By Robin Anne Smith Recently while visiting the National Museum of Natural History in Washington, D.C., I found myself pondering the noggins of some very, very, old apes. Along one wall of the Hall of Human Origins — an exhibit on human evolution that opened in 2010 — were 76 fossil skulls from 15 species of early humans. Looking at these skulls, one thing was clear: millions of years of evolution have given us much bigger brains. In the 8 million to 6 million years since the ancestors of humans and chimps went their separate ways, the human brain more than tripled in size. If the earliest humans had brains the size of oranges, today’s human brains are more akin to cantaloupes. As for our closest primate relatives, the chimps? Their brains haven’t budged. With our big brains we compose symphonies, write plays, carve sculptures and do math. But our big brains came at a cost, some scientists say. In two recent studies, researchers from Duke University suggest the human brain boost may have been powered by a metabolic shift that meant more fuel for brains, and less fuel for muscles. Co-author Olivier Fedrigo told me the full story one morning over coffee near his home in Durham, North Carolina. The human brain isn’t just big, he explained. It’s also hungry. © 2012 Scientific American

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior
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Link ID: 16421 - Posted: 02.23.2012

Christian Keysers Every time my 18-month-old daughter sees me using a tool, she tries to copy me. She steals my pen to write, and excitedly brushes the few teeth she has when I brush mine. Such a capacity for connecting with and learning from other minds also manifests itself in the empathy we feel with other people's emotions, and in our ability to understand others' goals and help them. Through that ability, we can create and manage the complex social world that is arguably the key to our species' dominance. Ten years ago, human minds were thought to be unique in their ability to connect. But as The Primate Mind shows, there has been a revolution in our understanding. This collection of essays, the result of a 2009 conference organized by primatologist Frans de Waal and ethologist Pier Francesco Ferrari, presents an authoritative, surprising and enriching picture of our monkey and ape cousins. We now know that they have remarkably sophisticated social minds, and that their poor performance in social tasks set by humans was more a result of researchers asking the wrong questions than deficiencies in their experimental subjects. For example, a chapter by psychologists April Ruiz and Laurie Santos explores whether non-human primates can monitor where others are looking and use that information in their own decision-making — a test of whether the animal understands what another perceives. Primatologists first tested this by seeing whether monkeys followed an experimenter's gaze to find a box containing food. The animals performed unexpectedly poorly. But changing the task from cooperation to competition unleashed the primates' true potential: macaques readily stole food from humans who looked away, but refrained from doing so when watched. Placing the task in a setting more relevant to macaque social life, which is less cooperative than our own, emphasized the continuity between our social mind and that of our primate ancestors. © 2012 Nature Publishing Group,

Related chapters from BP7e: Chapter 18: Attention and Higher Cognition; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 14: Attention and Consciousness
Link ID: 16365 - Posted: 02.11.2012

by Lisa Grossman Clint Eastwood might sound an unlikely candidate to help investigate the evolution of the brain, but he has lent a helping hand to researchers doing just that. It turns out that brain regions that do the same job in monkeys and humans aren't always found in the same part of the skull. Previous studies comparing brains across species tended to assume that human brains were just blown-up versions of monkey brains and that functions are carried out by anatomically similar areas. To test this idea, Wim Vanduffel of Harvard Medical School in Boston and the Catholic University of Leuven (KUL) in Belgium, and colleagues scanned the brains of 24 people and four rhesus monkeys while they watched The Good, The Bad and The Ugly. They compared the brain responses of each individual to the same sensory stimulation, and identified which brain areas had similar functions. The majority of the human and monkey brain maps lined up, but some areas with a similar function were in completely different places. The team say the discovery is crucial to building more accurate models of our evolution. "You can't assume that because A and B are close together in the monkey brain, they need to be close together in the human brain," Vanduffel says. Journal reference: Nature Methods, DOI: 10.1038/nmeth.1868 © Copyright Reed Business Information Ltd.

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior; Chapter 18: Attention and Higher Cognition
Related chapters from MM:Chapter 0: ; Chapter 14: Attention and Consciousness
Link ID: 16355 - Posted: 02.07.2012

By Bruce Bower A chimpanzee in need gets help indeed, on two conditions. Another chimp must both see his or her predicament and receive a blatant help request from the needy animal, a new study finds. Observations in the wild and in previous experiments indicate that chimps seldom help others (SN: 8/27/11, p. 10), but that’s not because the chimps don’t understand their peers’ motivations, as some researchers suspect, says primatologist Shinya Yamamoto of Kyoto University in Japan. In a series of lab tests, chimps who saw one of their relatives unsuccessfully reach for a juice box and then request help picked out a useful tool and passed it to their kin, Yamamoto and colleagues report online February 6 in the Proceedings of the National Academy of Sciences. “Chimpanzees can understand others’ goals from obvious cues and then provide help,” Yamamoto says. This ability to grasp that another individual has a goal in mind based on his or her behavior represents one element of what psychologists call theory of mind — an ability to attribute beliefs, desires, pretending and other mental states to oneself and others. Until now, scientists had studied chimps’ understanding of other chimps’ goals only in competitive situations, such as clashes over food and mates. That fueled suspicion that chimps discern others’ goals only in the heat of such struggles. © Society for Science & the Public 2000 - 2012

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior; Chapter 18: Attention and Higher Cognition
Related chapters from MM:Chapter 0: ; Chapter 14: Attention and Consciousness
Link ID: 16351 - Posted: 02.07.2012

Brian Switek The largest mammals to walk Earth evolved from shrew-like creatures that proliferated after the dinosaurs died out, 65 million years ago. But the change from pipsqueak to behemoth took a while: 24 million generations. Researchers led by Alistair Evans, an evolutionary biologist at Monash University in Clayton, Australia, investigated how maximum body mass increased among 28 orders of mammals on multiple continents during the past 70 million years. By comparing the sizes of the largest members of mammal groups at different points in time, and using modern mammals to estimate the length of a generation for each group, Evans and colleagues tracked the speed at which mammals expanded. Their work is published online in the Proceedings of the National Academy of Sciences1 today. The top speed of mammal inflation was slower than had been thought. Previous estimates of the time it takes for a mouse-sized mammal to grow to the size of an elephant — a 100,000-fold size increase — had been based on observations of much smaller, 'microevolutionary' changes in mice, and ranged from 200,0002 to 2 million generations. “This tells us how much slower so-called macroevolution is compared to microevolution,” says Evans, explaining that small size changes can occur quickly, but larger-scale alterations require more time. To put this into perspective, “if we wiped out everything above the size of a rabbit, it would take at least 5 million generations to get to elephant-sized animals”, a 1,000-fold increase. That translates to about 20 million years. Bucking the trend But not all groups followed the same rule. Whales, the largest mammals ever, grew much more quickly than land-dwelling mammals, needing only about 3 million generations for a 1,000-fold size increase. Evans says that the difference was probably the result of different evolutionary constraints of life in the sea, such as the need to retain body heat, which is easier with a larger body mass. © 2012 Nature Publishing Group

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior
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Link ID: 16326 - Posted: 01.31.2012

By NATALIE ANGIER Meet the African crested rat, or Lophiomys imhausi, a creature so large, flamboyantly furred and thickly helmeted it hardly seems a member of the international rat consortium. Yet it is indeed a rat, a deadly dirty rat, its superspecialized pelt permeated with potent toxins harvested from trees. As a recent report in the journal Proceedings of the Royal Society B makes clear, the crested rat offers one of the most extreme cases of a survival strategy rare among mammals: deterring predators with chemical weapons. Venoms and repellents are hardly rare in nature: Many insects, frogs, snakes, jellyfish and other phyletic characters use them with abandon. But mammals generally rely, for defense or offense, on teeth, claws, muscles, keen senses or quick wits. Every so often, however, a mammalian lineage discovers the wonders of chemistry, of nature’s burbling beakers and tubes. And somewhere in the distance a mad cackle sounds. Skunks and zorilles mimic the sulfurous, anoxic stink of a swamp. The male duck-billed platypus infuses its heel spurs with a cobralike poison. The hedgehog declares: Don’t quite get the point of my spines? Allow me to sharpen their sting with a daub of venom I just chewed off the back of a Bufo toad. © 2012 The New York Times Company

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior; Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 0: ; Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 16324 - Posted: 01.31.2012

By Devin Powell A boa constrictor knows to stop squeezing a juicy rat by sensing the heartbeat of its prey, easing up only when the pulse stops, a new study finds. Detecting heartbeats may give snakes like the boa constrictor an edge for hunting iguanas and other large cold-blooded animals that can cling to life for a long time when cut off from oxygen, researchers report online January 18 in Biology Letters. Taking the pulse of such creatures would be a surefire way to know when to let go. To pinpoint the snake’s sensitivity to this particular vital sign, researchers at Dickinson College in Carlisle, Pa., started with rat corpses lacking any signs of life. The scientists then implanted pressure sensors and artificial hearts, small bulbs pumped with fluid that produce the illusion of a regular pulse. Wild boa constrictors attacked the carcasses with or without the simulated heartbeat. But the snakes hugged harder and for about twice as long when the pulse was switched on. If the pulse stopped, the squeezing also stopped. Lab-raised snakes never exposed to live prey responded the same way, suggesting the behavior is innate, not learned. © Society for Science & the Public 2000 - 2012

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 0:
Link ID: 16271 - Posted: 01.19.2012

By Michelle Clement I like video games (I will rip up some Assassin’s Creed whenever I get a long weekend, do NOT get me started). My cat likes video games too, even though she doesn’t understand that she’s playing them. On a whim not too long ago, I downloaded a “games for cats” app on my iPad that simulates a dancing laser pointer or a skittering mouse, and my cat gets so into the game that she’ll push my iPad all the way across the floor in her excitement. Here’s a video of someone else’s kitten playing the same game: The phenomenon isn’t restricted to domesticated cats, either: Cats aren’t the only animals that are mentally stimulated by flashing and dancing lights, though. As it turns out, researchers at Wageningen University, in the course of their research on ethical livestock farming, noticed that pigs like to play with dancing lights as well. European regulations currently require that pig farmers provide mentally-stimulating activity for their pigs in order to reduce boredom, which leads to aggression and biting, and researchers at Wageningen University, in collaboration with the Utrecht School of the Arts, are currently developing a video game called “Pig Chase” for livestock pigs that is not unlike my cat’s iPad app. The key difference, however, is that this game would be an interspecies two-player game. [EDIT: I was contacted this afternoon by Nate at Hiccup, and he informed me that Game For Cats has also recently incorporated interspecies functionality. I didn't know that, so thanks for the update!] © 2012 Scientific American,

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior; Chapter 18: Attention and Higher Cognition
Related chapters from MM:Chapter 0: ; Chapter 14: Attention and Consciousness
Link ID: 16235 - Posted: 01.10.2012

by Jeff Hecht Tortoises aren’t noted for their speed but they are surprisingly quick-witted "IT ALL stems from Moses," says Anna Wilkinson. Moses is her pet red-footed tortoise and a bit of a celebrity in the science world. Why? First, he outsmarted rats in a maze. Then he was the inspiration for a new lab studying reptile intelligence and the evolutionary origins of cognition. Now he has helped Wilkinson win an Ig Nobel prize. Victory for slow and steady. This fruitful partnership began in 2004, after Wilkinson, now at the University of Lincoln, UK, started graduate school at the University of York, also in the UK. She was studying bird cognition but had earlier become fascinated by tortoises while employed in education and research at Flamingo Land zoo in North Yorkshire, UK. Although working with primates, she found herself drawn to the tortoise enclosure. Even when most of the group was basking in the sun, she recalls, at least one tortoise was exploring or feeding, and when a person walked in they all perked up, sensing that food was likely to follow. "They were always just fascinating," she says. So, a tortoise was the obvious choice as a pet. Moses's first big academic break came in 2006. Wilkinson was attending a lecture on how rats remember their paths through a maze, when she started thinking: "Moses can do that." Afterwards, she asked the lecturer, Geoffrey Hall, if anyone had tried putting tortoises in such mazes. A literature search indicated that reptiles in general have proved pretty dim when subjected to cognitive tests. Undeterred, Hall and Wilkinson decided to see what Moses was capable of. © Copyright Reed Business Information Ltd.

Related chapters from BP7e: Chapter 17: Learning and Memory; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 13: Memory, Learning, and Development
Link ID: 16193 - Posted: 12.27.2011

by Jeff Warren What if we merged brains with other species? Would we have very different psychology? Or wordlessly swap intimate feelings? I'VE spent years thinking about consciousness and my current obsession is whether we can know anything about what it is like is to be a dog, a dolphin, or a bat. The most influential answer came from philosopher Thomas Nagel in his 1974 paper, "What is it like to be a bat?" Unlike some of the era's behaviourists, who saw animals as little more than automatons that respond to stimulus, Nagel didn't doubt bats had experience, that it was "like something" being a nimble, echo-locating mammal swooping through the night. But he doubted our ability to say anything true about it beyond projection or imagination. Nagel may be right, but for me the human-to-animal mind question is simply an extreme form of the human-to-human mind question: we can't know another's experience, but there are deep points of overlap we can expand. What follows is from a conversation with two of the smartest people I know in the field: Lori Marino, a comparative neuroanatomist at Emory University in Atlanta, Georgia, and Ben Goertzel, a mathematician, and a former research director of the Singularity Institute for Artificial Intelligence in San Francisco. JEFF: Imagine that in front of us are the disarticulated brains of a human, a dog and a dolphin. What might we learn by combining the pieces of the animals in unusual ways? LORI: Something similar is going on in Leipzig. For example, researchers inserted a human gene into a mouse brain, causing it to grow human-like neurons in the language area: the mouse's vocalisations were deeper. © Copyright Reed Business Information Ltd.

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior; Chapter 18: Attention and Higher Cognition
Related chapters from MM:Chapter 0: ; Chapter 14: Attention and Consciousness
Link ID: 16191 - Posted: 12.27.2011

By Susan Milius Pigeons, who aren’t even distant uncles to a monkey, have matched primates in a test of learning an abstract numerical concept. Trained on one-two-three, the pigeons then had to put pairs of numbers up to nine in order, says comparative psychologist Damian Scarf of the University of Otago in New Zealand. Pigeons rivaled rhesus monkeys tested earlier at the same task, Scarf and his colleagues report in the Dec. 23 Science. The results “suggest that despite completely different brain organization and hundreds of millions of years of evolutionary divergence, pigeons and monkeys solve this problem in a similar way,” says Elizabeth Brannon of Duke University, a coauthor of the original study of numerical order in monkeys. Humankind may be pretty proud of its numerical prowess, but numbers — four succulent fruits versus eight, one lurking lion versus three — matter very much in animal life, too. Research is uncovering various kinds of number-related abilities in animals as diverse as the honeybee, mosquitofish, grey parrot, Plethodon salamanders and a waterbird called a coot. So pigeons could be compared with other species, Scarf used Brannon’s numerical-order test, which baboons and lemurs as well as some monkeys have passed. For training, pigeons saw computer screens displaying sets of three images, each with one, two or three shapes. The shapes varied so that a bird couldn’t get the number order right just by pecking at increasing surface area. Scarf then rewarded birds for pecking in one-shape, two-shapes, three-shapes order. © Society for Science & the Public 2000 - 2011

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior; Chapter 18: Attention and Higher Cognition
Related chapters from MM:Chapter 0: ; Chapter 14: Attention and Consciousness
Link ID: 16178 - Posted: 12.23.2011

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.

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior
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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

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 0:
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.

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior; Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 0: ; Chapter 11: Emotions, Aggression, and Stress
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,

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior
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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.

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior
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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

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 0:
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
Related chapters from MM:Chapter 0: ; Chapter 4: The Chemistry of Behavior: Neurotransmitters and Neuropharmacology
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

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior; Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 0: ; Chapter 13: Memory, Learning, and Development
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,

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior; Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 0: ; Chapter 11: Emotions, Aggression, and Stress
Link ID: 15868 - Posted: 10.04.2011