Chapter 6. Evolution of the Brain and Behavior

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By C. CLAIBORNE RAY Insects have an odor-sensing system that is roughly analogous to that of vertebrates, according to “The Neurobiology of Olfaction,” a survey published in 2010. Different species have varying numbers of odor receptors, special molecules that are attuned to specific odor molecules. Genes govern the production of each kind of receptor; the more genes, the more kinds of receptor. A big difference with insects is that their olfactory receptors are basically external, often within hairlike groups of cells, called sensilla, on the antennas, not inside a collection organ like a nose. Sign Up for the Science Times Newsletter Every week, we'll bring you stories that capture the wonders of the human body, nature and the cosmos. The odorant molecules encounter odorant-binding proteins, assumed to guide them to the long receptor nerve cells, called axons. Electrical signals are sent along the axons. The axons are usually connected to specific processing centers in the brain called glomeruli, held in a region called the antennal lobe. There the signals are analyzed. Depending on the nature, quantity and timing of the odor signals received, still other cells appear to excite or inhibit reactions. Exactly how the reaction system works is not yet fully understood. The Florida carpenter ant and the Indian jumping ant both have wide-ranging abilities to sense odors, with more than 400 genes to make different odor receptors, a 2012 study found. The fruit fly has only 61. The research also found marked differences in the smelling ability of the sexes, with the female ants well ahead. © 2016 The New York Times Company

Keyword: Chemical Senses (Smell & Taste); Evolution
Link ID: 22316 - Posted: 06.14.2016

By Devi Shastri Calling someone a “bird brain” might not be the zinger of an insult you thought it was: A new study shows that—by the total number of forebrain neurons—some birds are much brainier than we thought. The study, published online today in the Proceedings of the National Academy of Sciences, found that 28 bird species have more neurons in their pallial telencephalons, the brain region responsible for higher level learning, than mammals with similar-sized brains. Parrots and songbirds in particular packed in the neurons, with parrots (like the gray parrot, above) ranging from 227 million to 3.14 billion, and songbirds—including the notoriously intelligent crow—from 136 million to 2.17 billion. That’s about twice as many neurons as primates with brains of the same mass and four times as many as rodent brains of the same mass. To come up with their count, the researchers dissected the bird brains and then dissolved them in a detergent solution, ensuring that the cells were suspended in what neuroscientist Suzana Herculano-Houzel of Vanderbilt University in Nashville calls “brain soup.” This allowed them to label, count, and estimate how many neurons were in a particular brain region. The region that they focused on allows some birds to hone skills like tool use, planning for the future, learning birdsong, and mimicking human speech. One surprising finding was that the neurons were much smaller than expected, with shorter and more compact connections between cells. The team’s next step is to examine whether these neurons started out small or instead shrank in order to keep the birds light enough for flights. One thing, at least, is clear: It’s time to find a new insult for your less brainy friends. © 2016 American Association for the Advancement of Science

Keyword: Evolution; Animal Communication
Link ID: 22315 - Posted: 06.14.2016

Michael Graziano Ever since Charles Darwin published On the Origin of Species in 1859, evolution has been the grand unifying theory of biology. Yet one of our most important biological traits, consciousness, is rarely studied in the context of evolution. Theories of consciousness come from religion, from philosophy, from cognitive science, but not so much from evolutionary biology. Maybe that’s why so few theories have been able to tackle basic questions such as: What is the adaptive value of consciousness? When did it evolve and what animals have it? The Attention Schema Theory (AST), developed over the past five years, may be able to answer those questions. The theory suggests that consciousness arises as a solution to one of the most fundamental problems facing any nervous system: Too much information constantly flows in to be fully processed. The brain evolved increasingly sophisticated mechanisms for deeply processing a few select signals at the expense of others, and in the AST, consciousness is the ultimate result of that evolutionary sequence. If the theory is right—and that has yet to be determined—then consciousness evolved gradually over the past half billion years and is present in a range of vertebrate species. Even before the evolution of a central brain, nervous systems took advantage of a simple computing trick: competition. Neurons act like candidates in an election, each one shouting and trying to suppress its fellows. At any moment only a few neurons win that intense competition, their signals rising up above the noise and impacting the animal’s behavior. This process is called selective signal enhancement, and without it, a nervous system can do almost nothing. © 2016 by The Atlantic Monthly Group

Keyword: Consciousness; Evolution
Link ID: 22306 - Posted: 06.09.2016

By Rachel Feltman Archerfish are already stars of the animal kingdom for their stunning spit-takes. They shoot high-powered water jets from their mouths to stun prey, making them one of just a few fish species known to use tools. But by training Toxotes chatareus to direct those jets of spit at certain individuals, scientists have shown that the little guys have another impressive skill: They seem to be able to distinguish one human face from another, something never before witnessed in fish and spotted just a few times in non-human animals. The results, published Tuesday in the Nature journal Scientific Reports, could help us understand how humans got so good at telling each other apart. Or how most people got to be good at that, anyway. I'm terrible at it. It's generally accepted that the fusiform gyrus, a brain structure located in the neocortex, allows humans to tell one another apart with a speed and accuracy that other species can't manage. But there's some debate over whether human faces are so innately complex — and that distinguishing them is more difficult than other tricks of memory or pattern recognition — that this region of the brain is a necessary facilitator of the skill that evolved especially for it. Birds, which have been shown to distinguish humans from one another, have the same structure. But some researchers still think that facial recognition might be something that humans learn — it's not an innate skill — and that the fusiform gyrus is just the spot where we happen to process all the necessary information.

Keyword: Attention; Evolution
Link ID: 22299 - Posted: 06.08.2016

By Virginia Morell Sex is never simple—even among lizards. Unlike mammals, the sex of central bearded dragons, large lizards found in eastern Australia, is determined by their chromosomes and the environment. If the eggs are incubated in high temperatures, male embryos turn into females. Such sex-reversed lizards still retain the chromosomal makeup of a male, but they develop into functional superfemales, whose output of eggs exceeds that of the regular females. Now, a new study predicts that—in some cases—these superfemales may be able to drive regular ones to extinction. That’s because superfemales not only produce more eggs, but they’re also exceptionally bold. Looking at the shape, physiology, and behavior of 20 sex-reversed females, 55 males, and 40 regular females, scientists found that the sex-reversed dragons were physically similar to regular males: They had a male dragon’s long tail and high body temperature. They were also behaviorally similar, acting like bold, active males—even as they produced viable eggs. Indeed, the scientists report in the current issue of the Proceedings of the Royal Society B that these sex-reversed females were behaviorally more malelike than the genetic males. Because of these advantages, this third sex could reproductively outcompete normal females, the scientists say, possibly causing some populations to lose the female sex chromosome. (Females are the heterogametic sex, like human males.) In such a population, the dragons’ sex would then be determined solely by temperature instead of genetics—something that’s occurred in the lab within a single generation. Could it happen in the wild? The scientists are still investigating. © 2016 American Association for the Advancement of Science

Keyword: Sexual Behavior; Evolution
Link ID: 22296 - Posted: 06.08.2016

By Karin Brulliard Think about how most people talk to babies: Slowly, simply, repetitively, and with an exaggerated tone. It’s one way children learn the uses and meanings of language. Now scientists have found that some adult birds do that when singing to chicks — and it helps the baby birds better learn their song. The subjects of the new study, published last week in the journal Proceedings of the National Academy of Sciences, were zebra finches. They’re good for this because they breed well in a lab environment, and “they’re just really great singers. They sing all the time,” said McGill University biologist and co-author Jon Sakata. The males, he means — they’re the singers, and they do it for fun and when courting ladies, as well as around baby birds. Never mind that their melody is more “tinny,” according to Sakata, than pretty. Birds in general are helpful for vocal acquisition studies because they, like humans, are among the few species that actually have to learn how to make their sounds, Sakata said. Cats, for example, are born knowing how to meow. But just as people pick up speech and bats learn their calls, birds also have to figure out how to sing their special songs. Sakata and his colleagues were interested in how social interactions between adult zebra finches and chicks influences that learning process. Is face-to-face — or, as it may be, beak-to-beak — learning better? Does simply hearing an adult sing work as well as watching it do so? Do daydreaming baby birds learn as well as their more focused peers? © 1996-2016 The Washington Post

Keyword: Language; Evolution
Link ID: 22286 - Posted: 06.06.2016

By Simon Makin Other species are capable of displaying dazzling feats of intelligence. Crows can solve multistep problems. Apes display numerical skills and empathy. Yet, neither species has the capacity to conduct scientific investigations into other species' cognitive abilities. This type of behavior provides solid evidence that humans are by far the smartest species on the planet. Besides just elevated IQs, however, humans set themselves apart in another way: Their offspring are among the most helpless of any species. A new study, published recently in Proceedings of the National Academy of Sciences (PNAS), draws a link between human smarts and an infant’s dependency, suggesting one thing led to the other in a spiraling evolutionary feedback loop. The study, from psychologists Celeste Kidd and Steven Piantadosi at the University of Rochester, represents a new theory about how humans came to possess such extraordinary smarts. Like a lot of evolutionary theories, this one can be couched in the form of a story—and like a lot of evolutionary stories, this one is contested by some scientists. Kidd and Piantadosi note that, according to a previous theory, early humans faced selection pressures for both large brains and the capacity to walk upright as they moved from forest to grassland. Larger brains require a wider pelvis to give birth whereas being bipedal limits the size of the pelvis. These opposing pressures—biological anthropologists call them the “obstetric dilemma”—could have led to giving birth earlier when infants’ skulls were still small. Thus, newborns arrive more immature and helpless than those of most other species. Kidd and Piantadosi propose that, as a consequence, the cognitive demands of child care increased and created evolutionary pressure to develop higher intelligence. © 2016 Scientific American

Keyword: Development of the Brain; Evolution
Link ID: 22277 - Posted: 06.02.2016

By David Z. Hambrick If you’re a true dog lover, you take it as one of life’s simple truths that all dogs are good, and you have no patience for scientific debate over whether dogs really love people. Of course they do. What else could explain the fact that your dog runs wildly in circles when you get home from work, and, as your neighbors report, howls inconsolably for hours on end when you leave? What else could explain the fact that your dog insists on sleeping in your bed, under the covers—in between you and your partner? At the same time, there’s no denying that some dogs are smarter than others. Not all dogs can, like a border collie mix named Jumpy, do a back flip, ride a skateboard, and weave through pylons on his front legs. A study published in the journal Intelligence by British psychologists Rosalind Arden and Mark Adams confirms as much. Consistent with over a century of research on human intelligence, Arden and Adams found that a dog that excels in one test of cognitive ability will likely excel in other tests of cognitive ability. In more technical terms, the study reveals that there is a general factor of intelligence in dogs—a canine “g” factor. For their study, Arden and Adams devised a battery of canine cognitive ability tests. All of the tests revolved around—you guessed it—getting a treat. In the detour test, the dog’s objective was to navigate around barriers arranged in different configurations to get to a treat. In the point-following test, a researcher pointed to one of two inverted beakers concealing a treat, and recorded whether the dog went to that beaker or the other one. Finally, the quantity discrimination test required the dog to choose between a small treat (a glob of peanut butter) and a larger one (the “correct” answer). Arden and Adams administered the battery to 68 border collies from Wales; all had been bred and trained to do herding work on a farm, and thus had similar backgrounds. © 2016 Scientific American

Keyword: Intelligence; Evolution
Link ID: 22272 - Posted: 06.01.2016

By C. CLAIBORNE RAY Q. Does the size of an animal’s brain really correlate with intelligence on a species-by-species basis? A. “It’s not necessarily brain size but rather the ratio of brain size to body size that really tells the story,” said Rob DeSalle, a curator at the Sackler Institute for Comparative Genomics at the American Museum of Natural History. Looking at this ratio over a large number of vertebrate animals, he said, scientists have found that “brain size increases pretty linearly with body size, except for some critical species like Homo sapiens and some cetaceans,” the order of mammals that includes whales, dolphins and porpoises. “So if there is a deviation from this general ratio, one can predict how smart a vertebrate might be,” Dr. DeSalle continued. Therefore, living vertebrates that deviate so that their brains are inordinately bigger compared with their bodies are for the most part smarter, he said. As for dinosaurs, he said, scientists really can’t tell how smart they may have been. “But the Sarmientosaurus, with its lime-sized brain, was a big animal, so the extrapolation is that it would have been pretty dense,” he said. “On the other hand, Troodon, a human-sized dinosaur, had a huge brain relative to its body size and is widely considered the smartest dinosaur ever found.” © 2016 The New York Times Company

Keyword: Evolution
Link ID: 22261 - Posted: 05.30.2016

By RUSSELL GOLDMAN There’s an elephant at a zoo outside Seoul that speaks Korean. — You mean, it understands some Korean commands, the way a dog can be trained to understand “sit” or “stay”? No, I mean it can actually say Korean words out loud. — Pics or it didn’t happen. Here, watch the video. To be fair, the elephant, a 26-year-old Asian male named Koshik, doesn’t really speak Korean, any more than a parrot can speak Korean (or English or Klingon). But parrots are supposed to, well, parrot — and elephants are not. And Koshik knows how to say at least five Korean words, which are about five more than I do. The really amazing part is how he does it. Koshik places his trunk inside his mouth and uses it to modulate the tone and pitch of the sounds his voice makes, a bit like a person putting his fingers in his mouth to whistle. In this way, Koshik is able to emulate human speech “in such detail that Korean native speakers can readily understand and transcribe the imitations,” according to the journal Current Biology. What’s in his vocabulary? Things he hears all the time from his keepers: the Korean words for hello, sit down, lie down, good and no. Elephant Speaks Korean | Video Video by LiveScienceVideos Lest you think this is just another circus trick that any Jumbo, Dumbo or Babar could pull off, the team of international scientists who wrote the journal article say Koshik’s skills represent “a wholly novel method of vocal production and formant control in this or any other species.” Like many innovations, Koshik’s may have been born of sad necessity. Researchers say he started to imitate his keepers’s sounds only after he was separated from other elephants at the age of 5 — and that his desire to speak like a human arose from sheer loneliness. © 2016 The New York Times Company

Keyword: Language; Animal Communication
Link ID: 22253 - Posted: 05.26.2016

Susan Milius Forget it, peacocks. Nice try, elk. Sure, sexy feathers and antlers are showy, but the sperm of a fruit fly could be the most over-the-top, exaggerated male ornamentation of all. In certain fruit fly species, such as Drosophila bifurca, males measuring just a few millimeters produce sperm with a tail as long as 5.8-centimeters, researchers report May 25 in Nature. Adjusted for body size, the disproportionately supersized sperm outdoes such exuberant body parts as pheasant display feathers, deer antlers, scarab beetle horns and the forward-grasping forceps of earwigs. Fruit flies’ giant sperm have been challenging to explain, says study coauthor Scott Pitnick of Syracuse University in New York. Now he and his colleagues propose that a complex interplay of male and female benefits has accelerated sperm length in a runaway-train scenario. Males with longer sperm deliver fewer sperm, bucking a more-is-better trend. Yet, they still manage to transfer a few dozen to a few hundred per mating. And as newly arrived sperm compete to displace those already waiting in a female’s storage organ, longer is better. Fewer sperm per mating means females tend to mate more often, intensifying the sperm-vs.-sperm competition. Females that have the longest storage organs, which favor the longest sperm, benefit too: Males producing megasperm, the researchers found, tend to be the ones with good genes likely to produce robust offspring. “Sex,” says Pitnick, “is a powerful force.” © Society for Science & the Public 2000 - 2016

Keyword: Sexual Behavior; Evolution
Link ID: 22249 - Posted: 05.26.2016

By Andy Coghlan It’s a tear-jerker worthy of Hollywood – and one of the first examples of compassionate care and grief in a wild monkey. The alpha male of a group of snub-nosed monkeys and his dying partner spent a final, tender hour together beneath the tree from which she had fallen minutes earlier, cracking her head on a rock. Before she succumbed, he gently touched and groomed her. And after she was dead he remained by her side for 5 minutes, touching her and pulling gently at her hand, as if to try and revive her (for a full account of what happened, see “A monkey tends to his dying mate – as it unfolded”, below). “The case we’ve reported is particularly important because of the exclusively gentle nature of the interactions, and the special treatment of the dying female shown by the adult male,” says James Anderson of Kyoto University, Japan. “The events suggest that in the case of strongly bonded individuals at least, monkeys may show compassionate behaviour to ailing or dying individuals.” Together, the reports add to evidence that humans may not be the only species to display grieving behaviour following bereavement, or to show respect for dead individuals with whom they have forged ties. They also hint that animals have some recognition of the finality of death. “It seems likely that in long-lived species such as many primates, repeated exposure to death within the group leads to an understanding of the irreversibility of death,” says Anderson. “I believe the adult male and other members of his unit understood the dead female was no longer alive.” © Copyright Reed Business Information Ltd.

Keyword: Emotions; Evolution
Link ID: 22240 - Posted: 05.24.2016

Bret Stetka We've all been caught in that hazy tug of war between wakefulness and sleep. But the biology behind how our brains drive us to sleep when we're sleep-deprived hasn't been entirely clear. For the first time scientists have identified the neurons in the brain that appear to control sleep drive, or the growing pressure we feel to sleep after being up for an extended period of time. The findings, published online Thursday by the journal Cell, could lead to better understanding of sleep disorders in humans. And perhaps, one day, if the work all pans out, better treatments for chronic insomnia could be developed. To explore which brain areas might be involved in sleep drive, Johns Hopkins neuroscientist Dr. Mark Wu and his colleagues turned to fruit flies, that long tinkered-with subject of scientific inquiry. Despite our rather obvious physical distinctions, humans and fruit flies – or Drosophila – have a good deal in common when it comes to genes, brain architecture and even behaviors. Included in the study were over 500 strains of fly, each with unique brain activation profiles (meaning certain circuits are more active in certain flies). By employing a genetic engineering technique in which specific groups of neurons can be activated with heat, the researchers were able to monitor the firing of nearly all the major circuits in the fruit fly brain and monitor the resulting effects on sleep. Moreover, the neurons of interest were engineered to glow green when activated allowing specific cells to be identified with fluorescent microscopy. Wu found that activating a group of cells called R2 neurons, which are found in a brain region known as the ellipsoid body, put fruit flies to sleep, even for hours after the neurons were "turned off." © 2016 npr

Keyword: Sleep; Evolution
Link ID: 22233 - Posted: 05.21.2016

By JONATHAN BALCOMBE Washington — IN March, two marine biologists published a study of giant manta rays responding to their reflections in a large mirror installed in their aquarium in the Bahamas. The two captive rays circled in front of the mirror, blew bubbles and performed unusual body movements as if checking their reflection. They made no obvious attempt to interact socially with their reflections, suggesting that they did not mistake what they saw as other rays. The scientists concluded that the mantas seemed to be recognizing their reflections as themselves. Mirror self-recognition is a big deal. It indicates self-awareness, a mental attribute previously known only among creatures of noted intelligence like great apes, dolphins, elephants and magpies. We don’t usually think of fishes as smart, let alone self-aware. As a biologist who specializes in animal behavior and emotions, I’ve spent the past four years exploring the science on the inner lives of fishes. What I’ve uncovered indicates that we grossly underestimate these fabulously diverse marine vertebrates. The accumulating evidence leads to an inescapable conclusion: Fishes think and feel. Because fishes inhabit vast, obscure habitats, science has only begun to explore below the surface of their private lives. They are not instinct-driven or machinelike. Their minds respond flexibly to different situations. They are not just things; they are sentient beings with lives that matter to them. A fish has a biography, not just a biology. Those giant manta rays have the largest brains of any fish, and their relative brain-to-body size is comparable to that of some mammals. So, an exception? Then you haven’t met the frillfin goby. © 2016 The New York Times Company

Keyword: Intelligence; Evolution
Link ID: 22221 - Posted: 05.16.2016

By Linda Zajac For nearly 65 million years, bats and tiger moths have been locked in an aerial arms race: Bats echolocate to detect and capture tiger moths, and tiger moths evade them with flight maneuvers and their own ultrasonic sounds. Scientists have long wondered why certain species emit these high-frequency clicks that sound like rapid squeaks from a creaky floorboard. Does the sound jam bat sonar or does it warn bats that the moths are toxic? To find out, scientists collected two types of tiger moths: red-headed moths (pictured above) and Martin’s lichen moths. They then removed the soundmaking organs from some of the insects. In a grassy field in Arizona they set up infrared video cameras, ultrasonic microphones, and ultraviolet lights, the last of which they used to attract bats. In darkness, they released one tiger moth at a time and recorded the moth-bat interactions. They found that the moths rarely produced ultrasonic clicks fast enough to jam bat sonar. They also discovered that without sound organs, 64% of the red-headed moths and 94% of the Martin’s lichen moths were captured and spit out. Together, these findings reported late last month in PLOS ONE suggest that instead of jamming sonar like some tiger moths, these species act tough, flexing their soundmaking organs to warn predators of their toxin. © 2016 American Association for the Advancement of Science

Keyword: Hearing; Evolution
Link ID: 22185 - Posted: 05.07.2016

By Virginia Morell After defeating other males in boxing matches and winning a territorial roost—and a bevy of females—a male Seba’s short-tailed bat (Carollia perspicillata, pictured) might think his battles for reproductive rights are over. But the defeated males of this neotropical species have a trick up their sleeve: clandestine matings with willing females. The tactic works, and now researchers know why. Scientists studied bats in a captive colony in Switzerland, removing alpha males from their harems for 3 days, and examining their sperm—as well as that of their rivals. A previous study showed that the sneaky males have faster, longer lived sperm, which gives them a leg-up on the alpha male. Researchers had suspected this was because the sneakers produced this supersperm to compete. But the new study finds that after the 3 days of abstinence, the alpha male’s sperm is as agile and vigorous as that of his rivals. Thus, the team reports today in the Journal of Experimental Biology, the sneaky males aren’t generating special sperm—they just mate less, so their sperm is in better shape when it comes time to race to the egg. © 2016 American Association for the Advancement of Science.

Keyword: Sexual Behavior; Evolution
Link ID: 22180 - Posted: 05.05.2016

By Sarah Kaplan The ancient Greeks spoke of a mythological society composed entirely of warrior women. The medieval traveler John Mandeville wrote of a place whose female rulers "never would suffer man to dwell amongst them." "Paradise Island," home of Wonder Woman, was a feminist utopia where no one with a Y chromosome was allowed. Sadly, those places only exist in fiction. But something like them does exist in the real world. It's in a wetland in rural Ohio. And it's full of salamanders. "They’re pretty incredible," said Robert Denton, a biologist at Ohio State who studies an unusual group of salamander species that literally don't need men. These creatures – all female – reproduce by cloning themselves. To keep their gene pool diverse, they sometimes "steal" sperm left behind on trees and leaves by male salamanders of other species and incorporate that DNA into their offspring. Most sexually reproducing organisms have two sets of chromosomes to make up their genome – one from each parent. But one of these strange salamanders can have between two and five times that much genetic material lying in wait within her cells. It's as if they have multiple genomes to fall back on, and that's made them incredibly successful. "Polyploid" salamanders have been around some 6 million years, Denton said — far longer than most other animal species that reproduce asexually. Since a lack of diversity means having a smaller arsenal of genetic variation to fall back on when living conditions change, these groups usually go extinct relatively quickly. © 1996-2016 The Washington Post

Keyword: Sexual Behavior; Evolution
Link ID: 22176 - Posted: 05.04.2016

by Susan Milius There’s nothing like a guy doing all the child care to win female favor, even among giant water bugs. Thumbnail-sized Appasus water bugs have become an exemplar species for studying paternal care. After mating, females lay eggs on a male’s back and leave him to swim around for weeks tending his glued-on load. For an A. major water bug, lab tests show an egg burden can have the sweet side of attracting more females, researchers in Japan report May 4 in Royal Society Open Science. Given a choice of two males, females strongly favored, and laid more eggs on, the one already hauling around 10 eggs rather than the male that researchers had scraped eggless. Females still favored a well-egged male even when researchers offered two males that a female had already considered, but with their egg-carrying roles switched from the previous encounter. That formerly spurned suitor this time triumphed. A similar preference, though not as clear-cut, showed up in the slightly smaller and lighter A. japonicus giant water bug. “We conclude that sexual selection plays an important role in the maintenance of elaborate paternal care,” says study coauthor Shin-ya Ohba of Nagasaki University. © Society for Science & the Public 2000 - 2016

Keyword: Sexual Behavior; Evolution
Link ID: 22175 - Posted: 05.04.2016

By Emily Benson Baby birds are sometimes known to shove their siblings out of the nest to gain their parents’ undivided attention, but barn owl chicks appear to be more altruistic. Scientists recorded the hissing calls of hungry and full barn owl nestlings (Tyto alba, pictured), then played the sounds back to single chicks settled in nests stocked with mice. The young owls that heard the squawks of their hungry kin delayed eating each rodent by an average of half an hour; those that heard cries indicating their invisible nest-mate was full ate the mice more quickly. The findings suggest that barn owl chicks give hungrier siblings a chance to eat first even when the nest is full of food, the researchers will report in an upcoming issue of Behavioral Ecology and Sociobiology. So is it true altruism? Maybe not. Nestlings may share food in exchange for help with grooming or to get the first crack at a later meal, the team says, suggesting a possible ulterior motive. © 2016 American Association for the Advancement of Science

Keyword: Evolution
Link ID: 22174 - Posted: 05.04.2016

By ERICA GOODE Horses snooze in their stalls. Fish take their 40 winks floating in place. Dogs can doze anywhere, anytime. And even the lowly worm nods off now and then. All animals, most scientists agree, engage in some form of sleep. But the stages of sleep that characterize human slumber had until now been documented only in mammals and birds. A team of researchers in Germany announced in a report published on Thursday, however, that they had found evidence of similar sleep stages in a lizard: specifically, the bearded dragon, or Pogona vitticeps, a reptile native to Australia and popular with pet owners. Recordings from electrodes implanted in the lizards’ brains showed patterns of electrical activity that resembled what is known as slow-wave sleep and another pattern resembling rapid eye movement, or REM, sleep, a stage of deep slumber associated with brain activity similar to that of waking. Some researchers had argued that these stages were of relatively recent origin in evolutionary terms because they had not been found in more primitive animals like amphibians, fish, reptiles other than birds, and other creatures with backbones. But the new finding, said Gilles Laurent, director of the department of neural systems at the Max Planck Institute for Brain Research and the principal author of the study, “increases the probability that sleep evolved in all these animals from a common ancestor.” He added that it also raised the possibility that staged sleep evolved even earlier and that some version of it might exist in animals like amphibians or fish. The report appeared in Thursday’s issue of the journal Science. Other researchers said the study could help scientists understand more about the purpose and mechanisms of sleep. But the finding, they added, is bound to generate more controversy about whether the resting state of primitive animals is really the same as sleep, and whether the brain activity seen in a lizard can be compared to that in mammals. © 2016 The New York Times Company

Keyword: Sleep; Evolution
Link ID: 22164 - Posted: 04.30.2016