600w, https://images.theconversation.com/files/508776/original/file-20230208-29-1s2l0s.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=415&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/508776/original/file-20230208-29-1s2l0s.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=415&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/508776/original/file-20230208-29-1s2l0s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=521&fit=crop&dpr=1 754w, https://images.theconversation.com/files/508776/original/file-20230208-29-1s2l0s.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=521&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/508776/original/file-20230208-29-1s2l0s.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=521&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">Relative to their large body size, ostriches are among the smallest-brained birds.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
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<p>Note that we are referring here to relative brain size. In other words, we are interested in the size of the brain in relation to the animal’s whole body. After all, it is easy to have a large brain (in absolute terms) if you are a large animal in general. Such body-size-related increases in brain size also would not necessarily lead to improved cognition.</p>
<p>Our analysis included more than 1,000 bird species for which we had data on brain size. We also collected many other variables that might be relevant as potential drivers of brain size: the climate each species lives in; whether it is migratory or not; how it feeds and what its main food source is.</p>
<p>Most importantly, for all included species, we were able to find records on how social and co-operative they were, and how much parental care they provided to their offspring.</p>
<h2>It starts in the nest</h2>
<p>Our analysis revealed that, in combination with all included variables, social factors were only weakly related to brain size variation in birds.</p>
<p>It turned out that co-operation and living in larger groups – circumstances commonly assumed to be strongly linked to large and complex brains – almost did not matter as causes of exceptional braininess.</p>
<p>Of all analysed species traits, only those directly linked to parental care and offspring provisioning showed strong relationships with brain size. Our data showed species that fed their young for a longer time were species with some of the biggest brains (again, relative to body size).</p>
<p>The development style mattered a lot, too. Birds can be easily divided into two large groups. Precocial species are those where juveniles hatch from eggs already relatively well developed (such as chickens, ducks, geese), requiring little to no feeding.</p>
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<a href="https://images.theconversation.com/files/508733/original/file-20230207-15-nkv56x.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two baby birds in a nest with mouths open for food." src="https://images.theconversation.com/files/508733/original/file-20230207-15-nkv56x.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/508733/original/file-20230207-15-nkv56x.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/508733/original/file-20230207-15-nkv56x.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/508733/original/file-20230207-15-nkv56x.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/508733/original/file-20230207-15-nkv56x.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/508733/original/file-20230207-15-nkv56x.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/508733/original/file-20230207-15-nkv56x.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>
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<span class="caption">Altricial birds are born helpless, but being fed for long periods by their parents lets them grow bigger brains.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
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<p>Altricial birds, in contrast, hatch severely underdeveloped. Usually their hatchlings are blind, naked and fully dependent on their parents’ care. This group includes some of the best-known bird groups we encounter every day, such as sparrows, tits, robins and finches. </p>
<p>Because altricial birds receive relatively more care from their parents, we predicted that they should also be able to evolve bigger brains – a pattern that we see clearly in our data.</p>
<p>Even if challenging from the point of view of other existing hypotheses (such as the “social brain hypothesis” mentioned earlier), our results make a lot of sense.</p>
<p>As said earlier, brains are huge consumers of energy. If this energy cannot be provided in the usual way (because a juvenile has an underdeveloped brain and cannot feed itself independently), it must be supplied by parental feeding. </p>
<h2>Did human brain evolution follow the bird path?</h2>
<p>Our results raise an interesting question – did the evolutionary history of mammalian and human brains follow the same logic? Did it depend more on parental care than on the expansion of social behaviours and co-operative interactions?</p>
<p>Probably yes. Evidence exists that large acceleration of human brain-size evolution was associated with <a href="https://www.jstor.org/stable/10.1086/667623">increased number of caregivers</a> and <a href="https://www.unm.edu/%7Ehkaplan/KaplanHillLancasterHurtado_2000_LHEvolution.pdf">prolonged provisioning</a> of juveniles well into their adolescence.</p>
<p>It also seems mammalian brain size is indeed constrained by the amount of energy mothers can transfer to their offspring until weaning. When it comes to having a large brain, it appears parental love and care come before any subsequent learning.</p>
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Read more:
<a href="https://theconversation.com/mammals-brains-new-research-shows-bigger-doesnt-always-mean-smarter-159141">Mammals' brains: new research shows bigger doesn't always mean smarter</a>
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<img src="https://counter.theconversation.com/content/198767/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Szymon Drobniak receives funding from the Australian Research Council and the National Science Centre, Poland. Co-authors of the paper were also supported by the Heisenberg grant from the German Research Foundation DFG (Michael Griesser) and the Max Planck Fellowship (Carel van Schaik).</span></em></p>In birds, big brains aren’t associated with living in large social groups – instead, they’re linked to long stints of parental feeding.Szymek Drobniak, DECRA Fellow, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1760922022-03-03T11:44:54Z2022-03-03T11:44:54ZAnimals have evolved to avoid overexploiting their resources – can humans do the same?<p>People have been trying to understand how predators and prey are able to stay balanced within our planet’s ecosystems for at least 2,400 years. The Greek author Herodotus even raised the question in his historical treatise “<a href="https://penelope.uchicago.edu/Thayer/E/Roman/Texts/Herodotus/3d*.html">Histories</a>”, written around 430 BC.</p>
<p>And when Charles Darwin published in 1859 his revolutionary theory of <a href="https://theconversation.com/150-years-ago-charles-darwin-wrote-about-how-expressions-evolved-pre-empting-modern-psychology-by-a-century-170880">evolution</a> in “<a href="https://royalsocietypublishing.org/doi/10.1098/rsnr.2018.0015">On the Origin of Species</a>”, this raised an even more difficult question: why do predators not evolve to become so aggressive that they eat all their prey and then go extinct themselves? </p>
<p>Scientists have since doubted whether it’s possible for the process of evolution to create “prudent predators” able to avoid extinguishing their own prey. The American ecologist Lawrence Slobodkin proposed the idea of prudent predation in 1960, but was strongly criticised by evolutionary biologists. </p>
<p><a href="http://doi.org/10.1016/j.shpsc.2004.09.007">Perhaps</a> under the influence of anti-communist sentiment linked to the <a href="https://www.history.com/topics/cold-war/cold-war-history">cold war</a> between the Soviet Union and the US, biologists argued that prudent predation would require evolution to act on groups rather than single individuals of a species – and that such “<a href="https://doi.org/10.1002/cplx.20209">group selection</a>” was unlikely to occur. </p>
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<img alt="Male lion on grass with wildebeests in the background." src="https://images.theconversation.com/files/449199/original/file-20220301-19-ffsknh.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/449199/original/file-20220301-19-ffsknh.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=498&fit=crop&dpr=1 600w, https://images.theconversation.com/files/449199/original/file-20220301-19-ffsknh.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=498&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/449199/original/file-20220301-19-ffsknh.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=498&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/449199/original/file-20220301-19-ffsknh.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=626&fit=crop&dpr=1 754w, https://images.theconversation.com/files/449199/original/file-20220301-19-ffsknh.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=626&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/449199/original/file-20220301-19-ffsknh.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=626&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">Predators must avoid overexploiting their prey if they are to survive.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/jonasb/6987003364/in/photolist-bDqdFf-2H3ZAk-5969fe-9eTf4e-5tpw1a-eka8x-eka6T-5tu5yQ-hj8ytR-5tpEzz-37FN4s-8mxDou-9hP4V-79WA6M-5tu6Ly-eka73-beWr4i-beX7TR-piLQnr-79X5yR-eka7w-hj7eFK-bSksur-hj8y7D-5tyvKF-mojYV-5tyyTe-DaRbXE-5tCS6J-5kzbnm-6qhqqb-5tCRiU-5tCUD7-peLRRb-nwoD13-37BcvF-5tywxH-e262h5-7qmBzX-3516kY-bCQC6h-bSkuXi-2hPTJNs-a5rz64-mojZQ-8V4TR3-4N3LEE-5kZPSQ-brdbrs-5rfRdN/">Jonas Bengtsson/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
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<p>Although modern evolutionary theory has moved beyond this <a href="https://doi.org/10.1016/j.tree.2011.01.006">dichotomy</a> between individual and group selection, scepticism about the latter – and about prudent predation – <a href="https://www.researchgate.net/publication/228465713_Truth_and_reconciliation_for_group_selection">lingers</a> among many scientists.</p>
<p>However, in a recent <a href="http://doi.org/10.1111/ele.13979">study</a> published in Ecology Letters, my colleagues and I show – using complex predator-prey models – how this delicate equilibrium between predator and prey could have evolved.</p>
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<a href="https://theconversation.com/explainer-theory-of-evolution-2276">Explainer: Theory of evolution</a>
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<p>Prudent predation means that a predator species has evolved to avoid consuming as much and as aggressively as its own physical limits permit. Effectively – though not knowingly – prudent predators are restraining themselves for the benefit of other members of their species, as well as for future generations.</p>
<p>Even when predators are prudent in their natural habitat, they may overexploit the prey around them if they are moved to places where they don’t belong. An example is the <a href="https://aquadocs.org/bitstream/handle/1834/30743/etd.pdf?sequence=1&isAllowed=y">Indo-Pacific lionfish</a>, whose populations have rapidly <a href="https://oceanservice.noaa.gov/facts/lionfish-facts.html">expanded</a> in and around the Gulf of Mexico and the eastern Mediterranean Sea. </p>
<p>Lionfish feed on smaller fish and shellfish that live in reefs. They are such ferocious predators that ecologists became concerned that, especially in the Gulf of Mexico, few other fish species would survive their presence. Instead, something else happened.</p>
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<img alt="A red lionfish swims" src="https://images.theconversation.com/files/446742/original/file-20220216-17-1uxlnra.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/446742/original/file-20220216-17-1uxlnra.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/446742/original/file-20220216-17-1uxlnra.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/446742/original/file-20220216-17-1uxlnra.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/446742/original/file-20220216-17-1uxlnra.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/446742/original/file-20220216-17-1uxlnra.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/446742/original/file-20220216-17-1uxlnra.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">
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<span class="caption">Invasive lionfish endanger their own colonies when they consume too much prey.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Red_lionfish_near_Gilli_Banta_Island.JPG">Alexander Vasenin/Wikimedia</a></span>
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<p>Lionfish populations suddenly began falling in Gulf of Mexico reefs, while their native competitors remained. It appears that, because lionfish overexploit their prey, they are not such strong competitors after all. </p>
<p>These dwindling lionfish populations are therefore experiencing evolutionary pressure to feed less ferociously, so they can occupy reefs longer and have more opportunities to spread to other reefs. Eventually, we expect them to adapt to their new habitat by becoming prudent predators. </p>
<h2>Implications</h2>
<p>There’s more to be learned from this than just ecology. In modern, westernised societies, there’s a deep-seated idea that everybody’s pursuit of personal benefit will ultimately benefit society as a whole. For example, CEOs of public corporations are <a href="https://doi.org/10.1007/s10551-014-2427-x">expected</a> to act for the benefit of their shareholders alone. They will not support a market competitor, even if loss of the competitor would mean less consumer choice.</p>
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Read more:
<a href="https://theconversation.com/what-does-survival-of-the-fittest-mean-in-the-coronavirus-pandemic-look-to-the-immune-system-137355">What does 'survival of the fittest' mean in the coronavirus pandemic? Look to the immune system</a>
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<p>This thinking hinges on an <a href="https://www.thefreelibrary.com/Economic+competition+and+evolution%3a+are+there+lessons+from+ecology%3f-a0115930304">analogy</a> between market economics and evolution, which both rely on the <a href="https://www.ncl.ac.uk/media/wwwnclacuk/teacherstoolkit/liviastellaputradjaja/Darwin%20theory%20survial%20of%20the%20fittest.pdf#">survival of the fittest</a>. “Survival of the fittest” refers to the principle that those variants of a gene, species, business model or technology that are best adapted to current circumstances will prevail, while others will die out.</p>
<p>Prudent predation also follows the survival of the fittest principle. However, the “fittest” organism here isn’t the one able to produce the greatest number of surviving offspring. Rather, it’s the one that succeeds in generating the greatest number of new colonies.</p>
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<img alt="A view over dark tar sands to the horizon" src="https://images.theconversation.com/files/446726/original/file-20220216-17-ccvmob.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/446726/original/file-20220216-17-ccvmob.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/446726/original/file-20220216-17-ccvmob.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/446726/original/file-20220216-17-ccvmob.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/446726/original/file-20220216-17-ccvmob.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/446726/original/file-20220216-17-ccvmob.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/446726/original/file-20220216-17-ccvmob.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">Tar sands, that damage the environment, can provide fossil fuel energy to communities thousands of miles away.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/kk/6880115375">kris krüg/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<p>Colonies of species that overexploit their resources are not fit in this sense, because they collapse before getting the chance to spread to other places. In the past, when societies weren’t globally connected, similar principles applied to human choices. Societies that overexploited their resources would eventually <a href="https://medium.com/thrice-removed/collapse-2ef6ae96bb94">collapse</a>, making room for more prudent societies to expand. </p>
<p>However, in today’s globalised world, the imprudent actions of people in one place can harm people at entirely different places. For example, the oil heating my poorly insulated home might be coming from tar sand fields polluting the environment in Canada.</p>
<p>The mechanism by which survival-of-the-fittest brings about prudence therefore cannot work any more. The analogy with nature has broken down. It can no longer support the belief that the pursuit of individual benefits will ultimately lead to balance in society and economics.</p><img src="https://counter.theconversation.com/content/176092/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Axel G. Rossberg receives funding from the UK's Natural Environment Research Council. He is chair of the International Initiative for Theoretical Ecology. </span></em></p>New research sheds light on why predators don’t evolve to become so aggressive that they eat all their prey – and then go extinct themselves.Axel G. Rossberg, Reader in Theoretical Ecology, Queen Mary University of LondonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1747372022-02-03T14:27:07Z2022-02-03T14:27:07ZFig wasp sex ratios show that not all of nature is by design<figure><img src="https://images.theconversation.com/files/440616/original/file-20220113-19-1c80d6.png?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A female pollinating wasp, _Platyscapa awekei_, which pollinates the Wonderboom fig, a famous fig tree in South Africa.</span> <span class="attribution"><span class="source">Simon van Noort</span></span></figcaption></figure><p>In his 1859 book, <a href="https://www.britannica.com/biography/Charles-Darwin/On-the-Origin-of-Species">On the Origin of Species</a>, British naturalist Charles Darwin put forward his theory of natural selection. This, he argued, was the mechanism of biological evolution: like an animal or plant breeder selects for certain characteristics, individuals with better survival ability leave more offspring. In this way nature favours traits that increase the survival of organisms. These traits are called adaptations. For instance the internal structure of an eye, comprising a lens and a light-sensitive retina, leaves little doubt that the organ is an adaptation for vision. When viewed from outside science, adaptations appear to have been designed. </p>
<p>However, animals and plants often have characteristics perceived as advantageous, but for which there is no evidence of evolutionary adaptation. The red colour of blood has some advantages – it allows humans to rapidly notice and react to injuries – but there’s no evidence that the colour is an adaptation or has been designed. Rather it is the fortuitous biochemical consequence of an iron molecule bound to each haemoglobin molecule in the blood.</p>
<p>Assuming that natural selection shapes all animal and plant traits is a false impression. Natural selection is <a href="https://evolution-outreach.biomedcentral.com/articles/10.1186/s12052-020-00130-y">not all-encompassing</a>.
Since humans are largely predisposed to see purpose and design, it may be hard to understand traits that appear to have been designed, but which just came about by chance. In a <a href="https://frontiersinzoology.biomedcentral.com/articles/10.1186/s12983-021-00447-4">recent article</a>, we showed that what seemed to be an example of adaptation – variation in female-biased sex-ratios of fig wasps – is in fact not.</p>
<h2>Imperfection in nature</h2>
<p>Fig wasps are tiny insects (about 2mm long) that <a href="http://figweb.org/Interaction/index.htm">pollinate fig trees</a>. Fig wasp sex ratios have been touted as one of <a href="https://era.ed.ac.uk/bitstream/handle/1842/480/WestHerreSheldon00.PDF?sequence=1&isAllowed=y">the best examples</a> of natural selection’s effectiveness. Only one or a few mothers lay eggs in a single fig, in which mating between offspring also takes place. When only one mother occupies a fig, about 10% of her offspring are sons. In line with predictions, when more mothers lay their eggs in a fig, they lay a larger percentage of sons to use the mating opportunities provided by the daughters of other mothers. By varying the percentage of sons the mothers’ number of grandchildren can be maximised. </p>
<p><a href="https://frontiersinzoology.biomedcentral.com/articles/10.1186/s12983-021-00447-4">Our research</a> debunks this notion. We reviewed sex ratios in 24 species of fig wasps and found that mothers sharing a fig with other mothers laid fewer sons than would be expected if this were an adaptation. Although the ratio of sons to daughters increases with the number of mothers, as theory suggests, the increase is significantly smaller than predicted.</p>
<p>This sort of work is important as it reminds scientists that apparent adaptations may merely be fortuitous consequences. It is a reminder that sometimes there is no point or evolutionary purpose of animal characteristics, even when it looks that way – natural selection is not the only process that changes species. </p>
<h2>Sex ratios in single mother broods</h2>
<p>Some species, resistant to the ill effects of inbreeding, have very female-biased sex-ratios. The British evolutionary theorist William Hamilton argued in 1967 that this is expected when one or a few mothers of a species such as wasps lay eggs in isolated patches and matings among offspring are restricted to within these patches. </p>
<p>Changing the sex ratio of offspring does not affect a mother’s number of offspring; it does, however, change her expected number of grandchildren. By laying more daughter eggs rather than son eggs, the competition between brothers is reduced and there are more mating opportunities for the remaining sons. Since a single son can fertilise many daughters, selection favours a mother that lays just a sufficient number of male eggs to fertilise all her daughters – a heavily female-biased sex-ratio. Fig wasps represent one such group of species.</p>
<h2>Broods involving several mothers</h2>
<p><a href="https://pubmed.ncbi.nlm.nih.gov/17815055/">Research</a> in the 1980s <a href="https://pubmed.ncbi.nlm.nih.gov/28561492/">established</a> that single mothers in a patch have more daughters than each mother in a patch with two mothers, who in turn have more daughters than each mother in a patch with three mothers. Even though they have fewer daughters, they still have more daughters than sons. The theoretical benefit of the reduction in female bias stems from the mother’s sons competing less with each other and more with other males, and from a son benefiting from fertilising other females’ many daughters. </p>
<p><a href="https://frontiersinzoology.biomedcentral.com/articles/10.1186/s12983-021-00447-4">We reviewed</a> sex ratios in 24 fig wasp species that have been studied. We found that although the ratio of sons to daughters increased with the number of mothers in each fig, as theory suggests, the increase was significantly smaller than predicted.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/442217/original/file-20220124-15-7vo28w.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/442217/original/file-20220124-15-7vo28w.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=518&fit=crop&dpr=1 600w, https://images.theconversation.com/files/442217/original/file-20220124-15-7vo28w.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=518&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/442217/original/file-20220124-15-7vo28w.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=518&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/442217/original/file-20220124-15-7vo28w.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=651&fit=crop&dpr=1 754w, https://images.theconversation.com/files/442217/original/file-20220124-15-7vo28w.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=651&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/442217/original/file-20220124-15-7vo28w.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=651&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The percentage of sons given a certain number of mothers in a fig. Model predictions in black and the observed percentages in red. The circle, square and triangle distinguish three species.</span>
<span class="attribution"><a class="source" href="https://frontiersinzoology.biomedcentral.com/articles/10.1186/s12983-021-00447-4">From https://frontiersinzoology.biomedcentral.com/articles/10.1186/s12983-021-00447-4</a></span>
</figcaption>
</figure>
<p>Mother fig wasps tend to lay most of their sons first, followed by mostly daughters. In wasps unfertilised eggs develop into males and fertilised eggs into daughters. When there are several mothers in a single fig, egg-laying sites (the small flowers inside a fig) become limited and mothers cannot lay all their eggs. Since these unlaid eggs would have been daughter eggs, the ratio of sons to daughters increases automatically.</p>
<p>Since these unlaid eggs would have been daughter eggs, the ratio of sons to daughters increases automatically. In about half the studied fig wasp species this mechanism is sufficient to explain skewed sex ratios in these wasps. In the other half of the studied fig wasp species, mothers actually increase the number of sons as if they sense other mothers. However, despite this change, there are still fewer sons per daughter as compared to theory involving adaptation.</p>
<p>So although natural selection could favour the observed shift in sex ratios, there is no evidence that it is the result of natural selection. This is a good example of a trait that appears to be adaptive, but is not. Our review suggests that even apparently “designed” traits may not be the result of natural selection – instead they may be be fortuitously advantageous consequences.</p><img src="https://counter.theconversation.com/content/174737/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jaco Greeff received funding from the National Research Foundation to study sex ratios.</span></em></p><p class="fine-print"><em><span>Jan Willem Helenus Ferguson 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>Assuming that natural selection shapes all animal and plant traits is a false impression. Natural selection is a mindless process.Jaco Greeff, Professor in Genetics, University of PretoriaJan Willem Helenus Ferguson, Emeritus Professor, University of PretoriaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1609372021-05-18T16:18:07Z2021-05-18T16:18:07ZIncest isn’t a taboo in the animal kingdom – new study<figure><img src="https://images.theconversation.com/files/401261/original/file-20210518-17-z7s0r5.jpeg?ixlib=rb-1.1.0&rect=7%2C0%2C2578%2C1624&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-illustration/lovemaking-ladybugs-couple-on-dewy-grass-70632820">Kletr/Shutterstock</a></span></figcaption></figure><p>We humans tend to regard incest as <a href="https://www.theguardian.com/lifeandstyle/2002/jan/09/familyandrelationships.features103">deeply disturbing</a>. It’s a strong <a href="https://theconversation.com/the-greatest-taboo-the-surprising-truth-of-what-the-bible-says-about-incest-57693">social taboo</a>, and it’s underpinned by sound biological reasoning. Mixing genes with a non-relative is beneficial because it increases genetic diversity, while <a href="https://www.bbcearth.com/news/what-are-the-effects-of-inbreeding">genetic defects</a> often occur in the offspring of related parents.</p>
<p>We’d expect to see the same attitude extend to animals, who may lack a social distaste for incest but are, in the end, subject to the same biological pressures to produce the fittest offspring – which we assume means <a href="https://www.sciencedirect.com/science/article/abs/pii/0169534796100288">breeding with an unrelated mate</a>.</p>
<p>But <a href="https://www.nature.com/articles/s41559-021-01453-9">our recent study</a> has called this assumption into question. We reviewed 40 years of scholarship on animal mate selection, and found that animals don’t tend to differentiate between relatives and non-relatives when choosing a mate. </p>
<p>This may seem surprising or unsettling, but evolutionary theorists have pointed out for decades that inbreeding <a href="https://onlinelibrary.wiley.com/doi/10.1111/j.0014-3820.2006.tb01128.x">is not always bad</a> – and that in some cases, for instance where mate choice is limited, it might even be beneficial.</p>
<h2>Selecting a mate</h2>
<p>Animals account for a variety of factors when <a href="https://www.sciencedirect.com/science/article/abs/pii/0169534796100501">choosing a mate</a>. One of them is their degree of relatedness, but animals are also interested in the resources the partner can provide, and whether they carry desirable genes.</p>
<p>Choosing an unrelated mate is attractive, seeing as it increases the <a href="https://www.nature.com/articles/nrg.2016.58">genetic diversity</a> of the resultant offspring. Mating with a relative, on the other hand, increases the likelihood that parents will pass <a href="https://www.bbcearth.com/news/what-are-the-effects-of-inbreeding">rare genetic diseases</a> to their offspring. </p>
<p>This happens because <a href="https://pubmed.ncbi.nlm.nih.gov/25608820/">half of the offspring’s genes</a> come from each parent. Usually, if a parent carries a gene for a rare genetic disease, the other parent will carry the healthy version of that gene, which is then expressed in their offspring. But when parents are related, there’s a higher chance that both parents will carry the same unhealthy genes, which the offspring must then inherit.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-animal-genes-go-into-battle-to-dominate-their-offspring-82417">How animal genes go into battle to dominate their offspring</a>
</strong>
</em>
</p>
<hr>
<p>So there are strong reasons for animals to avoid mating with a relative – but are there any situations where inbreeding might actually be beneficial? </p>
<h2>Mating with a relative</h2>
<p>One obvious scenario in which animals mate with their relatives is when there’s just no other option. If animals are compelled to pass on their genes, you’d expect they’d prefer to produce offspring with a relative than to not reproduce at all.</p>
<p>But there could also be a more counter-intuitive reason behind some animal inbreeding. As Richard Dawkins set out in <a href="https://www.nature.com/articles/529462a">The Selfish Gene</a>, animals want to pass on as many of their genes as possible. From this perspective, the more genes an animal passes on to the next generation, the better they do. </p>
<p>Mating with a relative can be a great way to do this. Because so many genes are shared between relatives, a higher proportion of both of their genes will be passed on to the next generation if they do mate – a win for their genetic legacy.</p>
<p>Animals who avoid inbreeding also have to expend energy to do so, including when they learn how to distinguish relatives from unrelated individuals. Saving energy is sometimes crucial for an animal’s survival – and by extension the survival of their genes – so learning to avoid inbreeding may not always be <a href="https://www.sciencedaily.com/releases/2016/09/160928083012.htm">the best strategy</a> for some animals.</p>
<figure class="align-center ">
<img alt="Two monkeys hugging on a tree branch" src="https://images.theconversation.com/files/401263/original/file-20210518-17-7edcxs.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/401263/original/file-20210518-17-7edcxs.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/401263/original/file-20210518-17-7edcxs.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/401263/original/file-20210518-17-7edcxs.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/401263/original/file-20210518-17-7edcxs.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/401263/original/file-20210518-17-7edcxs.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/401263/original/file-20210518-17-7edcxs.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">In harsh environments, animals may benefit from being less picky in their choice of mate.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/two-monkey-friends-on-tree-110270648">Hung Chung Chih/Shutterstock</a></span>
</figcaption>
</figure>
<h2>Measuring inbreeding</h2>
<p>Theoretical scientists have used <a href="https://global.oup.com/academic/product/modeling-evolution-9780199571147?cc=ro&lang=en&">mathematical modelling</a> to predict how animals should behave in different scenarios, weighing up the costs and benefits of their actions.</p>
<p>When applied to inbreeding, the costs include the risk of passing on rare genetic diseases or defects, while the benefits include passing on genes more efficiently – as well as increasing mating opportunities. Even when accounting for <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6435235/">other factors</a> such as habitats and population size, the models have concluded that tolerating inbreeding is the most successful strategy for animals to employ. </p>
<p>This hypothesis has been experimentally tested in a wide variety of animal species, from <a href="https://www.sciencedirect.com/science/article/abs/pii/S0921448809000613">mammals</a> down to the <a href="https://www.sciencedirect.com/science/article/abs/pii/S0003347212003715">fruit fly</a>. In these experiments, animals are given the option to mate with a relative or an unrelated individual, with researchers looking out for a trend or bias.</p>
<p>These studies also account for another dimension to mate selection. While animals choose who they copulate with, they also have some control over the subsequent fertilisation. Males can <a href="https://royalsocietypublishing.org/doi/abs/10.1098/rspb.2004.2843">influence the sperm</a> they allocate to females, while females that mate with more than one partner can influence whether <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/jeb.12545">sperm from related or unrelated males</a> fertilises their eggs. This has been observed in a wide range of animals, from <a href="https://royalsocietypublishing.org/doi/10.1098/rsbl.2007.0578">insects</a> to <a href="https://pubmed.ncbi.nlm.nih.gov/18081715/">mammals</a>. </p>
<p>Over the past 40 years, these choices – mate selection both before and after mating – have been observed in 139 individual studies of 88 different species. But we’ve always missed the big picture of whether animals generally tend to avoid mating with their relatives.</p>
<h2>Reviewing the literature</h2>
<p><a href="https://www.nature.com/articles/s41559-021-01453-9">Our study</a> provides that picture, finding no evidence that animals differentiate between related and unrelated individuals when given a choice of mate. Not all species have been studied for inbreeding, but our study did include a broad range of species – from <a href="https://academic.oup.com/mollus/article/82/1/213/2460032">snails</a> and <a href="https://academic.oup.com/biolinnean/article/98/4/851/2448054">spiders</a> to <a href="https://academic.oup.com/biolinnean/article/120/4/762/2929386">fish</a>, <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1439-0310.1981.tb01922.x">birds</a>, <a href="https://www.pnas.org/content/97/7/3324">rodents</a> and <a href="https://www.sciencedirect.com/science/article/abs/pii/S0921448809000613">other mammals</a>.</p>
<p>This finding was consistent for males and females and across a range of experimental conditions. Inbreeding avoidance occurred in just 17% of the 139 studies we reviewed. It seems the evolutionary theorists were right.</p>
<p>It’s important to note that the experiments we reviewed were conducted in controlled laboratory settings. Animals living in the wild face very different challenges and conditions to those living under laboratory conditions – which could influence how they choose a mate.</p>
<p>Today’s animal conservation efforts aim to boost the population size of endangered species, mating unrelated individuals in order to increase the species’ genetic diversity. A famous example is China’s <a href="https://www.nationalgeographic.com/animals/article/151215-giant-pandas-animals-science-mating-sex-china">giant panda</a>, which has proven difficult to encourage to mate. </p>
<p>Our study suggests that conservation efforts shouldn’t <a href="https://www.nature.com/articles/ncomms10125">focus solely on mating unrelated individuals</a>. Given a choice, animals may well opt to mate with a relative. And while this would be bad news for genetic diversity, it would at least produce a new generation.</p><img src="https://counter.theconversation.com/content/160937/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Raïssa de Boer received funding from the Carl Tryggers Foundation (17:152). </span></em></p><p class="fine-print"><em><span>Regina Vega Trejo receives funding from the Swedish Research Council 2017-04957. </span></em></p>Reviewing studies of 88 species, researchers found little evidence that animals avoid inbreeding.Raïssa de Boer, Researcher & Computer Scientist, Rheumatology, Lund UniversityRegina Vega Trejo, Postdoctoral Research Associate, Department of Zoology, Stockholm UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1533022021-01-19T19:07:10Z2021-01-19T19:07:10ZFamily matters: why people can hold political views that disadvantage their own sex<p>The views of women and men can differ on important gendered issues such as abortion, gender equity and government spending priorities. Surprisingly, however, average differences in sex on this front are usually small. Many women adopt social and political positions that favour men and many men favour women-friendly positions. </p>
<p>In our <a href="https://doi.org/10.1016/j.evolhumbehav.2020.12.002">latest research</a> we tried to make sense of this “paradox”. We did so by understanding how people’s politics and practices don’t just track what’s good for them, but also what’s good for their relatives. </p>
<h2>Election campaign games</h2>
<p>A mere three days after his 2016 inauguration, US President Donald Trump reinstated the Mexico City policy, also called the “<a href="https://www.hrw.org/news/2018/02/14/trumps-mexico-city-policy-or-global-gag-rule">global gag rule</a>” — which Joe Biden is expected to <a href="https://www.devex.com/news/biden-said-he-ll-rescind-the-global-gag-rule-what-then-98582">rescind</a> soon after being inaugurated this week.</p>
<p>The rule denies US health funding to foreign non-governmental organisations that provide abortions, refer patients for abortions, offer abortion-related counselling or advocate for more liberal abortion laws.</p>
<p>It wasn’t just Trump’s haste to reinstate the rule that galled pro-choice Americans. It was also the <a href="https://www.theguardian.com/commentisfree/2017/jan/24/photo-trump-womens-rights-protest-reproductive-abortion-developing-contries">supporting cast of men</a> Trump lined up for the photo-op.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/378985/original/file-20210115-13-1dqki0a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/378985/original/file-20210115-13-1dqki0a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/378985/original/file-20210115-13-1dqki0a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=311&fit=crop&dpr=1 600w, https://images.theconversation.com/files/378985/original/file-20210115-13-1dqki0a.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=311&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/378985/original/file-20210115-13-1dqki0a.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=311&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/378985/original/file-20210115-13-1dqki0a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=391&fit=crop&dpr=1 754w, https://images.theconversation.com/files/378985/original/file-20210115-13-1dqki0a.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=391&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/378985/original/file-20210115-13-1dqki0a.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=391&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">One of the first executive orders that Donald Trump signed was to reinstate the Mexico City Policy (also called the ‘global gag order’), concerning non-governmental organisations and abortion access.</span>
<span class="attribution"><span class="source">Donald J. Trump/Facebook</span></span>
</figcaption>
</figure>
<p>Access to abortion is seen as a women’s issue as it impinges on women’s bodily autonomy and reproductive <a href="https://www.amnesty.org/en/what-we-do/sexual-and-reproductive-rights/">rights</a>. Had Trump not been <a href="https://www.pewresearch.org/fact-tank/2016/11/09/behind-trumps-victory-divisions-by-race-gender-education/">appealing to male voters</a>, he could have gathered several prominent anti-choice women to stand behind him instead.</p>
<p>But despite expectations and rhetoric, support for abortion is far more complicated than a simple tussle between the interests of women and men. </p>
<h2>Think of the children</h2>
<p>Polling conducted in the US by <a href="https://news.gallup.com/poll/244709/pro-choice-pro-life-2018-demographic-tables.aspx">Gallup</a> between 2018 and 2020 found 49% of men and 46% of women identified as “pro-life”. A similar gap was observed between “pro-choice” men and women, at 46% and 48% respectively.</p>
<p>“Pro-choice” policies give women options to control their own reproduction and, therefore, an important part of their lives. It would seem rational then for women to support these policies more than men. </p>
<p>Other policies relating to gender equity, sexual harassment, health-care spending and education also impact women and men differently. And while both genders’ views on these topics differ, the difference is quite small on average – in the order <a href="https://www.sciencedirect.com/science/article/pii/S1090513820301495#bbb0110">of 5%</a>.</p>
<p>Variation of social and political views <em>within</em> a sex group is actually far greater. While this is commonly thought to be due to differences in experience, we wanted to know whether the composition of a person’s family might change their views.</p>
<p>Our line of inquiry was inspired by a range of studies that have shown a child’s gender can change their parents’ views. </p>
<p>For instance, firms led by male CEOs with daughters tend to adopt more socially and environmentally-progressive <a href="https://www.sciencedirect.com/science/article/pii/S1090513820301495#bbb0070">corporate policies</a>. They’re also more likely to appoint <a href="https://www.sciencedirect.com/science/article/pii/S1090513820301495#bbb0075">female directors</a> and hire <a href="https://www.sciencedirect.com/science/article/pii/S1090513820301495#bbb0160">female partners</a>, with positive effects on firm performance. </p>
<p>On the other hand, male CEOs of Danish firms who <a href="https://doi.org/10.1177/0001839212466521">fathered a son</a>, rather than a daughter, paid their employees less generously and paid themselves more generously.</p>
<p>A similar pattern emerges in politics. In the US, legislators <a href="https://www.sciencedirect.com/science/article/pii/S1090513820301495#bbb0330">with daughters</a> are more likely to vote for “pro-woman” laws than those with sons. And in both the <a href="https://www.sciencedirect.com/science/article/pii/S1090513820301495#bbb0320">US and Canada</a>, parents with daughters favour gender equity more than those with sons.</p>
<p>Sometimes the effects become visible even before offspring have had much chance to experience the world.</p>
<p><a href="https://www.sciencedirect.com/science/article/pii/S1090513820301495#bbb0295">In one study</a>, the birth of a son caused parents’ voting intentions to swerve immediately to the right, while a daughter prompted a swerve to the left. In another, the effects kicked in as soon as the parents learned their child’s sex at a <a href="https://www.sciencedirect.com/science/article/pii/S0167629617304538">prenatal ultrasound</a>. </p>
<h2>How your family’s composition can impact you</h2>
<p>Research <a href="https://www.sciencedirect.com/science/article/pii/016230959290006P">published in 1992</a> found people’s attitudes towards abortion varied depending on how many of their female relatives were in the age group considered “at risk” of unwanted pregnancy.</p>
<p>The more female relatives someone had aged between 15–50, the more likely they were to favour pro-choice policies. In turn, the more male relatives they had of a reproductive age, the more likely they were to support pro-life policies. </p>
<p>This study inspired us to consider whether gendered issues might depend not only on an individual’s own sex, but also the sex composition of their family. Humans, like other animals, are more invested in their close genetic relatives.</p>
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Read more:
<a href="https://theconversation.com/origins-of-altruism-why-hamilton-still-rules-50-years-on-27223">Origins of altruism: why Hamilton still rules 50 years on</a>
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<p>We propose a new metric called “gendered fitness interests”. This not only looks at how many genetic relatives of each sex a person has, but also how closely related they are and how many potential reproductive years remain for them.</p>
<p>People with many close, younger female relatives (such as daughters and sisters) have a pro-female bias, while those with plenty of young brothers, sons or grandsons have a bias that favours males. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/379404/original/file-20210119-24-wggy42.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Outdoors, a woman kneels by her young daughter wearing a backpack." src="https://images.theconversation.com/files/379404/original/file-20210119-24-wggy42.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/379404/original/file-20210119-24-wggy42.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/379404/original/file-20210119-24-wggy42.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/379404/original/file-20210119-24-wggy42.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/379404/original/file-20210119-24-wggy42.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/379404/original/file-20210119-24-wggy42.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/379404/original/file-20210119-24-wggy42.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">For parents, few things are as important as the wellbeing of their children. So it’s reasonable a child’s gender may impact how their parents feel about certain gendered issues.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>For her PhD studies at the University of New South Wales, <a href="https://sites.google.com/view/malekefourati/home">Maleke Fourati</a> gathered data on attitudes towards Islamic veiling practices in Tunisia — specifically on mandatory veiling — which provided an <a href="https://www.sciencedirect.com/science/article/pii/S109051381730363X">early test</a> of our idea of gendered fitness interests.</p>
<p>As predicted, men were more likely than women to support mandatory veiling. But women with more sons were more likely to wear veils themselves and to think other women should too. These mothers, we argue, take this position as it serves their sons over their daughters-in-law.</p>
<p>In our <a href="https://doi.org/10.1016/j.evolhumbehav.2020.12.002">model</a>, sex differences in social and political attitudes are likely to be greatest in young adulthood, when a person’s own gender impacts them greatly. However, as an individual’s potential to have children diminishes, their current children and other relatives start to have a greater influence. Since most people have a balance of male and female relatives, this means a shift towards the centre.</p>
<h2>Separating sex from identity</h2>
<p>The web of conflicting interests that give shape to our social and political attitudes is never easy to trace and there are always multiple factors at play. </p>
<p>Perhaps the most interesting implication of our proposal is it undermines the idea that the interests of women and men sit at odds with one another. Some individuals’ values will align more with the opposite sex than with their own, weakening the importance of gender as a distinct part of social and political identity.</p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/expanding-the-definition-of-family-to-reflect-our-realities-131743">Expanding the definition of family to reflect our realities</a>
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<img src="https://counter.theconversation.com/content/153302/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Rob Brooks receives funding from the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Khandis R Blake receives funding from the Australian Research Council and is an adjunct lecturer in the School of Biological, Earth and Environmental Sciences at UNSW Sydney.</span></em></p>According to this theory, our social and political views can be impacted not only by the sex of our children, but also whether we have more male or female relatives.Rob Brooks, Scientia Professor of Evolutionary Ecology; Academic Lead of UNSW's Grand Challenges Program, UNSW SydneyKhandis R Blake, Lecturer in Psychology, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1395602020-06-02T20:02:31Z2020-06-02T20:02:31ZA 515 million-year-old freeloader: this nutrient-stealing marine worm is the oldest known parasite<figure><img src="https://images.theconversation.com/files/339052/original/file-20200602-95018-ht3j2w.png?ixlib=rb-1.1.0&rect=9%2C23%2C3185%2C1772&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption"></span> <span class="attribution"><span class="license">Author provided</span></span></figcaption></figure><p>The COVID-19 outbreak has put into stark relief the disruption parasites can cause, both in human society and ecosystems. </p>
<p>Researchers have long sought to better understand the evolutionary importance of parasites, to help lessen their impact. </p>
<p>Although parasites are <a href="https://www.sciencedirect.com/science/article/pii/B9780080454054005267">common in modern ecosystems</a>, we actually know little about parasitism in the distant past. And <em>when</em> parasites first evolved remains a mystery.</p>
<p>But our research, published today in <a href="https://doi.org/10.1038/s41467-020-16332-3">Nature Communications</a>, brings us one step closer to an answer, as we document the oldest known example of a parasite-host relationship. </p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/2WoQkcaCYdE?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">This clip provides a 3D rendering of what brachiopods may have looked like on the seafloor.</span></figcaption>
</figure>
<h2>The tricky task of identifying parasitism</h2>
<p>Parasitism is typically defined as an ongoing relationship in which one organism, the parasite, increases its own success by exploiting another organism known as the host. </p>
<p>Importantly, parasitism is a form of symbiosis. Symbioses are commonly thought of as positive partnerships. For instance, the relationship between coral polyps and microscopic algae that is <a href="https://advances.sciencemag.org/content/2/11/e1601122.full">crucial to the formation of coral reefs</a> benefits both organisms. </p>
<p>However, the term symbiosis can be applied to <em>any</em> persistent relationship between organisms. In the case of parasitism, the parasite always benefits while the host is harmed.</p>
<p>This definition of parasitism is perhaps one of the reasons why the history of parasites remains relatively unknown. </p>
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<strong>
Read more:
<a href="https://theconversation.com/why-evolution-must-be-at-the-centre-of-fighting-parasitic-infections-55880">Why evolution must be at the centre of fighting parasitic infections</a>
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<p>Much of our understanding of the evolution of life comes from the fossil record. And although fossils provide abundant evidence of evolutionary and ecological change, evidence of direct interaction between fossil organisms is less likely to be preserved. It’s often difficult to demonstrate a suspected fossil parasite was actually exploiting a host. </p>
<p>Also, many parasites that live inside a host – including bacteria and viruses – are unlikely to be fossilised as they often decompose too quickly to be preserved.</p>
<h2>The origins of parasitism</h2>
<p>Despite these issues, there are demonstrated examples of fossil parasites. </p>
<p>And <a href="https://doi.org/10.1038/s41467-020-16332-3">our latest findings</a> have identified the earliest parasite-host interaction in the fossil record.</p>
<p>We examined exquisitely preserved, 515-million-year-old fossils from southern China belonging to organisms called <a href="https://www.bgs.ac.uk/discoveringGeology/time/fossilfocus/brachiopod.html">brachiopods</a> (<em>Neobolus wulongqingensis</em>). Brachiopods are marine invertebrates that resemble clams but are actually quite different. They are rare today, but were much more common in the geological past. </p>
<p>Our research revealed the hardened tubes encrusting the surface of fossil brachiopod shells were once occupied by parasitic worms. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/338761/original/file-20200601-83264-9ihqa8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/338761/original/file-20200601-83264-9ihqa8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=480&fit=crop&dpr=1 600w, https://images.theconversation.com/files/338761/original/file-20200601-83264-9ihqa8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=480&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/338761/original/file-20200601-83264-9ihqa8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=480&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/338761/original/file-20200601-83264-9ihqa8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=603&fit=crop&dpr=1 754w, https://images.theconversation.com/files/338761/original/file-20200601-83264-9ihqa8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=603&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/338761/original/file-20200601-83264-9ihqa8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=603&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">Fossil of brachiopod shell (<em>Neobolus wulongqingensis</em>). The tubes on the shell surface would have been occupied by parasitic worms.</span>
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<p>We know the worms were parasites because we identified a clear negative effect on the host, as brachiopods without parasites grew larger than those with them. </p>
<p>While the parasites in question were almost certainly worms, we don’t know exactly what type of worm. What we do know is the worm would have been attached to its host brachiopod for its entire life. </p>
<p>Based on the orientation of the tubes, we also know the worms were <a href="https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/kleptoparasitism">kleptoparasites</a>, meaning they stole food from the host before it could be ingested. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/338762/original/file-20200601-83297-o9jwq.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/338762/original/file-20200601-83297-o9jwq.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=516&fit=crop&dpr=1 600w, https://images.theconversation.com/files/338762/original/file-20200601-83297-o9jwq.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=516&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/338762/original/file-20200601-83297-o9jwq.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=516&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/338762/original/file-20200601-83297-o9jwq.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=649&fit=crop&dpr=1 754w, https://images.theconversation.com/files/338762/original/file-20200601-83297-o9jwq.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=649&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/338762/original/file-20200601-83297-o9jwq.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=649&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">A reconstruction of <em>Neobolus wulongqingensis</em> with parasites on the surface of the shell.</span>
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<p>Other remarkable discoveries of parasites in the fossil record include spiral-shaped bacteria, almost identical to the bacteria responsible for <a href="https://www.health.nsw.gov.au/Infectious/factsheets/Pages/Lyme_disease.aspx#:%7E:text=Lyme%20disease%20is%20a%20tick,eye%20appearance%20called%20erythema%20migrans.">Lyme Disease</a>, discovered inside a 15 million-year-old <a href="https://www.livescience.com/46007-lyme-disease-ancient-amber-tick.html">fossil tick</a> entombed in amber. </p>
<p>“<a href="https://www.sciencedirect.com/science/article/abs/pii/S0065308X08603425?via%3Dihub">Tongue worms</a>” (<em>Pentastomida</em>), a parasite still found today, have a fossil record stretching back <a href="https://news.yale.edu/2015/05/21/requiem-ancient-tongue-worm">hundreds of millions of years</a>. We even have evidence of damage to dinosaur feathers <a href="https://www.nature.com/articles/s41467-019-13516-4">caused by lice</a>.</p>
<h2>An explosive period of evolution</h2>
<p>The age of these newly discovered fossil parasites coincides with what is known as the <a href="https://burgess-shale.rom.on.ca/en/science/origin/04-cambrian-explosion.php">Cambrian Explosion</a>.</p>
<p>This event began roughly 540 million years ago during the <a href="https://www.geosociety.org/GSA/Education_Careers/Geologic_Time_Scale/GSA/timescale/home.aspx">Cambrian Period</a>. It was a time of rapid evolutionary change, and includes the first appearance of animals with <a href="https://www.australasianscience.com.au/article/issue-december-2011/rapid-evolution-eyes-have-it.html">eyes</a>, <a href="https://science.sciencemag.org/content/363/6433/1338">organs and limbs</a>. </p>
<p>These changes had a marked affect on how organisms interact with each other. For example, <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/brv.12365">active predation</a> is thought to have first begun during this time. </p>
<p>Our discovery indicates parasitism is perhaps another important biological interaction that arose during this critical event.</p>
<h2>The importance of understanding the history of parasites</h2>
<p>Determining when parasites may have first evolved is the first step in understanding their impact on the history of life. </p>
<p>Many questions still remain. Perhaps the most important is <em>how</em> parasitism first evolved.</p>
<p>Some modern parasites <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5035383/">exploit multiple hosts</a> throughout their life. And many parasites that live inside a host are capable of <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4984516/">surviving without a host</a> at least part of the time. This suggests the first parasites may not have needed to rely on a single host for survival. </p>
<p>We know parasitism has <a href="https://royalsocietypublishing.org/doi/10.1098/rsbl.2016.0324">evolved multiple times</a>, and almost every animal group includes one or more parasites. </p>
<p>There are even parasitic mammals. For instance, <a href="https://www.nationalgeographic.com/animals/mammals/c/common-vampire-bat/">vampire bats</a> are considered a type of parasite. Transitioning to becoming a parasite seems to be a <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4413784/">ubiquitous evolutionary strategy</a>.</p>
<p>Parasites may have also driven major changes in evolution. The origin of sexual reproduction has been connected to the need for host organisms to <a href="https://www.pnas.org/content/pnas/87/9/3566.full.pdf">develop greater resistance to parasites</a>. Parasites also dominate food web links. In fact, parasitism may be the most common consumer strategy in <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1544067/">modern food webs</a>.</p>
<p>Nonetheless, we still don’t know how common parasites were in the past, or what innovations in life’s history occurred due to biological pressures exerted by parasites. </p>
<p>Because of this, identifying if parasitism is the cause of major evolutionary changes remains an ongoing challenge.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/bites-and-parasites-vector-borne-diseases-and-the-bugs-spreading-them-24072">Bites and parasites: vector-borne diseases and the bugs spreading them</a>
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<img src="https://counter.theconversation.com/content/139560/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Luke Strotz receives funding from a Shaanxi Province Research Grant (2019-2024) through Northwest University, Xi'an, China</span></em></p><p class="fine-print"><em><span>Glenn A Brock receives funding from the Shaanxi Provincial Recruitment Program of Global High-level Talent (2019-2022) through Northwest University, Xi'an, China </span></em></p>We studied 515 million-year-old brachiopod fossils from southern China. These marine invertebrates were common in the geological past.Luke Strotz, Professor, Northwest University, Xi'anLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1281232020-01-16T19:01:11Z2020-01-16T19:01:11ZHomosexuality may have evolved for social, not sexual reasons<figure><img src="https://images.theconversation.com/files/307834/original/file-20191219-11939-s5zoa8.jpg?ixlib=rb-1.1.0&rect=34%2C0%2C4558%2C3050&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">We propose same-sex attraction evolved to allow greater social integration and stronger same-sex social bonds. </span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/young-male-couple-holding-hands-standing-287829986">SHUTTERSTOCK</a></span></figcaption></figure><p>How did homosexuality in humans evolve? </p>
<p>Typically, <a href="https://www.ncbi.nlm.nih.gov/pubmed/19539396">this question</a> is posed as <a href="https://www.amazon.com.au/Goodness-Paradox-Evolution-Made-Violent/dp/1781255830">a paradox</a>. </p>
<p>The argument is this: gay sex alone can’t produce children, and for traits to evolve, they have to be passed onto children, who get some form of competitive advantage from them. </p>
<p>From this perspective, some argue homosexuality should not have evolved.</p>
<p><a href="https://www.frontiersin.org/articles/10.3389/fpsyg.2019.02955/full?utm_source=F-NTF&utm_medium=EMLX&utm_campaign=PRD_FEOPS_20170000_ARTICLE">In a paper published yesterday</a> by myself and Duke University professor Brian Hare, we propose human sexuality (including homosexuality) evolved as an outcome of the evolution of increased sociability in humans. </p>
<p>We argue many of the evolutionary forces that shaped human sexuality were social, rather than based on reproductive ability. </p>
<p>This is our “sociosexual hypothesis” for the evolution of gay sex and attraction. </p>
<h2>Sex for bonding</h2>
<p>For humans, and many other animals, sex is not just about reproduction. </p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/310400/original/file-20200116-181608-16veogf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/310400/original/file-20200116-181608-16veogf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/310400/original/file-20200116-181608-16veogf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=901&fit=crop&dpr=1 600w, https://images.theconversation.com/files/310400/original/file-20200116-181608-16veogf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=901&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/310400/original/file-20200116-181608-16veogf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=901&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/310400/original/file-20200116-181608-16veogf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1133&fit=crop&dpr=1 754w, https://images.theconversation.com/files/310400/original/file-20200116-181608-16veogf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1133&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/310400/original/file-20200116-181608-16veogf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1133&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Bonobos and chimpanzees share about 99.6% of their DNA with humans.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/bonobo-green-tropical-jungle-natural-background-1596689767">shutterstock</a></span>
</figcaption>
</figure>
<p><a href="https://global.oup.com/academic/product/primate-sexuality-9780199544646?cc=au&lang=en&">In our closest primate relative</a>, the bonobo, <a href="https://link.springer.com/article/10.1007%2Fs10329-010-0229-z">straight and gay sex have vital roles</a> in play, social transactions, barter of food, same-sex social bonding and bonding between mating pairs.</p>
<p>We shouldn’t limit our thinking about the evolution of sex to its reproductive functions. We must also consider its social functions.</p>
<p>Based on the social behaviour of primates (and other social mammals), we argue our species’ recent cognitive and behavioural evolution was driven by natural selection favouring traits that allowed better social integration. This is called prosociality.</p>
<p>Early humans that could quickly and easily access the benefits of group living had a strong selective advantage. We believe this led to the evolution of a whole range of traits including reduced aggression, increased communication, understanding, social play and affiliation.</p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/gay-gene-search-reveals-not-one-but-many-and-no-way-to-predict-sexuality-122459">'Gay gene' search reveals not one but many – and no way to predict sexuality</a>
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<p>Species such as the bonobo, that evolved for high prosociality, evolved to use sexual behaviour in many social contexts. This results in an increase of sex in general, greater diversity in the contexts of sex, and an increase in gay sex.</p>
<p>We believe something similar happened in recent human evolution. Gay sex and attraction may have evolved because individuals with a degree of same-sex attraction benefited from greater social mobility, integration and stronger same-sex social bonds. </p>
<p>This may sound counterintuitive, given <a href="https://journals.sagepub.com/doi/full/10.1177/1529100616637616?url_ver=Z39.88-2003&rfr_id=ori%3Arid%3Acrossref.org&rfr_dat=cr_pub%3Dpubmed">gay people are socially marginalised, ostracised and even criminalised in many societies.</a> </p>
<p>However, our argument addresses the early evolution of human sexuality, not how relatively recent phenomena like religion and religion-based legal structures have responded to sexual minorities.</p>
<h2>Supporting facts</h2>
<p>Many studies since the <a href="https://www.jstor.org/stable/j.ctt173zmgn">pioneering</a> <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1447861/">research</a> of Alfred Kinsey and colleagues have emphasised that <a href="https://journals.sagepub.com/doi/full/10.1177/1529100616637616?url_ver=Z39.88-2003&rfr_id=ori%3Arid%3Acrossref.org&rfr_dat=cr_pub%3Dpubmed">sexual minorities occur across all cultures</a>, and the levels of gay and bisexual people in populations have been quite stable over time.</p>
<p>Our hypothesis predicts that bisexuality and people who identify as “mostly straight” should be more common than people who identify as exclusively gay, <a href="https://journals.sagepub.com/doi/full/10.1177/1529100616637616?url_ver=Z39.88-2003&rfr_id=ori%3Arid%3Acrossref.org&rfr_dat=cr_pub%3Dpubmed">and this is the case</a>. </p>
<p>Recent genetic analyses confirm <a href="https://science.sciencemag.org/content/365/6456/eaat7693">hundreds of genes influence sexuality</a> in complex ways. </p>
<p>We quite randomly inherit half our genes from each parent. Each person’s genetic makeup is unique, so it would be highly unlikely to find two people with exactly the same set of genes influencing their sexuality. </p>
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Read more:
<a href="https://theconversation.com/born-this-way-an-evolutionary-view-of-gay-genes-26051">Born this way? An evolutionary view of 'gay genes'</a>
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<p>Thus, variation is expected, and individuals fall along a spectrum ranging from a majority who are straight, to a minority who identify as gay.</p>
<p>Our hypothesis for the evolution of homosexuality would predict this kind of variation in human sexuality, and can help explain why it is generally stable across cultures. </p>
<p>We believe sexuality is a highly complex trait, interwoven with sociality. Attraction, sexual behaviour, social bonds and desire all contribute to its complexity.</p>
<h2>Asking the right questions</h2>
<p>Height is another feature influenced by hundreds of genes, many of which interact with our external environments in complex ways. </p>
<p>We see a continuous variation in human height – some very tall and very short people exist. </p>
<p>We might draw on nutritional ecology to explore the evolution of human height, but would not feel the need to introduce special evolutionary arguments to explain the existence of tall or short people. </p>
<p>No special explanation is necessary. They are simply exhibiting natural, genetically influenced variations in height.</p>
<p>Similarly, we think asking how gay sex and attraction evolved is the wrong question. </p>
<p>A more useful question to ask is: how did human sexuality evolve in all its forms?</p>
<p>In doing do, we acknowledge homosexuality does not present a paradox needing a special explanation. It is simply a result of our species’ recent sociosexual evolution.</p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/gay-gene-testing-apps-arent-just-misleading-theyre-dangerous-126522">'Gay gene' testing apps aren't just misleading – they're dangerous</a>
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<img src="https://counter.theconversation.com/content/128123/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew Barron currently receives funding from Macquarie University, The Australian Research Council and the Templeton World Charity Foundation</span></em></p>Scientists don’t ask how some people evolved to be tall. In the same way, asking how homosexuality evolved is the wrong question. We need to ask how human sexuality evolved in all its forms.Andrew Barron, Professor, Macquarie UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1279252019-12-09T19:01:42Z2019-12-09T19:01:42ZWork is a fundamental part of being human. Robots won’t stop us doing it<figure><img src="https://images.theconversation.com/files/305111/original/file-20191204-70101-198v360.jpg?ixlib=rb-1.1.0&rect=8%2C0%2C5982%2C3000&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A recent study conducted by Brookings Institute researchers found artificial intelligence could "affect work in virtually every occupational group". However, it's yet to be seen exactly how jobs will be impacted. </span> <span class="attribution"><span class="source">SHUTTERSTOCK</span></span></figcaption></figure><p>Hardly a week goes by without a report announcing the end of work as we know it.</p>
<p>In 2013, Oxford University academics Carl Frey and Michael Osborne were the first to capture this anxiety in a paper titled: <a href="https://www.oxfordmartin.ox.ac.uk/downloads/academic/The_Future_of_Employment.pdf">“The Future of Employment: How susceptible are jobs to computerisation?”</a>.</p>
<p>They concluded 47% of US jobs were threatened by automation. Since then, Frey has taken <a href="https://press.princeton.edu/books/hardcover/9780691172798/the-technology-trap">multiple</a> <a href="https://www.oxfordmartin.ox.ac.uk/publications/technology-at-work-4/">opportunities</a> to repeat his predictions of major labour market disruptions due to automation. </p>
<p>In the face of threats to employment, some progressive thinkers advocate jettisoning our work ethic and building a world <a href="https://www.versobooks.com/books/2315-inventing-the-future">without work</a>. </p>
<p>If machines can do our work, why not reduce the working week drastically? We should be mature enough to decide what truly matters to us, without tying our identity to a job, or measuring happiness in dollars and professional status. Right?</p>
<p>Not quite. </p>
<p>The reality is that work is tied to our constitution as a species. And this fact is too often overlooked in discussions about the future of work. </p>
<h2>Work is a feature of the human species</h2>
<p><a href="https://www.brookings.edu/research/what-jobs-are-affected-by-ai-better-paid-better-educated-workers-face-the-most-exposure/?te=1&nl=bits&emc=edit_tu_20191122?campaign_id=26&instance_id=14021&segment_id=19015&user_id=f277084664f1238c137b66be7de11d81&regi_id=1006148832019112">Recent studies</a> have raised alarms that advances in automation and artificial intelligence (AI) will leave all sectors open to the threat of machines replacing human workers.</p>
<p>The power of AI will supposedly, according to these studies, even make high-skilled specialists redundant - threatening medical practitioners, bank associates, and legal professionals.</p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/the-benefits-of-job-automation-are-not-likely-to-be-shared-equally-90859">The benefits of job automation are not likely to be shared equally</a>
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<p>Predictions about the <a href="https://www.basicbooks.com/titles/martin-ford/rise-of-the-robots/9780465097531/">rise of the robots</a>
either take a pessimistic stance, focusing on disruptions to economic organisations, or view “<a href="https://www.cornellpress.cornell.edu/book/9781501748448/undoing-work-rethinking-community">undoing work</a>” as an opportunity to move to a fairer social model.</p>
<p>However, these views disregard the central role work has played in humanity’s development.</p>
<h2>Working on environments</h2>
<p>Philosophers including <a href="https://www.marxists.org/archive/marx/works/1867-c1/ch07.htm">Karl Marx</a>, <a href="https://www.gutenberg.org/files/26163/26163-h/26163-h.htm">Henri Bergson</a>, and <a href="http://www.gutenberg.org/ebooks/41386">John Dewey</a> argued that working is a defining trait of humans. </p>
<p>Findings over the past two decades have confirmed that features of <a href="https://australianmuseum.net.au/learn/science/human-evolution/homo-sapiens-modern-humans/">modern <em>Homo sapiens</em></a> are directly tied to their tendency to work. </p>
<p>Three basic ideas of the old philosophers are reaffirmed by contemporary research in archaeology, anthropology and genetics.</p>
<p>First, humans haven’t evolved to fit into their environments as seamlessly as other animals. Humans have had to compensate for a lack of fit. </p>
<p>They did this by learning about the ecosystems around them, the plants and animals they could eat, and the natural processes they could use, or should avoid. This knowledge was applied to create instruments, tools and weapons. </p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/resume-robot-wars-how-employees-could-match-employers-use-of-tech-in-job-applications-80615">Resume robot wars: how employees could match employers' use of tech in job applications</a>
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<p>Very early on, humans mobilised their knowledge and skills to <a href="https://islandpress.org/books/dominant-animal">shape their immediate surroundings</a> and become the dominant animal. </p>
<p>Knowledge of nature, technical skills and intervention in the environment are all characteristics of humans’ capacity to work. These allowed us to adapt to highly diverse geographies and climates.</p>
<h2>Working on ourselves, and with others</h2>
<p>Each new generation has to learn the skills and knowledge that will enable it to sustain its particular mode of survival. </p>
<p>Australian philosopher Kim Sterelny has <a href="https://mitpress.mit.edu/books/evolved-apprentice">shown in detail</a> how evolution selected genetic traits that sustain humans’ capacity to learn, specifically by enhancing social behaviour and tolerance towards the young. </p>
<p>And as humans worked on nature, they also worked in ways that influenced their minds, and <a href="https://www.octopusbooks.co.uk/titles/vybarr-cregan-reid/primate-change/9781788401081/">their bodies</a>.</p>
<p><a href="https://press.princeton.edu/books/paperback/9780691158167/a-cooperative-species">It has been demonstrated</a> that cooperation in humans reaches a level unknown in other species. This cooperative capacity has its roots in each individual’s dependency on the knowledge, skills and efforts of others. </p>
<p>No human is able to sustain themself on their own, and collaboration exceeds what each person can produce alone. Even the most brilliant astrophysicist calls the plumber to fix a broken toilet. </p>
<p>Humans have to work to survive, and this entails working with, and for, others.</p>
<h2>The future of work</h2>
<p>Acknowledging the anthropological depth of work means admitting current scenarios advocating “the end of work” are not the right answer. They take an unrealistic view of who we are. </p>
<p>We need to recognise work as a human need. <a href="https://www.marxists.org/archive/marx/works/1875/gotha/ch01.htm">As Marx said</a>: </p>
<blockquote>
<p>… labour has become not only a means of life, but life’s prime want. </p>
</blockquote>
<p>The question should not be whether there’s room for human work in an automated future. The question should be: how will human work find its place next to machines and robots?</p>
<p>Even if automation becomes widespread, we’ll still apply our minds, bodies and hands to productive tasks. We’ll still experiment and learn from others.</p>
<p>If machines could truly do all human work, then they’d make humans redundant, as <a href="https://www.sparknotes.com/lit/2001/">2001: A Space Odyssey</a> anticipated back in 1968. While this isn’t a pleasant scenario, it’s not a likely one either. </p>
<p>Automation might bring major social and economic disruptions in the short-term, but it won’t get rid of the need for humans to work. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/dont-be-alarmed-ai-wont-leave-half-the-world-unemployed-54958">Don’t be alarmed: AI won’t leave half the world unemployed</a>
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<p>Human needs are also infinitely complex. Nobody can foretell what new activities, techniques, and consequent modes of working will fulfil future needs.</p>
<p>Even if we reject the modern work ethic, we’ll still find ways to learn through action and emulate experts. </p>
<p>Human intelligence is geared towards producing useful goods, so we’ll continue to look for purposeful activities, too. And we’ll seek collaboration with others for mutual benefit. </p>
<p>This is the influence of work on us. We are heir to thousands of years of evolution, and it would be pretentious to assume evolution could stop with us.</p><img src="https://counter.theconversation.com/content/127925/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jean-Philippe Deranty receives funding from THE AUSTRALIAN RESEARCH COUNCIL. </span></em></p>As machine automation and artificial intelligence surge, there’s paranoia our jobs will be overrun by robots. But even if this happens, work won’t disappear, because humans need it.Jean-Philippe Deranty, Professor, Macquarie UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/935172018-03-28T12:57:42Z2018-03-28T12:57:42ZWould standing on the first butterfly really change the history of evolution?<figure><img src="https://images.theconversation.com/files/212431/original/file-20180328-109207-12h38q.jpg?ixlib=rb-1.1.0&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/textured-grunge-old-paper-background-boots-274803299?src=I6RQSRvM1gPTgmuOvH6rIA-1-31">Shutterstock</a></span></figcaption></figure><blockquote>
<p><strong>Martha Jones:</strong> It’s like in those films: if you step on a butterfly, you change the future of the human race.</p>
<p><strong>The Doctor:</strong> Then don’t step on any butterflies. What have butterflies ever done to you? </p>
</blockquote>
<p>Science fiction writers can’t seem to agree on the rules of time travel. Sometimes, as in Doctor Who (above), characters can travel in time and affect small events without appearing to alter the grand course of history. In other stories, such as Back To The Future, even the tiniest of the time travellers’ actions in the past produce major ripples that unpredictably change the future.</p>
<p>Evolutionary biologists have been holding a similar debate about how evolution works for decades. In 1989 (the year of Back To The Future Part II), the American palaeontologist Stephen Jay Gould published his timeless book Wonderful Life, named after <a href="http://www.imdb.com/title/tt0038650/">the classic movie</a> that also involves time travel of sorts. In it, he proposed a thought experiment: what would happen if you could replay life’s tape, rewinding the history of evolution and running it again? Would you still see the same movie with all the evolutionary events playing out as before? Or would it be more like a reboot, with species evolving in different ways?</p>
<p>Gould’s answer was the latter. In his view, unpredictable events played a major role in natural history. If you were to travel back in time and step on the first butterfly (reminiscent of the 1952 short story <a href="http://web1.nbed.nb.ca/sites/ASD-S/1820/J%20Johnston/short%20stories/A%20Sound%20of%20Thunder%20with%20questions%20--Ray%20Bradbury.pdf">A Sound of Thunder</a> by Ray Bradbury), then butterflies wouldn’t evolve ever again.</p>
<p>This is supposedly because the variation we see in nature - the many different physical features and forms of behaviour that lifeforms can have – is caused by random genetic events, such as genetic mutations <a href="https://www.nature.com/scitable/topicpage/genetic-recombination-514">and recombination</a>. Natural selection filters this variation, preserving and spreading the features that give organisms the best reproductive advantage. In Gould’s view, because the series of mutations that led to the first butterfly were random, they would be unlikely to occur a second time.</p>
<h2>Convergent evolution</h2>
<p>But not everyone agrees with this picture. <a href="https://www.templetonpress.org/books/runes-evolution">Some scientists</a> defend the idea of “convergent evolution”. This is when organisms that aren’t related to each other independently evolve similar features in response to their environment. For example, bats and whales are very different animals, but both have evolved the ability to “see” by listening to how sound echoes around them (<a href="http://www.sciencemag.org/news/2013/09/bats-and-dolphins-evolved-echolocation-same-way">echolocation</a>). Both pandas and humans have evolved <a href="https://daily.jstor.org/why-do-pandas-have-thumbs/">opposable thumbs</a>. Powered flying has evolved <a href="https://academic.oup.com/icb/article/56/5/1044/2420642">at least four times</a>, in birds, bats, pterosaurs, and insects like butterflies. And eyes have independently evolved <a href="https://www.annualreviews.org/doi/abs/10.1146/annurev.ne.15.030192.000245">at least 50 times</a> in animal history.</p>
<p>Even intelligence has evolved multiple times. The famous palaeontologist Simon Conway-Morris was once asked if dinosaurs would have become intelligent if they were still here. <a href="http://www.bbc.co.uk/news/science-environment-28488044">His answer</a> was that “the experiment has been done and we call them crows”, referring to the fact that birds, including the <a href="https://theconversation.com/clever-crows-can-plan-for-the-future-like-humans-do-80627">very intelligent crow species</a>, evolved <a href="https://theconversation.com/how-did-dinosaurs-evolve-beaks-and-become-birds-scientists-think-they-have-the-answer-84633">from a group of dinosaurs</a>.</p>
<p>Convergent evolution suggests that there are a few optimal ways in which species can adapt to their environment, which means that (if you have enough information) you could predict how a species is likely to evolve over a long time. If you were to step on the first butterfly, another butterfly-like insect will eventually evolve because other mutations will eventually produce the same features that will be favoured by natural selection.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/212433/original/file-20180328-109199-u1mzs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/212433/original/file-20180328-109199-u1mzs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/212433/original/file-20180328-109199-u1mzs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/212433/original/file-20180328-109199-u1mzs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/212433/original/file-20180328-109199-u1mzs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/212433/original/file-20180328-109199-u1mzs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/212433/original/file-20180328-109199-u1mzs.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">Gold stick spider.</span>
<span class="attribution"><span class="source">George Roderick</span></span>
</figcaption>
</figure>
<p>A <a href="http://www.cell.com/current-biology/fulltext/S0960-9822(18)30149-0?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0960982218301490%3Fshowall%3Dtrue">recent study</a> in the journal Current Biology seems to tip the scale in favour of convergent evolution. This study investigates how stick spiders have evolved in the Hawaiian Islands and provides evidence for different, isolated groups of animals evolving the same features independently.</p>
<p>Islands are often referred to as natural laboratories because they are effectively closed environments. Every time a species colonises a new island, a new independent experiment on adaptation takes place. An iconic example is the finches that have adapted to the various food sources on each island of the Galapagos, a fact that helped Charles Darwin develop his theory of natural selection. Some of these populations have even been caught in the act of becoming new <a href="http://www.bbc.co.uk/news/science-environment-42103058">species of finch</a>.</p>
<p>Most of the stick spiders on the Hawaiian Islands have gold, dark or white body colouring as camouflage to hide from predators, such as birds. The scientists used the DNA of the various spider species to reconstruct the history of how they evolved. They showed that the dark spiders and the white spiders have repeatedly evolved from ancestral gold spiders, six times in the case of the dark spiders and twice in the case of the white ones.</p>
<h2>Chance or necessity?</h2>
<p>This study is a remarkable example of convergent evolution taking place in the same geographical area. It’s reminiscent of the classic studies on <a href="http://www.cell.com/current-biology/abstract/S0960-9822(09)00722-2">Anolis lizards</a> by evolutionary ecologist Jonathan Losos, who noticed lizards on different Caribbean islands had independently evolved the <a href="http://www.sciencemag.org/news/1998/03/lizards-take-convergent-evolution-extreme">same adaptations multiple times</a>. All this suggests that lifeforms living in a specific environment over a long enough time period are likely to evolve certain features. </p>
<p>But the evidence for convergent evolution doesn’t rule out the role of chance. There is no doubt that mutations and the biological variations they create are random. Organisms are a mosaic of multiple traits, each with different evolutionary histories. And that means whatever evolved in the butterfly’s place might well not look exactly the same. </p>
<p>The evidence isn’t conclusive either way, but maybe both chance and necessity play a role in evolution. If we were to run the tape of life again, I think we would end up with the same types of organisms we have today. There would probably be primary producers extracting nutrients from the soil and energy from the sun, and other organisms that move around and eat the primary producers. Many of these would have eyes, some would fly, and some would be intelligent. But they might look quite different from the plants and animals we know today. There might not even be any intelligent two-legged mammals.</p>
<p>So just in case you ever find yourself travelling back in time, don’t step on any butterflies.</p><img src="https://counter.theconversation.com/content/93517/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jordi Paps receives funding from the University of Essex, the Royal Society, and the Wellcome Trust.</span></em></p>More and more evidence shows evolution isn’t as random as often thought.Jordi Paps, Lecturer, School of Biological Sciences, University of EssexLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/927942018-03-22T10:42:06Z2018-03-22T10:42:06ZMitochondria mutation mystery solved: Random sorting helps get rid of duds<figure><img src="https://images.theconversation.com/files/211047/original/file-20180319-31633-1sxhx6g.jpg?ixlib=rb-1.1.0&rect=2%2C16%2C590%2C453&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">When a cell divides, mitochondria are randomly allotted to the resulting new cells.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/wellcomeimages/25937295324">Odra Noel. Wellcome Images</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span></figcaption></figure><p>You probably know about the 23 pairs of chromosomes safely stowed in your cells’ nuclei. That’s where the vast majority of your genes can be found. But there are 37 special genes — a very tiny fraction of the human genome — located in mitochondria, the structures inside your cells that breathe and produce energy.</p>
<p>Repeated copying of mitochondrial DNA introduces errors; if not kept in check, these mutations can give rise to incurable diseases like <a href="https://ghr.nlm.nih.gov/condition/leigh-syndrome">Leigh syndrome</a> and <a href="https://ghr.nlm.nih.gov/condition/leber-hereditary-optic-neuropathy">Leber’s optic neuropathy</a>. Worldwide, <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4737121/">more than 1 in 10,000</a> people are affected by disorders resulting from mitochondrial genome defects.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/211067/original/file-20180319-31614-14j8noq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/211067/original/file-20180319-31614-14j8noq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/211067/original/file-20180319-31614-14j8noq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=671&fit=crop&dpr=1 600w, https://images.theconversation.com/files/211067/original/file-20180319-31614-14j8noq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=671&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/211067/original/file-20180319-31614-14j8noq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=671&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/211067/original/file-20180319-31614-14j8noq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=843&fit=crop&dpr=1 754w, https://images.theconversation.com/files/211067/original/file-20180319-31614-14j8noq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=843&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/211067/original/file-20180319-31614-14j8noq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=843&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Mitochondrial DNA is inherited only from the mother, based on what mitochondria happen to be in the egg.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Mitochondrial_DNA_lg.jpg">National Human Genome Research Institute</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Unlike nuclear chromosomes that we get from both parents, only mothers’ mitochondria are passed on to offspring. This makes the usual process of sexual recombination, in which pieces of maternal and paternal chromosomes combine to repair genome defects, impossible. For decades, biologists predicted that without this repair mechanism, mitochondrial genes should rapidly accumulate harmful mutations and <a href="http://rspb.royalsocietypublishing.org/content/early/2009/02/09/rspb.2008.1758.short">lose their function</a>.</p>
<p>Despite these predictions, mitochondrial disorders in humans, while debilitating, are relatively rare. A <a href="https://doi.org/10.1038/s41556-017-0017-8">set of experiments</a> with human embryos has recently found low levels of mitochondrial mutations in most of the studied cells, that, strikingly, were otherwise perfectly healthy. If mitochondrial defects are so common, what keeps them from reaching dangerous disease-causing levels?</p>
<h2>Dealing out mitochondria by chance</h2>
<p>A typical human cell contains hundreds of mitochondria. Each mitochondrion in turn has many genome copies jointly responsible for <a href="https://en.wikipedia.org/wiki/Cellular_respiration">energy production</a>. If only a few of these copies become faulty, the rest of the mitochondria can still produce enough energy, and the cell does perfectly fine. In fact, some of the most severe disorders develop only when <a href="https://doi.org/10.1111/dgd.12420">60 to 90 percent</a> of mitochondria within each cell become mutated. This means that low levels of mitochondrial mutations are essentially invisible, and can lurk within human cells for generations without causing a disease. </p>
<p>Recent <a href="https://doi.org/10.1534/genetics.117.300273">theoretical work</a> by <a href="https://scholar.google.com/citations?user=yi-SnYcAAAAJ&hl=en&oi=ao">me</a> and my colleagues predicted a number of solutions that likely evolved to expose and eventually eliminate these hidden defects. The general principle we proposed is based on simple sorting of healthy and faulty mitochondria.</p>
<p>Whenever a cell within a developing embryo divides, mitochondria are partitioned into the two daughter cells more or less randomly. By chance, one of the two daughter cells inherits more mitochondrial defects than the other. Initially, this difference is barely noticeable. But repeat the process many times and a sizeable proportion of all daughter cells will have enough mutations to ensure that the cell does not survive. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/211432/original/file-20180321-165583-11ye0fl.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/211432/original/file-20180321-165583-11ye0fl.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/211432/original/file-20180321-165583-11ye0fl.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=277&fit=crop&dpr=1 600w, https://images.theconversation.com/files/211432/original/file-20180321-165583-11ye0fl.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=277&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/211432/original/file-20180321-165583-11ye0fl.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=277&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/211432/original/file-20180321-165583-11ye0fl.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=348&fit=crop&dpr=1 754w, https://images.theconversation.com/files/211432/original/file-20180321-165583-11ye0fl.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=348&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/211432/original/file-20180321-165583-11ye0fl.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=348&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 mitochondria make copies in preparation for a cell dividing. Which version winds up in each daughter cell is essentially random. By chance, the bottom cell has even fewer of the red version than the original cell.</span>
<span class="attribution"><a class="source" href="https://doi.org/10.1371/journal.pbio.2000410">Radzvilavicius et al</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>On the opposite side of the spectrum, this leaves cells that have fewer mutations even than the original cell that started dividing. This simple mechanism of cell division and random sorting of mitochondria can therefore produce cells packed with healthy mitochondria that can then go on to divide further and to eventually produce mutation-free reproductive cells (eggs in females).</p>
<p>But there’s more. Scientists now believe that many features of the human reproductive system evolved to increase the efficiency of this random mitochondrial sorting. For instance, mutations would pile up faster if both paternal and maternal mitochondria were inherited by the offspring – mixing of two unrelated types of organelles would make it easier for rare defects to hide. It is very likely that we inherit mitochondrial genes only from our mothers precisely because it slows down the accumulation of defective genes.</p>
<p>The number of genome replication cycles also matters, because new defects are introduced each time genes are copied. In a paper published in 2016, my colleagues and I suggest this <a href="https://doi.org/10.1371/journal.pbio.2000410">could be the reason</a> why the number of cell divisions to produce an egg in females is strictly limited to 24. In males – whose mitochondria are not transmitted to the offspring – sperm are produced continually with more than 400 cell divisions by the age of 30. By capping the number of times a cell divides before an egg is made, females reduce the risk of introducing new copying errors in their mitochondrial genes.</p>
<p>Likewise, theory predicts that random sorting of healthy and sickly mitochondria works best when the number of mitochondria in a cell is low. With only a few mitochondria, even slightly defective genes cannot hide; their harmful effects are immediately obvious at the level of the cell, which can then be eliminated.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/211068/original/file-20180319-31596-p49o9j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/211068/original/file-20180319-31596-p49o9j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/211068/original/file-20180319-31596-p49o9j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/211068/original/file-20180319-31596-p49o9j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/211068/original/file-20180319-31596-p49o9j.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/211068/original/file-20180319-31596-p49o9j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/211068/original/file-20180319-31596-p49o9j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/211068/original/file-20180319-31596-p49o9j.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">Less hearty mitochondria may already be getting weeded out in an eight-cell embryo.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Embryo,_8_cells.jpg">eked</a></span>
</figcaption>
</figure>
<h2>Observing what theory predicts</h2>
<p>Confirming these predictions, a recent study involving human embryos has indeed discovered that the <a href="https://doi.org/10.1038/s41556-017-0017-8">number of mitochondria is sharply reduced throughout development</a> – from 1 million in a fertilized egg to only around 1,500 per cell in a 4-week-old embryo. Researchers also found that cells taken from older embryos had fewer mitochondrial mutations, meaning that cells with the most defects were somehow eliminated throughout embryonic development.</p>
<p>It is not yet clear how cells with the most mitochondrial mutations are selectively removed in human embryos. But because most of the harmful mutations were eliminated at the stage of embryonic development when cells start breathing more actively, scientists think that damaged mitochondria simply fail to produce enough energy for the cell to survive. </p>
<p>Many questions remain. For instance, why do cells with high levels of defective mitochondria sometimes escape these quality-control mechanisms, resulting in incurable disorders? Ultimately, greater understanding of these mechanisms should suggest better ways of estimating the risk of mitochondrial diseases, or even develop new interventions to prevent them completely.</p><img src="https://counter.theconversation.com/content/92794/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Arunas L. Radzvilavicius receives funding from Defense Advanced Research Projects Agency.</span></em></p>The genes in our cells’ mitochondria are passed on in a different way than the vast majority of our DNA. New studies shed light on how the unique process isn’t derailed by mutations.Arunas L. Radzvilavicius, Postdoctoral Researcher of Evolutionary Biology, University of PennsylvaniaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/863712017-11-02T23:38:41Z2017-11-02T23:38:41ZIt’s mostly mothers who pass on mitochondria – and a new theory says it’s due to the first sexual conflict<figure><img src="https://images.theconversation.com/files/193092/original/file-20171102-26478-lwqk5w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Is this how we got the sperm and the egg?</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/sperm-egg-1762515">Sebastian Kaulitzki/Shutterstock</a></span></figcaption></figure><p>Evolutionary interests of males and females do not always coincide. This is known as sexual conflict: male innovations that allow them to reproduce more sometimes hurt females, and vice versa.</p>
<p>Male fruit flies, for instance, inject their partners with <a href="http://www.nytimes.com/1995/01/24/science/sex-and-the-fruit-fly-price-of-promiscuity-is-premature-death.html">toxic chemicals</a> during sex. These toxins destroy sperm of the female’s previous mates, improving his own chances for becoming the sole father of her offspring. But the toxins also make female flies sick and reduce their lifespan. Females, in turn, have evolved defenses to counter the chemicals, sometimes at the expense of males’ success. </p>
<p>Biologists believe that sexual conflicts are rooted in the <a href="http://www.cell.com/trends/ecology-evolution/abstract/S0169-5347(02)00004-6">size and number of reproductive cells</a> – eggs and sperm. Males typically produce large numbers of sperm that can fertilize multiple eggs. Females, on the other hand, produce a small number of large reproductive cells, and so invest more energy and resources in each. </p>
<p><a href="http://www.ucl.ac.uk/%7Eucbhpom/people.html">My team</a> of evolutionary biologists at University College London <a href="https://doi.org/10.1186/s12915-017-0437-8">has now identified a different kind of sexual conflict</a>, dating back to the days when the most complex organisms were made of single cells, possibly as far as 1.5 billion years ago. This ancient sexual conflict – before the two sexes even existed – had to do with whose mitochondria would be passed on to offspring.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/192858/original/file-20171101-19894-1jdkw1c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/192858/original/file-20171101-19894-1jdkw1c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/192858/original/file-20171101-19894-1jdkw1c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=544&fit=crop&dpr=1 600w, https://images.theconversation.com/files/192858/original/file-20171101-19894-1jdkw1c.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=544&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/192858/original/file-20171101-19894-1jdkw1c.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=544&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/192858/original/file-20171101-19894-1jdkw1c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=684&fit=crop&dpr=1 754w, https://images.theconversation.com/files/192858/original/file-20171101-19894-1jdkw1c.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=684&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/192858/original/file-20171101-19894-1jdkw1c.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=684&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Eukaryotic cells have a nucleus (blue) and numerous mitochondria (green).</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/nihgov/20495441928">Dylan Burnette and Jennifer Lippincott-Schwartz, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span>
</figcaption>
</figure>
<h2>Whose mitochondria will be passed on?</h2>
<p>We studied inheritance of genes located in <a href="https://www.livescience.com/50679-mitochondria.html">mitochondria</a> – the structures inside our cells that breathe and produce energy. In many animals and plants, when the egg is fertilized, only the mother’s mitochondrial genes survive, while the father’s mitochondria are lost.</p>
<p>This is not by accident: Females have evolved many mechanisms to recognize a partner’s mitochondria entering the egg. Once detected, an army of enzymes is sent to digest them. Previous research has shown that <a href="https://doi.org/10.1098/rspb.2013.1920">getting rid of male mitochondria</a> is a way to keep descendents’ mitochondrial genes mutation-free. In the long run, inheritance of healthy maternal mitochondria is good news for the offspring.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/192864/original/file-20171101-19845-1rugssj.gif?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/192864/original/file-20171101-19845-1rugssj.gif?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/192864/original/file-20171101-19845-1rugssj.gif?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=511&fit=crop&dpr=1 600w, https://images.theconversation.com/files/192864/original/file-20171101-19845-1rugssj.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=511&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/192864/original/file-20171101-19845-1rugssj.gif?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=511&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/192864/original/file-20171101-19845-1rugssj.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=642&fit=crop&dpr=1 754w, https://images.theconversation.com/files/192864/original/file-20171101-19845-1rugssj.gif?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=642&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/192864/original/file-20171101-19845-1rugssj.gif?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=642&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">For the most part mitochondria come from the mother’s line. But there are exceptions.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Mitochondrial_DNA_versus_Nuclear_DNA.gif">University of California Museum of Paleontology and the National Center for Science Education</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>But there are many exceptions that remain unexplained. In some species, <a href="https://doi.org/10.1038/hdy.2012.60">paternal mitochondria remain undigested</a>, as if the father had found a way to protect them from being detected. Stranger still, in organisms such as fruit flies and many plants, it is the father that destroys most of his own mitochondria during production of sperm.</p>
<p>If maternal inheritance is as beneficial as previous research shows, why are there so many exceptions?</p>
<h2>Taking the long or the short view</h2>
<p>In our new study, we show that these exceptions arise because of a <a href="https://doi.org/10.1186/s12915-017-0437-8">sexual conflict over the control of mitochondrial inheritance</a>.</p>
<p>Using mathematical modeling, we found that evolution in females tends to focus on long-term effects. Destroying paternal mitochondria makes it easier to weed out harmful mutations in the future, but this effect unfolds over many generations. This strategy works well in females, because the same healthy set of maternal mitochondria is passed down the female line over and over again. </p>
<p>But males don’t have a long evolutionary time horizon to deal with in this case. Since most of their mitochondria are replaced by maternal ones at the start of every generation, evolution cannot detect long-term benefits from males’ mitochondrial genes. Because there’s no long-term link, they can benefit only in the immediate future, and that often means passing on some of their mitochondria right now. Males therefore seek to improve the fitness of their offspring in the short-term, even if the long-term effects are harmful.</p>
<p>It’s these different interests of males and females that can lead to an evolutionary arms race, as selection in the two sexes acts in opposite directions. Evolution in females strives to keep the future generations free of male mitochondria, while males make every effort to get some of theirs into the mix.</p>
<p>“Over and over again, males have come up with ways to subvert female destruction of their mitochondria,” said my co-author, geneticist <a href="http://www.ucl.ac.uk/%7Eucbhpom/">Andrew Pomiankowski</a>. “So females had to develop new ways to block male mitochondria. Our model explains nicely why there are so many different mechanisms used to exclude male mitochondria, and why males sometimes do it themselves.”</p>
<p>It’s all about the control of mitochondrial inheritance – and for males it’s better to be in the driver’s seat to decide how many mitochondria they contribute to the mix than be completely excluded.</p>
<h2>A sexual conflict that led to the sexes</h2>
<p>There is evidence that this conflict dates back to the days when all organisms were made of single cells. Male and female sexes did not exist, because all reproductive cells were of the same size. </p>
<p>“One of the strategies an organism can use to win in this conflict is to simply have more mitochondria than their partner, for example, by increasing the size of their sex cells,” Andrew Pomiankowski said. “Strikingly, this might have been the impetus to evolve two sexes in the first place.” Larger sex cells – the future eggs – garnered an advantage in the battle over mitochondrial inheritance, simply by swamping smaller sex cells – the forerunners of sperm – that had fewer mitochondria to contribute.</p>
<p>Most biologists currently think that <a href="https://doi.org/10.1098/rspb.2002.2161">two sexes evolved through division of labor</a> – a so-called “disruptive selection” theory. Large female sex cells can survive longer but cannot move much, while smaller sperm are fragile but move faster and can find more mating partners.</p>
<p>Our hypothesis on the origin of sexes, if true, adds a new angle to this origins story, tracing it back to an ancient conflict over mitochondrial inheritance. Females may have won this ancient battle by simply producing larger sex cells packed with mitochondria, ensuring that mitochondrial transmission is effectively one-sided (and reaping the long-term fitness benefits). But ultimately, as with all scientific hypotheses, this one will have to stand the test of thorough experimental verification.</p><img src="https://counter.theconversation.com/content/86371/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Arunas L Radzvilavicius receives funding from David and Lucille Packard Foundation.</span></em></p>An ancient sexual conflict over mitochondrial inheritance may be responsible for the evolution of the two sexes as we know them.Arunas L. Radzvilavicius, Postdoctoral Researcher of Evolutionary Biology, University of PennsylvaniaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/668522016-10-12T05:31:18Z2016-10-12T05:31:18ZIf we were like mice we could live to 400 – but we’re not, so we don’t<figure><img src="https://images.theconversation.com/files/141351/original/image-20161012-8418-1x6rscg.jpg?ixlib=rb-1.1.0&rect=8%2C116%2C2959%2C2241&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Mice can slow the wheel of ageing almost at will. Humans, not so much.</span> <span class="attribution"><span class="source">Ron and Joe/Shutterstock.com</span></span></figcaption></figure><p>You may have seen the news that the human lifespan <a href="https://theconversation.com/is-there-a-natural-limit-to-how-long-humans-can-live-66460">cannot be extended beyond about 115 years</a>, as shown by a <a href="http://www.nature.com/nature/journal/vaop/ncurrent/full/nature19793.html">demographic analysis</a> confirming that the steady improvements in lifespan seen for many populations over recent decades has stalled since the 1990s.</p>
<p>The researchers’ conclusion that “the maximum lifespan of humans is fixed and subject to natural constraints” is sobering reading for those who dream that human ageing can one day be successfully hacked. But for evolutionary ecologists, it should not come as a surprise.</p>
<p>As well as striking a note of biological realism, this research also highlights how research on human ageing often neglects the insights available from evolutionary theory – and particularly from a research field called “comparative life-history ecology”. </p>
<p>This genre of research explains why mice and humans grow old at such different rates (more on why this is a problem for ageing research later). It aims to bring us closer to understanding the “ultimate” reasons why we age – which in turn can tell us whether the hundreds of millions of dollars poured into ageing research are actually a good investment. </p>
<p>Strive as we might, an evolutionary perspective tells us that maximum lifespans will not be extended by simply solving one symptom of ageing after another.</p>
<h2>Growing old – the ‘why’ as well as the ‘how’</h2>
<p>Ageing – or “senescence”, to use the biological term – is defined as a decline in physiological condition with age. You might wonder why natural selection allows this to happen at all. The answer is that senescence happens in a “selection shadow” – that is, after organisms have already reproduced and passed on their genes. There is no real evolutionary penalty for failing to ward off the ravages of old age, because in animal populations relatively few individuals make it into their geriatric years anyway, thanks to predators, disease, hardship or bad luck.</p>
<p>Natural selection reaches a crescendo at sexual maturity, when most individuals in a population are alive and striving to produce viable offspring. This is the age at which the genetic baton is passed to the next generation. Unfortunately for those of us over 40, it’s all downhill from here in terms of the evolutionary pressure to maintain a healthy body.</p>
<p>This knowledge – that selection pressure changes with age in a way that depends not just on the expected lifespan but also on the timing of reproductive effort – is fundamental to evolutionary theories of ageing. It is also fundamental to how we design and interpret the research that aims to help us prolong our own maximum lifespans.</p>
<p>Many of the species most frequently studied by biologists – such as mice, flies and worms – are chosen precisely because their short lifespans and fast generational turnover make them quicker and easier to work with. But their short lives and adaptable reproductive strategies actually make them unsuitable models for testing drugs or other anti-ageing interventions aimed at slowing human ageing.</p>
<p>Short-lived species seem to be able to “trade in” their investment in growth and sexual reproduction in return for slowing down the ageing process – <a href="http://rspb.royalsocietypublishing.org/content/282/1806/20150209">switching to a physiological state</a> in which they instead invest in maintenance of body condition and warding off senescence. </p>
<p>This strategy makes sense for species whose brief lives can be subject to wide variability in environmental conditions. For a small rodent, having a litter of pups would be rather pointless if food is too scarce for them to grow and survive to adulthood. Hamsters, for example, can instead enter a torpid state that actually <a href="http://rsbl.royalsocietypublishing.org/content/8/2/304">protects their cells from ageing</a> over winter.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/141349/original/image-20161012-8401-tvejbw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/141349/original/image-20161012-8401-tvejbw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/141349/original/image-20161012-8401-tvejbw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/141349/original/image-20161012-8401-tvejbw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/141349/original/image-20161012-8401-tvejbw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/141349/original/image-20161012-8401-tvejbw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/141349/original/image-20161012-8401-tvejbw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/141349/original/image-20161012-8401-tvejbw.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">For mice, having babies really can age you faster.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File%3ABabymouse.jpg">ShwSie/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>In contrast, species with long expected natural lifespans (which have reduced their mortality risk by evolving to a large size, or being able to fly or hibernate, or having a large brain) have already invested strongly, and perhaps maximally, in protecting their cells from ageing. This suggests there is no “anti-ageing switch” available to flick for a species such as ourselves. Whether or not we have children, it seems we’re already naturally geared to live as long as we possibly can.</p>
<p>This might sound weird, but it’s supported by a <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0012019">simple comparative analysis</a> that a colleague and I published back in 2010, in which we compared the <em>average expected</em> lifespan with the <em>maximum recorded</em> lifespan for various mammals. From this we can calculate a simple ratio of average to maximum lifespan, which tells you, for a given species, how much it is theoretically possible to expand lifespan.</p>
<p>If we take the ratio of a short-lived species like a mouse and apply it to humans, we would predict a maximum lifespan of about 400 years! But despite all of our efforts to push the boundaries through medicine and nutrition, humans (along with elephants and other highly durable animals) don’t come close to these biblical lifespans.</p>
<p>So if mice find it much easier to slow down the ageing process than we do, what does that mean for anti-ageing studies using mice? Sadly, the implication is that most tactics shown to prolong lifespan in mice – such as calorie restriction – will be <a href="http://www.nature.com/nature/journal/v489/n7415/full/nature11432.html">far less effective in humans</a>. </p>
<p>If we are to break the evolutionary constraints on maximum lifespan in humans, we need to better take account of life-history ecology. This theory tells us that the causes of ageing are to be found not at the end of our lives, but at the beginning. </p>
<p>How our maximum lifespan is ultimately limited will be understood by research that seeks to answer why the pace of life varies so much among different animals. For me, this is the take-home message from this recent excellent research.</p><img src="https://counter.theconversation.com/content/66852/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Christopher Turbill's research has been funded by a Discovery Early Career Researcher Award (DECRA) from the Australian Government.</span></em></p>Anti-ageing research often uses short-lived model species such as mice. But these species age in a very different way to us, so they may not tell us all that much about boosting our own lifespans.Christopher Turbill, Senior Lecturer in Animal Ecology, Western Sydney UniversityLicensed 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">
<figcaption>
<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>
</figcaption>
</figure>
<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/623642016-07-14T10:37:58Z2016-07-14T10:37:58ZGoing naked in public is a joyful release for mind and body<p>I doubt I shall ever see blue in the same way again, since blue paint on my skin was the only thing covering my nakedness. I was among the 3,200 people – strangers to one another when it all began – who took part in the <a href="http://www.theguardian.com/artanddesign/2016/jul/09/thousands-strip-naked-in-hull-for-spencer-tunick-photographs">largest naked photo shoot in Britain</a>, wearing nothing but four shades of blue body paint. </p>
<p>This work of performance art, named The Sea of Hull, was conceived by New York-based photographer <a href="http://www.spencertunick.com">Spencer Tunick</a> and commissioned by the <a href="https://www.hull2017.co.uk/whatson/events/seaofhull/">Ferens Art Gallery</a> in Hull in north-east England as part of the city’s place as <a href="http://www.hull2017.co.uk">UK Capital of Culture</a> in 2017, with Tunick’s exhibition as one of its highlights. </p>
<p>Tunick’s work has been widely discussed in academic literature as much as in the tabloids. But in the book <a href="https://www.routledge.com/Judging-the-Image-Art-Value-Law/Young/p/book/9780415301848">Judging the Image</a> by sociologist Alison Young, she describes Tunick’s early years and struggles against the law in the US, and also includes comments from those who have participated in his many installations. The <a href="http://www.independent.co.uk/voices/letters/the-sea-of-hull-was-the-feel-good-story-that-this-country-needed-a7129476.html">spectrum of feelings</a> aroused in those participating in Tunick’s work – as described in the book – echo the sentiments I have just heard expressed from my fellow participants in Hull.</p>
<p>My nude buddy summarised the event as joy, community, and release. And these are the three words with which I want to develop an approach to Tunick’s work and try to explain the reasons that led me to be a part of his human sea. </p>
<h2>Joy, community and release: human essentials</h2>
<p>I first came across Tunick’s work in 2002, when I saw his exhibition at the <a href="http://www.macm.org/en/">Museum of Contemporary Art in Montreal</a>, Canada. It has taken 14 years for me to be able to make it to one of his installations, but my desire to do so never faded – something for which Young provides an explanation in her book: </p>
<blockquote>
<p>Tunick’s great achievement as an artist is that his work is premised upon offering individuals the uncanny experience of being simultaneously the object of the image and the performance.</p>
</blockquote>
<p>The dynamics of the acceptance or rejection of human bodies, either naked or clothed, rely on many factors and are culturally determined. The human body, as the physical essence of humanity, is at the core of the controversy. (I am not even going to approach the issue of sex. Not least because there is no sexual element in Tunick’s installations at all, but also because the complexities of human sexuality have already been masterly summarised by <a href="https://www.umb.edu/academics/cla/faculty/patrick_clarkin">Patrick Clarkin</a> in his fascinating series <a href="https://kevishere.com/2016/04/21/wrapping-up-the-blank-ogamous-series/">Humans are (Blank)-ogamous</a>.)</p>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/130369/original/image-20160713-12353-6qs7tl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/130369/original/image-20160713-12353-6qs7tl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1068&fit=crop&dpr=1 600w, https://images.theconversation.com/files/130369/original/image-20160713-12353-6qs7tl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1068&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/130369/original/image-20160713-12353-6qs7tl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1068&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/130369/original/image-20160713-12353-6qs7tl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1342&fit=crop&dpr=1 754w, https://images.theconversation.com/files/130369/original/image-20160713-12353-6qs7tl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1342&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/130369/original/image-20160713-12353-6qs7tl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1342&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Ines Varela-Silva at the end of the event.</span>
<span class="attribution"><span class="source">David Kennedy</span></span>
</figcaption>
</figure>
<p>Being part of Tunick’s installations provides an overwhelming sense of joy. It is exhilarating to realise that we can break socially prescribed barriers. Ultimately, the struggle is with ourselves: will we be brave enough to bare it all? Once nude, the feeling of joy is indescribable. From a purely physiological point of view, our “hormones of happiness” – endorphins, dopamine, and serotonin – will be unleashed, with knock-on effects on the body, including <a href="http://www.sciencedirect.com/science/article/pii/S1568997206000279">boosting the immune system</a>. </p>
<p>Humans are social mammals, and cooperation and altruism are core evolutionary traits. In his book <a href="http://www.ucpress.edu/book.php?isbn=9780520269712">Race, monogamy, and other lies they told you</a>, anthropologist <a href="http://anthropology.nd.edu/faculty-and-staff/faculty-by-alpha/agustin-fuentes/">Agustin Fuentes</a> explained that cooperation is what humans do best, and what makes us such a successful species.</p>
<p>Tunick’s installations provide a feeling of community that is not easy to find in our daily lives, but one to which we are evolutionarily hardwired to seek. The sense of release emerges when the feelings of joy and community lead us to realise that we have become better human beings – more inclusive, and with a greater capacity for acceptance.</p>
<h2>What next?</h2>
<p>If you assumed Tunick would take a break for a little while after navigating the Sea of Hull, you’d be wrong: he is already channelling all his creative energy into, of all places, the <a href="http://www.huffingtonpost.com/entry/sign-up-to-pose-nude-at-the-republican-national-convention_us_5734bb67e4b08f96c1826b18">Republican National Conference</a>, in Cleveland, Ohio. Tunick is now looking for 100 women who will pose naked while holding mirrors to reflect:</p>
<blockquote>
<p>… the knowledge and wisdom of progressive women and the concept of “mother nature” … The mirrors communicate that we are a reflection of ourselves, each other, and of the world that surrounds us. The woman becomes the future and the future becomes the woman.</p>
</blockquote>
<p>I am seriously considering dropping everything I have currently going on and hopping on a plane, right now, to be one of those rays of sunshine in Cleveland. This will be an installation focused on equal rights, specifically on women’s rights – values I treasure and fight for everyday. Do I need any other reason? I don’t think so.</p><img src="https://counter.theconversation.com/content/62364/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Inês Varela-Silva receives funding from The Bill & Melinda Gates Foundation</span></em></p>Going naked in public has its own benefits.Inês Varela-Silva, Senior Lecturer in Human Biology, Loughborough UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/575382016-05-05T10:09:08Z2016-05-05T10:09:08ZSimulating evolution: how close do computer models come to reality?<figure><img src="https://images.theconversation.com/files/121082/original/image-20160503-13603-1w9luwb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Computers can be our prediction machines.</span> <span class="attribution"><a class="source" href="http://www.shutterstock.com/pic.mhtml?id=284581217&src=lb-29877982">Data image via www.shutterstock.com.</a></span></figcaption></figure><p>Darwin’s <a href="https://en.wikipedia.org/wiki/Evolution">theory of evolution</a> is a simple but powerful framework that explains how complexity can come from simplicity: how everything biological around us – from the microbial biofilms on your teeth to the majestic redwood trees – emerged from the very simplest of beginnings.</p>
<p>How exactly this happened is, of course, a matter of intense research. Each species is finely adapted to thrive in its environment, which in turn has shaped that species’ evolutionary history. But those environmental forces exerted on a species occurred over a very long period of time, in the often very distant past. How can we understand which environmental features were responsible for which adaptations we see today?</p>
<p>As an example, my research group recently got interested in what makes people dislike taking risks. Of course we can’t travel through time to go back and run a controlled experiment on our early human ancestors to see how that tendency might have evolved. But as scientists, we want to do more than just come up with an untestable hypothesis.</p>
<p>So we turned to computers to simulate the dynamics of ancient people for thousands of generations. By carefully choosing the starting parameters for our computer simulation, we were able to see how in small groups of about 150 people – the size common during the Stone Age – gambles that pay off big time (but only rarely) end up being genetically costly. <a href="http://www.nature.com/articles/srep08242">We also found</a> that risky behavior had no consequences as long as populations were large. I can’t think of another way an evolutionary study like this could have been carried out. Here’s why we can believe what these kinds of computer simulations tell us.</p>
<h2>Passing on a constant flux of traits</h2>
<p>Darwin’s theory of evolution is simple in the sense that it requires only three necessary (and sufficient) components for the process to work: inheritance, variations and differential survival (sometimes called “selection”).</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/121053/original/image-20160503-19871-182nnx2.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/121053/original/image-20160503-19871-182nnx2.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/121053/original/image-20160503-19871-182nnx2.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=544&fit=crop&dpr=1 600w, https://images.theconversation.com/files/121053/original/image-20160503-19871-182nnx2.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=544&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/121053/original/image-20160503-19871-182nnx2.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=544&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/121053/original/image-20160503-19871-182nnx2.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=683&fit=crop&dpr=1 754w, https://images.theconversation.com/files/121053/original/image-20160503-19871-182nnx2.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=683&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/121053/original/image-20160503-19871-182nnx2.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=683&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Natural selection is one mechanism for how evolution happens.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Mutation_and_selection_diagram.svg">Elembis</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
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<p>Inheritance guarantees that anything new discovered by the process is not lost. Variation ensures that new things are being tried out constantly. And differential survival implies that differences matter – variations that help rather than hurt have consequences for the descendants of the first individual that carried that beneficial change.</p>
<p>But even though these principles are straightforward, how they play out in a complex world is far from simple. We might be able to work out in our head how one beneficial change (say, a larger body size that allows an individual to withstand a predator’s assaults) can also have negative consequences (more time spent foraging to support the body weight exposes the individual to more predation). Such simple trade-offs can be captured by mathematical formulas, and their consequences can be worked out. </p>
<p>But in real biology, every single trait could conceivably affect every other. It’s not easy to work out the net benefit of a set of traits, either in your head or with mathematics. This is where computers come in. </p>
<h2>Computers run through scenarios, fast</h2>
<p>What computers really do within scientific research is often misrepresented or misunderstood. I frequently hear the phrase: “With a computer, you can get any result you want.” But this is not true. What a computer does is keep track of things for you.</p>
<p>To a large extent, this is what mathematics does too. I like to point out that mathematics is “the crutch of the feeble-minded”; it allows us to use symbols to embody complex relationships that we can then manipulate according to strict rules.</p>
<p>The computer is no different, except it allows us to keep track of vastly more variables, and to work out the consequences of the relationships over long periods of time. Since we set strict rules, of course, we can’t get “anything we want.” We get only what is allowed according to the rules.</p>
<p>But what are those rules?</p>
<p>In mathematics, you start with a set of assumptions, and you work out the consequences according to the rules of logic. This is still true inside a computer, but now we can also implement very specific rules – for example, the laws of chemistry, the effects of friction or the cost of finding a mate. </p>
<p>Researchers in a variety of fields turn to computer simulations to help them test ideas that they can’t investigate any other way. Astrophysicists use these kinds of models to <a href="http://doi.org/10.1111/j.1365-2966.2008.14106.x">simulate how stars form</a>. Material scientists simulate the <a href="https://en.wikipedia.org/wiki/Stockpile_stewardship">aging of nuclear weapons</a> to predict if they will still work in the future. </p>
<p>In evolutionary biology, we might ask which factor shaped a particular trait or behavior. For instance, my colleague <a href="http://hyenas.zoology.msu.edu/">Kay Holekamp</a> has been observing hyenas in Kenya for over 25 years, and she’s collected an enormous data set pertaining to the hunting habits (among other traits) of these animals. But even all those observations can’t tell us <em>why</em> she sees what she sees in the field. The reasons may lie in pressures that the population was under in the past, or maybe the pressures manifest themselves only over thousands of generations.</p>
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<a href="https://images.theconversation.com/files/121055/original/image-20160503-27777-l56foy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/121055/original/image-20160503-27777-l56foy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/121055/original/image-20160503-27777-l56foy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=195&fit=crop&dpr=1 600w, https://images.theconversation.com/files/121055/original/image-20160503-27777-l56foy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=195&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/121055/original/image-20160503-27777-l56foy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=195&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/121055/original/image-20160503-27777-l56foy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=244&fit=crop&dpr=1 754w, https://images.theconversation.com/files/121055/original/image-20160503-27777-l56foy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=244&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/121055/original/image-20160503-27777-l56foy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=244&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">Even decades of observation leave us with questions about why animals behave in certain ways.</span>
<span class="attribution"><a class="source" href="http://hyenas.zoology.msu.edu/index.php?mact=Album,m4,default,1&m4albumid=1&m4returnid=52&page=52">Anne Engh</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
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<p>To answer questions such as “Why don’t the highest-ranking female hyenas participate in the hunt?,” we have to study the consequences of different assumptions on the long-term survival of the group. </p>
<p>Evolutionary theory says that only beneficial traits survive in the long run, but it can often be hard to understand how a certain trait might help. This is because of all those trade-offs I mentioned, and sometimes the benefit of a trait only becomes clear after a long time. After all, evolution has had millions of years of trials, failures and successes. Even 50 years of observation might not reveal to us the long-term consequences of a set of traits and how they interact and play out in a complex world.</p>
<p>But a computer might work this out in minutes, as a population of 1,000 gazelles and a group of, say, 150 hyenas can be followed over thousands of simulated generations. </p>
<h2>Matching theory to observation</h2>
<p>In evolutionary science, computers thus are prediction machines: they answer questions like “What would happen under these rules, given I started in <em>this</em> world with <em>these</em> starting conditions?” </p>
<p>In our study of the evolutionary origins of risk aversion, for example, we could ask what happens to risk aversion if the total population was large, but composed of small groups with migration between them. Running the scenario, we found that risk aversion still evolved unless the migration rate was exceedingly high. </p>
<p>Of course, if you start with the wrong rules, or inappropriate starting conditions, the results may not match what we observe in reality. But this is exactly what we require in the scientific process. If the predictions are wrong, then we must modify either the rules, or the initial conditions (or both).</p>
<p>Once we do obtain a match between the computer simulations and real-world observations, we can’t stop there and conclude we’ve discovered the rules that correctly reflect what is happening in nature. We must, instead, test whether these rules <em>also</em> predict other things that we didn’t set out to test in the first place. For example, do the same set of rules also explain the observation that the spoils of a kill are not distributed equally among the hyenas? </p>
<p>This kind of thinking is no different from the way theory and experiment have worked in unison to build the complex and powerful framework of theoretical physics. In that quest, theories were laid down, for the most part, mathematically. In evolutionary biology, though, this is usually not possible simply because biology is too complicated.</p>
<p>Evolutionary simulations allow us to test hypotheses, but they’re not asking or even answering questions. <em>We</em> ask “What if,” and the computer dutifully responds: “In this case, this is what you would get.” The computer helps us “think forward in time” with blazing speed, and in evolutionary science this is precisely what is required to generate understanding.</p><img src="https://counter.theconversation.com/content/57538/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Christoph Adami receives funding from the National Science Foundation. </span></em></p>Scientists of all kinds turn to computer models to investigate questions they can’t get at any other way. Here’s how models work and why we can trust them.Christoph Adami, Professor of Microbiology and Molecular Genetics & Physics and Astronomy, Michigan State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/521182015-12-14T16:37:56Z2015-12-14T16:37:56ZFive lessons in seduction from the males of the animal kingdom<figure><img src="https://images.theconversation.com/files/105775/original/image-20151214-9515-1rlj4rg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Biting your partner's nose - a winner for birds, not always for humans.</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Some men are naturally handsome, attracting women with little difficulty. But most have to rely on their wits, charm and the occasional bit of clever seduction to find a partner. And things are pretty similar in the animal kingdom.</p>
<p>Males produce millions of sperm so have the potential to father many offspring. But females produce relatively few eggs so have to be choosy about whom they mate with. If a male chooses a dud female there are few repercussions as he can quickly move onto another female, but if a female chooses a dud male it can be disastrous. For example, an elephant has a gap of around five years between offspring due to long gestation and weaning periods. That’s a long time to wait to choose a better mate.</p>
<p>As a result, it’s usually the males who compete over females via an evolutionary process termed <a href="http://evolution.berkeley.edu/evolibrary/article/evo_28">sexual selection</a>. For this, individuals produce traits such as ornate plumage that have no survival benefit. They have evolved purely to increase mating success.</p>
<p>Here’s the animal kingdom’s code for attracting members of the opposite sex and upping their game in the sexual selection competition.</p>
<h2>1. Be a snappy dresser</h2>
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<p>Females are commonly attracted to males who have the largest, brightest, and boldest traits. The peacock is the <a href="http://www.nature.com/scitable/knowledge/library/sexual-selection-13255240">perfect example</a> of everything that is sexy to a peahen. He has bright and bold blue/green colouration combined with a very long tail. But why are traits like this attractive to the females?</p>
<p>The handicap hypothesis suggests that if a male can survive despite <a href="https://www.blackwellpublishing.com/ridley/a-z/Zahavis_handicap.asp">having a handicap</a> such as a long tail, which would hinder escape from a predator, he must be a fit male and possess good genes which would be beneficial to any offspring. Indeed, it <a href="http://www.nature.com/news/2011/110418/full/news.2011.245.html#B2">has been shown</a> that male peacocks with fewer eyespots have lower success with the females, and also have a weaker immune system.</p>
<h2>2. Serenade them</h2>
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<p>Apart from a visual attraction, females can also be attracted to males acoustically. Again, females generally <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2390678/">prefer males</a> with longer, louder and more complex vocalisations, possibly as these advertise the stamina of the males. Typical serenades come from bird or whale song, amphibian vocalisations and invertebrate chirps. But <a href="http://www.sciencedirect.com/science/article/pii/S0003347285801391">certain fish</a> known as gymnotoids have also been found to attract mates with an electric “song”, and mice have been found to <a href="http://www.theguardian.com/science/2015/apr/01/squeaky-serenade-male-mice-woo-females-with-song-scientists-discover">serenade mates</a> with an ultrasonic song: apparently, the males break into song when they sense female urine.</p>
<h2>3. Stand out from the crowd</h2>
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<p>Many organisms build structures to attract members of the opposite sex such as the intricate nests constructed by weaver birds. But, perhaps the best creations are built by <a href="http://www.bbc.co.uk/programmes/p00z45cw">bower birds</a>. These ground-dwelling birds build various constructions depending on their specific species. Some build maypole-like structures while others create an avenue or platform on which they strut their stuff.</p>
<p>The bowers are usually highly decorated with ornaments such as rocks, flowers and berries, thought to allow the males to present themselves in the best way. Bowers have even been found decorated with brightly coloured plastic pegs, drinking straws and crisp packets, often stolen from the bowers of other males. The females check out the bowers then choose their mate, usually based on the best structure with the most objects.</p>
<h2>4. Offer a gift</h2>
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<p>Gifts are often seen as a good way of attracting a mate, and flowers, chocolates and jewellery are often replaced in the animal kingdom by nesting material, food items and pond weed, thought to advertise the attentiveness of the males. Some male spiders such as the <em>Paratrechalea ornata</em> <a href="http://www.ncbi.nlm.nih.gov/pubmed/24424786">offer their females</a> prey wrapped in silk. The females often choose the males based on the size of this nuptial gift. Once the females start feasting, the male starts mating with her. Great crested grebes, meanwhile, form an elaborate courtship dance which culminates in the pair offering each other pond weed to build their nest with.</p>
<p>However, the male praying mantis offers the ultimate gift – himself. In this form of sexual cannibalism, the female devours the male during or after mating, for nourishment. How does this benefit the male? In evolutionary terms, an organism’s aim is to produce offspring and pass on its genes. So usually the the male has done his job once he has copulated with the female. But if he can help the offspring by feeding their mother, this will give them the best possible start in life, ensuring his genes survive.</p>
<h2>5. If you can’t get a dance, try drag</h2>
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<p>There are lots of cheating strategies in the animal kingdom and for one species of bird, a method is to pretend to be a member of the opposite sex. The ruff is a bird that forms “leks”, where males aggregate to compete and display to females, rather <a href="http://www.theguardian.com/world/shortcuts/2015/nov/17/ruff-sandpiper-gender-fluid-bird">like a nightclub</a>. Females choose the males for one thing only, so the males provide no parental role.</p>
<p>The males usually strut their stuff for the females, and the most impressive males win. But there are also satellite males who hang around the edge of the “dancefloor” and grab a sneaky mating wherever possible. The most cunning mating strategy comes from the males who look like females and dupe the real females into spending time with them, then grab a sneaky mating whenever they can.</p><img src="https://counter.theconversation.com/content/52118/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>From dancing to giving presents, animals have evolved some effective and surprisingly familiar ways of wooing a mate.Louise Gentle, Senior Lecturer in Animal Behaviour, Nottingham Trent UniversityLicensed as Creative Commons – attribution, no derivatives.