Chapter 6. Evolution of the Brain and Behavior
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By Catherine Matacic Twenty-three years ago, a bonobo named Kanzi (above) aced a test in understanding human language. But a new study reveals he may not be as brainy as scientists thought—at least when it comes to grammar. The original test consisted of 660 verbal commands, in English, that asked Kanzi to do things like "show me the hot water" and "pour cold water in the potty." Overall, the ape did well, responding correctly 71.5% of the time (compared with 66.6% for an infant human). But when the researchers asked him to perform an action on more than one item, his performance plummeted to just 22.2%, according to the new analysis. When he was asked to "give the lighter and the shoe to Rose," for example, he gave Rose the lighter, but no shoe. When asked to "give the water and the doggie to Rose," he gave her the toy dog, but no water. The cause? Animals like bonobos may have a harder time than humans in processing complex noun phrases like “water and doggie,” linguist Robert Truswell of the University of Edinburgh reported in New Orleans, Louisiana, this week at the Evolution of Language conference. This feature of grammar—which effectively “nests” one unit within the bigger construct of a sentence—is easily picked up by humans, allowing us to communicate—and understand—more complex ideas. But Truswell cautions that humans probably aren’t born with the ability to interpret this kind of nesting structure. Instead, we must be taught how to use it. © 2016 American Association for the Advancement of Science
By NATALIE ANGIER Juan F. Masello never intended to study wild parrots. Twenty years ago, as a graduate student visiting the northernmost province of Patagonia in Argentina, he planned to write his dissertation on colony formation among seabirds. But when he asked around for flocks of, say, cormorants or storm petrels, a park warden told him he was out of luck. “He said, ‘This is the only part of Patagonia with no seabird colonies,’” recalled Dr. Masello, a principal investigator in animal ecology and systematics at Justus Liebig University in Germany. Might the young scientist be interested in seeing a large colony of parrots instead? The sight that greeted Dr. Masello was “amazing” and “incredible,” he said. “It was almost beyond words.” On a 160-foot-high sandstone cliff that stretched some seven miles along the Atlantic coast, tens of thousands of pairs of burrowing parrots had used their powerful bills to dig holes — their nests — deep into the rock face. And when breeding season began not long afterward, the sky around the cliffs erupted into a raucous carnival of parrot: 150,000 crow-size, polychromed aeronauts with olive backsides, turquoise wings, white epaulets and bright red belly patches ringed in gold. Dr. Masello was hooked. Today, Dr. Masello’s hands are covered with bite scars. He has had four operations to repair a broken knee, a broken nose — “the little accidents you get from working with parrots,” he said. Still, he has no regrets. “Their astonishing beauty and intelligence,” Dr. Masello said, “are inspirational.” © 2016 The New York Times Company
Giant manta rays have been filmed checking out their reflections in a way that suggests they are self-aware. Only a small number of animals, mostly primates, have passed the mirror test, widely used as a tentative test of self-awareness. “This new discovery is incredibly important,” says Marc Bekoff, of the University of Colorado in Boulder. “It shows that we really need to expand the range of animals we study.” But not everyone is convinced that the new study proves conclusively that manta rays, which have the largest brains of any fish, can do this – or indeed, that the mirror test itself is an appropriate measure of self-awareness. Csilla Ari, of the University of South Florida in Tampa, filmed two giant manta rays in a tank, with and without a mirror inside.The fish changed their behaviour in a way that suggested that they recognised the reflections as themselves as opposed to another manta ray. They did not show signs of social interaction with the image, which is what you would expect if they perceived it to be another individual. Instead, the rays repeatedly moved their fins and circled in front of the mirror (click on image below to see one in action). This suggests they could see whether their reflection moved when they moved. The frequency of these movements was much higher when the mirror was in the tank than when it was not. manta © Copyright Reed Business Information Ltd.
By Manuel Valdes For nearly every step of his almost 12-mile walks around Seattle, Darryl Dyer has company. Flocks of crows follow him, signaling each other, because they all know that he’s the guy with the peanuts. “They know your body type. The way you walk,” Dyer said. “They’ll take their young down and say: ‘You want to get to know this guy. He’s got the food.’ ” Scientists have known for years that crows have great memories, that they can recognize a human face and behavior, that they can pass that information on to their offspring. Researchers are trying to understand more about the crow’s brain and behavior, specifically what the birds do when they see one of their own dead. They react loudly, but the reasons aren’t entirely known. Among the guesses is that they are mourning; given that crows mate for life, losing a partner could be a significant moment for the social animals. There are anecdotes of crows placing sticks and other objects on dead birds — a funeral of sorts. Using masks with dark-haired wigs that looked creepily nonhuman, researchers showed up at Seattle parks carrying a stuffed crow and recorded the reactions. One crow signals an alarm, then dozens show up. They surround the dead crow, looking at it as they perch on trees or fly above it, a behavior called mobbing. “Crows have evolved to have these complex social relationships, and they have a big brain,” said Kaeli Swift, a University of Washington graduate student who led the study.
How did evolution produce a monstrous killer like T. rex? A fossil find in Central Asia is giving scientists a glimpse of the process. T. rex and other tyrannosaurs were huge, dominant predators, but they evolved from much smaller ancestors. The new discovery from Uzbekistan indicates that this supersizing happened quickly, and only after the appearance of some anatomical features that may have helped the monster tyrannosaurs hunt so effectively. The finding was reported Monday by Hans-Dieter Sues of the Smithsonian's National Museum of Natural History in Washington, Stephen Brusatte of the University of Edinburgh in Scotland, and others in a paper released by the Proceedings of the National Academy of Sciences. The discovery They report finding bones of a previously unknown member of the evolutionary branch that led to the huge tyrannosaurs. This earlier dinosaur lived about 90 million years ago, south of what is now the Aral Sea. It looked roughly like a T. rex, but was only about 10 to 12 feet long and weighed only about 600 pounds at most, Sues said. T. rex grew about four times as long and weighed more than 20 times as much. The discovery helps fill in a frustrating gap in the tyrannosaur fossil record. Before that gap, which began some 100 million years ago, the ancestral creatures were only about as big as a horse. Right after the gap, at about 80 million years ago, tyrannosaurs were multi-ton behemoths like T. rex. The new finding shows the forerunners were still relatively small even just 90 million years ago. So the size boom happened pretty quickly. Standard equipment ©2016 CBC/Radio-Canada.
Link ID: 21989 - Posted: 03.15.2016
Carl Zimmer Scientists recently turned Harvard’s Skeletal Biology Laboratory into a pop-up restaurant. It would have fared very badly on Yelp. Katherine D. Zink, then a graduate student, acted as chef and waitress. First, she attached electrodes to the jaws of diners to record the activity in the muscles they use to chew food. Then she brought out the victuals. Some volunteers received a three-course vegetarian meal of carrots, yams or beets. In one course, the vegetables were cooked; in the second, they were raw and sliced; in the last course, Dr. Zink simply served raw chunks of plant matter. Other patrons got three courses of meat (goat, in this case). Dr. Zink grilled the meat in the first course, but offered it raw and sliced in the second. In the third course, her volunteers received an uncooked lump of goat flesh. In some of the trials, the volunteers chewed the food until it was ready to swallow and then spat it out. Dr. Zink painstakingly picked apart those food bits and measured their size. Every week, we'll bring you stories that capture the wonders of the human body, nature and the cosmos. “If that was all my dissertation was, I would have quit graduate school,” Dr. Zink said. “It was as lovely as it sounds.” Dr. Zink persevered, however, because she was exploring a profound question about our origins: How did our ancestors evolve from small-brained, big-jawed apes into large-brained, small-jawed humans? Scientists studying the fossil record have long puzzled over this transition, which happened around two million years ago. Before then, early human relatives — known as hominins — were typically about the size of chimpanzees, with massive teeth and a brain only a third the size of humans’ current brains. © 2016 The New York Times Company
By Jerome Siegel To say whether an animal sleeps requires that we define sleep. A generally accepted definition is that sleep is a state of greatly reduced responsiveness and movement that is homeostatically regulated, meaning that when it is prevented for a period of time, the lost time is made up—an effect known as sleep rebound. Unfortunately, the application of this definition is sometimes difficult. Can an animal sleep while it is moving and responsive? How unresponsive does an animal have to be? How much of the lost sleep has to be made up for it to be considered homeostatically regulated? Is the brain activity that characterizes sleep in humans necessary and sufficient to define sleep in other animals? Apart from mammals, birds are the only other animals known to engage in both slow-wave and rapid eye movement (REM) sleep. Slow-wave sleep, also called non-REM sleep, is characterized by slow, high-amplitude waves of electrical activity in the cortex and by slow, regular respiration and heart rate. During REM sleep, animals exhibit a waking-like pattern of cortical activity, as well as physiological changes including jerky eye twitches and increased variability of heart rate and respiration. (See “The A, B, Zzzzs.”) But many more animals, including some insects and fish, engage in behaviors that might be called sleep, such as resting with slow but regular respiration and heart rates and a desensitization to environmental stimuli. In addition to diversity in the neural and physiological correlates of sleep, species vary tremendously in the intensity, frequency, and duration of sleep. Some animals tend to nap intermittently throughout the day, while others, including humans, tend to consolidate their sleep into a single, long slumber. The big brown bat is the current sleep champion, registering 20 hours per day; giraffes and elephants doze less than four hours daily. © 1986-2016 The Scientist
It’s the most ancient nervous system we’ve ever seen, preserved inside 520 million-year-old fossils. What’s more, the nervous systems of these creatures’ modern-day descendants are less intricate, proving that evolution isn’t a one-way street to complexity. Found in South China, the five Cambrian fossils belonged to a group of organisms that gave rise to the arthropods, including insects, spiders and crustaceans. The fossils are of Chengjiangocaris kunmingensis, a creature around 10 centimetres long, with a segmented body, multiple pairs of legs and a heart-shaped head. But most interesting of all is its nerve cord and associated neurons. Together, the fossils show the entire nervous system of the organism, apart from its brain – making this the oldest preserved nervous system that has ever been found. “The detail of this fossil is exquisite,” says Rob DeSalle of the American Museum of Natural History in New York, who was not involved in the work. “The information from this specimen unravels transitions in how the nervous systems of arthropods evolved.” The animal had a nerve cord that ran the length of its body, with bulbous nodes of neurons called ganglia located between each pair of legs. “It’s almost like a mini-brain for each pair of legs,” says Javier Ortega-Hernández of the University of Cambridge, whose team analysed and described the fossil. Surprisingly, the team found dozens of fine, subsidiary nerves fanning out across the entire length of the nerve cord, making this nervous system more complex than those seen in today’s descendants. © Copyright Reed Business Information Ltd.
Link ID: 21941 - Posted: 03.01.2016
The dodo is an extinct flightless bird whose name has become synonymous with stupidity. But it turns out that the dodo was no bird brain, but instead a reasonably brainy bird. Scientists said on Wednesday they figured out the dodo's brain size and structure based on an analysis of a well-preserved skull from a museum collection. They determined its brain was not unusually small but rather completely in proportion to its body size. They also found the dodo may have had a better sense of smell than most birds, with an enlarged olfactory region of the brain. This trait, unusual for birds, probably let it sniff out ripe fruit to eat. The research suggests the dodo, rather than being stupid, boasted at least the same intelligence as its fellow members of the pigeon and dove family. Mauritius Dodo bird A skeleton of a Mauritius Dodo bird stands at an exhibition in the Mauritius Institute Museum in Port Louis in this Dec. 27, 2005 file photo. (Reuters) "If we take brain size — or rather, volume, as we measured here — as a proxy for intelligence, then the dodo was as smart as a common pigeon," paleontologist Eugenia Gold of Stony Brook University in New York state said. "Common pigeons are actually smarter than they get credit for, as they were trained as message carriers during the world wars." ©2016 CBC/Radio-Canada.
By Ann Gibbons Depressed? Your inner Neandertal may be to blame. Modern humans met and mated with these archaic people in Europe or Asia about 50,000 years ago, and researchers have long suspected that genes picked up in these trysts might be shaping health and well-being today. Now, a study in the current issue of Science details their impact. It uses a powerful new method for scanning the electronic health records of 28,000 Americans to show that some Neandertal gene variants today can raise the risk of depression, skin lesions, blood clots, and other disorders. Neandertal genes aren’t all bad. “These variants sometimes protect against a disease, sometimes make people more susceptible to disease,” says paleogeneticist Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. Two other new studies identified three archaic genes that boost immune response. And most archaic genes that persist in humans were likely beneficial in prehistoric times. But some now cause disease because modern lifestyles and environments are so different. Living people carry only trace amounts of Neandertal DNA, which makes its impact on health more striking. “The Neandertal genetic contribution to present-day people seems to have larger physiological effects than I would have naïvely thought,” says Pääbo, who helped launch this avenue of research by sequencing the first ancient genomes but was not involved in these studies. On average, Europeans and Asians have inherited about 1.5% of their genomes from Neandertals. Island Melanesians carry an additional 2% to 3% of DNA inherited from another extinct group, the Denisovans. Most Africans lack this archaic DNA because the interbreeding happened after modern humans left Africa. © 2016 American Association for the Advancement of Science
By Virginia Morell Like fearful humans, horses raise the inner brow of their eyes when threatened or surprised. Altogether their faces can convey 17 emotions (ours express 27), and they readily recognize the expressions on their fellow equines. But can they read our facial cues? To find out, researchers tested 28 horses, including 21 geldings and seven mares, from stables in the United Kingdom. Each horse was led by his/her halter rope to a position in the stable, and then presented with a life-size color photograph of the face of a man. The man was either smiling or frowning angrily. The scientists recorded the animals’ reactions, and measured their heart rates. Other studies have shown that stressed horses’ heart rates fluctuate, and when the horses looked at the angry man, their hearts reached a maximum heart rate more quickly than when they viewed the smiling image. When shown the angry face, 20 of the horses also turned their heads so that they could look at it with their left eye—a response that suggests they understood the expression, the scientists report online today in Biology Letters, because the right hemisphere of the brain is specialized for processing negative emotions. Dogs, too, have this “left-gaze bias” when confronting angry faces. Also, like dogs, the horses showed no such bias, such as moving their heads to look with the right eye, when viewing the happy faces—perhaps because the animals don’t need to respond to nonthreatening cues. But an angry expression carries a warning—the person may be about to strike. The discovery that horses as well as dogs—the only two animals this has been tested in—can read our facial expressions spontaneously and without training suggests one of two things: Either these domesticated species devote a lot of time to learning our facial cues, or the ability is innate and more widespread in the animal kingdom than previously thought. © 2016 American Association for the Advancement of Scienc
Fears over surveillance seem to figure large in the bird world, too. Ravens hide their food more quickly if they think they are being watched, even when no other bird is in sight. It’s the strongest evidence yet that ravens have a “theory of mind” – that they can attribute mental states such as knowledge to others. Many studies have shown that certain primates and birds behave differently in the presence of peers who might want to steal their food. While some researchers think this shows a theory of mind, others say they might just be reacting to visual cues, rather than having a mental representation of what others can see and know. Through the peephole Thomas Bugnyar and colleagues at the University of Vienna, Austria, devised an experiment to rule out the possibility that birds are responding to another’s cues. The setup involved two rooms separated by a wooden wall, with windows and peepholes that could be covered. First, a raven was given food with another raven in the next room, with the window open or covered, to see how quickly it caches its prize. With the window open, the birds hid their food more quickly and avoided going back to conceal it further. Then individual ravens were then trained to use the peephole to see where humans were putting food in the other room. The idea here was to allow the bird to realise it could be seen through the peephole. © Copyright Reed Business Information Ltd.
By SINDYA N. BHANOO Several studies suggest that men find women more attractive when they are in the ovulatory phase of their menstrual cycle. The thesis takes a strange turn in a new study in which women were questioned: Each subject was asked whether a woman in an image was likely to entice a man that she was dating. Although women do not find images of ovulatory women particularly attractive, scientists found, women with higher estrogen levels did perceive such images to be more threatening. Women with high estrogen, the researchers noted, have a high potential for fertility. “We’re still trying to pinpoint exactly what all is involved in this,” said Janek S. Lobmaier, a psychologist at the University of Bern. © 2016 The New York Times Company
Heidi Ledford Addie plays hard for an 11-year-old greater Swiss mountain dog — she will occasionally ignore her advanced years to hurl her 37-kilogram body at an unwitting house guest in greeting. But she carries a mysterious burden: when she was 18 months old, she started licking her front legs aggressively enough to wear off patches of fur and draw blood. Addie has canine compulsive disorder — a condition that is thought to be similar to human obsessive–compulsive disorder (OCD). Canine compulsive disorder can cause dogs to chase their tails for hours on end, or to suck on a toy or body part so compulsively that it interferes with their eating or sleeping. Addie may soon help researchers to determine why some dogs are more prone to the disorder than others. Her owner, Marjie Alonso of Somerville, Massachusetts, has enrolled her in a project called Darwin’s Dogs, which aims to compare information about the behaviour of thousands of dogs against the animals’ DNA profiles. The hope is that genetic links will emerge to conditions such as canine compulsive disorder and canine cognitive dysfunction — a dog analogue of dementia and possibly Alzheimer’s disease. The project organizers have enrolled 3,000 dogs so far, but hope to gather data from at least 5,000, and they expect to begin analysing DNA samples in March. “It’s very exciting, and in many ways it’s way overdue,” says Clive Wynne, who studies canine behaviour at Arizona State University in Tempe. © 2016 Nature Publishing Group,
James Gorman Spotted hyenas are the animals that got Sarah Benson-Amram thinking about how smart carnivores are and in what ways. Dr. Benson-Amram, a researcher at the University of Wyoming in Laramie, did research for her dissertation on hyenas in the wild under Kay E. Holekamp of Michigan State University. Hyenas have very complicated social structures and they require intelligence to function in their clans, or groups. But the researchers also tested the animals on a kind of intelligence very different from figuring out who ranks the highest: They put out metal boxes that the animals had to open by sliding a bolt in order to get at meat inside. Only 15 percent of the hyenas solved the problem in the wild, but in captivity, the animals showed a success rate of 80 percent. Dr. Benson-Amram and Dr. Holekamp decided to test other carnivores, comparing species and families. They and other researchers presented animals in several different zoos with a metal puzzle box with a treat inside and recorded the animals’ efforts. They tested 140 animals in 39 species that were part of nine families. They reported their findings on Monday in the Proceedings of the National Academy of Sciences. They compared the success rates of different families with absolute brain size, relative brain size, and the size of the social groups that the species form in the wild. Just having a bigger brain did not make difference, but the relative size of the brain, compared with the size of the body, was the best indication of which animals were able to solve the problem of opening the box. © 2016 The New York Times Company
By SINDYA N. BHANOO Climate change may affect wood rats in the Mojave Desert in a most unusual way. A new study finds that warmer weather reduces their ability to tolerate toxins in the creosote bush, which they rely on for sustenance. The consequences may be dire for the wood rats. “There’s not much more they can eat out there,” said Patrice Kurnath, a biologist at the University of Utah and one of the study’s authors. She and her colleagues reported their findings in Proceedings of the Royal Society B: Biological Sciences. The leaves of the creosote bush contain a resin full of toxic compounds. They are known to cause kidney cysts and liver failure in laboratory rats. Wild wood rats, however, generally tolerate the poisons. Ms. Kurnath and her colleagues monitored the wood rats as they ate the leaves in warmer temperatures — around 83 degrees Fahrenheit. Although highs in the Mojave can reach the 80s and 90s during the summer, much of the year is cooler. The rats became less tolerant of the toxins and began to lose weight. The reason may have to do with how the liver functions in warmer weather, Ms. Kurnath said. The liver is the body’s primary detoxifying organ. When a mammalian liver is active, it increases internal body temperature. “In warmer weather, maybe you’re not producing huge amounts of heat and you’re not breaking down the toxins,” Ms. Kurnath said. © 2016 The New York Times Company
By Christof Koch While “size does not matter” is a universally preached dictum among the politically correct, everyday experience tells us that this can't be the whole story—under many conditions, it clearly does. Consider the size of Woody Allen's second favorite organ, the brain. Adjectives such as “highbrow” and “lowbrow” have their origin in the belief, much expounded by 19th-century phrenologists, of a close correspondence between a high forehead—that is, a big brain—and intelligence. Is this true? Does a bigger brain make you necessarily smarter or wiser? And is there any simple connection between the size of a nervous system, however measured, and the mental powers of the owner of this nervous system? While the answer to the former question is a conditional “yes, somewhat,” the lack of any accepted answer to the second one reveals our ignorance of how intelligent behavior comes about. The human brain continues to grow until it reaches its peak size in the third to fourth decade of life. An MRI study of 46 adults of mainly European descent found that the average male had a brain volume of 1,274 cubic centimeters (cm3) and that the average female brain measured 1,131 cm3. Given that a quart of milk equals 946 cm3, you could pour a bit more than that into a skull without any of it spilling out. Of course, there is considerable variability in brain volume, ranging from 1,053 to 1,499 cm3 in men and between 975 and 1,398 cm3 in women. As the density of brain matter is just a little bit above that of water plus some salts, the average male brain weighs about 1,325 grams, close to the proverbial three pounds often cited in U.S. texts. © 2016 Scientific American
by Sarah Zielinski When you get a phone call or a text from a friend or acquaintance, how fast you respond — or whether you even bother to pick up your phone — often depends on the quality of the relationship you have with that person. If it’s your best friend or mom, you probably pick up right away. If it’s that annoying coworker contacting you on Sunday morning, you might ignore it. Ring-tailed lemurs, it seems, are even pickier in who they choose to respond to. They only respond to calls from close buddies, a new study finds. These aren’t phone calls but contact calls. Ring-tailed lemurs live in female-dominated groups of 11 to 16, and up to 25, animals, and when the group is on the move, it’s common for one member to yell out a “meow!” and for other members to “meow!” back. A lemur may also make the call if it gets lost. The calls serve to keep the group together. The main way ring-tailed lemurs (and many other primates) build friendships, though, is through grooming. Grooming helps maintain health and hygiene and, more importantly, bonds between members. It’s a time-consuming endeavor, and animals have to be picky about who they bother to groom. Ipek Kulahci and colleagues at Princeton University wanted to see if there was a link between relationships built through grooming and vocal exchanges among ring-tailed lemurs. Contact calls don’t require nearly as much time or effort as grooming sessions, so it is possible that animals could be less discriminating when they respond to calls. But, the researchers reasoned, if the vocalizations were a way of maintaining the relationships built through painstaking grooming sessions, then the lemurs would be as picky in their responses as in their grooming partners. © Society for Science & the Public 2000 - 2015.
By Elahe Izadi Tiny cameras attached to wild New Caledonian crows capture, for the first time, video footage of these elusive birds fashioning hooked stick tools, according to researchers. These South Pacific birds build tools out of twigs and leaves that they use to root out food, and they're the only non-humans that make hooked tools in the wild, write the authors of a study published Wednesday in the journal Biology Letters. Humans have previously seen the crows making the tools in artificial situations, in which scientists baited feeding sites and provided the raw tools; but researchers say the New Caledonian crows have never been filmed doing this in a completely natural setting. "New Caledonian crows are renowned for their unusually sophisticated tool behavior," the study authors write. "Despite decades of fieldwork, however, very little is known about how they make and use their foraging tools in the wild, which is largely owing to the difficulties in observing these shy forest birds." Study author Jolyon Troscianko of the University of Exeter in England described the tropical birds as "notoriously difficult to observe" because of the terrain of their habitat and their sensitivity to disturbance, he said in a press release. "By documenting their fascinating behavior with this new camera technology, we obtained valuable insights into the importance of tools in their daily search for food," he added.
Carl Zimmer Over the past few million years, the ancestors of modern humans became dramatically different from other primates. Our forebears began walking upright, and they lost much of their body hair; they gained precision-grip fingers and developed gigantic brains. But early humans also may have evolved a less obvious but equally important advantage: a peculiar sleep pattern. “It’s really weird, compared to other primates,” said Dr. David R. Samson, a senior research scientist at Duke University. In the journal Evolutionary Anthropology, Dr. Samson and Dr. Charles L. Nunn, an evolutionary biologist at Duke, reported that human sleep is exceptionally short and deep, a pattern that may have helped give rise to our powerful minds. Until recently, scientists knew very little about how primates sleep. To document orangutan slumber, for example, Dr. Samson once rigged up infrared cameras at the Indianapolis Zoo and stayed up each night to watch the apes nod off. By observing their movements, he tracked when the orangutans fell in and out of REM sleep, in which humans experience dreams. “I became nocturnal for about seven months,” Dr. Samson said. “It takes someone who wants to get their Ph.D. to be motivated enough to do that.” In the new study. Dr. Samson and Dr. Nunn combined that information with studies of 19 other primate species. The researchers found wide variations in how long the animals slept. Mouse lemurs doze for seventeen hours a day, for example, while humans sleep just seven hours or so a day — “the least of any primate on the planet,” said Dr. Samson. © 2015 The New York Times Company