Links for Keyword: Evolution
Follow us on Facebook and Twitter, or subscribe to our mailing list, to receive news updates. Learn more.
By Michael Harré As humans, we aren't born with formidable armaments or defenses, nor are we the strongest, fastest, or biggest species, yet despite this we are amazingly successful. For a long time it was thought that this success was because our enlarged brains allows each of us to be smarter than our competitors: better at abstract thinking, better with tools and better at adapting our behavior to those of our prey and predators. But are these really the most significant skills our brains provide us with? Another possibility is that we are successful because we can form long-lasting relationships with many others in diverse and flexible ways, and that this, combined with our native intelligence, explains why homo sapiens came to dominate the planet. In every way from teaching our young to the industrial division of labour we are a massively co-operative species that relies on larger and more diverse networks of relationships than any other species. In 1992 British anthropologist Robin Dunbar published an article showing that, in primates, the ratio of the size of the neo-cortex to that of the rest of the brain consistently increases with increasing social group size. For example, the Tamarin monkey has a brain size ratio of about 2.3 and an average social group of size of about 5 members. On the other hand, a Macaque monkey has a brain size ratio of around 3.8 but a very large average group size of about 40 members. From this work Dunbar put forward what is now known as the “social brain hypothesis.” The relative size of the neo-cortex rose as social groups became larger in order to maintain the complex set of relationships necessary for stable co-existence. Most famously, Dunbar suggested that given the human brain ratio we have an expected social group size of around 150 people, about the size of what Dunbar called a “clan.” © 2012 Scientific American,
By Tina Hesman Saey Expeditions to Africa may have brought back evidence of a hitherto unknown branch in the human family tree. But this time the evidence wasn’t unearthed by digging in the dirt. It was found in the DNA of hunter-gatherer people living in Cameroon and Tanzania. Buried in the genetic blueprints of 15 people, researchers found the genetic signature of a sister species that branched off the human family tree at about the same time that Neandertals did. This lineage probably remained isolated from the one that produced modern humans for a long time, but its DNA jumped into the Homo sapiens gene pool through interbreeding with modern humans during the same era that other modern humans and Neandertals were mixing in the Middle East, researchers report in the August 3 Cell. The evidence for ancient interbreeding is surprisingly convincing, says Richard “Ed” Green, a genome biologist at the University of California, Santa Cruz. “There is a signal that demands explanation, and archaic admixture seems to be the most reasonable one at this point,” he says. Scientists have discovered that some people with ancestry outside Africa have DNA inherited from Neandertals or Denisovans, a mysterious group known only through DNA derived from a fossil finger bone found in a Siberian cave (SN: 6/5/10, p. 5; SN: 1/15/11, p.10). But those researchers had DNA from fossils to guide their research. This time, researchers led by Sarah Tishkoff at the University of Pennsylvania in Philadelphia didn’t have fossil DNA, or even fossils. © Society for Science & the Public 2000 - 2012
By JOHN NOBLE WILFORD In the widening search for the origins of modern human evolution, genes and fossils converge on Africa about 200,000 years ago as the where and when of the first skulls and bones that are strikingly similar to ours. So this appears to be the beginning of anatomically modern Homo sapiens. But evidence for the emergence of behaviorally modern humans is murkier — and controversial. Recent discoveries establish that the Homo sapiens groups who arrived in Europe some 45,000 years ago had already attained the self-awareness, creativity and technology of early modern people. Did this behavior come from Africa after gradual development, or was it an abrupt transition through some profound evolutionary transformation, perhaps caused by hard-to-prove changes in communication by language? Now, the two schools of thought are clashing again, over new research showing that occupants of Border Cave in southern Africa, who were ancestors of the San Bushmen hunter-gatherers in the area today, were already engaged in relatively modern behavior at least 44,000 years ago, twice as long ago as previously thought. Two teams of scientists reported these findings Monday in the journal Proceedings of the National Academy of Sciences. Since this early date for the San culture is close to when modern humans first left Africa and reached Europe, proponents of the abrupt-change hypothesis took the findings as good news. Richard G. Klein, a paleoanthropologist at Stanford University, said in an e-mail from South Africa that the new evidence “supports my view that fully modern hunter-gatherers emerged in Africa abruptly around 50,000 years ago, and I remain convinced that the behavior shift, or advance, underlies the successful expansion of modern Africans to Eurasia.” © 2012 The New York Times Company
Matt Kaplan Neanderthals have long been viewed as meat-eaters. The vision of them as inflexible carnivores has even been used to suggest that they went extinct around 25,000 years ago as a result of food scarcity, whereas omnivorous humans were able to survive. But evidence is mounting that plants were important to Neanderthal diets — and now a study reveals that those plants were roasted, and may have been used medicinally. The finding comes from the El Sidrón Cave in northern Spain, where the roughly 50,000-year-old skeletal remains of at least 13 Neanderthals (Homo neanderthalensis) have been discovered. Many of these individuals had calcified layers of plaque on their teeth. Karen Hardy, an anthropologist at the Autonomous University of Barcelona in Spain, wondered whether it might be possible to use this plaque to take a closer look at the Neanderthal menu. Using plaque to work out the diets of ancient animals is not entirely new, but Hardy has gone further by looking for organic compounds in the plaque. To do this she and a team including Stephen Buckley, an archaeological chemist at the University of York, UK, used gas chromatography and mass spectrometry to analyse the plaque collected from ten teeth belonging to five Neanderthal individuals from the cave. The plaque contained a range of carbohydrates and starch granules, hinting that the Neanderthals had consumed a variety of plant species. By contrast, there were few lipids or proteins from meat. © 2012 Nature Publishing Group
Emma Marris Large-brained animals may be less likely to go extinct in a changing world, perhaps because they can use their greater intelligence to adapt their behaviour to new conditions, according to an analysis presented to a meeting of conservation biologists this week. The finding hints at a way to prioritize future conservation efforts for endangered species. Brain size relative to body size is fairly predictable across all mammals, says Eric Abelson, who studies biological sciences at Stanford University in Palo Alto, California. “As body size grows, brain size grows too, but at slower rate,” he says. Plotting brain size against body size creates a tidy curve. But some species have bigger or smaller brains than the curve would predict for their body size. And a bigger brain-to-body-size ratio usually means a smarter animal. Abelson looked at the sizes of such deviations from the curve and their relationships to the fates of two groups of mammalian species — ‘palaeo’ and ‘modern’. The palaeo group contained 229 species in the order Carnivora from the last 40 million years, about half of which are already extinct. The modern group contained 147 species of North American mammals across 6 orders. Analysis of each group produced similar results: species that weighed less than 10 kilograms and had big brains for their body size were less likely to have gone extinct or be placed on the International Union for Conservation of Nature red list for endangered species. For species larger than about 10 kilograms, the advantage of having a large brain seems to be swamped by the disadvantage of being big. Large species tend to reproduce later in life, have fewer offspring, require more resources and larger territories, and catch the attention of humans, either as food or as predators. Hunting pressure or reductions in available space can hit them particularly hard. © 2012 Nature Publishing Group
Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior; Chapter 13: Homeostasis: Active Regulation of the Internal Environment
Related chapters from MM:Chapter 0: ; Chapter 9: Homeostasis: Active Regulation of the Internal Environment
Link ID: 17063 - Posted: 07.18.2012
By Jennifer Viegas Dolphins may use complex nonlinear mathematics when hunting, according to a new study that suggests these brainy marine mammals could be far more skilled at math than was ever thought possible before. Inspiration for the new study, published in the latest Proceedings of the Royal Society A, came after lead author Tim Leighton watched an episode of the Discovery Channel's "Blue Planet" series and saw dolphins blowing multiple tiny bubbles around prey as they hunted. "I immediately got hooked, because I knew that no man-made sonar would be able to operate in such bubble water," explained Leighton, a professor of ultrasonics and underwater acoustics at the University of Southampton, where he is also an associate dean. "These dolphins were either 'blinding' their most spectacular sensory apparatus when hunting -- which would be odd, though they still have sight to reply on -- or they have a sonar that can do what human sonar cannot…Perhaps they have something amazing," he added. Leighton and colleagues Paul White and student Gim Hwa Chua set out to determine what the amazing ability might be. They started by modeling the types of echolocation pulses that dolphins emit. The researchers processed them using nonlinear mathematics instead of the standard way of processing sonar returns. The technique worked, and could explain how dolphins achieve hunting success with bubbles. © 2012 Discovery Communications, LLC.
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: 17062 - Posted: 07.18.2012
By JOHN NOBLE WILFORD Who are we, and where did we come from? Scientists studying the origin of modern humans, Homo sapiens, keep reaching deeper in time to answer those questions — toward the last common ancestor of great apes and humans, then forward to the emergence of people more and more like us in body and behavior. Their research is advancing on three fronts. Fossils of skulls and bones expose anatomical changes. Genetics reveals the timing and place of the Eve of modern humans. And archaeology turns up ancient artifacts reflecting abstract and creative thought, and a growing self-awareness. Just last month, researchers made the startling announcement that Stone Age paintings in Spanish caves were much older than previously thought, from a time when Neanderthals were still alive. To help make sense of this cascade of new information, a leading authority on modern human evolution — the British paleoanthropologist Chris Stringer — recently sat for an interview in New York that ranged across many recent developments: the evidence of interbreeding between Neanderthals and Homo sapiens; the puzzling extinct species of little people nicknamed the hobbits; and the implications of a girl’s 40,000-year-old pinkie finger found in a Siberian cave. Dr. Stringer, an animated man of 64, is an anthropologist at the Natural History Museum in London and a fellow of the Royal Society. But he belies the image of a don: He showed up for our interview wearing a T-shirt and jeans, looking as if he had just come in from the field. © 2012 The New York Times Company
by Elizabeth Pennisi OTTAWA—With big brains comes big intelligence, or so the hypothesis goes. But there may be trade-offs as well. Humans and other creatures with large brains relative to their body size tend to have smaller guts and possibly fewer offspring. Scientists have debated for decades whether the two phenomena are related. Now a team of researchers says that they are—and that big brains do indeed make us smart. The finding comes thanks to an unusual experiment reported here yesterday at the Evolution Ottawa evolutionary biology meeting in which scientists shrank and grew the brains of guppies over several generations. "This is a real experimental result," says David Reznick, an evolutionary biologist at the University of California, Riverside, who was not involved in the study. "The earlier results were just correlations." Researchers first began to gather evidence that big brains were advantageous after 19th century U.S. biologist Hermon Bumpus examined the brains of sparrows, some of whom had succumbed in a blizzard and some of whom survived. The survivors had relatively larger brains. More recently, evolutionary biologist Alexei Maklakov from Uppsala University in Sweden found evidence that songbirds that colonize cities tend to have larger brains relative to their body size than species still confined to the countryside. The challenge of urban life might require bigger brains, he and his colleagues concluded last year in Biology Letters. Yet in humans and in certain electric fish, larger brain size seems to have trade-offs: smaller guts and fewer offspring. That's led some scientists to suggest there are constraints on how big brains can become because they are expensive to build and maintain. © 2010 American Association for the Advancement of Science.
Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior; Chapter 1: Biological Psychology: Scope and Outlook
Related chapters from MM:Chapter 0: ; Chapter 1: An Introduction to Brain and Behavior
Link ID: 17026 - Posted: 07.11.2012
By Eric Michael Johnson What would it take for you to give your life to save another? The answer of course is two siblings or eight cousins, that is, if you’re thinking like a geneticist. This famous quip, attributed to the British biologist J.B.S. Haldane, is based on the premise that you share on average 50% of your genes with a brother or sister and 12.5% with a cousin. For altruism to be worth the cost it should ensure that you break even, genetically speaking. This basic idea was later formalized by the evolutionary theorist William Hamilton as “inclusive fitness theory” that extended Darwin’s definition of fitness–the total number of offspring produced–to also include the offspring of close relatives. Hamilton’s model has been highly influential, particularly for Oxford evolutionary biologist Richard Dawkins who spent considerable time discussing its implications in his 1976 book The Selfish Gene. But in the last few years an academic turf war has developed pitting the supporters of inclusive fitness theory (better known as kin selection) against a handful of upstarts advocating what is known as group selection, the idea that evolutionary pressures act not only on individual organisms but also at the level of the social group. The latest row was sparked by the publication of Edward O. Wilson’s new book, The Social Conquest of Earth, which followed up on his 2010 paper in the journal Nature written with theoretical biologists Martin Nowak and Corina Tarniţă. In both cases Wilson opposes kin selection theory in favor of the group selection model. For a revered scientist like Wilson–a Harvard biologist, recipient of the Crafoord Prize (the Nobel of the biosciences) and two-time Pulitzer prizewinner–to adopt a marginal and widely disputed concept has received a lot of attention and caused other prominent scientists to step forward and defend the mainstream point of view. © 2012 Scientific American
Related chapters from BP7e: Chapter 15: Emotions, Aggression, and Stress; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 11: Emotions, Aggression, and Stress
Link ID: 17016 - Posted: 07.10.2012
SETH BORENSTEIN, AP Science Writer WASHINGTON (AP) — The more we study animals, the less special we seem. Baboons can distinguish between written words and gibberish. Monkeys seem to be able to do multiplication. Apes can delay instant gratification longer than a human child can. They plan ahead. They make war and peace. They show empathy. They share. "It's not a question of whether they think — it's how they think," says Duke University scientist Brian Hare. Now scientists wonder if apes are capable of thinking about what other apes are thinking. The evidence that animals are more intelligent and more social than we thought seems to grow each year, especially when it comes to primates. It's an increasingly hot scientific field with the number of ape and monkey cognition studies doubling in recent years, often with better technology and neuroscience paving the way to unusual discoveries. This month scientists mapping the DNA of the bonobo ape found that, like the chimp, bonobos are only 1.3 percent different from humans. Says Josep Call, director of the primate research center at the Max Planck Institute in Germany: "Every year we discover things that we thought they could not do." Call says one of his recent more surprising studies showed that apes can set goals and follow through with them. © 2012 Hearst Communications Inc.
Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior; Chapter 17: Learning and Memory
Related chapters from MM:Chapter 0: ; Chapter 13: Memory, Learning, and Development
Link ID: 16961 - Posted: 06.25.2012
by Michael Balter The basic questions about early European cave art—who made it and whether they developed artistic talent swiftly or slowly—were thought by many researchers to have been settled long ago: Modern humans made the paintings, crafting brilliant artworks almost as soon as they entered Europe from Africa. Now dating experts working in Spain, using a technique relatively new to archaeology, have pushed dates for the earliest cave art back some 4000 years to at least 41,000 years ago*, raising the possibility that the artists were Neandertals rather than modern humans. And a few researchers say that the study argues for the slow development of artistic skill over tens of thousands of years. Figuring out the age of cave art is fraught with difficulties. Radiocarbon dating has long been the method of choice, but it is restricted to organic materials such as bone and charcoal. When such materials are lying on a cave floor near art on the cave wall, archaeologists have to make many assumptions before concluding that they are contemporary. Questions have even arisen in cases like the superb renditions of horses, rhinos, and other animals in France's Grotte Chauvet, the cave where researchers have directly radiocarbon dated artworks executed in charcoal to 37,000 years ago. Other archaeologists have argued that artists could have entered Chauvet much later and picked up charcoal that had been lying around for thousands of years. Now in a paper published online today in Science, applied a technique called uranium-series (U-series) dating to artworks from 11 Spanish caves. U-series dating has been around since the 1950s and is often used to date caves, corals, and other proxies for climate and sea level changes. But it has been used only a few times before on cave art, including by Pike and Pettit, who used it to date the United Kingdom's oldest known cave art at Cresswell Crags in England. © 2010 American Association for the Advancement of Science.
by Ann Gibbons Chimpanzees now have to share the distinction of being our closest living relative in the animal kingdom. An international team of researchers has sequenced the genome of the bonobo for the first time, confirming that it shares the same percentage of its DNA with us as chimps do. The team also found some small but tantalizing differences in the genomes of the three species—differences that may explain how bonobos and chimpanzees don't look or act like us even though we share about 99% of our DNA. "We're so closely related genetically, yet our behavior is so different," says team member and computational biologist Janet Kelso of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. "This will allow us to look for the genetic basis of what makes modern humans different from both bonobos and chimpanzees." Ever since researchers sequenced the chimp genome in 2005, they have known that humans share about 99% of our DNA with chimpanzees, making them our closest living relatives. But there are actually two species of chimpanzees that are this closely related to humans: bonobos (Pan paniscus) and the common chimpanzee (Pan troglodytes). This has prompted researchers to speculate whether the ancestor of humans, chimpanzees, and bonobos looked and acted more like a bonobo, a chimpanzee, or something else—and how all three species have evolved differently since the ancestor of humans split with the common ancestor of bonobos and chimps between 5 million and 7 million years ago in Africa. © 2010 American Association for the Advancement of Science.
By Gareth Cook How aware are plants? This is the central question behind a fascinating new book, “What a Plant Knows,” by Daniel Chamovitz, director of the Manna Center for Plant Biosciences at Tel Aviv University. A plant, he argues, can see, smell and feel. It can mount a defense when under siege, and warn its neighbors of trouble on the way. A plant can even be said to have a memory. But does this mean that plants think — or that one can speak of a “neuroscience” of the flower? Chamovitz answered questions from Mind Matters editor Gareth Cook. 1. How did you first get interested in this topic? My interest in the parallels between plant and human senses got their start when I was a young postdoctoral fellow in the laboratory of Xing-Wang Deng at Yale University in the mid 1990s. I was interested in studying a biological process that would be specific to plants, and would not be connected to human biology (probably as a response to the six other “doctors” in my family, all of whom are physicians). So I was drawn to the question of how plants sense light to regulate their development. It had been known for decades that plants use light not only for photosynthesis, but also as a signal that changes the way plants grow. In my research I discovered a unique group of genes necessary for a plant to determine if it’s in the light or in the dark. When we reported our findings, it appeared these genes were unique to the plant kingdom, which fit well with my desire to avoid any thing touching on human biology. But much to my surprise and against all of my plans, I later discovered that this same group of genes is also part of the human DNA. © 2012 Scientific American
Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior; Chapter 2: Functional Neuroanatomy: The Nervous System and Behavior
Related chapters from MM:Chapter 0: ; Chapter 2: Cells and Structures: The Anatomy of the Nervous System
Link ID: 16878 - Posted: 06.06.2012
by Michael Balter Three years ago, a stone-throwing chimpanzee named Santino jolted the research community by providing some of the strongest evidence yet that nonhumans could plan ahead. Santino, a resident of the Furuvik Zoo in Gävle, Sweden, calmly gathered stones in the mornings and put them into neat piles, apparently saving them to hurl at visitors when the zoo opened as part of angry and aggressive "dominance displays." But some researchers were skeptical that Santino really was planning for a future emotional outburst. Perhaps he was just repeating previously learned responses to the zoo visitors, via a cognitively simpler process called associative learning. And it is normal behavior for dominant male chimps to throw things at visitors, such as sticks, branches, rocks, and even feces. Now Santino is back in the scientific literature, the subject of new claims that he has begun to conceal the stones so he can get a closer aim at his targets—further evidence that he is thinking ahead like humans do. The debate over Santino is part of a larger controversy over whether some humanlike animal behaviors might have simpler explanations. For example, Sara Shettleworth, a psychologist at the University of Toronto in Canada, argued in a widely cited 2010 article entitled, "Clever animals and killjoy explanations in comparative psychology," that the zookeepers and researchers who observed Santino's stone-throwing over the course of a decade had not seen him gathering the stones, and thus could not know why he originally starting doing so. Santino, Shettleworth and some others argued, might have had some other reasons for caching the stones, and the stone throwing might have been an afterthought. © 2010 American Association for the Advancement of Science
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: 16777 - Posted: 05.10.2012
Ewen Callaway Humans walk on two feet and (mostly) lack hair-covered bodies, but the feature that sets us furthest apart from other apes is a brain capable of language, art, science, and other trappings of civilisation. Now, two studies published online today in Cell1, 2 suggest that DNA duplication errors that happened millions of years ago might have had a pivotal role in the evolution of the complexity of the human brain. The duplications — which created new versions of a gene active in the brains of other mammals — may have endowed humans with brains that could create more neuronal connections, perhaps leading to greater computational power. The enzymes that copy DNA sometimes slip extra copies of a gene into a chromosome, and scientists estimate that such genetic replicas make up about 5% of the human genome. However, gene duplications are notoriously difficult to study because the new genes differ little from their forebears, and tend to be overlooked. Evan Eichler, a geneticist at the University of Washington in Seattle, and lead author of one of the Cell papers, previously found that humans have four copies of a gene called SRGAP2, and he and his colleagues decided to investigate. In their new paper, they report that the three duplicated versions of SRGAP2 sit on chromosome 1, along with the original ancestral gene, but they are not exact copies. All of the duplications are missing a small part of the ancestral form of the gene, and at least one duplicate, SRGAP2C, seems to make a working protein. Eichler’s team has also found SRGAP2C in every individual human genome his team has examined – more than 2,000 so far – underscoring its significance. © 2012 Nature Publishing Group,
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: 16753 - Posted: 05.05.2012
William G. Eberhard, William T. Wcislo A basic fact of life is that the size of an animal’s brain depends to some extent on its body size. A long history of studies of vertebrate animals has demonstrated that the relationship between brain and body mass follows a power-law function. Smaller individuals have relatively larger brains for their body sizes. This scaling relationship was popularized as Haller’s Rule by German evolutionary biologist Bernhard Rensch in 1948, in honor of Albrecht von Haller, who first noticed the relationship nearly 250 years ago. Little has been known, however, about relative brain size for invertebrates such as insects, spiders and nematodes, even though they are among Earth’s more diverse and abundant animal groups. But a recent wave of studies of invertebrates confirms that Haller’s Rule applies to them as well, and that it extends to much smaller body sizes than previously thought. These tiny animals have been able to substantially shift their allometric lines—that is, the relationship between their brain size and their overall body size—from those of vertebrates and other invertebrates. Animals that follow a given allometric line belong to the same grade and changes from one grade to another are known as grade shifts. The result is that different taxonomic groups have different, variant, versions of Haller’s Rule. The mechanisms that are responsible for grade shifts are only beginning to be understood. But this combination of generality and variability in Haller’s Rule appears to call into question some basic assumptions regarding the uniformity of how the central nervous system functions among animals. It also reveals a number of overlooked design challenges faced by tiny organisms. Because neural tissue is metabolically expensive, minute animals must pay relatively higher metabolic costs to power their proportionally larger brains, and they thus face different ecological challenges. © Sigma Xi, The Scientific Research Society
Related chapters from BP7e: Chapter 13: Homeostasis: Active Regulation of the Internal Environment; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 9: Homeostasis: Active Regulation of the Internal Environment
Link ID: 16651 - Posted: 04.16.2012
by Helen Fields The average adult human's brain weighs about 1.3 kilograms, has 100 billion or so neurons, and sucks up 20% of the oxygen we breathe. It's much bigger than an animal our size needs. According to a new computer model, the brains of humans and related primates are so large because we evolved to be social creatures. If we didn't play well with others, our brains would be puny. The idea behind the so-called social intelligence hypothesis is that we need pretty complex computers in our skulls to keep track of all the complex relationships we have with each other—who's a friend, who's an enemy, who's higher in the social ranks. Some studies have supported this idea, showing for example that bigger-brained primates tend to live in bigger social groups. The same appears to hold true for dolphins. But these studies only identified associations between brain and group size; they don't show how evolution might have worked. Since they didn't have a few million years of time on their hands, Ph.D. student Luke McNally and colleagues at Trinity College Dublin simulated evolution on a computer. They started with 50 simple brains. Each had just three to six neurons. The researchers then made each brain challenge the others to one of two classic games: the prisoner's dilemma or the snowdrift game. In the prisoner's dilemma, two people have been taken in for questioning by the police. If both keep their mouths shut, they'll both be set free. If one sells out the other, the snitch will get off and the other will do a long stint in jail. If they tell on each other, both get shorter sentences. © 2010 American Association for the Advancement of Science.
by Virginia Morell The male dolphins of Shark Bay, Australia, are known to marine biologists for their messy social entanglements. Their relationships with each other are so unusual—they're more like the intricate webs of the Mafia than the vertical hierarchies of chimpanzees—that, in a new paper, one team of scientists argues that the dolphins live in a social system that is "unique among mammals." Intriguingly, the researchers also suggest that these complex, and often cooperative, relationships may stem in part from one simple, unexpected factor: the dolphins' low cruising speed. Mammals have evolved a variety of social structures. For example, chimpanzees live in what ethologists call "semiclosed groups"—that is, a community comprised of individuals who are well-known to each other. The members generally aren't friendly to chimps in other communities; the males practice what's known as community defense, patrolling and guarding their territory and fighting their neighbors. Inside that tight group, the chimpanzees also have male-male alliances. At first glance, dolphins seem to have a somewhat similar social system. Two or three adult males form a tight alliance and cooperate to herd a female for mating. (Female dolphins rarely form strong alliances.) Other male teams may try to spirit away the female—particularly if she is in estrus. To fight back, the first-level alliances form partnerships with other first-level alliances, thus creating a larger second-level alliance. Some of these second-level alliances have as many as 14 dolphins and can last 15 years or more. On some occasions, the second-level alliance can call in the troops from yet another group, "a third-order alliance," as the researchers call them—leading to huge battles with more than 20 dolphins biting and bashing each other with their heads and tails over the right to keep or steal a single female. © 2010 American Association for the Advancement of Science.
Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 16588 - Posted: 03.29.2012
By Bruce Bower An ancient member of the human evolutionary family has put what’s left of a weird, gorillalike foot forward to show that upright walking evolved along different paths in East Africa. A 3.4 million-year-old partial fossil foot unearthed in Ethiopia comes from a previously unknown hominid species that deftly climbed trees but walked clumsily, say anthropologist Yohannes Haile-Selassie of the Cleveland Museum of Natural History and his colleagues. Their report appears in the March 29 Nature. To the scientists’ surprise, this creature lived at the same time and in the same region as Australopithecus afarensis, a hominid species best known for a partial skeleton dubbed Lucy. Another recent fossil discovery in Ethiopia suggests that Lucy’s kind walked much as people do today (SN: 7/17/10, p. 5). “For the first time, we have evidence of another hominid lineage that lived at the same time as Lucy,” says anthropologist and study coauthor Bruce Latimer of Case Western Reserve University in Cleveland. “This new find has a grasping big toe and no arch, suggesting [the species] couldn’t walk great distances and spent a lot of time in the trees.” Lucy’s flat-footed compatriot adds to limited evidence that some hominids retained feet designed for adept tree climbing several million years after the origin of an upright gait, writes Harvard University anthropologist Daniel Lieberman in a comment published in the same issue of Nature. © Society for Science & the Public 2000 - 2012
Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior; Chapter 11: Motor Control and Plasticity
Related chapters from MM:Chapter 0: ; Chapter 5: The Sensorimotor System
Link ID: 16583 - Posted: 03.29.2012
By Eric Michael Johnson In my cover article out this week in Times Higher Education I featured the life and work of famed primatologist and evolutionary theorist Sarah Blaffer Hrdy. While she never intended to be a radical, she has nevertheless had a radical influence on how primatology and evolutionary biology address female strategies as well as the evolutionary influences on infants. Hrdy graduated summa cum laude from Radcliffe College in Cambridge, Massachusetts and received her Ph.D. in anthropology from Harvard. She is a former Guggenheim fellow and a member of the National Academy of Sciences, the American Academy of Arts and Sciences, and the California Academy of Sciences. She is currently professor emeritus at the University of California, Davis. In our discussion, Hrdy explores both her own life as well as how her personal experiences inspired her to ask different questions than many of her scientific colleagues. While it may not seem like a particularly dramatic idea to emphasize the evolutionary selection pressures on mothers and their offspring, it is a telling insight into the unconscious (and at times fully conscious) sexism that has long been a part of the scientific process. Through her work, in books such as The Woman that Never Evolved, selected by the New York Times as one of its Notable Books of 1981, Mother Nature: A History of Mothers, Infants and Natural Selection, chosen by both Publisher’s Weekly and Library Journal as one of the “Best Books of 1999″ and, her latest, Mothers and Others: The Evolutionary Origins of Mutual Understanding, Hrdy has challenged, and transcended, many of the flawed assumptions that biologists have held dating back to the Victorian era. It is a body of work that continues to provoke and inspire a new generation of scientists and was highly influential in my own scientific work. © 2012 Scientific American,
Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 16541 - Posted: 03.19.2012