Chapter 6. Evolution of the Brain and Behavior
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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
Megan Scudellari In 1997, physicians in southwest Korea began to offer ultrasound screening for early detection of thyroid cancer. News of the programme spread, and soon physicians around the region began to offer the service. Eventually it went nationwide, piggybacking on a government initiative to screen for other cancers. Hundreds of thousands took the test for just US$30–50. LISTEN James Harkin, a researcher for the British TV trivia show QI, talks to Adam Levy about how he finds facts and myths for the show — and then runs a mini-quiz to see whether the Podcast team can discern science fact from science fiction 00:00 Across the country, detection of thyroid cancer soared, from 5 cases per 100,000 people in 1999 to 70 per 100,000 in 2011. Two-thirds of those diagnosed had their thyroid glands removed and were placed on lifelong drug regimens, both of which carry risks. Such a costly and extensive public-health programme might be expected to save lives. But this one did not. Thyroid cancer is now the most common type of cancer diagnosed in South Korea, but the number of people who die from it has remained exactly the same — about 1 per 100,000. Even when some physicians in Korea realized this, and suggested that thyroid screening be stopped in 2014, the Korean Thyroid Association, a professional society of endocrinologists and thyroid surgeons, argued that screening and treatment were basic human rights. © 2015 Nature Publishing Group,
Parrots can dance and talk, and now apparently they can use and share grinding tools. They were filmed using pebbles for grinding, thought to be a uniquely human activity – one that allowed our civilisations to extract more nutrition from cereal-based foods. Megan Lambert from the University of York, UK, and her colleagues were studying greater vasa parrots (Coracopsis vasa) in an aviary when they noticed some of the birds scraping shells in their enclosure with pebbles and date pips. “We were surprised,” says Lambert. “Using tools [to grind] seashells is something never seen before in animals.” Afterwards, the birds would lick the powder from the tool. Some of the parrots even passed tools to each other, which is rarely seen in animals. This behaviour was exclusively male to female. Lambert and her team, who watched the parrots for six months, noticed that the shell-scraping was more frequent before their breeding season. Since seashells contain calcium, which is critical for females before egg-laying, they suspect that the parrots could be manufacturing their own calcium supplements, as the mineral is probably better absorbed in powder form. Greater vasa parrots are native to Madagascar and have breeding and social systems unique among parrots. For example, two or more males have an exclusive sexual relationship with two or more females, and they are unusually tolerant of their group members. The reproductive ritual of sharing tools and grinding could be yet another one of their quirks. © Copyright Reed Business Information Ltd.
By Kelli Whitlock Burton Evolutionarily speaking, we are born to make babies. Our bodies—and brains—don’t fall apart until we come to the end of our child-bearing years. So why are grandmothers, who don’t reproduce and who contribute little to food production, still around and still mentally sound? A new study offers an intriguing genetic explanation. Scientists have proposed several explanations for why our species lives as long and as healthily as it does. One idea is that grandmothers help out with child rearing. A 1998 study found, for example, that a Hadza group of hunter-gatherers in Tanzania had more babies if grandmothers helped feed their newly-weaned young grandchildren. The researchers speculated this kind of care freed up young mothers to reproduce, and ensured that the caregiver grandmother’s genes were passed on to more young. They called their theory the “grandmother hypothesis.” But grandmothers need to have all their wits about them to help out in this way, and the new study may explain how this happens. Physician-scientist Ajit Varki and evolutionary biologist Pascal Gagneux of the University of California, San Diego, arrived at the findings accidentally. The pair was studying a gene that helps control the body’s inflammatory and immune response to injury or infection. Previous studies have linked two forms of the gene—CD33—to Alzheimer’s disease. While one CD33 variant, or allele, predisposes a person to the disease, the other appears to protect against it by preventing the formation of protein clumps in the brain. © 2015 American Association for the Advancement of Science.
By Diana Kwon The human brain is unique: Our remarkable cognitive capacity has allowed us to invent the wheel, build the pyramids and land on the moon. In fact, scientists sometimes refer to the human brain as the “crowning achievement of evolution.” But what, exactly, makes our brains so special? Some leading arguments have been that our brains have more neurons and expend more energy than would be expected for our size, and that our cerebral cortex, which is responsible for higher cognition, is disproportionately large—accounting for over 80 percent of our total brain mass. Suzana Herculano-Houzel, a neuroscientist at the Institute of Biomedical Science in Rio de Janeiro, debunked these well-established beliefs in recent years when she discovered a novel way of counting neurons—dissolving brains into a homogenous mixture, or “brain soup.” Using this technique she found the number of neurons relative to brain size to be consistent with other primates, and that the cerebral cortex, the region responsible for higher cognition, only holds around 20 percent of all our brain’s neurons, a similar proportion found in other mammals. In light of these findings, she argues that the human brain is actually just a linearly scaled-up primate brain that grew in size as we started to consume more calories, thanks to the advent of cooked food. Other researchers have found that traits once believed to belong solely to humans also exist in other members of the animal kingdom. Monkeys have a sense of fairness. Chimps engage in war. Rats show altruism and exhibit empathy. In a study published last week in Nature Communications, neuroscientist Christopher Petkov and his group at Newcastle University found that macaques and humans share brain areas responsible for processing the basic structures of language. © 2015 Scientific American
by Sarah Zielinski Call someone a “bird brain” and they are sure to be offended. After all, it’s just another way of calling someone “stupid.” But it’s probably time to retire the insult because scientists are finding more and more evidence that birds can be pretty smart. Consider these five species: We may call pigeons “flying rats” for their penchant for hanging out in cities and grabbing an easy meal. (Long before there was “pizza rat,” you know there had to be “pizza pigeons” flying around New York City.) But there may be more going on in their brains than just where to find a quick bite. Richard Levenson of the University of California, Davis Medical Center and colleagues trained pigeons to recognize images of human breast cancers. In tests, the birds proved capable of sorting images of benign and malignant tumors. In fact, they were just as good as humans, the researchers report November 18 in PLOS ONE. In keeping with the pigeons’ reputation, though, food was the reward for their performance. No one would suspect the planet’s second-best toolmakers would be small black birds flying through mountain forests on an island chain east of Australia. But New Caledonian crows have proven themselves not only keen toolmakers but also pretty good problem-solvers, passing some tests that even dogs (and pigeons) fail. For example, when scientists present an animal with a bit of meat on a long string dangling down, many animals don’t ever figure out how to get the meat. Pull it up with one yank, and the meat is still out of reach. Some animals will figure out how to get it through trial and error, but a wild New Caledonian crow solved the problem — pull, step on string, pull some more — on its first try. © Society for Science & the Public 2000 - 2015
Human DNA is 1 to 2% Neandertal, or more, depending on where your ancestors lived. Svante Pääbo, founder of the field of paleogenetics and winner of a 2016 Breakthrough Prize, explains why that matters © 2015 Scientific American