By Susana Martinez-Conde This week’s illusion was discovered by Dartmouth College neuroscientist Peter Tse, author of “The Neural Basis of Free Will: Criterial Causation“, and presented as a Top 10 finalist at the recent Best Illusion of the Year Contest. The Knobby Sphere Illusion tricks your sense of touch. To experience it, you will need a regular pencil (for instance, with a hexagonal cross-section, and a small hard sphere (such a marble or ball bearing). Squeeze the pencil lengthwise very hard between your thumb and first finger for a full minute, until you can see deep indentations in your skin. Now feel the sphere by rolling it around against the parts of your fingers where the indentations are. The sphere no longer feels round, but bumpy. Your brain assumes that the touch receptors in your skin lie on a flat sheet, and misattributes the skin deformations to the sphere. © 2013 Scientific American

Keyword: Pain & Touch
Link ID: 18243 - Posted: 06.08.2013

by Debora MacKenzie YOUR eye colour is a product of your DNA, but what about your IQ? The biggest-ever search for genes that affect intelligence, and the first to give reproducible results, has found 10 variations in DNA that seem to influence intelligence – but not by much. Studies of families show intelligence is 40 to 50 per cent inherited, and otherwise depends on environment. Since mass-analysis of DNA variations became possible, a number of studies have sought the genes involved in this inheritance, and some papers have claimed strong associations between particular genes and IQ. Yet results have varied widely and none have been replicated. "Many of the published findings of the last decade are wrong," says John Hewitt of the University of Colorado in Boulder, who was not involved in the new study. So if intelligence is inherited, where are the genes hiding? The research may have hit problems because each gene linked with IQ has only a tiny effect on overall intelligence. This means you need data on a large number of people to reliably distinguish such effects from measurement error. Most studies have involved between 100 and 2000 subjects. Now, some 200 researchers have assembled 54 sets of data on more than 126,000 people who have had their genomes analysed for 2.5 million common, small mutations called SNPs. Information was also available for how long they spent in education and the level they reached. © Copyright Reed Business Information Ltd.

Keyword: Intelligence; Genes & Behavior
Link ID: 18242 - Posted: 06.06.2013

by Jennifer Viegas Dogs with obsessive compulsive disorder show nearly the same brain abnormalities of humans who have OCD, a new study finds. The discovery, published in Progress in Neuro-Psychopharmacology & Biological Psychiatry, adds another notch to the dog-human connection and holds promise for better treatments for OCD. “While the study sample was small and further research is needed, the results further validate that dogs with CCD (Canine Compulsive Disorder) can provide insight and understanding into anxiety disorders that affect people,” Nicholas Dodman, a professor of clinical sciences at the Cummings School of Veterinary Medicine at Tufts University who worked on the study, said in a press release. Dodman said that, in addition to having the same structural brain abnormalities as people with OCD, dogs also show similar behaviors, respond to the same medications and seem to have similar genetic roots to the disorder. Dogs with CCD engage in repetitious and destructive behaviors, such as flank and blanket-sucking, tail chasing and chewing. The main thing — and this is true for humans as well — is that the activity or thought is repetitive and persistent, such that it’s time consuming and interferes with normal daily routines. For dogs, Dobermans appear to be a breed that is most at risk, likely due to their genetics. © 2013 Discovery Communications, LLC

Keyword: OCD - Obsessive Compulsive Disorder
Link ID: 18241 - Posted: 06.06.2013

Sid Perkins The near-complete fossil of a tiny creature unearthed in China in 2002 has bolstered the idea that the anthropoid group of primates — whose modern-day members include monkeys, apes and humans — had appeared by at least 55 million years ago. The fossil primate does not belong to that lineage, however: it is thought to be the earliest-discovered ancestor of small tree-dwelling primates called tarsiers, showing that even at this early time, the tarsier and anthropoid groups had split apart. The slender-limbed, long-tailed primate, described today in Nature1, was about the size of today’s pygmy mouse lemur and would have weighed between 20 and 30 grams, the researchers estimate. The mammal sports an odd blend of features, with its skull, teeth and limb bones having proportions resembling those of tarsiers, but its heel and foot bones more like anthropoids. “This mosaic of features hasn’t been seen before in any living or fossil primate,” says study author Christopher Beard, a palaeontologist at the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania. By analysing almost 1,200 morphological aspects of the fossil and comparing them to those of 156 other extant and extinct mammals, the team put the ancient primate near the base of the tarsier family tree. The creature is dubbed Archicebus achilles, in which the genus name Archicebus roughly translates as 'original long-tailed monkey', while the species name achilles is a wry nod to the primate's anthropoid-like heel bone. © 2013 Nature Publishing Group

Keyword: Evolution
Link ID: 18240 - Posted: 06.06.2013

By GRETCHEN REYNOLDS For thousands of years, coffee has been one of the two or three most popular beverages on earth. But it’s only recently that scientists are figuring out that the drink has notable health benefits. In one large-scale epidemiological study from last year, researchers primarily at the National Cancer Institute parsed health information from more than 400,000 volunteers, ages 50 to 71, who were free of major diseases at the study’s start in 1995. By 2008, more than 50,000 of the participants had died. But men who reported drinking two or three cups of coffee a day were 10 percent less likely to have died than those who didn’t drink coffee, while women drinking the same amount had 13 percent less risk of dying during the study. It’s not clear exactly what coffee had to do with their longevity, but the correlation is striking. Other recent studies have linked moderate coffee drinking — the equivalent of three or four 5-ounce cups of coffee a day or a single venti-size Starbucks — with more specific advantages: a reduction in the risk of developing Type 2 diabetes, basal cell carcinoma (the most common skin cancer), prostate cancer, oral cancer and breast cancer recurrence. Perhaps most consequential, animal experiments show that caffeine may reshape the biochemical environment inside our brains in ways that could stave off dementia. In a 2012 experiment at the University of Illinois at Urbana-Champaign, mice were briefly starved of oxygen, causing them to lose the ability to form memories. Half of the mice received a dose of caffeine that was the equivalent of several cups of coffee. After they were reoxygenated, the caffeinated mice regained their ability to form new memories 33 percent faster than the uncaffeinated. Close examination of the animals’ brain tissue showed that the caffeine disrupted the action of adenosine, a substance inside cells that usually provides energy, but can become destructive if it leaks out when the cells are injured or under stress. The escaped adenosine can jump-start a biochemical cascade leading to inflammation, which can disrupt the function of neurons, and potentially contribute to neurodegeneration or, in other words, dementia. Copyright 2013 The New York Times Company

Keyword: Drug Abuse; Alzheimers
Link ID: 18239 - Posted: 06.06.2013

By James Gallagher Health and science reporter, BBC News An experimental treatment to stop the body attacking its own nervous system in patients with multiple sclerosis (MS) appears safe in trials. The sheath around nerves cells, made of myelin, is destroyed in MS, leaving the nerves struggling to pass on messages. A study on nine patients, reported in Science Translational Medicine, tried to train the immune system to cease its assault on myelin. The MS Society said the idea had "exciting potential". As nerves lose their ability to talk to each other, the disease results in problems moving and balancing and can affect vision. There are drugs that can reduce number and severity of attacks, but there is no cure. The disease is caused by the body's immune system thinking that myelin is a foreign body like a flu virus. Researchers at the Northwestern University Feinberg School of Medicine developed a technique to retrain the immune system. They took blood samples and coupled white blood cells, a part of the immune system, to fragments of myelin. This was injected back into the patients to make them tolerate myelin. BBC © 2013

Keyword: Multiple Sclerosis; Neuroimmunology
Link ID: 18238 - Posted: 06.06.2013

By Breanna Draxler Is it a coincidence that the word vole is an anagram of love? Probably so, but since prairie voles mate for life, they have since been designated as the unofficial species used to study monogamy in lab animals. And a new study finds that their rare partnerships are cemented by chemical changes on their genes, called epigenetic changes, that result from their sexual encounters. When a prairie vole (Microtus ochrogaster) finds a mate, the two form a strong bond. Not only do they stay together for life and share child care duties, but the lovers will guard their mates aggressively against voles of the opposite sex. Scientists knew from previous studies that this bonding was regulated by neurotransmitters—chemical communicators in the brain such as oxytocin, which is linked to sex and reproduction, and vasopressin, associated with social recognition. However researchers were unsure what the biological basis was for such a sharp behavioral shift after mating. To find out, scientists at Florida State University paired up virgin male and female voles and gave the couples a cage together for a number of hours. Some couples were allowed to mate while others were prevented from doing so. The non-mating female voles instead received drug injections in the nucleus accumbens, a part of the brain’s pleasure center. The drugs affected the voles’ epigenetics by unwinding their DNA so that genes for vasopressin and oxytocin receptors were more highly transcribed.

Keyword: Sexual Behavior; Hormones & Behavior
Link ID: 18237 - Posted: 06.06.2013

A patient at the Kwong Wah and Queen Elizabeth Hospitals discovered he was also a woman when he came for treatment for a swelling abdomen. Photo: Nora Tam A 66-year-old apparently male patient made a stunning discovery when he sought treatment for swelling in his abdomen. The swelling was a cyst on his ovary and he was in fact a woman. The condition was caused by a very rare combination of two genetic disorders. One, Turner syndrome, causes women to lack some female features, including the ability to get pregnant. Sufferers usually look like women, but in this case the patient also had congenital adrenal hyperplasia (CAH), which boosted the male hormones and made the patient look like a man. The case was reported by doctors from Kwong Wah Hospital and Queen Elizabeth Hospital, who treated the patient. It was published in the Hong Kong Medical Journal yesterday. "The patient, by definition, is a woman who cannot get pregnant. But she also has CAH, which gave her the appearance of a man," Chinese University paediatrics professor Ellis Hon Kam-lun said. "It's an interesting and very rare case of having the two combinations. It probably won't be seen again in the near future." The 66-year-old Vietnam-born Chinese man is an orphan. He has a beard, small penis and no testes. Just 1.37 metres tall, he has decided to continue perceiving himself as a male and may receive male hormone treatment, the report said. © 2013 South China Morning Post Publishers Ltd

Keyword: Sexual Behavior; Hormones & Behavior
Link ID: 18236 - Posted: 06.06.2013

By Geoffrey Mohan Hyperactive brain cells firing together could be an early indicator of autism and developmental disabilities, a team of UCLA researchers has found. Networks of neurons were found to be firing in a highly synchronized and seemingly unrelenting fashion, even through sleep, in the brains of juvenile mice that have a genetic abnormality similar to one that causes mental retardation and autism symptoms in humans, according to the research published online Monday in Nature Neuroscience. Without independently firing neurons, the human brain would be about as functionally complicated as a digital switch. With it, we compose poetry and send robotic carts to Mars. "If you want to code information, you can’t just have all the cells fire together or not, because then that’s just binary. It goes up and down," said UCLA neuroscientist Carlos Portera-Cailliau, a lead author of the report. “But if you have billions of neurons, all firing independently or in small clusters, then you can code a lot of information.” That “de-synchronization” was greatly diminished in the neocortex of the juvenile mice that had been altered so that they lack the same protein known to cause mental retardation and autistic behaviors in humans. These so-called Fmr1 Knockout mice, named for the gene that is knocked out, exhibit autism behaviors, among them social deficits – they don’t go over and sniff and examine a new mouse introduced to the cage, like wild mice would. Copyright 2013

Keyword: Autism
Link ID: 18235 - Posted: 06.05.2013

by Kim Krieger The song of the cicada has been romanticized in mariachi music, used to signify summer in Japanese cinematography, and cursed by many an American suburbanite wishing for peace and quiet. Despite the bugs' ubiquity, scientists haven't uncovered how they sing so loudly—some are as noisy as a jet engine—and why they don't expend much energy doing it. But researchers reported in Montreal yesterday at the 21st International Congress on Acoustics that they now have the answer. The detailed mechanism of the cicada's song is far from fully understood, says Paulo Fonseca, an animal acoustician at the University of Lisbon who was not involved in the project. The work by the researchers "is innovative and paves our way to a better understanding of this complex system allowing such small animals to produce such powerful sound." Cicadas aren't just a natural curiosity. Small devices that produce extremely loud noises while requiring very little power appeal to the U.S. Navy, which uses sonar for underwater exploration and communication. Derke Hughes, a research engineer at the Naval Undersea Warfare Center in Newport, Rhode Island, says that the loudest cicadas can make a noise 20 to 40 dB louder than the compact off-the-shelf RadioShack speaker in his office using the same amount of power. Intrigued, he and his colleagues used microcomputed tomography)—a kind of CT scan that picks up details as small as a micron in size—to image a cicada's tymbal, which helps the insect make its deafening chirp. © 2010 American Association for the Advancement of Science

Keyword: Hearing; Sexual Behavior
Link ID: 18234 - Posted: 06.05.2013

Matt Kaplan Just as city slickers have faster-paced lives than country folk, so too do urban birds, compared with their forest-dwelling cousins. The reason, researchers report today, is that urban noise and light have altered the city birds’ biological clocks1. The finding helps to explain prior reports that urban songbirds adopt more nocturnal lifestyles2–4 — data that prompted Davide Dominoni, an ecologist at the Max Planck Institute for Ornithology in Radolfzell, Germany, to investigate whether the birds’ activity patterns were merely behavioural responses to busy cities or were caused by an actual shift in the animals' body clocks. For the study, published in Proceedings of the Royal Society B, Dominoni and his colleagues set up an experiment with European blackbirds (Turdus merula). The scientists attached tiny 2.2-gram radio-pulse transmitters to blackbirds living in Munich, Germany, as well as to those living in a nearby forest. The transmitters monitored the birds’ activity for three weeks. Dominoni found that whereas forest birds started their activity at dawn, city birds began 29 minutes earlier, on average, and remained active for 6 minutes longer in the evening. Keen to determine these differences were due to physiological changes, Dominoni collected blackbirds from both locations and placed them into light- and sound-proof enclosures. For ten days these enclosures were illuminated with a constant, dim light so the birds had no idea what time of day it was, and their activity patterns were monitored. © 2013 Nature Publishing Group,

Keyword: Biological Rhythms
Link ID: 18233 - Posted: 06.05.2013

By Piercarlo Valdesolo The posed stare-down is a staple of the pre-fight ritual. Two fighters, one day removed from attempting to beat the memories from each other, stand impossibly close, raise their clenched fists and fix their gaze on the other’s eyes as cameras click away. This has always seemed little more than a vehicle for media hype, but new research from psychologists at the University of Illinois suggests that there may be clues in this bit of theatre that predict the results of the fight to come. Specifically, the researchers hypothesized that there’s something about the fighters’ facial expressions in this standoff that reveal the competitive dynamics between them. A subtle, and perhaps unintentional, communication of submission from one fighter to the other. A recognition of the opponent’s power. The smile. Facial expressions have long been thought to be reliable indicators of a person’s true feelings. Indeed, in his book “The Expression of the Emotions in Man and Animals” Darwin suggested that such expressions have evolved precisely because they serve this important function. The smile has attracted much empirical attention and has generally been interpreted as a signal of an individuals’ immediate, as well as long-term, well-being. In a particularly interesting study, the frequency and “authenticity” of smiles in high school yearbook photos tended to predict higher levels of subjective well-being years later. But smiles can mean different things in different contexts. The researchers here were particularly interested in what a smile might mean when displayed between competitors. Instead of merely communicating a fighter’s good spirits, the researchers hypothesized that it would be a submissive signal that reveals a fighter’s reduced hostility and lower willingness to aggress towards the opponent. © 2013 Scientific American,

Keyword: Aggression; Emotions
Link ID: 18232 - Posted: 06.05.2013

Devin Powell A model helicopter can now be steered through an obstacle course by thought alone, researchers report today in the Journal of Neural Engineering. The aircraft's pilot operates it remotely using a cap of electrodes to detect brainwaves that are translated into commands.1 Ultimately, the developers of the mind-controlled copter hope to adapt their technology for directing artificial robotic limbs and other medical devices. Today's best neural prosthetics require electrodes to be implanted in the body and are thus reserved for quadriplegics and others with disabilities severe enough justify invasive surgery. "We want to develop something non-invasive that can benefit lots of people, not just a limited number of patients," says Bin He, a biomedical engineer at the University of Minnesota in Minneapolis, whose new results build on his previous work with a virtual thought-controlled helicopter.2 But He's mechanical whirlybird isn't the first vehicle to be flown by the brain. In 2010 a team at the University of Illinois at Urbana-Champaign reported an unmanned aircraft that flies a fixed altitude but adjusts its heading to the left or right in response to a user's thoughts.3 The new chopper goes a step further. It can be guided up and down, as well as left or right, and it offers more precise control. To move it in a particular direction, a user imagines clenching his or her hands — the left one to go left, for instance, or both to go up. That mental image alters brain activity in the motor cortex. Changes in the strength and frequency of signals recorded by electrodes on the scalp using electroencephalography (EEG), and deciphered by a computer program, reveal the pilot's intent. © 2013 Nature Publishing Group

Keyword: Robotics
Link ID: 18231 - Posted: 06.05.2013

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

Keyword: Sexual Behavior; Evolution
Link ID: 18230 - Posted: 06.05.2013

By Scicurious Most people have heard of ECT: Electroconvulsive Therapy. A lot of people will immediately think of the scene during One Flew Over the Cuckoo’s Nest, which doesn’t give you a very good picture. People think of ECT and think of horrible seizures, something terribly dangerous. But it’s not like that anymore. Now, ECT is usually done during a light anesthesia as well as a muscle relaxant. The huge seizures don’t happen anymore, though it’s still uncomfortable to watch (that’s a warning for the video below). So while ECT is no longer horrifying, it’s not something to be taken lightly. Aside from the fact that you’re getting an induced seizure, there are side effects, often people have deficits in working memory for a while afterward. But for people with severe depression who are truly desperate, it’s sometimes their best hope. But while we know that, in many patients, ECT does work, we still don’t know HOW. There are lots of antidepressants on the market today. All of them currently act on neurotransmitters, chemical messengers in the brain, and most of them act, at least in part, on serotonin. But the problem is, antidepressants don’t work for everyone. In fact, about 60% of patients being treated for depression won’t respond to the first drug they are given, and require trials of several different different drugs. And, sadly, 20% of patients don’t respond to all of the drugs tried. That’s a lot of people. And those people, who have often exhausted all of the drug options, sometimes turn to ECT. © 2013 Scientific American

Keyword: Depression
Link ID: 18229 - Posted: 06.04.2013

By ANAHAD O'CONNOR The number of middle-aged men with prescriptions for testosterone is climbing rapidly, raising concerns that increasing numbers of men are abusing the powerful hormone to boost their libidos and feel younger, researchers reported on Monday. Testosterone replacement therapy is approved specifically for the treatment of abnormally low testosterone levels, a condition called hypogonadism. The hormone helps build muscle, reduce body fat and improve sex drive. But a study published in the journal JAMA Internal Medicine found that many men who get prescriptions for the hormone have no evidence of a deficiency at all. The new study is the largest of testosterone prescribing patterns to date, involving nearly 11 million men who were tracked through a large health insurer. The report showed that the number of older and middle-aged men prescribed the hormone has tripled since 2001. Men in their 40s represent the fastest-growing group of users. About half of men prescribed testosterone had a diagnosis of hypogonadism, and roughly 40 percent had erectile or sexual dysfunction. One third had a diagnosis of fatigue. The medical group that sets clinical guidelines for testosterone replacement therapy, the Endocrine Society, recommends treatment only in men who have unequivocally low testosterone levels. That finding requires a blood test. But the new report found that a quarter of men did not have their levels tested before they received the hormone. It was also unclear what proportion of men who did undergo testing actually had results showing a deficiency. Copyright 2013 The New York Times Company

Keyword: Hormones & Behavior
Link ID: 18228 - Posted: 06.04.2013

by Helen Thomson TWO years ago, Antonio Melillo was in a car crash that completely severed his spinal cord. He has not been able to move or feel his legs since. And yet here I am, in a lab at the Santa Lucia Foundation hospital in Rome, Italy, watching him walk. Melillo is one of the first people with lower limb paralysis to try out MindWalker – the world's first exoskeleton that aims to enable paralysed and locked-in people to walk using only their mind. Five people have been involved in the clinical trial of MindWalker over the past eight weeks. The trial culminates this week with a review by the European Commission, which funded the work. It's the end of a three-year development period for the project, which has three main elements. There is the exoskeleton itself, a contraption that holds a person's body weight and moves their legs when instructed. People learn how to use it in the second element: a virtual-reality environment. And then there's the mind-reading component. Over in the corner of the lab, Thomas Hoellinger of the Free University of Brussels (ULB) in Belgium is wearing an EEG cap, which measures electrical activity at various points across his scalp. There are several ways he can use it to control the exoskeleton through thought alone – at the moment, the most promising involves wearing a pair of glasses with flickering diodes attached to each lens. © Copyright Reed Business Information Ltd.

Keyword: Robotics
Link ID: 18227 - Posted: 06.04.2013

By JOHN MARKOFF JERUSALEM — Liat Negrin, an Israeli who has been visually impaired since childhood, walked into a grocery store here recently, picked up a can of vegetables and easily read its label using a simple and unobtrusive camera attached to her glasses. Ms. Negrin, who has coloboma, a birth defect that perforates a structure of the eye and afflicts about 1 in 10,000 people, is an employee at OrCam, an Israeli start-up that has developed a camera-based system intended to give the visually impaired the ability to both “read” easily and move freely. Until now reading aids for the visually impaired and the blind have been cumbersome devices that recognize text in restricted environments, or, more recently, have been software applications on smartphones that have limited capabilities. In contrast, the OrCam device is a small camera worn in the style of Google Glass, connected by a thin cable to a portable computer designed to fit in the wearer’s pocket. The system clips on to the wearer’s glasses with a small magnet and uses a bone-conduction speaker to offer clear speech as it reads aloud the words or object pointed to by the user. The system is designed to both recognize and speak “text in the wild,” a term used to describe newspaper articles as well as bus numbers, and objects as diverse as landmarks, traffic lights and the faces of friends. It currently recognizes English-language text and beginning this week will be sold through the company’s Web site for $2,500, about the cost of a midrange hearing aid. It is the only product, so far, of the privately held company, which is part of the high-tech boom in Israel. © 2013 The New York Times Company

Keyword: Vision; Robotics
Link ID: 18226 - Posted: 06.04.2013

By Felicity Muth If you grew up with brothers or sisters you will know that competition is a key part of childhood. Personally, I experienced competition for food resources (the last bar of chocolate), parental investment (attention) and other more unusual resources (the best colour of lego pieces). As we age, we continue competing, although what we compete for changes. We compete in sports, for partners and for jobs. Like humans, pretty much all other animals will compete in one way or another. Even if they live a solitary life they may be still competing indirectly with others. But, like humans, animals need to choose which battles are worth fighting, and how much effort to put into it. One obvious way of deciding when to bother competing with another is the absolute worth of the thing you’re fighting over. If you and a stranger stumbled across some money in the street, you might fight vigorously for a $100 note, but more half-heartedly for $5 (this is of course an example using some very money-driven and aggressive individuals). However, how much value an individual puts on an item’s worth is going to be somewhat subjective. If you’re poor and starving, you might invest more into fighting for $5 than someone who is not. Thus, most competitions will contain both objective and subjective aspects: the intrinsic worth of an object (large food items are better than small), and the individual’s state when they’re assessing that item. © 2013 Scientific American

Keyword: Aggression
Link ID: 18225 - Posted: 06.04.2013

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

Keyword: Evolution; Obesity
Link ID: 18224 - Posted: 06.04.2013