tag:theconversation.com,2011:/us/topics/toolmaking-38488/articlesToolmaking – The Conversation2020-01-09T13:31:44Ztag:theconversation.com,2011:article/1241452020-01-09T13:31:44Z2020-01-09T13:31:44ZMonkeys smashing nuts with stones hint at how human tool use evolved<figure><img src="https://images.theconversation.com/files/308857/original/file-20200107-123403-11eithu.jpg?ixlib=rb-1.1.0&rect=347%2C155%2C3245%2C2502&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A capuchin monkey in Brazil hoists a stone tool to crack open nuts.</span> <span class="attribution"><span class="source">Luca Antonio Marino</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>Human beings <a href="https://www.janegoodall.org.uk/chimpanzees/chimpanzee-central/15-chimpanzees/chimpanzee-central/19-toolmaking">used to be defined</a> as “the tool-maker” species. But the uniqueness of this description was challenged in the 1960s when Dr. Jane Goodall discovered that chimpanzees will pick and modify grass stems to use to collect termites. Her observations called into question <em>homo sapiens</em>‘ very place in the world.</p>
<p>Since then scientists’ knowledge of animal tool use has expanded exponentially. We now know that <a href="https://doi.org/10.1002/ajp.20342">monkeys</a>, <a href="https://doi.org/10.1016/j.cub.2007.07.057">crows</a>, <a href="https://doi.org/10.1098/rsbl.2015.0861">parrots</a>, <a href="https://doi.org/10.1016/j.mambio.2019.08.003">pigs</a> and many other animals can use tools, and research on animal tool use changed our understanding of how animals think and learn.</p>
<p>Studying animal <a href="https://doi.org/10.1016/bs.asb.2018.01.001">tooling</a> – defined as the process of using an object to achieve a mechanical outcome on a target – can also provide clues to the mysteries of human evolution.</p>
<p>Our human ancestors’ shift to making and using tools is linked to evolutionary changes in <a href="https://doi.org/10.1098/rstb.2012.0414">hand anatomy</a>, a <a href="https://doi.org/10.1007/s12052-010-0257-6">transition to walking on two rather than four feet</a> and <a href="https://doi.org/10.1016/B978-0-12-804042-3.00085-3">increased brain size</a>. But using found stones as pounding tools doesn’t require any of these advanced evolutionary traits; it likely came about before humans began to manufacture tools. By studying this percussive tool use in monkeys, researchers like my colleagues and I can infer how early human ancestors practiced the same skills before modern hands, posture and brains evolved.</p>
<h2>Monkeys using tools</h2>
<p>Understanding wild animals’ memory, thinking and problem-solving abilities is no easy task. In experimental research where animals are asked to perform a behavior or <a href="https://doi.org/10.1016/j.anbehav.2012.11.003">solve a problem</a>, there should be no distractions – like a predator popping up. But wild animals come and go as they please, over large spaces, and researchers cannot control what is happening around them.</p>
<p>However, some field sites provide a unique opportunity to test wild animals’ cognition. Fazenda Boa Vista in Piauí, Brazil is one of those sites. Here, wild bearded capuchin monkeys (<em>Sapajus libidinosus</em>) naturally use stones and anvils to crack open nuts.</p>
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<a href="https://images.theconversation.com/files/308434/original/file-20200103-11924-5thx25.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/308434/original/file-20200103-11924-5thx25.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/308434/original/file-20200103-11924-5thx25.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/308434/original/file-20200103-11924-5thx25.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/308434/original/file-20200103-11924-5thx25.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/308434/original/file-20200103-11924-5thx25.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/308434/original/file-20200103-11924-5thx25.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/308434/original/file-20200103-11924-5thx25.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">Young capuchin monkey observes adult male monkey eating nuts cracked open using a stone tool.</span>
<span class="attribution"><span class="source">Luca Antonio Marino</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<p>Along with fruit, insects, fungi, and tubers, the Fazenda Boa Vista capuchin monkeys <a href="https://doi.org/10.1016/j.anbehav.2012.03.002">opportunistically crack open nuts</a> as an additional food source. Although these monkeys only spend about <a href="https://doi.org/10.1016/j.anbehav.2012.03.002">2% of their time using tools to access foods</a>, the nuts they eat are an important secondary food item that are available year-round. The challenge is that these nuts have tough shells that <a href="https://doi.org/10.1002/ajp.20578">can’t be cracked open without a tool</a>. This population of monkeys has figured out how to crack nuts by placing them on a wood or stone anvil and then smashing them with rocks that <a href="https://doi.org/10.1016/j.jhevol.2011.02.010">weigh around 25-50% of their body weight</a>.</p>
<p>These bearded capuchin monkeys were the first South American primates that scientists ever observed using tools – only spotted in 2003. Since this discovery, researchers have been studying the <a href="https://doi.org/10.1016/j.anbehav.2010.04.018">decision-making</a> and <a href="https://doi.org/10.1371/journal.pone.0056182">strategies</a> involved in capuchins’ stone tool use.</p>
<p>Because using stones to pound open food looks remarkably like what anthropologists imagine one of the <a href="https://doi.org/10.1038/nature14464">earliest forms of human tool use</a> looked like, researchers study these monkeys as a way to understand our own evolutionary past. </p>
<h2>What happens with a new tool?</h2>
<p>My colleagues and I carried out an <a href="https://doi.org/10.1002/ajp.22958">experimental field study</a> that focused on understanding how these monkeys prepare to use their tools. Just as a person might move her hands around a box to decide how best to lift it, monkeys at this site feel their way through tool use.</p>
<p>First, we placed unfamiliar stones and palm nuts around naturally-occurring wood or stone anvils. Since the monkeys frequently use stones to crack open these tough nuts on the anvils, it was only a matter of time before they tried out the experimental stones.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/tCzLWALwy8E?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Slow-motion video allowed for careful observation of how monkeys used new tools.</span></figcaption>
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<p>We filmed slow-motion videos of 12 monkeys cracking nuts to understand how monkeys adjust to using an unfamiliar tool. The idea, stemming from <a href="https://www.routledge.com/The-Ecological-Approach-to-Visual-Perception-Classic-Edition/Gibson/p/book/9781848725782">perception-action theory</a>, is that monkeys may obtain helpful information about the tool, like how heavy it is, and where they can hold it securely, by manipulating it before they use it. Like testing a hammer with a few light taps before you use it, this information may then help the monkeys to strike the nut forcefully and accurately.</p>
<p>Back in the U.S., we spent months carefully watching the slow-motion videos and recording the monkeys’ quick behaviors while using tools. The videos showed that for nut-cracking, monkeys grasp the sides of a stone, lift it to shoulder height, quickly move its hands to the top of the stone, then bring it down on the nut.</p>
<p>Given that the stones <a href="https://doi.org/10.1016/j.anbehav.2009.11.004">can weigh about half as much as an adult female monkey</a>, this is an impressive feat. But it’s not always done perfectly. If the monkey’s grip isn’t right, she might lose control of the stone, and if the stone comes down at an angle the nut is likely to fly off the anvil. When this happens, the monkeys lose precious time and energy trying to achieve their goal. </p>
<p>What we found, though, is that the monkeys might avoid these imperfect outcomes by spinning, flipping and doing partial lifts with the stones to test different grips and find the one that’s most likely to be successful. The preparatory lifts didn’t necessarily help the monkeys crack open more nuts, but they might be linked to “tuning” muscular coordination as the monkeys prepare themselves for a heavy lift. Essentially, the preparatory lifts may help the monkeys get a sense of what they’ll need their muscles to do when it comes time to lift the stone and strike the nut in earnest.</p>
<p>This same sort of <a href="https://www.sciencedirect.com/topics/neuroscience/haptic-perception">haptic perception</a> – the process of coming to understand an object by moving it around – plays a key role your own ability to use tools with dexterity. In human beings’ evolutionary past, increasingly refined haptic perception may have contributed to advancing tool use.</p>
<p>Studying how animals think about and use tool offers scientists like me an exciting glimpse into what human evolutionary history may have looked like, while also helping us to better understand animals in their own right.</p>
<p>[ <em>You’re smart and curious about the world. So are The Conversation’s authors and editors.</em> <a href="https://theconversation.com/us/newsletters?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=youresmart">You can read us daily by subscribing to our newsletter</a>. ]</p><img src="https://counter.theconversation.com/content/124145/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kristen S. Morrow 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>Capuchin monkeys in Brazil use big stones to crush the shells of nuts they want to eat. An experiment in the field investigated how these monkeys prepare to use new, unfamiliar tools.Kristen S. Morrow, PhD Student in Anthropology and Integrative Conservation, University of GeorgiaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/996712018-07-11T20:11:28Z2018-07-11T20:11:28ZHumankind’s odyssey from Africa began more than two million years ago<figure><img src="https://images.theconversation.com/files/227066/original/file-20180711-27030-1v51nmh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Looking for food, water and maybe adventure? </span> <span class="attribution"><a class="source" href="https://unsplash.com/photos/N64wTMsjnXU">Unsplash </a></span></figcaption></figure><p>Can you imagine walking 14,000km? Trekking across wide savannas, down creek beds, along mountain chains in terrain that is new and home to foreign types of plants and animals? Can I eat this? What is that? </p>
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<a href="https://images.theconversation.com/files/226920/original/file-20180710-70042-1y5fba6.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/226920/original/file-20180710-70042-1y5fba6.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/226920/original/file-20180710-70042-1y5fba6.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/226920/original/file-20180710-70042-1y5fba6.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/226920/original/file-20180710-70042-1y5fba6.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/226920/original/file-20180710-70042-1y5fba6.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/226920/original/file-20180710-70042-1y5fba6.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/226920/original/file-20180710-70042-1y5fba6.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>
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<span class="caption">One of the 2 million-year-old stone tools discovered at Shangchen, China.</span>
<span class="attribution"><span class="source">Photograph courtesy of R. Dennell.</span></span>
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<p>This long excursion – once thought only to have been attempted late in the journey of humankind – has been getting pushed further and further back in time thanks to advancing archaeological research. </p>
<p><a href="https://www.nature.com/articles/s41586-018-0299-4">Findings published in Nature</a> today have extended the start of our worldwide trekking back to beyond 2.1 million years ago. </p>
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Read more:
<a href="https://theconversation.com/worlds-scientists-turn-to-asia-and-australia-to-rewrite-human-history-88697">World's scientists turn to Asia and Australia to rewrite human history</a>
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<p>Previously, we knew that people were wandering around eastern Europe by 1.85 million years ago, as their bones and tools were discovered at a cave site called <a href="http://www.dmanisi.ge/page?id=2&lang=en">Dmanisi</a> in Georgia. </p>
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<a href="https://images.theconversation.com/files/227069/original/file-20180711-27015-p539r2.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/227069/original/file-20180711-27015-p539r2.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/227069/original/file-20180711-27015-p539r2.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=360&fit=crop&dpr=1 600w, https://images.theconversation.com/files/227069/original/file-20180711-27015-p539r2.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=360&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/227069/original/file-20180711-27015-p539r2.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=360&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/227069/original/file-20180711-27015-p539r2.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=452&fit=crop&dpr=1 754w, https://images.theconversation.com/files/227069/original/file-20180711-27015-p539r2.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=452&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/227069/original/file-20180711-27015-p539r2.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=452&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">Ancient sites of global hominin presence.</span>
<span class="attribution"><a class="source" href="https://www.nature.com/articles/s41586-018-0299-4">John Kappelman/Nature (no reuse)</a></span>
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<p>Presented in the <a href="https://www.nature.com/articles/s41586-018-0299-4">new paper</a> today, evidence for this earlier – and further – human movement comes in the form of flaked stone tools found in sediments at Shangchen, in the southern Chinese Loess Plateau. </p>
<p>Some 96 tools were found <em>in situ</em> – that is, still in the ground and undisturbed – and have shapes and traces of working recognisable to the archaeologist as distinctly human-made. </p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/SrvPOkMs4U4?wmode=transparent&start=83" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">How are stone tools made? An expert explains.</span></figcaption>
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<h2>Out of Africa? Or Asia?</h2>
<p>Who were these early explorers? All signs point to hominids of the genus <em>Homo</em> (simply meaning “man”) – early people, <a href="http://humanorigins.si.edu/evidence/human-family-tree">some of whom led to our modern selves</a>. </p>
<p>An onslaught of recent findings from Asia has prompted some researchers to suggest that humans came “<a href="https://www.newscientist.com/article/mg23931850-200-asias-mysterious-role-in-the-early-origins-of-humanity/">Out of Asia</a>”. However, while it appears that people were in this region very early, humanity remains an African invention. </p>
<p>Our earliest ancestors arose in Africa some 6 million years ago, although the earliest remains of those belonging to our branch of the family tree – that of <em>Homo</em> – only date back to 2.8 million years ago. A single jawbone found in Ethiopia pushed back the <a href="https://www.smithsonianmag.com/science-nature/oldest-human-fossil-unearthed-ethiopia-180954470/">origins of our genus some 400,000 years</a>. </p>
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<a href="https://theconversation.com/age-of-jawbones-mean-the-origins-of-humans-just-got-older-38722">Age of jawbones mean the origins of humans just got older</a>
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<p>Currently, it seems that the earliest communities of <em>Homo</em> lived in eastern Africa for several hundred thousand years before heading out and away from the motherland. </p>
<h2>Human = adaptable = global conquest</h2>
<p>The apparent ease with which humankind has moved across vast landscapes continues to surprise scientists. Many of us now struggle with a hike that our ancestors would consider a relaxing stroll down the road. So how far did they walk at any one time? </p>
<p>Realistically, we have no way of answering this question for sure. Modern hunter-gatherers such as the Hadza regularly travel some ten (or more) kilometres each day in the course of their daily activities. Applying this rate of movement, someone could theoretically reach the new Chinese site of Shangchen from Africa in about four years. </p>
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<img alt="" src="https://images.theconversation.com/files/227082/original/file-20180711-27042-o0eyt6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/227082/original/file-20180711-27042-o0eyt6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/227082/original/file-20180711-27042-o0eyt6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/227082/original/file-20180711-27042-o0eyt6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/227082/original/file-20180711-27042-o0eyt6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/227082/original/file-20180711-27042-o0eyt6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/227082/original/file-20180711-27042-o0eyt6.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">A Hadza hunter with bow-and-arrow in Tanzania, 2013.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/lake-eyasi-tanzania-february-18-unidentified-134540183?src=3iHm0pYi_FRzRzIPC1b9Ew-1-19">from www.shutterstock.com</a></span>
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<p>In reality, the journey from Africa to Asia (and beyond) wasn’t one great trek undertaken by particularly adventurous individuals searching for… treasure? fame? glory? Instead, it is likely that small groups moved only a little at a time as their families expanded, or necessary resources ran dry. </p>
<p>One can imagine the family matriarch and/or patriach saying to their extended family, something along the lines of, “Let us go to the next valley (or the next river) where there are plenty of fish/deer and it isn’t so crowded.”</p>
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Read more:
<a href="https://theconversation.com/rhino-fossil-rewrites-the-earliest-human-history-of-the-philippines-95879">Rhino fossil rewrites the earliest human history of the Philippines</a>
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<p>Perhaps on occasion there were a few irrepressible people who wanted to explore new lands and did cover significant distances in a single spurt. Perhaps they set up a new home far from their ancestors. </p>
<p>Certainly, such things have happened in recent times – Western Europeans turning up in Australia or North America, for example. </p>
<p>For the first humans moving out of Africa, there would not have been anyone to parlay with on arrival to new territories. Instead, they would have been entirely on their own when learning how to avoid new and exotic dangerous animals, identify and locate new foods and toolmaking supplies, and develop new ways to navigate. Each new landscape would have presented a significant challenge. Successfully setting up home or simply passing through without serious incident was no small feat. </p>
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Read more:
<a href="https://theconversation.com/chickens-tell-tale-of-human-migration-across-pacific-24461">Chickens tell tale of human migration across Pacific</a>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/YrOlE3x5JRs?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Home on the Ocean. Colonisation of the Pacific and the last great human migration.</span></figcaption>
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<p>Humans are extremely flexible and adaptable to new environments. This trait has allowed a species that evolved in a hot grassy savanna to make its home in tropical rainforests, or the Arctic, or even on the ocean – as the <a href="http://www.abc.net.au/news/science/2016-10-04/dna-reveals-lapita-ancestors-of-pacific-islanders-came-from-asia/7893100">Lapita</a> people who colonised the Pacific did. </p>
<p>Ultimately, it allowed us to discover and colonise the entire globe as part of a multi-millenial human odyssey.</p><img src="https://counter.theconversation.com/content/99671/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michelle Langley is an Australian Research Council DECRA Research Fellow at the Australian Research Centre for Human Evolution at Griffith University.</span></em></p>Conquer the globe? You bet we did – but when did it start? A new paper shows early humans made tools in China two million years ago.Michelle Langley, ARC DECRA Research Fellow, Griffith UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/772312017-05-08T15:27:44Z2017-05-08T15:27:44ZBrain-imaging modern people making Stone Age tools hints at evolution of human intelligence<figure><img src="https://images.theconversation.com/files/168412/original/file-20170508-20729-j1gfbg.jpg?ixlib=rb-1.1.0&rect=0%2C349%2C4330%2C3096&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The stone flakes are flying, but what brain regions are firing?</span> <span class="attribution"><span class="source">Shelby S. Putt</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>How did humans get to be so smart, and when did this happen? To untangle this question, we need to know more about the intelligence of our human ancestors who lived 1.8 million years ago. It was at this point in time that a new type of stone tool hit the scene and the human brain nearly doubled in size. </p>
<p>Some researchers have suggested that this more advanced technology, coupled with a bigger brain, implies a higher degree of intelligence and perhaps even the first signs of language. But all that remains from these ancient humans are fossils and stone tools. Without access to a time machine, it’s difficult to know just what cognitive features these early humans possessed, or if they were capable of language. Difficult – but not impossible.</p>
<p>Now, thanks to cutting-edge brain imaging technology, my interdisciplinary research team is learning just how intelligent our early tool-making ancestors were. By scanning the brains of modern humans today as they make the same kinds of tools that our very distant ancestors did, we are <a href="http://nature.com/articles/doi:10.1038/s41562-017-0102">zeroing in on what kind of brainpower is necessary</a> to complete these tool-making tasks.</p>
<h2>A leap forward in stone tool technology</h2>
<p>The stone tools that have survived in the archaeological record can tell us something about the intelligence of the people who made them. Even our earliest human ancestors were no dummies; there is evidence for stone tools as early as <a href="https://doi.org/10.1038/nature14464">3.3 million years ago</a>, though they were probably making tools from perishable items even earlier. </p>
<p>As early as <a href="https://doi.org/10.1038/385333a0">2.6 million years ago</a>, some small-bodied and small-brained human ancestors chipped small flakes off of larger stones to use their sharp cutting edges. These types of stone tools belong to what is known as the <a href="http://www.stoneageinstitute.org/pdfs/oldowan-ch1-schick-toth.pdf">Oldowan industry</a>, named after <a href="http://www.olduvai-gorge.org/aboutus.html">Olduvai Gorge</a> in Tanzania, where remains of some of the earliest humans and their stone implements have been found.</p>
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<span class="caption">The more basic Oldowan chopper (left) and the more advanced Acheulian handaxe (right).</span>
<span class="attribution"><span class="source">Shelby S. Putt, courtesy of the Stone Age Institute</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<p>Around 1.8 million years ago, also in East Africa, a new type of human emerged, one with a larger body, a larger brain and a new toolkit. This toolkit, called the <a href="https://doi.org/10.1073/pnas.1221285110">Acheulian industry</a>, consisted of shaped core tools that were made by removing flakes from stones in a more systematic manner, leading to a flat handaxe with sharp edges all the way around the tool.</p>
<p>Why was this novel Acheulian technology so important for our ancestors? At a time <a href="https://doi.org/10.1126/science.1236828">when the environment and food resources were somewhat unpredictable</a>, early humans probably began to rely on technology more often to access food items that were more difficult to obtain than, say, low-hanging fruits. Meat, underground tubers, grubs and nuts may all have been on the menu. Those individuals with the better tools gained access to these energy-dense foods, and they and their offspring reaped the benefits. </p>
<p><a href="https://doi.org/10.1098/rstb.2011.0099">One group of researchers</a> has suggested that human language may have evolved by piggybacking on a preexisting brain network that was already being used for this kind of complex tool manufacture.</p>
<p>So were the Acheulian toolmakers smarter than any human relative that lived prior to 1.8 million years ago, and is this potentially the point in human evolution when language emerged? We used a neuroarchaeological approach to answer these questions.</p>
<h2>Imaging brain activity now to reconstruct brain activity in the past</h2>
<p>My research team, which consists of paleoanthropologists at the <a href="http://www.stoneageinstitute.org/staff.html">Stone Age Institute</a> and the <a href="https://clas.uiowa.edu/anthropology/people/robert-g-franciscus">University of Iowa</a> and <a href="https://www.uea.ac.uk/psychology/people/profile/s-wijeakumar">neuroscientists</a> at the <a href="https://www.uea.ac.uk/psychology/people/profile/j-spencer">University of East Anglia</a>, recruited modern human beings – all we have at our disposal these days – whose brains we could image while they made Oldowan and Acheulian stone tools. Our volunteers were recreating the behaviors of early humans to make the same types of tools they made so long ago; we can assume that the areas of their modern human brains that light up when making these tools are the same areas that were activated in the distant past.</p>
<p>We used a brain imaging technology called <a href="http://www.sciencedirect.com/science/journal/10538119/85/part/P1">functional near-infrared spectroscopy</a> (fNIRS). It is unique among brain imaging techniques because it allows the person whose brain is being imaged to sit up and move her arms, unlike other techniques that do not allow any movement at all.</p>
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<span class="caption">Participants in the study made stone tools while their brain activity was measured with fNIRS.</span>
<span class="attribution"><span class="source">Shelby S. Putt</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<p>Each of the subjects who participated in this study attended multiple training sessions to learn how to make Oldowan and Acheulian tools before going in for the final test – making tools while hooked up to the fNIRS system. </p>
<p>We needed to control for language in the design of our experiment to test the idea that language and tool-making share a common circuit in the brain. So we divided the participants into two groups: One learned to make stone tools via video with language instructions; the other group learned via the same videos, but with the audio muted, so without language.</p>
<p>If language and tool-making truly share a co-evolutionary relationship, then even those participants who were placed in the nonverbal group should still use language areas of the brain while making a stone tool. This is the result we should expect if language processing and stone tool production require the same neural circuitry in the brain. </p>
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<figcaption><span class="caption">Training video shown to participants. The verbal group heard the instructor’s voiced instructions, while the nonverbal group watched a muted version.</span></figcaption>
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<p>During the neuroimaging session, we had the participants complete three tasks: a motor baseline task during which they struck two round stones together without attempting to make flakes; an Oldowan task that involved making simple flakes without trying to shape the core; and an Acheulian task where they attempted to shape the core into a handaxe through a more advanced flake removal procedure.</p>
<h2>The evolution of human-like cognition</h2>
<p><a href="http://nature.com/articles/doi:10.1038/s41562-017-0102">What we found</a> was that only the participants who learned to make stone tools with language instruction used language processing areas of the brain. This probably means that they were recalling verbal instructions they’d heard during their training sessions. That explains why <a href="https://doi.org/10.1098/rstb.2008.0001">earlier studies</a> that did not control for language instruction in their experiment design found that stone tool production activates language processing areas of the brain. Those language areas lit up not because of anything intrinsic to making stone tools, but because while participants worked on the tools they also were likely playing back in their minds the language-based instruction they’d received.</p>
<p>Our study showed that people could make stone tools without activating language-related brain circuits. That means, then, that we can’t confidently state at this point that stone tool manufacture played a major role in the evolution of language. When exactly language made its appearance is therefore still a mystery to be solved. </p>
<p>We also discovered that Oldowan tool-making mainly activates brain areas involved in visual inspection and hand movement. More advanced Acheulian tool-making recruits a higher-order cognitive network that spans across a large portion of the cerebral cortex. This Acheulian cognitive network is involved in higher-level motor planning and holding in mind multi-sensory information using <a href="https://www.simplypsychology.org/working%20memory.html">working memory</a>. </p>
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<span class="caption">Areas of the brain that form the Acheulian cognitive network that are also active when trained pianists play the piano.</span>
<span class="attribution"><span class="source">Shelby S. Putt</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<p>It turns out that this Acheulian cognitive network is the same one that comes online <a href="https://doi.org/10.1016/j.neuroimage.2005.10.044">when a trained pianist plays the piano</a>. This does not necessarily mean that early humans could play Chopin. But our result may mean that the brain networks we rely on today to complete complex tasks involving multiple forms of information, such as playing a musical instrument, were likely evolving around 1.8 million years ago so that our ancestors could make relatively complex tools to exploit energy-dense foods.</p><img src="https://counter.theconversation.com/content/77231/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Shelby Putt received funding from the Leakey Foundation, the Wenner-Gren Foundation, and Sigma Xi, the Scientific Research Society, and the American Association of University Women. </span></em></p>We can’t observe the brain activity of extinct human species. But we can observe modern brains doing the things that our distant ancestors did, looking for clues about how ancient brains worked.Shelby Putt, Postdoctoral Research Fellow, The Stone Age Institute and The Center for Research into the Anthropological Foundations of Technology, Indiana UniversityLicensed as Creative Commons – attribution, no derivatives.