Chapter 6. Evolution of the Brain and Behavior
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By Susan Milius After death, male guppies can keep on siring offspring because females store sperm for so long. As a result, a living male in a stream in Trinidad can end up competing with long-gone fish from his grandfather’s generation. At its most posthumously successful, stored ghost sperm sired about one in four of the offspring among wild guppies released into a stream, evolutionary biologist Andrés López-Sepulcre of École Normale Supérieure in Paris and his colleagues report June 5 in Proceedings of the Royal Society B. Biologists have long known that female Poecilia reticulata guppies store sperm. The cells clump in little pockets in a female’s ovarian cavity and feed on sugars released by ovarian tissue. Storage in itself isn’t unusual, López-Sepulcre says. Some crabs, turtles, lizards, bats and other creatures preserve sperm for later use. Posthumous reproduction by stored sperm also isn’t unheard of. “The fun part of our study,” López-Sepulcre says, “is that you have males who are alive and males who are dead competing with each other.” Researchers deployed guppies in several streams as part of a study on evolutionary change. Every month researchers catch, check and release as many fish as possible to track deaths and births. They also genetically analyze parenthood of the fish. Female guppies give live birth to broods of two to about 10 youngsters, with not all sired by the same male. Females live about 15 months; males about three. © Society for Science & the Public 2000 - 2013
By Rachel Ehrenberg The salad days of human evolution saw a dietary shift toward grasses and probably grass-fed animals, analyses of more than 100 fossilized teeth from eight species of ancient hominids indicate. “These changes in diet have been predicted,” says paleoanthropologist Richard Klein of Stanford University. “But it’s very nice to have some data, and these data support it very strongly.” Changes in the size and shape of jaws and teeth in both ancient hominids and their ape relatives point to changes in diet. The new study adds to these lines of anatomical evidence chemical analyses that look at different forms of carbon in the fossilized teeth. The ratio of two types of carbon in tooth enamel reflects diet, says geochemist Thure Cerling of the University of Utah, who spent weeks in a vault in the National Museum of Kenya collecting milligram-sized samples of tooth enamel for the analyses. Grasses, grasslike sedges and many other plants in hot, arid environments have evolved a trick that helps prevent water loss. The metabolic adjustment results in taking up more of a heavier form of carbon, known as carbon-13, than most trees and shrubs do. The tooth studies, which cover more than 3 million years and include specimens from southern, eastern and central Africa, found greater quantities of this heavier carbon in hominids that are closer to humans on the evolutionary tree. This pattern suggests that, compared with humans’ more ancient relatives, recent ones were eating more grass or more grass-feeding animals, like zebras. The analyses appear June 3 in the Proceedings of the National Academy of Sciences. © Society for Science & the Public 2000 - 2013
By Susan Milius Cockroaches that don’t fall for traps’ sweet poisons have evolved taste cells that register sugar as bitter. In certain groups of the widespread German cockroach (Blattella germanica), nerve cells that normally detect bitter, potentially toxic compounds now also respond to glucose, says entomologist Coby Schal of North Carolina State University in Raleigh. The “bitter” reaction suppresses the “sweet” response from other nerve cells, and the roach stops eating, Schal and his colleagues report in the May 24 Science. Normally roaches love sugar. But with these populations, a dab of jelly with glucose in it makes them “jump back,” Schal says. “The response is: ‘Yuck! Terrible!’” This quirk of roach taste explains why glucose-baited poison traps stopped working among certain roaches, Schal says. Such bait traps combining a pesticide with something delicious became popular during the mid-1980s. But in 1993, Jules Silverman, also a coauthor on the new paper, reported roaches avoiding these once-appealing baits. “This is a fascinating piece of work because it shows how quickly, and how simply, the sense of taste can evolve,” says neurobiologist Richard Benton of the University of Lausanne in Switzerland. What pest-control manufacturers put in their roach baits now, and whether some still use glucose, isn’t public, Schal says. But humankind’s arms race with cockroaches could have started long ago, “in the caves,” he says. In this back-and-forth struggle, it’s important “to understand what the cockroach is doing from a molecular basis.” © Society for Science & the Public 2000 - 2013
By JOHN NOBLE WILFORD Modern mothers love to debate how long to breast-feed, a topic that stirs both guilt and pride. Now — in a very preliminary finding — the Neanderthals are weighing in. By looking at barium levels in the fossilized molar of a Neanderthal child, researchers concluded that the child had been breast-fed exclusively for the first seven months, followed by seven months of mother’s milk supplemented by other food. Then the barium pattern in the tooth enamel “returned to baseline prenatal levels, indicating an abrupt cessation of breast-feeding at 1.2 years of age,” the scientists reported on Wednesday in the journal Nature. While that timetable conforms with the current recommendations of the American Academy of Pediatrics — which suggests that mothers exclusively breast-feed babies for six months and continue for 12 months if possible — it represents a much shorter span of breast-feeding than practiced by apes or a vast majority of modern humans. The average age of weaning in nonindustrial populations is about 2.5 years; in chimpanzees in the wild, it is about 5.3 years. Of course, living conditions were much different for our evolutionary cousins, the Neanderthals, extinct for the last 30,000 years. The findings, which drew strong skepticism from some scientists, were meant to highlight a method of linking barium levels in teeth to dietary changes. In the Nature report, researchers from the United States and Australia described tests among human infants and captive macaques showing that traces of the element barium in tooth enamel appeared to accurately reflect transitions from mother’s milk through weaning. The barium levels rose during breast-feeding and fell off sharply on weaning. © 2013 The New York Times Company
By Bruce Bower Chaser isn’t just a 9-year-old border collie with her breed’s boundless energy, intense focus and love of herding virtually anything. She’s a grammar hound. In experiments directed by her owner, psychologist John Pilley of Wofford College in Spartanburg, S.C., Chaser demonstrated her grasp of the basic elements of grammar by responding correctly to commands such as “to ball take Frisbee” and its reverse, “to Frisbee take ball.” The dog had previous, extensive training to recognize classes of words including nouns, verbs and prepositions. “Chaser intuitively discovered how to comprehend sentences based on lots of background learning about different types of words,” Pilley says. He reports the results May 13 in Learning and Motivation. Throughout the first three years of Chaser’s life, Pilley and a colleague trained the dog to recognize and fetch more than 1,000 objects by name. Using praise and play as reinforcements, the researchers also taught Chaser the meaning of different types of words, such as verbs and prepositions. As a result, Chaser learned that phrases such as “to Frisbee” meant that she should take whatever was in her mouth to the named object. Exactly how the dog gained her command of grammar is unclear, however. Pilley suspects that Chaser first mentally linked each of two nouns she heard in a sentence to objects in her memory. Then the canine held that information in mind while deciding which of two objects to bring to which of two other objects. Pilley’s work follows controversial studies of grammar understanding in dolphins and a pygmy chimp. © Society for Science & the Public 2000 - 2013
By CARL ZIMMER Imagine a wolf catching a Frisbee a dozen times in a row, or leading police officers to a stash of cocaine, or just sleeping peacefully next to you on your couch. It’s a stretch, to say the least. Dogs may have evolved from wolves, but the minds of the two canines are profoundly different. Dog brains, as I wrote last month in The New York Times, have become exquisitely tuned to our own. Scientists are now zeroing in on some of the genes that were crucial to the rewiring of dog brains. Their results are fascinating, and not only because they can help us understand how dogs turned into man’s best friend. They may also teach us something about the evolution of our own brains: Some of the genes that evolved in dogs are the same ones that evolved in us. To trace the change in dog brains, scientists have first had to work out how dog breeds are related to one another, and how they’re all related to wolves. Ya-Ping Zhang, a geneticist at the Chinese Academy of Sciences, has led an international network of scientists who have compared pieces of DNA from different canines. They’ve come to the conclusion that wolves started their transformation into dogs in East Asia. Those early dogs then spread to other parts of the world. Many of the breeds we’re most familiar with, like German shepherds and golden retrievers, emerged only in the past few centuries. © 2013 The New York Times Company
by Michael Balter From the human perspective, few events in evolution were more momentous than the split among primates that led to apes (large, tailless primates such as today's gorillas, chimpanzees, and humans) and Old World monkeys (which today include baboons and macaques). DNA studies of living primates have estimated that the rift took place between 25 million and 30 million years ago, but the earliest known fossils of both groups date no earlier than 20 million years ago. Now, a team working in Tanzania has found teeth and partial jaws from what it thinks are 25-million-year-old ancestors of both groups. If the interpretations hold up, the finds would reconcile the molecular and fossil evidence and possibly provide insights into what led to the split in the first place. Researchers have long been frustrated by a paucity of fossils from this key period in evolution, which sits at the borderline between two major geological epochs: the Miocene (about 23 million to 5 million years ago) and the Oligocene (about 34 million to 23 million years ago). The earliest known fossils of early apes and Old World monkeys date from the early Miocene and have been found in just a handful of sites in Kenya, Uganda, and North Africa. Meanwhile, molecular studies of existing primates consistently suggest that these two groups arose during the Oligocene, leading scientists to wonder whether the molecular dates are wrong or if paleontologists have been looking in the wrong places. For more than a decade, researchers from the United States and Tanzania have been combing Tanzania's Rukwa Rift Basin, searching for fossils of all kinds. During the 2011 and 2012 seasons, a team led by Nancy Stevens, a vertebrate paleontologist at Ohio University in Athens, discovered fossils that it identified as belonging to two previously unknown species of primates: one, an apparent ape ancestor the team has named Rukwapithecus fleaglei; the other, a claimed Old World monkey ancestor dubbed Nsungwepithecus gunnelli. © 2010 American Association for the Advancement of Science.
Link ID: 18163 - Posted: 05.16.2013
By Jason G. Goldman There is a rich tradition in psychology and neuroscience of using animals as models for understanding humans. Humans, after all, are enormously complicated creatures to begin even from a strictly biological perspective. Tacking on the messiness that comes with culture makes the study of the human mind tricky, at best. So, just as biomedical scientists have relied upon the humble mouse, psychological and cognitive scientists have too turned to our evolutionary cousins in the animal kingdom as a means of better understanding ourselves. In her new book Animal Wise, journalist Virginia Morrell recounts a conversation with one researcher who pointed out that decades of research were built upon “rats, pigeons, and college sophomores, preferably male.” The college undergrads stood in for all of humanity, the rats served as representatives of all other mammals, and pigeons served as a model for the rest of the animal kingdom. The silly part isn’t that non-human animals can be used effectively as a means of understanding more about our own species. The idea is simple: understand how a simple system works, and you can make careful inferences about the way that complex systems work. That is (or should be) obvious. In his interview with CNN today, memory research pioneer and Nobel Prize winner Eric Kandel said as much: “Rather than studying the most complex form of memory in a very complicated animal, we had to take the most simple form — an implicit form of memory — in a very simple animal.” © 2013 Scientific American
Zoe Cormier A study of two ancient hominins from South Africa suggests that changes in the shape and size of the middle ear occurred early in our evolution. Such alterations could have profoundly changed what our ancestors could hear — and perhaps how they could communicate. Palaeoanthropologist Rolf Quam of Binghamton University in New York state and his colleagues recovered and analysed a complete set of the three tiny middle-ear bones, or ossicles, from a 1.8-million-year-old specimen of Paranthropus robustus and an incomplete set of ossicles from Australopithecus africanus, which lived from about 3.3 million to around 2.1 million years ago. The ossicles are the smallest bones in the human body, and are rarely preserved intact in hominin fossils, Quam says. In both specimens, the team found that the malleus (the first in the chain of the three middle-ear bones) was human-like — smaller in proportion compared to the ones in our ape relatives. Its size would also imply a smaller eardrum. The similarity between the two species points to a “deep and ancient origin” of this feature, Quam says. “This could be like bipedalism: a defining characteristic of hominins.” It is hard to draw conclusions about hearing just from the shape of the middle-ear bones because the process involves so many different ear structures, as well as the brain itself. However, some studies have shown that the relative sizes of the middle-ear bones do affect what primates can hear2. Genomic comparisons with gorillas have indicated that changes in the genes that code for these structures might also demarcate humans from apes3. © 2013 Nature Publishing Group
by Michael Balter Researchers debate when language first evolved, but one thing is sure: Language requires us not only to talk but also to listen. A team of scientists now reports recovering the earliest known complete set of the three tiny middle ear bones—the malleus ("hammer"), incus ("anvil"), and stapes ("stirrup")—in a 2.0-million-year-old skull of Paranthropus robustus, a distant human relative found in South Africa (see photo). Reporting online today in the Proceedings of the National Academy of Sciences, the researchers found that the malleus of P. robustus, as well one found earlier in the early human relative Australopithecus africanus, is similar to that of modern humans, whereas the two other ear bones most closely resemble existing African and Asian great apes. The team is not entirely sure what this precocious appearance of a human-like malleus means. But since the malleus is attached directly to the eardrum, the researchers suggest that it might be an early sign of the high human sensitivity to middle-range acoustic frequencies between 2 and 4 kilohertz—frequencies critical to spoken language, but which apes and other primates are much less sensitive to. © 2010 American Association for the Advancement of Science
Ed Yong Many moths have evolved sensitive hearing that can pick up the ultrasonic probes of bats that want to eat them. But one species comes pre-adapted for anything that bats might bring to this evolutionary arms race. Even though its ears are extremely simple — a pair of eardrums on its flanks that each vibrate four receptor cells — it can sense frequencies up to 300 kilohertz, well beyond the range of any other animal and higher than any bat can squeak. “A lot of previous work has suggested that some bats have evolved calls that are out of the hearing range of the moths they are hunting. But this moth can hear the calls of any bat,” says James Windmill, an acoustical engineer at the University of Strathclyde, UK, who discovered the ability in the greater wax moth (Galleria mellonella). His study is published in Biology Letters1. Windmill's collaborator Hannah Moir, a bioacoustician now at the University of Leeds, UK, played sounds of varying frequencies to immobilized wax moths. As the insects “listened”, Moir used a laser to measure the vibrations of their eardrums, and electrodes to record the activity of their auditory nerves. The moths were most sensitive to frequencies of around 80 kilohertz, the average frequency of their courtship calls. But when exposed to 300 kilohertz, the highest level that the team tested, the insects' eardrums still vibrated and their neurons still fired. © 2013 Nature Publishing Group
by Elizabeth Norton If you've ever cringed when your parents said "groovy," you'll know that spoken language can have a brief shelf life. But frequently used words can persist for generations, even millennia, and similar sounds and meanings often turn up in very different languages. The existence of these shared words, or cognates, has led some linguists to suggest that seemingly unrelated language families can be traced back to a common ancestor. Now, a new statistical approach suggests that peoples from Alaska to Europe may share a linguistic forebear dating as far back as the end of the Ice Age, about 15,000 years ago. "Historical linguists study language evolution using cognates the way biologists use genes," explains Mark Pagel, an evolutionary theorist at the University of Reading in the United Kingdom. For example, although about 50% of French and English words derive from a common ancestor (like "mere" and "mother," for example), with English and German the rate is closer to 70%—indicating that while all three languages are related, English and German have a more recent common ancestor. In the same vein, while humans, chimpanzees, and gorillas have common genes, the fact that humans share almost 99% of their DNA with chimps suggests that these two primate lineages split apart more recently. Because words don't have DNA, researchers use cognates found in different languages today to reconstruct the ancestral "protowords." Historical linguists have observed that over time, the sounds of words tend to change in regular patterns. For example, the p sound frequently changes to f, and the t sound to th—suggesting that the Latin word pater is, well, the father of the English word father. Linguists use these known rules to work backward in time, making a best guess at how the protoword sounded. They also track the rate at which words change. Using these phylogenetic principles, some researchers have dated many common words as far back as 9000 years ago. The ancestral language known as Proto-Indo-European, for example, gave rise to languages including Hindi, Russian, French, English, and Gaelic. © 2010 American Association for the Advancement of Science.
Symmetry study deemed a fraud Eugenie Samuel Reich Few researchers have tried harder than Robert Trivers to retract one of their own papers. In 2005, Trivers, an evolutionary biologist at Rutgers University in New Brunswick, New Jersey, published an attention-grabbing finding: Jamaican teenagers with a high degree of body symmetry were more likely to be rated ‘good dancers’ by their peers than were those with less symmetrical bodies. The study, which suggested that dancing is a signal for sexual selection in humans, was featured on the cover of this journal (W. M. Brown et al. Nature 438, 1148–1150; 2005). But two years later, Trivers began to suspect that the study data had been faked by one of his co-authors, William Brown, a postdoctoral researcher at the time. In seeking a retraction, Trivers self-published The Anatomy of a Fraud, a small book detailing what he saw as evidence of data fabrication. Later, Trivers had a verbal altercation over the matter with a close colleague and was temporarily banned from campus. An investigation of the case, completed by Rutgers and released publicly last month, now seems to validate Trivers’ allegations. Brown disputes the university’s finding, but it could help to clear the controversy that has clouded Trivers’ reputation as the author of several pioneering papers in the 1970s. For example, Trivers advanced an influential theory of ‘reciprocal altruism’, in which people behave unselfishly and hope that they will later be rewarded for their good deeds. He also analysed human sexuality in terms of the investments that mothers and fathers each make in child-rearing. © 2013 Nature Publishing Group
By Bruce Bower Human ancestors living in East Africa 2 million years ago weren’t a steak-and-potatoes crowd. But they had a serious hankering for gazelle meat and antelope brains, fossils discovered in Kenya indicate. Three sets of butchered animal bones unearthed at Kenya’s Kanjera South site provide the earliest evidence of both long-term hunting and targeted scavenging by a member of the human evolutionary family, anthropologist Joseph Ferraro of Baylor University in Waco, Texas, and his colleagues conclude. An early member of the Homo genus, perhaps Homo erectus, hunted small animals and scavenged predators’ leftovers of larger creatures, researchers report April 25 in PLOS ONE. Along with hunting relatively small game such as gazelles, these hominids scavenged the heads of antelope and wildebeests, apparently to add a side of fatty, nutrient-rich brain tissue to their diets, the scientists say. Those dietary pursuits could have provided the extra energy Homo erectus needed to support large bodies, expanded brains and extensive travel across the landscape, Ferraro says. A few East African sites dating to as early as 3.4 million years ago had previously produced small numbers of animal bones bearing butchery marks made by stone tools. Scientists think those bones indicate occasional meat eating (SN: 9/11/10, p. 8). Now Kanjera South has yielded several thousand complete and partial animal bones, representing at least 81 individual animals. A known reversal of Earth’s magnetic field preserved in an excavated soil layer allowed Ferraro’s team to determine the age of the finds, which accumulated over a few thousand years at most. © Society for Science & the Public 2000 - 2013
Karen Ravn Birds of a feather may flock together, but do birds that flock together develop distinct cultures? Two studies published today in Science1, 2 find strong evidence that, at the very least, monkeys that troop together and whales that pod together do just that. And they manage it in the same way that humans do: by copying and learning from each other. A team led by Erica van de Waal, a primate psychologist at the University of St Andrews, UK, created two distinct cultures — 'blue' and 'pink' — among groups of wild vervet monkeys (Chlorocebus aethiops) in South Africa1. The researchers trained two sets of monkeys to eat maize (corn) dyed one of those two colours but eschew maize dyed the other colour. The scientists then waited to see how the groups behaved when newcomers — babies and migrating males — arrived. Both sets of newcomers seemed to follow social cues when selecting their snacks. Baby monkeys ate the same colour maize as their mothers. Seven of the ten males that migrated from one colour culture to another adopted the local colour preference the first time that they ate any maize. The trend was even stronger when they first fed with no higher-ranking monkey around, with nine of the ten males choosing the locally preferred variety. The only immigrant to buck this trend was a monkey who assumed the top rank in his new group as soon as he got there — and he may not have given a fig what anyone else ate. “The take-home message is that social learning — learning from others rather than through individual trial and error — is a more potent force in shaping wild animals’ behaviour than has been recognized so far,” says Andrew Whiten, an evolutionary and developmental psychologist at St Andrews and co-author of the paper. © 2013 Nature Publishing Group
Posted by Christy Ullrich Elephants may use a variety of subtle movements and gestures to communicate with one another, according to researchers who have studied the big mammals in the wild for decades. To the casual human observer, a curl of the trunk, a step backward, or a fold of the ear may not have meaning. But to an elephant—and scientists like Joyce Poole—these are signals that convey vital information to individual elephants and the overall herd. Biologist and conservationist Joyce Poole and her husband, Petter Granli, both of whom direct ElephantVoices, a charity they founded to research and advocate for conservation of elephants in various sanctuaries in Africa, have developed an online database decoding hundreds of distinct elephant signals and gestures. The postures and movements underscore the sophistication of elephant communication, they say. Poole and Granli have also deciphered the meaning of acoustic communication in elephants, interpreting the different rumbling, roaring, screaming, trumpeting, and other idiosyncratic sounds that elephants make in concert with postures such as the positioning and flapping of their ears. Poole has studied elephants in Africa for more than 37 years, but only began developing the online gestures database in the past decade. Some of her research and conservation work has been funded by the National Geographic Society. “I noticed that when I would take out guests visiting Amboseli [National Park in Kenya] and was narrating the elephants’ behavior, I got to the point where 90 percent of the time, I could predict what the elephant was about to do,” Poole said in an interview. “If they stood a certain way, they were afraid and were about to retreat, or [in another way] they were angry and were about to move toward and threaten another.” © 1996-2012 National Geographic Society.
By Scicurious Generally, I don’t think of being tickled as a particularly pleasurable or calming activity. Most people who are ticklish go immediately on the defensive and tense up, and I always got the impression that most people prefer NOT to be tickled rather than otherwise. However, that’s just us. And we’re not rats. And it turns out, you can calm a rat with tickling. Life is stressful. Whether it’s running from predators, meeting tight deadlines, or trying to keep fed, there’s a lot that seems to bring us down. What saves us from tearing our hair out? Well, the happy things in life. Tasty food, friends, hugs, puppies. You know, the good stuff. These things elicit positive feeling, and positive feeling have been linked to protecting us from stress. Of course, in humans, it’s easy to say that a positive outlook on life makes someone resistant to stress…but is it really true? They may co-occur, but do positive feelings really decrease stress? If you want to get at causes, one of the best ways is to use an animal model. But how do you come up with an animal model for…happiness? Well, you can tickle rats. As you can see in the video above, rats like to be tickled. They even respond with “laughter”! Of course, it’s not laughter as we know it, or even something we can hear. Instead, these are ultrasonic vocalizations at a specific frequency (50 kilohertz). Scientists figured they must be pleasure-sounds because rats make them when they play with other rats. And it turns out that rats make the same noise at the same frequency when they get tickled! © 2013 Scientific American
By Kate Wong Odds are you carry DNA from a Neandertal, Denisovan or some other archaic human. Just a few years ago such a statement would have been virtually unthinkable. For decades evidence from genetics seemed to support the theory that anatomically modern humans arose as a new species in a single locale in Africa and subsequently spread out from there, replacing archaic humans throughout the Old World without mating with them. But in recent years geneticists have determined that, contrary to that conventional view, anatomically modern Homo sapiens did in fact interbreed with archaic humans, and that their DNA persists in people today. In the May issue of Scientific American, Michael Hammer of the University of Arizona in Tucson examines the latest genetic findings and explores the possibility that DNA from these extinct relatives helped H. sapiens become the wildly successful species it is today. As Scientific American’s anthropology editor, I have an enduring interest in the rise of H. sapiens; and as longtime readers of this blog may know, I’m fascinated (you might even say obsessed) with Neandertals. So naturally I’ve been keen to find out how much, if any, Neandertal DNA I have in my own genome. Several consumer genetic testing companies now test for Neandertal genetic markers as part of their broader ancestry analysis, and after 23andMe lowered the price of their kit to $99 in December, I decided to take the plunge. As it happens, National Geographic’s Genographic Project had recently updated their own genetic test to look for Neandertal DNA, and they sent me a kit (retail price: $299) for editorial review, much as publishers do with new books. And so it was on a chilly Saturday in late January that I found myself spitting into a test tube for 23andMe and swabbing my cheek for the Genographic Project. © 2013 Scientific American
By Susan Milius Zola the crow is about to face a test that has baffled animals from canaries to dogs. She’s a wild New Caledonian crow, and for the first time, she’s seeing a tidbit of meat dangling on a long string tied to a stick. She perches on the stick, bends down, grabs the string with her beak and pulls. But the string is too long. The meat still hangs out of reach. In similar tests, dogs, pigeons and many other species routinely falter. Some nibble at the string or keep tugging and dropping the same segment. Some pull at a string that’s not connected to food just as readily as a string that is. Eventually many get the hang of reeling in the tidbit, but they seem to learn by trial and error. Zola, however, does not fumble. On her first attempt, she anchors the first length of string by stepping on it and immediately bends down again for the next segment. With several more pulls and steps, Zola reels in the treat. Watching the crow, says Russell Gray, one of the researchers behind the string-pulling experiment, “people say, ‘Wow, it had a flash of insight.’ ” At first glance it seems Zola mentally worked through the problem as a human might, devising a solution in an aha moment. But Gray, of the University of Auckland in New Zealand, has had enough of such supposed animal geniuses. Asking whether the crow solves problems in the same way a human would isn’t a useful question, he says. He warns of a roller coaster that scientists and animal lovers alike can get stuck on: first getting excited and romanticizing a clever animal’s accomplishments, then crashing into disappointment when some killjoy comes up with a mundane explanation that’s not humanlike at all. © Society for Science & the Public 2000 - 2013
Sid Perkins The two-million-year-old remains of a novel hominin discovered in August 2008 are an odd blend of features seen both in early humans and in the australopithecines presumed to have preceded them. A battery of six studies1–6 published today in Science scrutinizes the fossils of Australopithecus sediba from head to heel and yields unprecedented insight into how the creature walked, chewed and moved. Together, the studies suggest that this hominin was close to the family tree of early humans — although it remains controversial whether it was one of our direct ancestors. “We see evolution in action across this skeleton,” says Lee Berger, a palaeoanthropologist at the University of the Witwatersrand in Johannesburg, South Africa. For instance, whereas the creature’s arms are ape-like, its hands and wrists are remarkably like those of humans. And although the hominin’s pelvis is shaped like a modern human's, its torso included a narrow upper rib cage like those found in apes. One of the six studies focused on Au. sediba’s teeth1, comparing 22 different aspects across hundreds of teeth from several other species of australopithecines and thousands of early human teeth. Tooth similarities among the species are more likely to signify common ancestry than independent evolution towards a beneficial design, says Debbie Guatelli-Steinberg, an anthropologist at Ohio State University in Columbus. That's because most of the characteristics the team chose to study, such as the subtle curvature of a portion of the tooth’s surface, are not likely to be evolutionarily useful. © 2013 Nature Publishing Group
Link ID: 18027 - Posted: 04.13.2013