By Judith Burns Science reporter, BBC News Humans living at high latitude have bigger eyes and bigger brains to cope with poor light during long winters and cloudy days, UK scientists have said. The Oxford University team said bigger brains did not make people smarter. Larger vision processing areas fill the extra capacity, they write in the Royal Society's Biology Letters journal. The scientists measured the eye sockets and brain volumes of 55 skulls from 12 populations across the world, and plotted the results against latitude. Lead author Eiluned Pearce told BBC News: "We found a positive relationship between absolute latitude and both eye socket size and cranial capacity." The team, from the Institute of Cognitive and Evolutionary Anthropology, used skulls dating from the 1800s kept at museums in Oxford and Cambridge. The skulls were from indigenous populations ranging from Scandinavia to Australia, Micronesia and North America. Largest brain cavities The largest brain cavities came from Scandinavia, while the smallest were from Micronesia. BBC © 2011

Related chapters from BP6e: 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: 15619 - Posted: 07.28.2011

by Virginia Morell Asian elephants have long been considered somewhat antisocial. Instead of living in large, tightly knit herds, as do female elephants on the African savanna, those in Asia were thought to have only small groups of friends and few outside connections. But a new study shows that many female Asian elephants are more like social butterflies, with numerous pals. And they're able to maintain strong friendships even with those they have not seen in a year or more. The study adds Asian elephants to a short list of other species, including dolphins, that are able to maintain complex social relationships despite not having daily contact, an ability regarded as being cognitively demanding. "People thought they knew what Asian elephants were doing [socially] based on what they saw them doing in captivity," says Shermin de Silva, a behavioral ecologist with the Elephant, Forest and Environment Conservation Trust in Colombo, Sri Lanka, and the lead author of the new study. Asian elephants are also extremely difficult to study in the wild, she adds. They inhabit dense forests, so researchers are usually able to observe the animals only by climbing tall trees or watching them when they gather at water holes. But 30 years ago, one population of Asian elephants on Sri Lanka became observable because it lost its forest home. People logged the trees, converted the land into teak plantations, and subsequently dammed the region's main river, creating the large Uda Walawe reservoir. In 1972, 308 square kilometers around the reservoir were made into the Udawalawe National Park. Some 800 to 1200 former forest elephants now live here on grass- and scrublands that resemble an East African savanna, de Silva says. © 2010 American Association for the Advancement of Science.

Related chapters from BP6e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 0:
Link ID: 15613 - Posted: 07.28.2011

By Laura Sanders Unlike humans, chimpanzees’ brains don’t shrink as they get older. That means that, so far, people seem to be the only lucky species whose brains wither with age, researchers report online July 25 in the Proceedings of the National Academy of Sciences. “Chimp aging seems to be on a different trajectory than humans’,” says aging and Alzheimer’s expert Caleb Finch of the University of Southern California in Los Angeles, who was not involved in the study. So far, the small number of great ape brains that have been studied show mild changes with age, Finch says, but nothing that approaches the damage seen in the brains of people with Alzheimer’s disease. Understanding differences in aging between humans and other primates may help scientists figure out why human brains are susceptible to age-related dementias. In the new study, anthropologist Chet Sherwood of George Washington University in Washington, D.C., and colleagues focused on chimpanzees, which have some of the most developed brains and longest life spans among primates. The researchers wondered if chimps experience brain decline in old age similar to that seen in humans. The researchers scanned the brains of 99 chimpanzees with ages representing the entire adult life span, from 10 to 51 years. For comparison, the team imaged the brains of 87 humans from 22 to 88 years old. © Society for Science & the Public 2000 - 2011

Related chapters from BP6e: 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: 15610 - Posted: 07.26.2011

Analysis by Kieran Mulvaney Whale-watching tourists off western Australia saw more than they expected - and perhaps more than many of them wanted - last week. As two boats of observers took in the action, a humpback whale mother desperately and vainly tried to protect a calf from four predatory orcas. The video below, shot from a light aircraft that circled overhead as the action unfolded, isn't always easy to make out, but it shows the orcas circling as the humpback attempts to protect the calf by lifting it on to her back. (If you pause the video at about 12 seconds, you can see the whale more or less center of the screen, and the lighter-colored calf just above it.) According to witnesses, the humpback was spotted with two calves, but the orcas swiftly came on the attack taking one. The mother only succeeded in protecting her second calf for about three-quarters of an hour before it, too, succumbed to the ambush: "I've been diving for three years and I've never seen anything like it," said Tamar Melen, who watched the 45-minute spectacle unfold metres from the boat. Sadly, the killer whales made off with both calves. Ms Melen, 31, said they grabbed the first in seconds, but the attack on the second lasted half an hour. "It was quite impressive," Ms Melen said. "The first hit was so quick, but then they took their time with the second. It was agonising to watch the mother humpback trying to protect her calf. © 2011 Discovery Communications, LLC.

Related chapters from BP6e: 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: 15603 - Posted: 07.26.2011

By CARL ZIMMER To study evolution, Jason Munshi-South has tracked elephants in central Africa and proboscis monkeys in the wilds of Borneo. But for his most recent expedition, he took the A train. Dr. Munshi-South and two graduate students, Paolo Cocco and Stephen Harris, climbed out of the 168th Street station lugging backpacks and a plastic crate full of scales, Ziploc bags, clipboards, rulers and tarps. They walked east to the entrance of Highbridge Park, where they met Ellen Pehek, a senior ecologist in the New York City Parks and Recreation Department. The four researchers entered the park, made their way past a basketball game and turned off the paved path into a ravine. They worked their way down the steep slope, past schist boulders, bent pieces of rebar, oaks and maples, hunks of concrete and freakish poison ivy plants with leaves the size of a man’s hands. The ravine flattened out at the edge of Harlem River Drive. The scientists walked north along a guardrail contorted by years of car crashes before plunging back into the forest to reach their field site. “We get police called on us a lot,” said Dr. Munshi-South, an assistant professor at Baruch College. “Sometimes with guns drawn.” Dr. Munshi-South has joined the ranks of a small but growing number of field biologists who study urban evolution — not the rise and fall of skyscrapers and neighborhoods, but the biological changes that cities bring to the wildlife that inhabits them. For these scientists, the New York metropolitan region is one great laboratory. © 2011 The New York Times Company

Related chapters from BP6e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 0:
Link ID: 15602 - Posted: 07.26.2011

By Katherine Harmon Just like our animal skin–clad ancestors, we gather food with zeal, lust over the most capable mates, and have an aversion to scammers. And we do still wear plenty of animal skins. But does more separate us from our Stone Age forebears than cartoonists and popular psychologists might have us believe? At first blush, parsing the modern human in terms of behaviors apparently hardwired into the brain over eons of evolution seems like a tidy, straightforward exercise. And 30 years ago, when the field of evolutionary psychology was gaining steam, some facile parallels between ancient and modern behaviors lodged themselves in the popular conceptions of human evolution. "It's very easy to slip into a very simplistic view of human nature," says Robert Kurzban, an associate professor of psychology at the University of Pennsylvania, citing the classic Flintstones stereotype. Advances in neuroscience and genetics now suggest that the human brain has changed more rapidly—and in different ways—than was initially thought, according to a new paper published online July 19 in PLoS Biology. "There's been a lot of recent evolution—far more than anyone envisioned in the 1980s when this idea came to prominence," says Kevin Laland, a professor at the University of Saint Andrew's School of Biology in Scotland and co-author of the new paper. He and his colleagues argue that today's better understanding of the pace of evolution, human adaptability and the way the mind works all suggest that, contrary to cartoon stereotypes, modern humans are not just primitive savages struggling to make psychological sense of an alien contemporary world. © 2011 Scientific American

Related chapters from BP6e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 0:
Link ID: 15587 - Posted: 07.21.2011

by Virginia Morell In 1991, researchers spotted dolphins doing something unusual in Shark Bay, Western Australia. When the animals got hungry, they ripped a marine basket sponge from the sea floor and fitted it over their beaks like a person would fit a glove over a hand. The scientists suspected that as the dolphins foraged for fish, the sponges protected their beaks, or rostra, from the rocks and broken chunks of coral that litter the sea floor, making this behavior the first example of tool use in this species. But why do dolphins go to all of this trouble when they could simply snag a fish from the open sea? The answer, researchers report online today in PLoS ONE, is that the bottom-dwelling fish are a lot more nutritious. Some species also don't have swim bladders, gas chambers that help other fish control their buoyancy as they travel up and down the water column. In the Bahamas, where dolphins are also known to forage for bottom-dwelling fish, dolphins hunt partly by echolocating these bladders, which give off a strong acoustic signal. That helps the cetaceans find prey even when it's buried in sea sand. But bottom-dwelling fish, such as barred sandperch, which are favored by some Shark Bay dolphins, don't have swim bladders and so are harder to find with echolocation. The sea floor is not nearly as soft here as it is in the Bahamas, so if dolphins want to probe for these fish, they risk injuring their rostra. © 2010 American Association for the Advancement of Science

Related chapters from BP6e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 0:
Link ID: 15586 - Posted: 07.21.2011

By Ella Davies Reporter, BBC Nature Stick insects have lived for one million years without sex, genetic research has revealed. Scientists in Canada investigated the DNA of Timema stick insects, which live in shrubland around the west coast of the US. They traced the ancient lineages of two species to reveal the insects' lengthy history of asexual reproduction. The discovery could help researchers understand how life without sex is possible. Scientists from Simon Fraser University, Canada, published their results in the journal Current Biology. Certain species of Timema stick insects were known to reproduce asexually, with females producing young in "virgin births" without the need for egg fertilisation by males. The insects instead produce genetic clones of themselves. Dr Tanja Schwander and her team set out to test how old these species were, and therefore to find out how long they had reproduced in this way. By analysing the DNA of the insects, scientists were able to trace back their lineages to identify when they became a distinct species. BBC © 2011

Related chapters from BP6e: Chapter 6: Evolution of the Brain and Behavior; Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 0: ; Chapter 8: Hormones and Sex
Link ID: 15578 - Posted: 07.19.2011

by Michael Marshall Life is all about making decisions, and often the answers boil down to your personality. Do I have the nerve to quit my job? If I work in London can I deal with crowds of smelly people on buses? Am I willing to accept a hangover tomorrow morning? (Answers at the bottom of the page.) Personality and the ability to make difficult choices seem like human characteristics, but other animals had them long before we came along. Even the beadlet anemone can boast these traits, and it doesn't even have a brain. Yet individual anemones have distinct personalities, and they can make decisions in a remarkably nuanced way. "Personality" is one of those words like "intelligence" or "consciousness" that means different things to different people. But shorn of cultural baggage, it simply means that individuals consistently behave in particular ways. In that sense, animals as diverse as monkeys, fish, squid and insects have personalities. Mark Briffa of the University of Plymouth, UK, wondered if personalities might be found even in some of the simplest multicellular animals. Sea anemones are cnidarians, like jellyfish and corals, and unlike most species that evolved later they don't have discrete brains. Instead they have diffuse nets of nerves running through their bodies. © Copyright Reed Business Information Ltd.

Related chapters from BP6e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 0:
Link ID: 15553 - Posted: 07.14.2011

by Rebecca Kessler While exploring Australia's Great Barrier Reef, professional diver Scott Gardner heard an odd cracking sound and swam over to investigate. What he found was a footlong blackspot tuskfish (Choerodon schoenleinii) holding a clam in its mouth and whacking it against a rock. Soon the shell gave way, and the fish gobbled up the bivalve, spat out the shell fragments, and swam off. Fortunately, Gardner had a camera handy and snapped what seem to be the first photographs of a wild fish using a tool. Tool use, once thought to be the distinctive hallmark of human intelligence, has been identified in a wide variety of animals in recent decades. Although other creatures don't have anything quite like a circular saw or a juice machine, capuchin monkeys select "hammer" rocks of an appropriate material and weight to crack open seeds, fruits, or nuts on larger "anvil" rocks, and New Caledonian crows probe branches with grass, twigs, and leaf strips to extract insects. In addition to primates and birds, many animals, including dolphins, elephants, naked mole rats, and even octopuses, have shown forms of the behavior. Tool-using fish have been few and far between, however, particularly in the wild. Archerfish target jets of water at terrestrial prey, but whether this constitutes tool use has been contentious. There have also been a handful of reports of fish cracking open hard-shelled prey, such as bivalves and sea urchins, by banging them on rocks or coral, but there's no photo or video evidence to back it up, according to Culum Brown, a behavioral ecologist at Macquarie University in Sydney, Australia, and a co-author of the present paper, to be published in a forthcoming issue of Coral Reefs. © 2010 American Association for the Advancement of Science

Related chapters from BP6e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 0:
Link ID: 15539 - Posted: 07.09.2011

By NATALIE ANGIER Among the Ache hunter-gatherers in eastern Paraguay, healthy adults with no dependent offspring are expected to donate as much as 70 to 90 percent of the food they forage to the needier members of the group. And as those strapping suppliers themselves fall ill, give birth or grow old, they know they can count on the tribe to provide. Among the !Kung bushmen of the Kalahari in Africa, a successful hunter who may be inclined to swagger is kept in check by his compatriots through a ritualized game called “insulting the meat.” You asked us out here to help you carry that pitiful carcass? What is it, some kind of rabbit? Among the Hadza foragers of northern Tanzania, people confronted by a stingy food sharer do not simply accept what’s offered. They hold out their hand, according to Frank Marlowe, an anthropologist at Durham University in England, “encouraging the giver to keep giving until the giver finally draws the line.” Among America’s top executives today, according to a study commissioned by The New York Times, the average annual salary is about $10 million and rising some 12 percent a year. At the same time, the rest of the tribe of the United States of America struggles with miserably high unemployment, stagnant wages and the worst economic crisis since the Great Depression. Now, maybe the wealth gap is a temporary problem, and shiny new quarters will soon rain down on us all. But if you’re feeling tetchy and surly about the lavished haves when you have not a job, if you’re tempted to go out and insult a piece of corporate meat, researchers who study the nature and evolution of human social organization say they are hardly surprised. © 2011 The New York Times Company

Related chapters from BP6e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 0:
Link ID: 15529 - Posted: 07.05.2011

by Sara Reardon When paleontologist Richard Owen dug up a dinosaur in 1842, he thought it looked like a reptile—a "terrible lizard" with scales, slow-moving legs, and cold blood. But many dinosaurs are now known to have been fast, powerful, and energetic. And since the 1960s, scientists have argued over whether the cold-blooded physiology of a lumbering reptile could have powered something nimble and speedy like a Velociraptor. Now, scientists using a technique once reserved for climatologists have found that big four-legged dinos had body temperatures similar to those of mammals—evidence that they either were warm-blooded or were better at conserving body heat than modern reptiles are. Evolutionary biologist Robert Eagle of the California Institute of Technology in Pasadena heard about a technique from Caltech colleagues, who were using it to reconstruct ancient climates. By analyzing minerals in old rocks, geochemists can determine the relative amounts of different chemical isotopes: atoms of the same chemical element that vary slightly in mass. Different isotopes tend to form depending on whether a chemical reaction took place at high or low temperatures. The method, called "clumped-isotope thermometry," focuses on a reaction involving the bond between carbon and oxygen. The lower the temperature at which a mineral forms, the more the rare isotopes carbon-13 and oxygen-18 tend to bond, or "clump," together. By studying CO2 trapped in minerals, geochemist John Eiler of Caltech and other researchers were trying to determine how warm Earth had been when they formed. © 2010 American Association for the Advancement of Science.

Related chapters from BP6e: Chapter 13: Homeostasis: Active Regulation of Internal States; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 9: Homeostasis: Active Regulation of the Internal Environment
Link ID: 15486 - Posted: 06.25.2011

By KAY E. HOLEKAMP After nine months trapped behind my desk in Michigan, I’m finally back in the African bush, the one place I love above all others on earth. Only here are the skies so vast you can see both rainbows and bright sunshine while sitting under a drenching downpour from a massive black thunderhead. Only here can you be sure to see some weird and interesting form of animal life no matter where you look. Ever heard of a duiker? A solifugid? A pangolin? A springhare? A cameroptera? They all live here, along with hundreds of other animal species. Elephants forage in the riverbed that runs beside our camp, hippos chuckle in the pool below my tent, the shrill calls of white-browed robin-chats tell me when I have overslept, baboons steal our sugar jar whenever one of us is dumb enough to leave it unattended, and giraffes browse silently through camp after dark like great ships drifting in the night. But the best thing about the African bush is that it is where you can find spotted hyenas. As I have done every spring since I joined the faculty in the department of zoology at Michigan State University, I’ve once again traded sitting through endless committee meetings and grading overwhelming stacks of student papers for life in a tented camp where my most pressing concern every day is whether or not I will encounter a grumpy hippo on the footpath connecting my sleeping tent to our lab tent and dining area. © 2011 The New York Times Company

Related chapters from BP6e: Chapter 6: Evolution of the Brain and Behavior; Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 0: ; Chapter 8: Hormones and Sex
Link ID: 15466 - Posted: 06.21.2011

By John Matson Does junior really have his father's nose? A common bit of parenting folklore holds that babies tend to look more like their fathers than their mothers, a claim with a reasonable evolutionary explanation. Fathers, after all, do not share a mother's certainty that a baby is theirs, and are more likely to invest whatever resources they have in their own offspring. Human evolution, then, could have favored children that resemble their fathers, at least early on, as a way of confirming paternity. The paternal-resemblance hypothesis got some scientific backing in 1995, when a study in Nature by Nicholas Christenfeld and Emily Hill of the University of California, San Diego, showed that people were much better at matching photos of one-year-old children with pictures of their fathers than with photos of their mothers. (Scientific American is part of Nature Publishing Group.) Case closed? Hardly. "It's a very sexy result, it's seductive, it's what evolutionary psychology would predict—and I think it's wrong," says psychologist Robert French of the National Center for Scientific Research in France. A subsequent body of research, building over the years in the journal Evolution & Human Behavior, has delivered results in conflict with the 1995 paper, indicating that young children resemble both parents equally. Some studies have even found that newborns tend to resemble their mothers more than their fathers. © 2011 Scientific American,

Related chapters from BP6e: Chapter 6: Evolution of the Brain and Behavior; Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 0: ; Chapter 8: Hormones and Sex
Link ID: 15459 - Posted: 06.20.2011

by Caroline Williams Octopuses' astonishing mental skills might help us unearth the roots of intelligence – but first we need to understand what makes them so smart BETTY the octopus is curled up in her den, eyes half-closed and clutching a piece of red Lego like a child with a teddy bear. She is, says Kerry Perkins, cephalopod researcher at the Sea Life aquarium in Brighton, UK, much better behaved than some of the octopuses she has worked with. One used to short-circuit a light in its tank by squirting water at it, and would do so whenever the bulb was left on at night. Another made a bid for freedom via the aquarium drainage system, which it seemed to know headed straight out to sea. "Any octopus tank worth its salt has a way of stopping the octopus from escaping," Perkins says as she adds two weights to the lid of Betty's tank. "They love to explore." Aristotle once took this kind of curiosity as a sign that octopuses are stupid - after all, he pointed out, just waving your hands in their direction brings them close enough to catch. We now know that it is just one example of how smart they are. Between them, cephalopods, which also include squids, cuttlefish and nautiluses, can navigate a maze, use tools, mimic other species, learn from each other and solve complex problems. If the latest analyses are to be believed, these skills might show a rudimentary form of consciousness. Cephalopods are the only invertebrates that can boast anything like this kind of mental prowess, and some of their more impressive tricks are shared with only the cleverest vertebrates, such as chimps, dolphins and crows. Yet they evolved along a completely separate path, from snail-like ancestors, and their brains look completely alien to our own (see "A brain apart"). © Copyright Reed Business Information Ltd.

Related chapters from BP6e: 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: 15431 - Posted: 06.14.2011

By Tina Hesman Saey Bad news for fans of the X-Men: It may take longer to create a new class of mutant superhumans than previous estimates suggested. The first direct measurements of human mutation rates reveal that the speed at which successive generations accumulate single-letter genetic changes is much slower than previously thought. The study, published online June 12 in Nature Genetics, also shows that some individuals mutate faster than others. That means it may be fairly common for people to inherit a disproportionate share of mutations from one parent. Researchers from an international collaboration known as the 1000 Genomes Project deciphered the genetic blueprints of six people from two families — a mother, father and child from each — and counted up the mutations inherited by each child. From there, the team calculated the human mutation rate. “We all mutate,” says study coauthor Philip Awadalla, a population geneticist at the University of Montreal. “And the mutation rate can be extraordinarily variable from individual to individual.” Combined with the results of three similar recent studies, the rate indicates that, on average, about one DNA chemical letter in every 85 million gets mutated per generation through copying mistakes made during sperm and egg production. The new rate means each child inherits somewhere in the neighborhood of 30 to 50 new mutations. © Society for Science & the Public 2000 - 2011

Related chapters from BP6e: 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: 15430 - Posted: 06.14.2011

By Bruce Bower Way back in the day, females came from far away and males didn’t stray — not far, anyway. That’s the implication, with apologies to Dr. Seuss, of a new study of members of two ancient species in the human evolutionary family. Adult females in both hominid lineages often moved from the places where they were born to distant locations, presumably to find mates among unrelated males, say anthropologist Sandi Copeland of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, and her colleagues. Most males in both hominid species spent their entire lives in a home region that covered no more than about 28 square kilometers, or about half the area of Manhattan, Copeland’s team proposes in the June 2 Nature. These ancient “home boys” might have occasionally gone further afield, exploiting resources along wooded areas atop bands of bedrock that extend about 30 kilometers in opposite directions from the South African cave sites where the fossils were found. It’s not clear how far females traveled to reach new groups, only that they did not grow up where they died. “We have the first direct glimpse of early hominids’ geographic movements,” Copeland says. “Ranging differences between males and females were surprising.” © Society for Science & the Public 2000 - 2011

Related chapters from BP6e: Chapter 6: Evolution of the Brain and Behavior; Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 0: ; Chapter 8: Hormones and Sex
Link ID: 15389 - Posted: 06.02.2011

By SEAN B. CARROLL I am not a big fan of reality TV, but I will confess that I am a loyal viewer of the Discovery Channel’s “Deadliest Catch” series. The show chronicles the adventures of the crews of several crabbing boats of the Alaskan fleet as they pursue red king crabs on the Bering Sea. What fascinates me, and I suspect other viewers, is the vicarious experience of watching the crews working for long stretches in unimaginable conditions. I know that this landlubber would not last an hour on any boat as it heaved in 30-foot seas, let alone while hauling 800-pound crab pots on an ice-covered deck, in 60-mile-an-hour winds, for 20 to 30 hours straight. That’s definitely not for me. My crab-catching is limited to plucking hermit crabs the size of golf balls off the sands of some quiet Florida beach in 80-degree weather. One might think that not only is there no comparison between my beachcombing and the dangerous business of Alaska crab fishing, but that the two kinds of crabs involved have very little in common. The typically diminutive hermit crabs have to contort their bodies into abandoned snail shells, while the four- to nine-pound red king crabs, the largest of the more than 100 species of king crabs, freely prowl the ocean bottom in search of worms, clams, mussels, starfish and other prey. Looking at those monsters of the deep, safely steamed on your plate at Red Lobster, one might think that such tasty beauties would be more closely related to other crabs on the menu, like stone crabs, than to the largely inedible hermit crabs. © 2011 The New York Times Company

Related chapters from BP6e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 0:
Link ID: 15355 - Posted: 05.24.2011

by Ann Gibbons While dinosaurs ruled the world some 200 million years ago, a group of nocturnal, shrewlike proto-mammals unwittingly sniffed out a strategy for survival that eventually led to the evolution of larger brains. Fossil skulls of two ancient, mammal-like reptiles suggest that natural selection for a keener sense of smell was the initial spur behind bigger brains in early mammals, according to a report online today in Science. “Mammals didn’t get our larger brains for thinking,” says co-author Zhe-Xi Luo, a paleontologist at the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania. “We got it for a more urgent and more basic need—our sense of smell was far more important.” Birds and mammals have brains that are up to 10 times larger, relative to body size, than those of reptiles and other animals. Why? Some researchers have proposed that the early, nocturnal mammals evolved larger brains to boost their hearing, because sight was less important at night. Others have suggested that mammals’ brains are proportionately larger because as many early mammals evolved smaller bodies, their brains failed to shrink to scale. By reconstructing the two oldest known skulls of proto-mammals—fossils of Morganucodon and Hadrocodium discovered in the famed Lufeng Formation in Yunnan, China, in 1986—Luo and colleagues found clues to how the mammalian brain began to enlarge. The researchers scanned the skulls with computed tomography (CT) scans, creating three-dimensional, virtual endocasts of the brain, based on the impressions brain tissue and spaces left on the inside of the skull. That gave them a detailed view of the surface of the brain and the nasal cavities. © 2010 American Association for the Advancement of Science.

Related chapters from BP6e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 15348 - Posted: 05.21.2011

By Adam Summers If you’ve ever chased a cat that’s trying to avoid a bath, you have every right to conclude that, for our size, we humans are pretty poor runners. But chasing a cat is sprinting. Where we excel is endurance running. Moreover, we run long distances at fast speeds: many joggers do a mile in seven-and-a-half minutes, and top male marathoners can string five-minute miles together for more than two hours. A quadruped of similar weight, about 150 pounds, prefers to run a mile at a trot, which takes nine-and-a-half minutes, and would have to break into a gallop to keep pace with a good recreational jogger. That same recreational jogger could keep up with the preferred trotting speed of a thousand-pound horse. Good endurance runners are rare among animals. Although humans share the ability with some other groups, such as wolves and dogs, hyenas, wildebeest, and horses, we alone among primates can run long distances with ease. But what evidence can support the idea that endurance running by itself gave early humans an evolutionary advantage, and that it wasn’t just “piggybacking” on our ability to walk? Many traits, after all, are useful for both activities; long legs, for instance, and the long stride they enable, are helpful to walking as well as to running. But running and walking are mechanically different gaits. A walking person, aided by gravity, acts as an inverted pendulum: the hip swings over the planted foot. In contrast, a runner bounces along, aided by tendons and ligaments that act as springs, which alternately store and release energy. © 2008–2011 Natural History Magazine, Inc

Related chapters from BP6e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 0:
Link ID: 15331 - Posted: 05.16.2011