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T. M. Luhrmann AMERICANS are a pretty anxious people. Nearly one in five of us — 18 percent — has an anxiety disorder. We spend over $2 billion a year on anti-anxiety medications. College students are often described as more stressed than ever before. There are many explanations for these nerves: a bad job market, less cohesive communities, the constant self-comparison that is social media. In 2002 the World Mental Health Survey found that Americans were the most anxious people in the 14 countries studied, with more clinically significant levels of anxiety than people in Nigeria, Lebanon and Ukraine. To be clear, research suggests that anxiety is at least partially temperamental. A recent study of 592 rhesus monkeys found that some of them responded more anxiously than others and that as much as 30 percent of early anxiety may be inherited. Yet what is inherited is the potential for anxiety, not anxiety itself. Life events obviously play a role. Another, less obvious factor may be the way we think about the mind: as an interior place that demands careful, constant attention. Humans seem to distinguish between mind and body in all cultures, but the sharp awareness of mind as a possession, distinct from soul and body, comes from the Enlightenment. It was then, in the aftermath of the crisis of religious authority and the scientific revolution, that there were intense debates about the nature of mental events. Between 1600 and 1815, the place where mental stuff happened — the “thing that thinks,” to use Descartes’s phrase — came to seem more and more important, as George Makari, a psychiatrist and psychoanalyst, explains in his forthcoming book, “Soul Machine: The Invention of the Modern Mind.” From this, Mr. Makari writes, was developed the psychological mind and psychoanalysis and an expectation that personal thoughts and feelings are the central drivers of human action — not roles, not values, not personal sensation, not God. In the United States, the enormous psychotherapeutic and self-help industry teaches us that we must pay scrupulous attention to inner experience. To succeed and be happy, we are taught, we need to know what we feel. © 2015 The New York Times Company
Link ID: 21189 - Posted: 07.20.2015
By THE EDITORIAL BOARD Scientific research has a gender gap, and not just among humans. In many disciplines, the animals used to study diseases and drugs are overwhelmingly male, which may significantly reduce the reliability of research and lead to drugs that won’t work in half the population. A new study published in the journal Nature Neuroscience suggests that research done on male animals may not hold up for women. Its authors reported that hypersensitivity to pain works differently in male and female mice. For males, immune cells called microglia appear to be required for pain hypersensitivity, and inhibiting their function also relieves the pain. But in female mice, different cells are involved, and targeting the microglia has no effect. If these differences occur in mice, they may occur in humans too. This means a pain drug targeting microglia might appear to work in male mice, but wouldn’t work on women. Failure to consider gender in research is very much the norm. According to one analysis of scientific studies that were published in 2009, male animals outnumbered females 5.5 to 1 in neuroscience, 5 to 1 in pharmacology, and 3.7 to 1 in physiology. Only 45 percent of animal studies involving depression or anxiety and only 38 percent involving strokes used females, even though these conditions are more common in women. In 1994, the National Institutes of Health confronted gender imbalance in clinical drug trials and began requiring that women and minorities be included in clinical studies; women now make up around half of clinical trial participants. In June, the N.I.H. announced that it would begin requiring researchers to take gender into account in preclinical research on animals as well. © 2015 The New York Times Company
Keyword: Sexual Behavior
Link ID: 21188 - Posted: 07.20.2015
By C. CLAIBORNE RAY Q. Can you hear without an intact eardrum? A. “When the eardrum is not intact, there is usually some degree of hearing loss until it heals,” said Dr. Ashutosh Kacker, an ear, nose and throat specialist at NewYork-Presbyterian Hospital and a professor at Weill Cornell Medical College, “but depending on the size of the hole, you may still be able to hear almost normally.” Typically, Dr. Kacker said, the larger an eardrum perforation is, the more severe the hearing loss it will cause. The eardrum, or tympanic membrane, is a thin, cone-shaped, pearly gray tissue separating the outer and middle ear canals, he explained. Soundwaves hit the eardrum, which in turn vibrates the bones of the middle ear. The bones pass the vibration to the cochlea, which leads to a signal cascade culminating in the sound being processed by the brain and being heard. There are several ways an eardrum can be ruptured, Dr. Kacker said, including trauma, exposure to sudden or very loud noises, foreign objects inserted deeply into the ear canal, and middle-ear infection. “Usually, the hole will heal by itself and hearing will improve within about two weeks to a few months, especially in cases where the hole is small,” he said. Sometimes, when the hole is larger or does not heal well, surgery will be required to repair the eardrum. Most such operations are done by placing a patch over the hole to allow it to heal, and the surgery is usually very successful in restoring hearing, Dr. Kacker said. © 2015 The New York Times Company
Link ID: 21187 - Posted: 07.20.2015
by Sarah Schwartz Brainlike cell bundles grown in a lab may expose some of the biological differences of autistic brains. Researchers chemically reprogrammed human stem cells into small bundles of functional brain cells that mimic the developing brain. These “organoids” appear to be different when built with cells from autistic patients compared with when they are built with cells from the patients’ non-autistic family members, researchers report July 16 in Cell. The brainlike structures created from cells taken from autistic children showed increased activity in genes that control brain-cell growth and development. Too much activity in one of these genes led to an overproduction of a certain type of brain cell that suppresses the activity of other brain cells. At an early stage of development, the miniature organs grown from autistic patients’ stem cells also showed faster cell division rates than those grown from the cells of non-autistic relatives. Though the study was small, using cells from only four autistic patients and eight family members, the results may indicate common factors underlying autism, the scientists say. © Society for Science & the Public 2000 - 2015.
Link ID: 21186 - Posted: 07.18.2015
It’s a good combination. Gene therapy to reverse blindness repairs damaged cells in the eye and also rearranges the brain to help process the new information. Visual pathways in the brain are made up of millions of interconnected neurons. When sensory signals are sent along them, the connections between neurons become strong. If underused – for example, as people lose their sight – the connections become weak and disorganised. Over the past few years, a type of gene therapy – injecting healthy genes into the eye to repair mutations – has emerged as a promising way to treat congenital and degenerative blindness. One of the first successful trials began in 2007. It involved 10 blind volunteers with a hereditary disease called Leber’s congenital amaurosis. The condition causes the retina to degenerate and leaves people completely blind early in life. Mutations in at least 19 genes can cause the disease, but all of the people in the trial had mutations in a gene called RPE65. The participants got an injection of a harmless virus in one of their eyes. The virus inserted healthy copies of RPE65 into their retina. Some of the volunteers went from straining to see a hand waving half a metre from their face to being able to read six lines on a sight chart. Others were able to navigate around an obstacle course in dim light – something that would have been impossible before the therapy. © Copyright Reed Business Information Ltd.
A study showed that scientists can wirelessly determine the path a mouse walks with a press of a button. Researchers at the Washington University School of Medicine, St. Louis, and University of Illinois, Urbana-Champaign, created a remote controlled, next-generation tissue implant that allows neuroscientists to inject drugs and shine lights on neurons deep inside the brains of mice. The revolutionary device is described online in the journal Cell. Its development was partially funded by the National Institutes of Health. “It unplugs a world of possibilities for scientists to learn how brain circuits work in a more natural setting.” said Michael R. Bruchas, Ph.D., associate professor of anesthesiology and neurobiology at Washington University School of Medicine and a senior author of the study. The Bruchas lab studies circuits that control a variety of disorders including stress, depression, addiction, and pain. Typically, scientists who study these circuits have to choose between injecting drugs through bulky metal tubes and delivering lights through fiber optic cables. Both options require surgery that can damage parts of the brain and introduce experimental conditions that hinder animals’ natural movements. To address these issues, Jae-Woong Jeong, Ph.D., a bioengineer formerly at the University of Illinois at Urbana-Champaign, worked with Jordan G. McCall, Ph.D., a graduate student in the Bruchas lab, to construct a remote controlled, optofluidic implant. The device is made out of soft materials that are a tenth the diameter of a human hair and can simultaneously deliver drugs and lights.
Keyword: Brain imaging
Link ID: 21184 - Posted: 07.18.2015
Jon Hamilton It's almost impossible to ignore a screaming baby. (Click here if you doubt that.) And now scientists think they know why. "Screams occupy their own little patch of the soundscape that doesn't seem to be used for other things," says David Poeppel, a professor of psychology and neuroscience at New York University and director of the Department of Neuroscience at the Max Planck Institute in Frankfurt. And when people hear the unique sound characteristics of a scream — from a baby or anyone else — it triggers fear circuits in the brain, Poeppel and a team of researchers report in Cell Biology. The team also found that certain artificial sounds, like alarms, trigger the same circuits. "That's why you want to throw your alarm clock on the floor," Poeppel says. The researchers in Poeppel's lab decided to study screams in part because they are a primal form of communication found in every culture. And there was another reason. "Many of the postdocs in my lab are in the middle of having kids and, of course, screams are very much on their mind," Poeppel says. "So it made perfect sense for them to be obsessed with this topic." The team started by trying to figure out "what makes a scream a scream," Poeppel says. Answering that question required creating a large database of recorded screams — from movies, from the Internet and from volunteers who agreed to step into a sound booth. A careful analysis of these screams found that they're not like any other sound that people make, including other loud, high-pitched vocalizations. The difference is something called the amplitude modulation rate, which is how often the loudness of a sound changes. © 2015 NPR
That song really is stuck in your head. The experience of hearing tunes in your mind appears to be linked to physical differences in brain structure. The study is the first to look at the neural basis for “involuntary musical imagery” – or “earworms”. They aren’t just a curiosity, says study co-author Lauren Stewart at Goldsmith’s, University of London, but could have a biological function. Stewart, a music psychologist, was first inspired to study earworms by a regular feature on the radio station BBC 6Music, in which listeners would write in with songs they had woken up with in their heads. There was a lot of interest from the public in what they are and where they had come from, but there was little research on the topic, she says. Once Stewart and her team started researching earworms, it became clear that some people are affected quite severely: one person even wrote to them saying he had lost his job because of an earworm. To find out what makes some people more susceptible to the phenomenon, the team asked 44 volunteers about how often they got earworms and how they were affected by them. Then they used MRI scans to measure the thickness of volunteers’ cerebral cortices and the volume of their grey matter in various brain areas. Brain differences People who suffered earworms more frequently had thicker cortices in areas involved in auditory perception and pitch discrimination. © Copyright Reed Business Information Ltd.
Austin Frakt It’s a Catch-22 that even those with a common cold experience: Illness disrupts sleep. Poor sleep makes the symptoms of the illness worse. What’s true for a cold also holds for more serious conditions that co-occur with insomnia. Depression, post-traumatic stress disorder, alcohol dependence, fibromyalgia, cancer and chronic pain often give rise to insomnia, just as sleeplessness exacerbates the symptoms of these diseases. Historically, insomnia was considered a symptom of other diseases. Today it is considered an illness in its own right and recognized as an amplifier of other mental and physical ailments. When a person is chronically tired, pain can be more painful, depression deeper, anxiety heightened. What should doctors address first, insomnia or the co-occurring condition? How about both at the same time? A new study suggests that a therapy that improves sleep also reduces symptoms of other illnesses that often disrupt it. The study published in JAMA Internal Medicine examined the effect of cognitive behavioral therapy for insomnia in patients with serious mental and physical conditions. As its name suggests, C.B.T.-I. is a treatment that works through the mind. As I wrote about a few weeks ago, the therapy treats insomnia without medications, combining good sleep hygiene techniques with more consistent wake times, relaxation techniques and positive sleep attitudes and thoughts. Several clinical trials have shown that C.B.T.-I. provides as good or better relief of symptoms of insomnia than prescription drugs, with improvements in sleep that are more durable. C.B.T.-I. can usually be delivered relatively inexpensively through an online course costing about $40. Compared with those who didn’t receive C.B.T.-I., patients who did increased the time asleep in bed by about 12 percentage points, fell asleep about 25 minutes faster and decreased the amount of time awake in the middle of the night by about 45 minutes, according to Jade Wu, lead study author and a Boston University doctoral student in psychology. © 2015 The New York Times Company
Link ID: 21181 - Posted: 07.18.2015
by Sarah Zielinski It may not be polite to eavesdrop, but sometimes, listening in on others’ conversations can provide valuable information. And in this way, humans are like most other species in the animal world, where eavesdropping is a common way of gathering information about potential dangers. Because alarm calls can vary from species to species, scientists have assumed that eavesdropping on these calls of “danger!” requires some kind of learning. Evidence of that learning has been scant, though. The only study to look at this topic tested five golden-mantled ground squirrels and found that the animals may have learned to recognize previously unknown alarm calls. But the experiment couldn’t rule out other explanations for the squirrels’ behavior, such as that the animals had simply become more wary in general. So Robert Magrath and colleagues at Australian National University in Canberra turned to small Australian birds called superb fairy-wrens. In the wild, these birds will flee to safety when they hear unfamiliar sounds that sound like their own alarm calls, but not when they hear alarm calls that sound different from their own. There’s an exception, though: They’ll take to cover in response to the alarm calls of other species that are common where they live. That suggests the birds learn to recognize those calls. In the lab, the team played the alarm call from a thornbill or a synthetic alarm call for 10 fairy-wrens. The birds didn’t respond to the noise. Then the birds went through two days of training in which the alarm call was played as a mock predator glided overhead. Another group of birds heard the calls but there was no pretend predator. © Society for Science & the Public 2000 - 2015
By Claire Asher Even fish have role models. In a new study, researchers paired up inexperienced fathead minnows (Pimephales promelas, pictured) with two types of mentors: a minnow raised in an environment free of predators or a minnow raised in a dangerous one simulated by the odors of predatory pike and sturgeon. Fish from dangerous environments were fearful of the smell of both unknown and familiar predators, whereas fish that grew up in safety hid when they smelled a known predator but were curious about new smells. Both types of fish passed on their fears to their protégés: Minnows that spent time with fish raised in dangerous environments were scared of all smells they came across, but those that learned from fish raised in safety feared only specific predators and took new experiences in stride, the team reports online this week in the Proceedings of the Royal Society B. The authors say this is the first experiment to show that environment can influence the social transmission of fear and reveals how risk aversion can be learned. The researchers also suggest their study may shed light on how fear disorders such as post-traumatic stress disorder (PTSD) develop in humans, which research shows can be influenced by social environment; PTSD symptoms can be acquired from friends or family who have suffered trauma, for example. © 2015 American Association for the Advancement of Science
By Emily Underwood Glance at a runner's wrist or smartphone, and you'll likely find a GPS-enabled app or gadget ticking off miles and minutes as she tries to break her personal record. Long before FitBit or MapMyRun, however, the brain evolved its own system for tracking where we go. Now, scientists have discovered a key component of this ancient navigational system in rats: a group of neurons called "speed cells" that alter their firing rates with the pace at which the rodents run. The findings may help explain how the brain maintains a constantly updated map of our surroundings. In the 1970s, neuroscientist John O'Keefe, now at University College London, discovered neurons called place cells, which fire whenever a rat enters a specific location. Thirty-five years later, neuroscientists May-Britt and Edvard Moser, now at the Norwegian University of Science and Technology in Trondheim, Norway, discovered a separate group of neurons, called grid cells, which fire at regular intervals as rats traverse an open area, creating a hexagonal grid with coordinates similar to those in GPS. The Mosers and O'Keefe shared last year's Nobel Prize in Physiology and Medicine for their findings, which hint at how the brain constructs a mental map of an animal's environment. Still mysterious, however, is how grid and place cells obtain the information that every GPS system requires: the angle and speed of an object's movement relative to a known starting point, says Edvard Moser, co-author of the new study along with May-Britt Moser, his spouse and collaborator. If the brain does indeed contain a dynamic, internal map of the world, "there has to be a speed signal" that tells the network how far an animal has moved in a given period of time, he says. © 2015 American Association for the Advancement of Science.
Keyword: Learning & Memory
Link ID: 21178 - Posted: 07.16.2015
By Laura Sanders Everybody knows people who seem to bumble through life with no sense of time — they dither for hours on a “quick” e-mail or expect an hour’s drive to take 20 minutes. These people are always late. But even for them, such minor lapses in timing are actually exceptions. We notice these flaws precisely because they’re out of the ordinary. Humans, like other animals, are quite good at keeping track of passing time. This talent does more than keep office meetings running smoothly. Almost everything our bodies and brains do requires precision clockwork — down to milliseconds. Without a sharp sense of time, people would be reduced to insensate messes, unable to move, talk, remember or learn. “We don’t think about it, but just walking down the street is an exquisitely timed operation,” says neuroscientist Lila Davachi of New York University. Muscles fire and joints steady themselves in a precisely orchestrated time series that masquerades as an unremarkable part of everyday life. A sense of time, Davachi says, is fundamental to how we move, how we act and how we perceive the world. Yet for something that forms the bedrock of nearly everything we do, time perception is incredibly hard to study. “It’s a quagmire,” says cognitive neuroscientist Peter Tse of Dartmouth College. The problem is thorny because there are thousands of possible intricate answers, all depending on what exactly scientists are asking. Their questions have begun to reveal an astonishingly complex conglomerate of neural timekeepers that influence each other. © Society for Science & the Public 2000 - 2015.
Link ID: 21177 - Posted: 07.16.2015
By Fredrick Kunkle A new study suggests that Alzheimer’s disease may affect the brain differently in black people compared with whites. The research, conducted by Lisa L. Barnes at the Rush University Medical Center, suggests that African Americans are less likely than Caucasians to have Alzheimer’s disease alone and more likely to have other pathologies associated with dementia. These include the presence of Lewy bodies, which are abnormal proteins found in the brain, and lesions arising from the hardening of tiny arteries in the brain, which is caused mainly by high blood pressure and other vascular conditions. The findings suggest that researchers should seek different strategies to prevent and treat Alzheimer’s disease in blacks. While many therapeutic strategies focus on removing or modifying beta amyloid – a key ingredient whose accumulation leads to the chain of event triggering the neurodegenerative disease – the study suggests that possible treatments should pursue additional targets, particularly for African Americans. But the study also points up the critical need to enroll more black people in clinical trials. Although Barnes said the research was the largest sample of its kind, she also acknowledged that the sample is still small. And that’s at least partially because blacks, for a variety of cultural and historical reasons, are less likely to participate in scientific research.
Link ID: 21176 - Posted: 07.16.2015
Nikki Stevenson Autism may represent the last great prejudice we, as a society, must overcome. History is riddled with examples of intolerance directed at the atypical. We can sometime fear that which diverges from the “norm”, and sometimes that fear leads us to frame those who are different as being in some way lesser beings than ourselves. Intolerances take generations to overcome. Racism is an obvious, ugly example. Other horrifying examples are easy to find: take, for instance the intolerance faced by the gay community. Countless gay people were diagnosed with “sociopathic personality disturbance” based upon their natural sexuality. Many were criminalised and forced into institutions, the “treatments” to which they were subject akin to torture. How many believed they were sociopathic and hated themselves, wishing to be free from the label they had been given? How many wished to be “cured” so that they could live their lives in peace? The greatest crime was the damage perpetuated by the image projected upon them by those claiming to be professionals. Autism is framed as a disability, with mainstream theories presenting autism via deficit models. Popular theory is often passed off as fact with no mention of the morphic nature of research and scientific process. Most mainstream theory is silent regarding autistic strengths and atypical ability; indeed, what is in print often presents a damning image of autism as an “epidemic”. Hurtful words such as risk, disease, disorder, impairment, deficit, pedantic, obsession are frequently utilised. © 2015 Guardian News and Media Limited
Link ID: 21175 - Posted: 07.16.2015
By Tori Rodriguez Many studies have examined the effects of sufficient versus insufficient sleep on mental health. A new study, published in February in the Journal of Youth and Adolescence, takes a more nuanced look, attempting to determine just how much each hour less per night really costs—where teenagers are concerned. The researchers surveyed an ethnically diverse sample of 27,939 suburban high school students in Virginia. Although teenagers need about nine hours of sleep a night on average, according to the National Institutes of Health, only 3 percent of students reported getting that amount, and 20 percent of participants indicated that they got five hours or less. The average amount reported was 6.5 hours every weekday night. After controlling for background variables such as family status and income, the researchers determined that each hour of lost sleep was associated with a 38 percent increase in the odds of feeling sad and hopeless, a 42 percent increase in considering suicide, a 58 percent increase in suicide attempts and a 23 percent increase in substance abuse. These correlational findings do not prove that lack of sleep is causing these problems. Certainly the reverse can be true: depression and anxiety can cause insomnia. “But the majority of the research evidence supports the causal direction being lack of sleep leading to problems rather than the other way around,” says study co-author Adam Winsler, a psychology professor at George Mason University. © 2015 Scientific American
By Lauran Neergaard, New research suggests it may be possible to predict which preschoolers will struggle to read — and it has to do with how the brain deciphers speech when it's noisy. Scientists are looking for ways to tell, as young as possible, when children are at risk for later learning difficulties so they can get early interventions. There are some simple pre-reading assessments for preschoolers. But Northwestern University researchers went further and analyzed brain waves of children as young as three. How well youngsters' brains recognize specific sounds — consonants — amid background noise can help identify who is more likely to have trouble with reading development, the team reported Tuesday in the journal PLOS Biology. If the approach pans out, it may provide "a biological looking glass," said study senior author Nina Kraus, director of Northwestern's Auditory Neuroscience Laboratory. "If you know you have a three-year-old at risk, you can as soon as possible begin to enrich their life in sound so that you don't lose those crucial early developmental years." Connecting sound to meaning is a key foundation for reading. For example, preschoolers who can match sounds to letters earlier go on to read more easily. Auditory processing is part of that pre-reading development: If your brain is slower to distinguish a "D" from a "B" sound, for example, then recognizing words and piecing together sentences could be affected, too. What does noise have to do with it? It stresses the system, as the brain has to tune out competing sounds to selectively focus, in just fractions of milliseconds. And consonants are more vulnerable to noise than vowels, which tend to be louder and longer, Kraus explained. ©2015 CBC/Radio-Canada
By Gretchen Reynolds Would soccer be safer if young players were not allowed to head the ball? According to a new study of heading and concussions in youth soccer, the answer to that question is not the simple yes that many of us might have hoped. Soccer parents — and nowadays we are legion — naturally worry about head injuries during soccer, whether our child’s head is hitting the ball or another player. The resounding head-to-head collision between Alexandra Popp of Germany and Morgan Brian of the United States during the recent Women’s World Cup sent shivers down many of our spines. People’s concerns about soccer heading and concussions have grown so insistent in the past year or so that some doctors, parents and former professional players have begun to call for banning the practice outright among younger boys and girls, up to about age 14, and curtailing it at other levels of play. Ridding youth soccer of heading, many of these advocates say, would virtually rid the sport of severe head injuries. But Dawn Comstock, for one, was skeptical when she heard about the campaign. An associate professor of public health at the University of Colorado in Denver and an expert on youth sports injuries, she is also, she said, “a believer in evidence-based decision making.” And she said she wasn’t aware of any studies showing that heading causes the majority of concussions in the youth game. In fact, she and her colleagues could not find any large-scale studies examining the causes of concussions in youth soccer at all. So, for a study being published this week in JAMA Pediatrics, she and her colleagues decided to investigate the issue themselves. © 2015 The New York Times Company
Keyword: Brain Injury/Concussion
Link ID: 21172 - Posted: 07.15.2015
Tina Hesman Saey The Earth has rhythm. Every 24 hours, the planet pirouettes on its axis, bathing its surface alternately in sunlight and darkness. Organisms from algae to people have evolved to keep time with the planet’s light/dark beat. They do so using the world’s most important timekeepers: daily, or circadian, clocks that allow organisms to schedule their days so as not to be caught off guard by sunrise and sunset. A master clock in the human brain appears to synchronize sleep and wake with light. But there are more. Circadian clocks tick in nearly every cell in the body. “There’s a clock in the liver. There’s a clock in the adipose [fat] tissue. There’s a clock in the spleen,” says Barbara Helm, a chronobiologist at the University of Glasgow in Scotland. Those clocks set sleep patterns and meal times. They govern the flow of hormones and regulate the body’s response to sugar and many other important biological processes (SN: 4/10/10, p. 22). Having timekeepers offers such an evolutionary advantage that species have developed them again and again throughout history, many scientists say. But as common and important as circadian clocks have become, exactly why such timepieces arose in the first place has been a deep and abiding mystery. Many scientists favor the view that multiple organisms independently evolved their own circadian clocks, each reinventing its own wheel. Creatures probably did this to protect their fragile DNA from the sun’s damaging ultraviolet rays. But a small group of researchers think otherwise. They say there had to be one mother clock from which all others came. That clock evolved to shield the cell from oxygen damage or perhaps provide other, unknown advantages. © Society for Science & the Public 2000 - 2015
By Michael Balter The human hand is a marvel of dexterity. It can thread a needle, coax intricate melodies from the keys of a piano, and create lasting works of art with a pen or a paintbrush. Many scientists have assumed that our hands evolved their distinctive proportions over millions of years of recent evolution. But a new study suggests a radically different conclusion: Some aspects of the human hand are actually anatomically primitive—more so even than that of many other apes, including our evolutionary cousin the chimpanzee. The findings have important implications for the origins of human toolmaking, as well as for what the ancestor of both humans and chimps might have looked like. Humans and chimps diverged from a common ancestor perhaps about 7 million years ago, and their hands now look very different. We have a relatively long thumb and shorter fingers, which allows us to touch our thumbs to any point along our fingers and thus easily grasp objects. Chimps, on the other hand, have much longer fingers and shorter thumbs, perfect for swinging in trees but much less handy for precision grasping. For decades the dominant view among researchers was that the common ancestor of chimps and humans had chimplike hands, and that the human hand changed in response to the pressures of natural selection to make us better toolmakers. But recently some researchers have begun to challenge the idea that the human hand fundamentally changed its proportions after the evolutionary split with chimps. The earliest humanmade stone tools are thought to date back 3.3 million years, but new evidence has emerged that some of the earliest members of the human line—such as the 4.4-million-year-old Ardipithecus ramidus (“Ardi”)—had hands that resembled those of modern humans rather than chimps, even though it did not make tools. © 2015 American Association for the Advancement of Science
Link ID: 21170 - Posted: 07.15.2015