by Peter Aldhous Itsy bitsy spiders have a big problem: where to store their bulging brains. For Anapisona simoni and other arachnid lightweights, the problem is so acute that their brains have literally spilled out of their body cavities and into their legs. Tiny creatures' brains and microelectronics have something in common, it turns out: ultimately, attempts to miniaturise the circuitry will hit a wall. Once the axons that transmit neural signals get down to 0.1 micrometre in diameter, for instance, channels that move ions across cell membranes get so "noisy" that signalling becomes unreliable. What's more, nervous tissue demands a lot of energy, and if nerve cells get too small they simply don't contain enough mitochondria – organelles that act as cellular power plants – to meet their needs. As a result, animals face a trade-off as natural selection pushes them towards the minuscule: either dumb down, or lug around brains that are much bigger, proportionate to body size, than those needed by a larger creatures with similar smarts. Weaving websMovie Camera is not for dullards, so tiny spiders haven't taken the evolutionary road to stupidity. In 2007, William Eberhard of the Smithsonian Tropical Research Institute in Panama and the University of Costa Rica found that the smallest spiders weave webs that are just as complex as those made by larger relatives. "There was no correlation between the size of the spider and the precision with which it built the sticky spiral in the web," he says. © Copyright Reed Business Information Ltd.

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Link ID: 16150 - Posted: 12.15.2011

By Bruce Bower Culturally speaking, ancient East Africans were a stone’s throw away from southern Arabia. Stone tools collected at several sites along a plateau in Oman, which date to roughly 106,000 years ago, match elongated cutting implements previously found at East African sites from around the same time, say archaeologist Jeffrey Rose of the University of Birmingham, England, and his colleagues. New finds also include cores — or rocks from which tools were pounded off with a hammer stone — that correspond to East African specimens, the researchers report online November 30 in PLoS ONE. East African sites that have yielded these distinctive stone artifacts extend southward along the Nile River to the Horn of Africa. “In the mountain of papers speculating about human dispersal out of Africa, a link between southern Arabia and the Nile Valley has never been considered,” Rose says. Either Africans crossed the Red Sea and trekked into southern Arabia well before an African exodus around 60,000 years ago, or ancient people from Arabia influenced African toolmaking, the scientists suggest. “The finds in Oman are rather spectacular,” comments archaeologist Michael Petraglia of the University of Oxford, England. “They have a date that is earlier than similar African artifacts, which could imply a migration back to Africa, or at least a flow between African and Arabian populations.” © Society for Science & the Public 2000 - 2011

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Link ID: 16141 - Posted: 12.13.2011

by Rowan Hooper WHAT was the basis for the earliest friendships? If wild chimps are any guide: support in a fight, borrowing a valued tool, and a bite to eat now and then. Quite similar to our friendships today, in fact. Indeed, some chimps are so modern they have relationships that we would classify as friends with benefits. Primatologists are reassessing the complexity of chimpanzee society in the light of new findings that also suggest answers to a long-standing question: why share things with non-relatives? For the first time wild chimps in Senegal have been observed taking plant foods and tools from other chimps, who don't react to the intrusion. The chimps donating their stuff don't get paid, but neither do they protest. Instead, the trade appears to help build social cohesion. What's more, in another west African study, this time in Ivory Coast, a "market" has been described where chimps exchange commodities in the shape of both social behaviours including grooming and sex, and resources such as meat. Christophe Boesch of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, says we have only recently begun to appreciate the time and energy chimps invest in reciprocal relationships, and he compares chimp relationships to friendship. "These findings have prompted primatologists to use some terms that have in the past been reserved for humans." © Copyright Reed Business Information Ltd.

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Link ID: 16119 - Posted: 12.08.2011

Clive Gamble Wondering what went on in the heads of Neanderthals has rarely produced positive thoughts. H. G. Wells set the bar low in his short story The Grisly Folk in 1921, writing: “We cannot conceive in our different minds the strange ideas that chased one another through those queerly shaped brains.” Wells's hatchet job was effective. Other authors have offered sympathetic alternatives, such as Isaac Asimov's 1958 short story The Ugly Little Boy. But the idea of a 'thinking Neanderthal' has become an evolutionary oxymoron on a par with 'military intelligence' and 'airline food'. Yet cognition certainly took place in the Neanderthal brain — the largest in human evolution, housed in a long, distinctively shaped skull. In How to Think Like a Neandertal, archaeologist Thomas Wynn and psychologist Frederick Coolidge provide one of the most rounded portraits yet of a fossil human. The book covers familiar areas — diet, symbolism and language — but also includes innovative assessments of Neanderthals' capacity to tell jokes, and even speculations on what they might have dreamed about. The authors use the Neanderthals as a means of discussing the evolutionary reasons for such cognitive abilities as humour and deception. We have learned much about Neanderthals in the past 150 years. They were powerfully built and top carnivores. Their stone tools are found across Eurasia. We know from their genome sequence that the last common ancestor of Neanderthals and ourselves lived some half a million years ago. They became extinct in southern Spain as recently as 30,000 years ago. © 2011 Nature Publishing Group,

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Link ID: 16065 - Posted: 11.22.2011

When the Society for Neuroscience gets together for their annual meeting each year, a city of scientists suddenly forms for a week. This year’s meeting has drawn 31,000 people to the Washington DC Convention Center. The subjects of their presentations ranged from brain scans of memories to the molecular details of disorders such as Parkinson’s and autism. This morning, a scientist named Svante Paabo delivered a talk. Its subject might make you think that he had stumbled into the wrong conference altogether. He delivered a lecture about Neanderthals. Yet Paabo did not speak to an empty room. He stood before thousands of researchers in the main hall of the convention center. His face was projected onto a dozen giant screens, as if he were opening for the Rolling Stones. When Paabo was done, the audience released a surging crest of applause. One neuroscientist I know, who was sitting somewhere in that huge room, sent me a one-word email as Paabo finished: “Amazing.” You may well know about Paabo’s work. In August, Elizabeth Kolbert published a long profile in the New Yorker. But he’s been in the news for fifteen years. I’ve also followed his work since the mid-1990s, having written about pieces of Paabo’s work in newspapers, magazines, and books. But it was bracing to hear him bring together the scope of his research in an hour–including new experiments that Paabo’s colleagues are presenting at the meeting. He has changed the way scientists study human evolution. Along with fossils, they can now study genomes that belonged to people who died 40,000 years ago. They can do experiments to see how some of those individual genes helped to make us human. During his talk, Paabo used this new research to sketch out a sweeping vision of how our ancestors evolved uniquely human brains as they swept out across the world. © 2011, Kalmbach Publishing Co.

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Link ID: 16042 - Posted: 11.17.2011

By Nick Bascom Primates may have evolved from living the lonely life to forming complex societies in two major steps, a new study of more than 200 species suggests. Understanding when and why the ancestors of Homo sapiens and its closest cousins adopted different social structures could help reveal more about the evolution of human society. About 52 million years ago, primates — an order of animals that includes, among others, humans and great apes — might have stopped foraging alone and banded together in large, loosely formed, same-sex groups to search for food, anthropologist Susanne Shultz of the University of Oxford and colleagues report in the Nov. 10 Nature. Then around 16 million years ago, primates began forming more stable social groups, such as male-female pairs and harems dominated by one male, the researchers suggest. Teaming up this way may have been prompted by a switch from a nocturnal lifestyle to moving about in the sunshine. “Being active during the day would have allowed primates to travel across larger spaces and exploit their environment more effectively, but it would have also exposed them to a huge predation risk,” says Shultz. To make it through the day, primates would have needed a new defense strategy to deal with both a greater number of predators and also new kinds of hunters. “What’s going to nail you at night is different than what’s going to nail you during the day,” says primatologist Anthony Di Fiore of the University of Texas at Austin, who was not involved in the study. © Society for Science & the Public 2000 - 2011

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Link ID: 16013 - Posted: 11.11.2011

by Helen Fields Hopping around in the Peruvian jungle, near the border with Brazil, is a menagerie of tiny poison dart frogs. Their wealth of colors and patterns—some have golden heads atop white-swirled bodies, others wear full-torso tattoos of black and neon-yellow stripes—act as the world's worst advertisement to predators: Don't eat me, I'm toxic. But why have so many designs evolved when a single one might do? Evolutionary biologist Mathieu Chouteau of the University of Montreal in Canada ventured into the rainforest to find out. He was on the trail of Ranitomeya imitator, a single species of poison dart frog that comes in about 10 different patterns. That variability should be confusing for predators, he says, because the warnings are supposed to be a message to them, and it would make more sense to give them only one design to keep track of. To figure out what was going on, Chouteau enlisted his girlfriend's help to make 3600 models of frogs, each 18 millimeters long. "It was, like, at least a month of working full-time," he says. They pressed black clay into frog-shaped molds and painted each one in one of two patterns: yellow striped or reticulated, like a giraffe, with green lines. They also made brown frogs as a nontoxic-looking control. Then Chouteau packed the frogs in his carryon baggage and flew to Peru. The models represent the frogs that live in two different sites: one in the Amazonian lowland and one in a valley at about 500 meters above sea level. The two sites are separated by a high ridge. In one very long day at each site, Chouteau set out 900 of the frogs on leaves along narrow trails used by locals to hunt in the forest. For the next 3 days, he went back and checked them to see whether the soft clay recorded evidence of attacks by birds. © 2010 American Association for the Advancement of Science

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior; Chapter 4: The Chemistry of Behavior: Neurotransmitters and Neuropharmacology
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Link ID: 15986 - Posted: 11.05.2011

By Tina Hesman Saey MONTREAL — Bigger, better human brains may be the result of a double dose of a gene that helps brain cells move around. At least twice in the past 3 million years, a gene called SRGAP2 has been duplicated within the human genome, says Megan Dennis of the University of Washington in Seattle. Dennis and her colleagues have now shown that extra copies of this gene may account for humans’ thicker brain cortex, the brain’s gray matter where thinking takes place. The team had previously discovered that SRGAP2 is one of 23 genes duplicated in humans but not in other primates. Dennis found that an ancient form of the gene, which is located on human chromosome 1, was partially duplicated on the same chromosome about 3.4 million years ago. That partial copy makes a shortened version of the SRGAP2 protein. Then, about 2.4 million years ago, a copy of the partial copy was created and added to the short arm of chromosome 1, Dennis reported October 13 at the International Congress of Human Genetics. But just having extra copies doesn’t mean the gene is evolutionarily important. So Dennis and her colleagues examined the duplicate genes in more than 150 people and found that the copy made 3.4 million years ago is missing in some people. But the younger version of the gene has become fixed in the human population, meaning that absolutely everyone has it. Millions of years may seem like a long time, but it is actually quite speedy for fixing duplicated genes, Dennis says. The rapid assimilation could indicate that the gene is important in human evolution. © Society for Science & the Public 2000 - 2011

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Link ID: 15913 - Posted: 10.15.2011

By Eric Michael Johnson Charles Darwin had more in common with chimpanzees than even he realized. Before he was universally known for his theory of natural selection, the young naturalist made a decision that has long been hailed as the type of behavior that fundamentally separates humans from other apes. In 1858, before Darwin published On the Origin of Species, his friend Alfred Russel Wallace​ mailed Darwin his own theory of evolution that closely matched what Darwin had secretly been working on for more than two decades. Instead of racing to publish and ignoring Wallace’s work, Darwin included Wallace’s outline alongside his own abstract so that the two could be presented jointly before the Linnean Society the following month. “I would far rather burn my whole book than that [Wallace] or any man should think that I had behaved in a paltry spirit,” Darwin wrote. This kind of prosocial behavior, a form of altruism that seeks to benefit others and promote cooperation, has now been found in chimps, the species that Darwin did more than any other human to connect us with. (This month's Science Agenda, about medical testing in chimps, notes other similarities that have been documented in chimps and humans.) In the study, published in the Proceedings of the National Academy of Sciences USA, primatologist Frans de Waal and his colleagues at the Yerkes National Primate Research Center at Emory University presented chimps with a simplified version of the choice that Darwin faced. Pairs of chimps were brought into a testing room where they were separated only by a wire mesh. On one side was a bucket containing 30 tokens that the chimpanzee could give to an experimenter for a food reward. Half of the tokens were of one color that resulted in only the chimpanzee that gave the token receiving a reward. The other tokens were of a different color that resulted in both chimpanzees receiving a food reward. If chimpanzees were motivated only by selfish interests, they would be expected to choose a reward only for themselves (or it should be 50–50 if they were choosing randomly). But individuals were significantly more likely to choose the prosocial outcome compared with the no-partner control. © 2011 Scientific American,

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Link ID: 15868 - Posted: 10.04.2011

Our brains followed a twisting path of development through creatures that swam, crawled and walked the Earth long before we did. Here are a few of these animals, and how they helped make us what we are. Our single-celled ancestors had sophisticated machinery for sensing and responding to the environment. Once the first multicellular animals arose, this machinery was adapted for cell-to-cell communication. Specialised cells that could carry messages using electrical impulses and chemical signals – the first nerve cells – arose very early on. The first neurons were probably connected in a diffuse network across the body of a creature like this hydra. This kind of structure, known as a nerve net, can still be seen in the quivering bodies of jellyfish and sea anemones

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Link ID: 15851 - Posted: 09.29.2011

by David Robson IT IS 30,000 years ago. A man enters a narrow cave in what is now the south of France. By the flickering light of a tallow lamp, he eases his way through to the furthest chamber. On one of the stone overhangs, he sketches in charcoal a picture of the head of a bison looming above a woman's naked body. In 1933, Pablo Picasso creates a strikingly similar image, called Minotaur Assaulting Girl. That two artists, separated by 30 millennia, should produce such similar work seems astonishing. But perhaps we shouldn't be too surprised. Anatomically at least, our brains differ little from those of the people who painted the walls of the Chauvet cave all those years ago. Their art, part of the "creative explosion" of that time, is further evidence that they had brains just like ours. How did we acquire our beautiful brains? How did the savage struggle for survival produce such an extraordinary object? This is a difficult question to answer, not least because brains do not fossilise. Thanks to the latest technologies, though, we can now trace the brain's evolution in unprecedented detail, from a time before the very first nerve cells right up to the age of cave art and cubism. The story of the brain begins in the ancient oceans, long before the first animals appeared. The single-celled organisms that swam or crawled in them may not have had brains, but they did have sophisticated ways of sensing and responding to their environment. "These mechanisms are maintained right through to the evolution of mammals," says Seth Grant at the Wellcome Trust Sanger Institute in Cambridge, UK. "That's a very deep ancestry." © Copyright Reed Business Information Ltd.

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Link ID: 15839 - Posted: 09.27.2011

by Ferris Jabr Slimy and often sluggish they may be, but some molluscs deserve credit for their brains – which, it now appears, they managed to evolve independently, four times. The mollusc family includes the most intelligent invertebrates on the planet: octopuses, squid and cuttlefishMovie Camera. Now, the latest and most sophisticated genetic analysis of their evolutionary history overturns our previous understanding of how they got so brainy. The new findings expand a growing body of evidence that in very different groups of animals – molluscs and mammals, for instance – central nervous systems evolved not once, but several times, in parallel. Kevin Kocot of Auburn University, Alabama, and his colleagues are responsible for the new evolutionary history of the mollusc family, which includes 100,000 living species in eight lineages. They analysed genetic sequences common to all molluscs and looked for differences that have accumulated over time: the more a shared sequence differs between two species, the less related they are. The findings, which rely on advanced statistical analyses, fundamentally rearrange branches on the mollusc family tree. In the traditional tree, snails and slugs (gastropods) are most closely related to octopuses, squid, cuttlefish and nautiluses (cephalopods), which appears to make sense in terms of their nervous systems: both groups have highly centralised nervous systems compared with other molluscs and invertebrates. Snails and slugs have clusters of ganglia – bundles of nerve cells – which, in many species, are fused into a single organ; cephalopods have highly developed central nervous systems that enable them to navigate a maze, use tools, mimic other species, learn from each other and solve complex problems. © Copyright Reed Business Information Ltd.

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Link ID: 15812 - Posted: 09.17.2011

by Alison George He has already revealed that early humans interbred with Neanderthals and discovered a whole new type of hominin from its DNA alone. Now Svante Pääbo is setting his sights on even more exotic discoveries. He tells Alison George why he thinks the bombshells will keep coming Last year you revealed a previously unknown type of hominin, called the Denisovans, from DNA in a pinkie bone found in a cave in Denisova, Siberia. Tell me about this. We knew people had lived in this cave, but thought they were either Neanderthals or modern humans. When we sequenced the DNA, I was in the US so a postdoc called me to tell me the results. He said: "Are you sitting down?" because it was immediately clear this was some other form of human; not a Neanderthal, not a modern human. We were totally shocked. This is the first time that a new form of human has been defined totally from molecular data, not from the morphology of fossils. I think this will happen much more in the future - that just from a tiny speck of bone we can determine the whole genome and reconstruct much of the history. You recently visited this cave. What was it like? The cave is in the Altai mountains in central Asia and it was the first time I had seen it. It is really beautiful. It's big, almost cathedral-like with light coming in through a natural chimney. And you know that in this cave there have been both the Denisovans and modern humans and perhaps Neanderthals too. I went there for a meeting where anatomists, palaeontologists and archaeologists came together for the first time to try to sort out what we can say about this group of humans. © Copyright Reed Business Information Ltd.

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Link ID: 15770 - Posted: 09.06.2011

by Michael Marshall WHEN wondering about the origins of our brain, don't look to Homo sapiens, chimpanzees, fish or even wormsMovie Camera. Many key components first appeared in single-celled organisms, long before animals, brains and even nerve cells existed. Dirk Fasshauer of the University of Lausanne, Switzerland, and colleagues were studying a pair of essential neural proteins called Munc18/syntaxin1 when they decided to look for them in very simple, single-celled organisms. Choanoflagellates are aquatic organisms found in oceans and rivers around the globe. Being a single cell, they do not have nerves, yet the team found both proteins in the choanoflagellate Monosiga brevicollis, and the interaction between the two was the same as in neurons (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1106189108). These proteins are found in every nerve cell and control the release of the chemicals which neurons use to talk to each other, called neurotransmitters. The finding is intriguing on its own, but much more significant when combined with a growing body of evidence that essential brain components evolved in choanoflagellates before multicellular life appeared. In 2008, Xinjiang Cai of Duke University in Durham, North Carolina, discovered that M. brevicollis has the same calcium channels in its cells as those used by neurons (Molecular Biology and Evolution, DOI: 10.1093/molbev/msn077). Then, in 2010, it emerged that M. brevicollis also has several proteins that neurons use to process signals from their neighbours (BMC Evolutionary Biology, DOI: 10.1186/1471-2148-10-34). © Copyright Reed Business Information Ltd

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Link ID: 15757 - Posted: 09.03.2011

Matt Kaplan The discovery of stone axes in the same sediment layer as cruder tools indicates that hominins with differing tool-making technologies may have coexisted. The axes, found in Kenya by Christopher Lepre, a palaeontologist at Columbia University in New York, and his team are estimated to be around 1.76 million years old. That's 350,000 years older than any other complex tools yet discovered. The finding, described today in Nature1, includes another important discovery: the hand axes, usually associated with the emergence around 1.5 million years ago of Homo erectus as the dominant hominin species, were found alongside primitive chopping tools that had already been in use for at least a million years. "This supports the idea that the two earliest stone-tool manufacturing techniques and traditions were, at least sometimes, utilized contemporaneously," says palaeoanthropologist Briana Pobiner at the Smithsonian Institution in Washington DC. Chip off the old block The hand axes, which have a distinctive, carefully made oval shape, are part of the Acheulian technology — those tools thought to have been developed around 1.6 million years ago. The more primitive tools, typically chunks of stone with crudely-chipped edges, belong to the earlier Oldowan toolkit. Because H. erectus is often associated with Acheulian tools, Lepre and his colleagues suggest that the hand axes they found might have been made by H. erectus, and the Oldowan tools by the less cognitively-capable Homo habilis. © 2011 Nature Publishing Group,

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Link ID: 15752 - Posted: 09.01.2011

By Matt McGrath Science reporter, BBC World Service Sexual relations between ancient humans and their evolutionary cousins are critical for our modern immune systems, researchers report in Science journal. Mating with Neanderthals and another ancient group called Denisovans introduced genes that help us cope with viruses to this day, they conclude. Previous research had indicated that prehistoric interbreeding led to up to 4% of the modern human genome. The new work identifies stretches of DNA derived from our distant relatives. In the human immune system, the HLA (human leucocyte antigen) family of genes plays an important role in defending against foreign invaders such as viruses. The authors say that the origins of some HLA class 1 genes are proof that our ancient relatives interbred with Neanderthals and Denisovans for a period. At least one variety of HLA gene occurs frequently in present day populations from West Asia, but is rare in Africans. The researchers say that is because after ancient humans left Africa some 65,000 years ago, they started breeding with their more primitive relations in Europe, while those who stayed in Africa did not. BBC © 2011

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Link ID: 15727 - Posted: 08.27.2011

By ALEXANDRA HOROWITZ and AMMON SHEA HUMANS have long been fascinated with animal intelligence. Scientific studies have asked if animals use language or tools; have culture; can imitate, cooperate, empathize or deceive. Inevitably, the results of these studies invite comparison with our own cognitive faculties. In such comparisons, humans nearly always come out on top. An impartial observer might suggest that the deck is stacked. After all, we are the ones running these tests. But if we look at some of the subtler aspects of animal behavior, the beasts begin to offer surprisingly stiff competition. A few recent research papers describe animal competence at social and cognitive tasks that humans often struggle with — mastering conversational etiquette, understanding botanical classification, competing on game shows and figuring out how to get a drink when you’re thirsty and the only glass of water is glued to the table and your hands are tied behind your back. “Aping Expressions? Chimpanzees Produce Distinct Laugh Types When Responding to Laughter of Others,” in the journal Emotion (2011). You’re at a dinner party. Your hostess regales you with a long, meandering tale of her recent back surgery. It ends with attempted humor: she laughs and glances at you. You laugh in response, trying to convey an appreciation for her humor that you don’t actually feel. Congratulations: you are now at the level of social politeness of chimpanzees. © 2011 The New York Times Company

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Link ID: 15701 - Posted: 08.23.2011

Gayathri Vaidyanathan Thump! Thump! Thump! As the hollow sound echoes through the Liberian rainforest, Vera Leinert and her fellow researchers freeze. Silently, Leinert directs the guide to investigate. Jefferson 'Bola' Skinnah, a ranger with the Liberian Forestry Development Authority, stalks ahead, using the thumping to mask the sound of his movement. In a sunlit opening in the forest, Skinnah spots a large adult chimpanzee hammering something with a big stone. The chimpanzee puts a broken nut into its mouth then continues pounding. When Skinnah tries to move closer, the chimp disappears into the trees. By the time Leinert and her crew get to the clearing, the animal is long gone. For the past year, Leinert has been trekking through Sapo National Park, Liberia's first and only protected reserve, to study its chimpanzee population. A student volunteer at the Max Planck Institute for Evolutionary Anthropology (EVA) in Leipzig, Germany, Leinert has never seen her elusive subjects in the flesh but she knows some of them well. There's an energetic young male with a big belly who hammers nuts so vigorously he has to grab a sapling for support. There are the stronger adults who can split a nut with three blows. And there are the mothers who parade through the site with their babies. They've all been caught by video cameras placed strategically throughout Sapo. Chimpanzees in the wild are notoriously difficult to study because they flee from humans — with good reason. Bushmeat hunting and human respiratory diseases have decimated chimpanzee populations1, while logging and mining have wiped out their habitat. Population numbers have plunged — although no one knows by exactly how much because in most countries with great apes, the animals have never been properly surveyed. © 2011 Nature Publishing Group,

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Link ID: 15690 - Posted: 08.20.2011

Jo Marchant Hyenas can count up to three. Researchers playing recorded calls to the wily carnivores found that wild spotted hyenas (Crocuta crocuta) responded differently depending on whether they heard one, two or three individuals. The result adds numerical assessment to the list of cognitive abilities that hyenas share with primates, and supports the idea that living in complex social groups — as both primates and hyenas do — is key to the evolution of big brains. Sarah Benson-Amram, a zoologist at Michigan State University in East Lansing, and her colleagues played recordings of hyena calls, or whoops, to members of two hyena clans in the Masai Mara National Reserve in southwestern Kenya1. The recordings were made in Tanzania, Malawi and Senegal, so the calls were unfamiliar to the Kenyan clans, and would have been interpreted as belonging to potential intruders. The recordings each consisted of three bouts of whooping, from one, two or three different animals. In 39 trials involving resting adults — mostly lone females — Benson-Amram measured how vigilant the animals became while the recordings were playing by comparing the amount of time they spent facing the speaker with the amount of time they spent looking away or resting. Although some females became equally watchful in response to all of the recordings, most of the animals distinguished between one, two or three intruders, their attentiveness increasing with the number of unique calls they heard. The finding is published in Animal Behaviour. © 2011 Nature Publishing Group,

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior; Chapter 19: Language and Hemispheric Asymmetry
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Link ID: 15689 - Posted: 08.20.2011

By Susan Milius Acts of apparent altruism in European paper wasps can be explained by plain old self-interest, a new study finds. Polistes dominulus females can either establish their own nests to raise young or join other females for joint homemaking. In those joint nests, though, one female fights her way to the top and does most of the egg-laying while the others do most of the drudge work in taking care of the top wasp’s young. When a subordinate helps her sister, that’s not hard to explain: The underling may not end up with her own offspring, but her reproductive success includes an indirect share of her sister’s brood, because relatives share genes. Forgoing her own direct offspring counts as a kind of altruism, in which an individual helping kin trades direct for indirect benefit. Either way, the wasp’s self-interest is served. But some 15 to 35 percent of co-queens slaving away are not closely related to the top wasp, so biologists have been puzzled about why those strangely helpful females don’t go off to found their own nests. They do it because joining an unrelated queen’s nest offers a chance of grabbing the throne, says Ellouise Leadbeater of the Zoological Society of London. She and her colleagues tracked the fortunes of 1,113 foundresses in 228 nests in southern Spain. In this epic population analysis, females that started out as subordinates to a nonrelative occasionally took over the whole nest and laid their own eggs. Their triumphs were rare but dramatic enough so that, overall, the strategy worked out better than being a single mom: Lone nest foundresses hardly managed to produce any offspring, the researchers report in the Aug. 12 Science. © Society for Science & the Public 2000 - 2011

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Link ID: 15672 - Posted: 08.13.2011