Chapter 6. Evolution of the Brain and Behavior
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By Meghan Rosen With parasitic flies gorging on her guts and the end approaching, a variable field cricket may have only one thing to do: Find a mate. Usually, female Gryllus lineaticeps prefer males with fast chirps. But when being eaten alive by fly larvae, female crickets don’t wait around for a snappy tune. Instead, they settle for slow-chirping sexual partners, evolutionary biologists Oliver Beckers of Indiana University in Bloomington and William Wagner Jr. of the University of Nebraska-Lincoln report in the April Animal Behaviour. Parasitic flies seek out crickets as potential homes (and meal tickets) for their young. Before the fly larvae chew through crickets’ bellies, female crickets have about a week to find a mate and lay eggs before dying. To find out whether infestation lowered females’ mating standards, Beckers and Wagner placed fly larvae on female crickets and then played slow and fast chirp recordings from loudspeakers set in separate corners of a square chamber. Healthy females walked toward the fast chirping sound about 80 percent of the time, while infested females split their devotion about equally. “They don’t invest a lot of time and energy finding the super sexy guy,” says Becker. “They’ll go for the average Joe.” © Society for Science & the Public 2000 - 2013
by Beth Skwarecki If you thought the battle of the genders was complicated, try having seven sexes. When Tetrahymena, a single-celled creature covered in cilia, mates, the offspring isn't necessarily the same sex as either parent—it can be any of seven. Now, researchers have figured out the complex dance of DNA that determines the offspring's sex, and it's a random selection, they report today in PLOS Biology. Each Tetrahymena has a gene for its own sex—or mating type—in its regular nucleus, but it also carries a second nucleus used only for reproduction. This "germline nucleus" contains incomplete versions of all seven mating type genes, which are cut and pasted together until one complete gene remains and the other six have been deleted. The newly rearranged DNA becomes part of the offspring's regular nucleus, determining its mating type. Because the mating type gene helps Tetrahymena recognize others of a different sex, the researchers say that the finding could shed light on how other cells, including those in humans, recognize those that are different from themselves. © 2010 American Association for the Advancement of Science.
By Susan Milius Hey evolution, thanks for nothing. When a mammal embryo develops, its middle ear appears to form in a pop-and-patch way that seals one end with substandard, infection-prone tissue. “The way evolution works doesn’t always create the most perfect, engineered structure,” says Abigail Tucker, a developmental biologist at King’s College London. “Definitely, it’s made an ear that’s slightly imperfect.” The mammalian middle ear catches sound and transfers it, using three tiny bones that jiggle against the eardrum, to the inner ear chamber. Those three bones — the hammer, anvil and stirrup — are a distinctive trait that distinguishes the group from other evolutionary lineages. Research in mouse embryos finds that the middle ear begins as a pouch of tissue. Then its lining ruptures at one end and the break lets in a different kind of tissue, which forms the tiny bones of the middle ear. This intruding tissue originates from what’s called the embryo’s neural crest, a population of cells that gives rise to bone and muscle. Neural crest tissue has never been known before to create a barrier in the body. Yet as the mouse middle ear forms, this tissue creates a swath of lining that patches the rupture, Tucker and colleague Hannah Thompson, report in the March 22 Science. © Society for Science & the Public 2000 - 2013
by Lizzie Wade Hundreds of millions of years ago, the Earth's seas teemed with trilobites, hard-shelled critters that resembled spiny aquatic cockroaches. Because their exoskeletons lent themselves to fossilization, scientists know a lot about what the outside of their bodies looked like. Their inner workings, however, have remained mysterious. Now, a new study has revealed the structure of the trilobite eye, bringing researchers one step closer to understanding the evolution of vision. Like today's insects and crustaceans, trilobites had compound eyes, with many different lenses focusing light onto clusters of sensory cells lying below them. The resulting image was put together a lot like a picture on your computer screen, with each lens producing one "pixel" of the whole. Because the lenses themselves were made of the mineral calcite, they often fossilized along with the rest of the trilobite's tough exoskeleton. The sensory cells underneath the lenses, however, were ephemeral, and scientists had always assumed that they had decayed without a trace. So imagine Brigitte Schoenemann's surprise when she spotted fossilized versions of these delicate sensory cells while x-raying a long dead trilobite with a computed tomography (CT) scanner. "I expected that we would see [something] in the lens of trilobites, but then suddenly we saw structures of cells below the lens," recalls Schoenemann, a physiologist at the University of Bonn and the University of Cologne, both in Germany. Inspired, she applied to take more fossils to the European Synchrotron Radiation Facility in Grenoble, France, where she could use a particle accelerator's high energy x-rays to peer deeper into the trilobites' eyes. Now, she says, she's created images of the extinct animal's entire visual system, down to the level of fossilized individual cells. © 2010 American Association for the Advancement of Science
by Jennifer Viegas Polly may want a cracker, but when a parrot wants a better deal, it will trade a so-so nut for an even better snack, a new study has found. The discovery, published in the journal Biology Letters, demonstrates that birds can do business in their own way, wheeling and dealing with nuts. It also shows that they can exhibit remarkable self restraint, even performing better than some children. In studies from the 1970s, kids were presented with a marshmallow and were told that they could either eat it now, or wait and receive a second one if they could hold out for a time delay of some minutes. Kids that were able to wait have been more successful now as adults than the other kids (who gulped down the first marshmallow). The ability to strategically wait therefore is very important in the course of human development. Now we can say that it’s important to bird development too. For the new study, Alice Auersperg of the University of Vienna’s Department of Cognitive Biology and colleagues presented an Indonesian cockatoo species, the Goffin’s cockatoo, with food snack options. The best of that bunch, from the bird’s perspective, were pecan nuts. Mirroring the kid-marshmallow experiment, the researchers next offered the birds an even better deal. If the birds did not eat the pecan, they could trade it for a cashew. (Who knew that cockatoos loved cashews so much? Apparently they are the yummiest nut of all, for at least this particular avian species.) © 2013 Discovery Communications, LLC
by Michael Marshall Neanderthals may have had bigger eyes than modern humans, but while this helped them see better, it may have meant that they did not have brainpower to spare for complex social lives. If true, this may have been a disadvantage when the ice age reduced access to food, as they would not have had the skills to procure help from beyond their normal social group, speculates Robin Dunbar at the University of Oxford. Neanderthals' brains were roughly the same size as modern humans, but may have been organised differently. To find out, a team led by Dunbar studied the skulls of 13 Neanderthals and 32 anatomically modern humans. The Neanderthals had larger eye sockets. There are no Neanderthal brains to examine, but primates with larger eyes tend to have larger visual systems in their brains, suggesting Neanderthals did too. Their large bodies would also have required extra brain power to manage. Together, their larger eyes and bodies would have left them with less grey matter to dedicate to other tasks. Neanderthals may have evolved enhanced visual systems to help them see in the gloom of the northern hemisphere, Dunbar says. "It makes them better at detecting things in grim, grey conditions." As a by-product of larger eyes, they may not have been able to expand their frontal lobes – a brain area vital for social interaction – as much as modern humans. As a result, Dunbar estimates they could only maintain a social group size of around 115 individuals, rather than the 150 that we manage. © Copyright Reed Business Information Ltd.
By Scicurious We humans love us some caffeine. The mild stimulant have saved many a student, parent, and hard working adult from nodding over their desks. And it’s a natural product of plants like the coffee plant and the tea bush. But the question is, why do these plants have it in the first place? It turns out that there are two answers to that question. First, caffeine is a natural pesticide, which can paralyze and kill insects that want to chomp on the leaves, berries, or other parts of the plant. It’s good for keeping a bug off your back. But these plants also produce flowers, and these flowers need bees. So it’s somewhat surprising to realize that the coffee plant, as well as plants from the Citrus genus (yup, that means oranges), have caffeine in their nectar. After all, if caffeine is a poison to some bugs, you don’t want to be poisoning your pollinators! But it turns out that bees aren’t like other bugs, and may enjoy themselves a jolt like humans do! Whether they enjoy it or not, they certainly remember it! The authors started out by examining exactly HOW much caffeine was in the nectar of various coffee and citrus plants. And the concentrations of caffeine in the nectar could get up to that of one cup of coffee (though, obviously, in a much smaller volume total). I’m starting to wonder if there’s a “honeyed nectar” energy drink in the future. © 2013 Scientific American
By JAMES GORMAN Nothing kicks the brain into gear like a jolt of caffeine. For bees, that is. And they don’t need to stand in line for a triple soy latte. A new study shows that the naturally caffeine-laced nectar of some plants enhances the learning process for bees, so that they are more likely to return to those flowers. “The plant is using this as a drug to change a pollinator’s behavior for its own benefit,” said Geraldine Wright, a honeybee brain specialist at Newcastle University in England, who, with her colleagues, reported those findings in Science on Thursday. The research, other scientists said, not only casts a new light on the ancient evolutionary interaction between plants and pollinators, but is an intriguing confirmation of deep similarities in brain chemistry across the animal kingdom. Plants are known to go to great lengths to attract pollinators. They produce all sorts of chemicals that affect animal behavior: sugar in nectar, memorable fragrances, even substances in fruit that can act like laxatives in the service of quick seed dispersal. Lars Chittka, who studies bee behavior at Queen Mary, University of London, and wrote a commentary on the research in the same issue of Science, said that in the marketplace of plants seeking pollinators, the plants “want their customers to remain faithful,” thus the sugary nectar and distinctive scents. © 2013 The New York Times Company
by Lizzie Wade With its complex interweaving of symbols, structure, and meaning, human language stands apart from other forms of animal communication. But where did it come from? A new paper suggests that researchers look to bird songs and monkey calls to understand how human language might have evolved from simpler, preexisting abilities. One reason that human language is so unique is that it has two layers, says Shigeru Miyagawa, a linguist at the Massachusetts Institute of Technology (MIT) in Cambridge. First, there are the words we use, which Miyagawa calls the lexical structure. "Mango," "Amanda," and "eat" are all components of the lexical structure. The rules governing how we put those words together make up the second layer, which Miyagawa calls the expression structure. Take these three sentences: "Amanda eats the mango," "Eat the mango, Amanda," and "Did Amanda eat the mango?" Their lexical structure—the words they use—is essentially identical. What gives the sentences different meanings is the variation in their expression structure, or the different ways those words fit together. The more Miyagawa studied the distinction between lexical structure and expression structure, "the more I started to think, 'Gee, these two systems are really fundamentally different,' " he says. "They almost seem like two different systems that just happen to be put together," perhaps through evolution. One preliminary test of his hypothesis, Miyagawa knew, would be to show that the two systems exist separately in nature. So he started studying the many ways that animals communicate, looking for examples of lexical or expressive structures. © 2010 American Association for the Advancement of Science.
By Tina Hesman Saey If someone shouts “look behind you,” tadpoles in Michael Levin’s laboratory may be ready. The tadpoles can see out of eyes growing from their tails, even though the organs aren’t directly wired to the animals’ brains, Levin and Douglas Blackiston, both of Tufts University in Medford, Mass., report online February 27 in the Journal of Experimental Biology. Levin and Blackiston’s findings may help scientists better understand how the brain and body communicate, including in humans, and could be important for regenerative medicine or designing prosthetic devices to replace missing body parts, says Günther Zupanc, a neuroscientist at Northeastern University in Boston. Researchers have transplanted frog eyes to other body parts for decades, but until now, no one had shown that those oddly placed eyes (called “ectopic” eyes) actually worked. Ectopic eyes on tadpoles’ tails allow the animals to distinguish blue light from red light, the Tufts team found. Levin wanted to know whether the brain is hardwired to get visual information only from eyes in the head, or whether the brain could use data coming from elsewhere. To find out, he and Blackiston started with African clawed frog tadpoles (Xenopus laevis) and removed the normal eyes. They then transplanted cells that would grow into eyes onto the animals’ tails. The experiment seemed like a natural to test how well the brain can adapt, Levin says. “There’s no way the tadpole’s brain is expecting an eye on its tail.” Expected or not, some of the tadpoles managed to detect red and blue light from their tail eyes. The researchers placed tadpoles with transplanted eyes in chambers in which half of the chamber was illuminated in blue light and the other half in red light. A mild electric shock zapped the tadpole when it was in one half of the dish so that the animal learned to associate the color with the shock. The researchers periodically switched the colors in the chamber so that the tadpoles didn’t learn that staying still would save them. © Society for Science & the Public 2000 - 2013
by Virginia Morell Every bottlenose dolphin has its own whistle, a high-pitched, warbly "eeee" that tells the other dolphins that a particular individual is present. Dolphins are excellent vocal mimics, too, able to copy even quirky computer-generated sounds. So, scientists have wondered if dolphins can copy each other's signature whistles—which would be very similar to people saying each others' names. Now, an analysis of whistles recorded from hundreds of wild bottlenose dolphins confirms that they can indeed "name" each other, and suggests why they do so—a discovery that may help researchers translate more of what these brainy marine mammals are squeaking, trilling, and clicking about. "It's a wonderful study, really solid," says Peter Tyack, a marine mammal biologist at the University of St. Andrews in the United Kingdom who was not involved in this project. "Having the ability to learn another individual's name is … not what most animals do. Monkeys have food calls and calls that identify predators, but these are inherited, not learned sounds." The new work "opens the door to understanding the importance of naming." Scientists discovered the dolphins' namelike whistles almost 50 years ago. Since then, researchers have shown that infant dolphins learn their individual whistles from their mothers. A 1986 paper by Tyack did show that a pair of captive male dolphins imitated each others' whistles, and in 2000, Vincent Janik, who is also at St. Andrews, succeeded in recording matching calls among 10 wild dolphins "But without more animals, you couldn't draw a conclusion about what was going on," says Richard Connor, a cetacean biologist at the University of Massachusetts, Dartmouth. Why, after all, would the dolphins need to copy another dolphin's whistle? © 2010 American Association for the Advancement of Science
By Erin Wayman BOSTON — The taste for alcohol may be an ancient craving. The ability to metabolize ethanol — the alcohol in beer, wine and spirits — might have originated in the common ancestor of chimpanzees, gorillas and humans roughly 10 million years ago, perhaps when this ancestor became more terrestrial and started eating fruits fermenting on the ground. Chemist Steven Benner of the Foundation for Applied Molecular Evolution in Gainesville, Fla., reached that conclusion by “resurrecting” the alcohol-metabolizing enzymes of extinct primates. Benner and his colleagues estimated the enzymes’ genetic code, built the enzymes in the lab and then analyzed how they work to understand how they changed over time. “It’s like a courtroom re-enactment,” said biochemist Romas Kazlauskas of the University of Minnesota in Minneapolis. Benner “can re-enact what happened in evolution.” Benner proposed the idea February 15 at the annual meeting of the American Association for the Advancement of Science. Today, humans rely on an enzyme called alcohol dehydrogenase 4, or ADH4, to break down ethanol. The enzyme is common throughout the esophagus, stomach and intestines, and is the first alcohol-metabolizing enzyme that comes into contact with what a person drinks. Among primates, not all ADH4s are the same — some can’t effectively metabolize ethanol. © Society for Science & the Public 2000 - 2013
If optimists see the world through rose-colored lenses, some birds see it through ultraviolet ones. Avians have evolved ultraviolet vision quite a few times in history, a new study finds. Birds depend on their color vision for selecting mates, hunting or foraging for food, and spotting predators. Until recently, ultraviolet vision was thought to have arisen as a one-time development in birds. But a new DNA analysis of 40 bird species, reported Feb. 11 in the journal BMC Evolutionary Biology, shows the shift between violet (shorter wavelengths on the electromagnetic spectrum) and ultraviolet vision has occurred at least 14 times. "Birds see color in a different way from humans," study co-author Anders Ödeen, an animal ecologist at Uppsala University in Sweden, told LiveScience. Human eyes have three different color receptors, or cones, that are sensitive to light of different wavelengths and mix together to reveal all the colors we see. Birds, by contrast, have four cones, so "they see potentially more colors than humans do," Ödeen said. Birds themselves are split into two groups based on the color of light (wavelength) that their cones detect most acutely. Scientists define them as violet-sensitive or ultraviolet-sensitive, and the two groups don't overlap, according to Ödeen. Birds of each group would see the same objects as different hues. The specialization of color vision has its advantages. For instance, a bird with ultraviolet-sensitive vision might have spectacularly bright plumage in order to impress a female, but that same plumage might appear dull to predator birds that see only in the violet range. © 2013 Discovery Communications, LLC.
Philip Ball In Fiji, a star is a kalokalo. For the Pazeh people of Taiwan, it is mintol, and for the Melanau people of Borneo, bitén. All these words are thought to come from the same root. But what was it? An algorithm devised by researchers in Canada and California now offers an answer — in this case, bituqen. The program can reconstruct extinct ‘root’ languages from modern ones, a process that has previously been done painstakingly ‘by hand’ using rules of how linguistic sounds tend to change over time. Statistician Alexandre Bouchard-Côté of the University of British Columbia in Vancouver, Canada, and his co-workers say that by making the reconstruction of ancestral languages much simpler, their method should facilitate the testing of hypotheses about how languages evolve. They report their technique in the Proceedings of the National Academy of Sciences1. Automated language reconstruction has been attempted before, but the authors say that earlier algorithms tended to be rather intractable and prescriptive. Bouchard-Côté and colleagues' method can factor in a large number of languages to improve the quality of reconstruction, and it uses rules that handle possible sound changes in flexible, probabilistic ways. The program requires researchers to input a list of words in each language, together with their meanings, and a phylogenetic ‘language tree’ showing how each language is related to the others. Linguists routinely construct such trees using techniques borrowed from evolutionary biology. © 2013 Nature Publishing Group,
by Michael Marshall Humans aren't built for giving birth. Babies' heads are big to accommodate their big brains, but the mother's hips are small because they walk upright. As a result, birth takes hours and is extremely painful – and midwives almost always help out. Other animals may find birth difficult, particularly if the babies have been gestating for a long time and have grown large. Nevertheless, most mammals have it easier than humans. Monkeys give birth in less than ten minutes. So it is a surprise that female black snub-nosed monkeys may be assisted by "midwives" when they give birth. This behaviour has only been seen once in this species, but it suggests that it's not just human mothers that need help giving birth. Black snub-nosed monkeys live in societies called bands, which can be over 400 strong. Each is divided into smaller groups of around 10 monkeys. Most groups contain one male and several females plus offspring, but there are also all-male groups. Wen Xiao of Dali University in Yunnan, China, and colleagues have been observing black snub-nosed monkeys in the province for years, but had never seen one give birth: the monkeys normally deliver at night. Then on 18 March last year, they got lucky. © Copyright Reed Business Information Ltd.
Link ID: 17781 - Posted: 02.11.2013
By Gareth Cook Just about every dog owner is convinced their dog is a genius. For a long time, scientists did not take their pronouncements particularly seriously, but new research suggests that canines are indeed quite bright, and in some ways unique. Brian Hare, an associate professor in the Department of Evolutionary Anthropology and the Center for Cognitive Neuroscience at Duke University, is one of the leading figures in the quest to understand what dogs know. The founder of the Duke Canine Cognition Center, Hare has now written a book, “The Genius of Dogs,” with his wife, the journalist Vanessa Woods. Hare answered questions from Mind Matters editor Gareth Cook. Cook: What is the biggest misconception people have about the dog mind? Hare: That there are “smart” dogs and “dumb” dogs. There’s still this throwback to a uni-dimensional version of intelligence, as though there is only one type of intelligence that you either have more or less of. In reality there are different types of intelligence. Different dogs are good at different things. Unfortunately, the very clever strategies some dogs are using are not apparent without playing a cognitive game. This means people can often underestimate the intelligence of their best friend. The pug drooling on your shoe may not look like the brightest bulb in the box, but she comes from a long line of successful dogs and is a member of the most successful mammal species on the planet besides us. Rest assured – she is a genius. © 2013 Scientific American
by Virginia Morell The male Eurasian jay is an accommodating fellow. When his mate has been feasting steadily on mealworm larvae, he realizes that she'd now prefer to dine on wax moth larvae, which he feeds her himself. The finding adds to a small but growing number of studies that show that some animals have something like the human ability to understand what others are thinking. "It's great for a first test of this ability in birds," says Thomas Bugnyar, a cognitive biologist at the University of Vienna in Austria who was not involved in the work. Scientists still debate about whether even our closest ape relatives can attribute an unseen, mental desire to another; some continue to argue that this is a peculiarly human talent. "But some of us think that some aspects of this ability should be found here and there in different species," Bugnyar says, "and so it is good to have this jay study to compare" with the other studies on primates, humans, and human children. Male Eurasian jays feed their mates during courtship displays, says Ljerka Ostojić, a comparative psychologist and postdoc at the University of Cambridge in the United Kingdom who led the study. Because of that behavior, Ostojić and her colleagues thought that the jays might be good subjects for testing whether these birds understand their mates' desires. The group's previous research had shown that Eurasian jays and scrub jays can plan for the future. "It is commonly thought that any action animals take is determined solely by whatever they want at that moment," Ostojić says, "but the jays also plan for needs in the future." © 2010 American Association for the Advancement of Science
By Erin Wayman The story of the Neandertals may need a new ending, a controversial study suggests. Using improved radiocarbon methods, scientists redated two of the youngest known Neandertal cave sites and concluded that they are at least 10,000 years older than previous studies have found. The findings cast doubt on the reliability of radiocarbon dates from other recent Neandertal sites, the researchers suggest online February 4 in the Proceedings of the National Academy of Sciences. This means the last Neandertals might have died out much earlier than previously thought, which could cause anthropologists to rethink how and why these hominids vanished. Researchers have long debated whether the harsh Ice Age climate, the appearance of modern humans migrating out of Africa, or some other factor drove Neandertals to extinction. “The paper is simply excellent,” says archaeologist Olaf Jöris of the Romano-Germanic Central Museum in Mainz, Germany. The new research supports Jöris’ own review of Neandertal dates, in which he concluded that the most-recent Neandertals probably lived around 42,000 years ago. The standard view suggests that the last of these hominids occupied Europe as recently as about 28,000 years ago. But other archaeologists are not convinced by the new work. “We shouldn’t get too carried away over results that amount to a few radiocarbon dates from two sites,” says Paul Pettitt, an archaeologist at Durham University in England. © Society for Science & the Public 2000 - 2013
Link ID: 17758 - Posted: 02.05.2013
IF TWO animals have identical brain cells, how different can they really be? Extremely. Two worm species have exactly the same set of neurons, but extensive rewiring allows them to lead completely different lives. Ralf Sommer of the Max Planck Institute for Developmental Biology in Tübingen, Germany, and colleagues compared Caenorhabditis elegans, which eats bacteria, with Pristionchus pacificus, which hunts other worms. Both have a cluster of 20 neurons to control their foregut. Sommer found that the clusters were identical. "These species are separated by 200 to 300 million years, but have the same cells," he says. P. pacificus, however, has denser connections than C. elegans, with neural signals passing through many more cells before reaching the muscles (Cell, doi.org/kbh). This suggests that P. pacificus is performing more complex motor functions, says Detlev Arendt of the European Molecular Biology Laboratory in Heidelberg, Germany. Arendt thinks predators were the first animals to evolve complex brains, to find and catch moving prey. He suggests their brains had flexible wiring, enabling them to swap from plant-eating to hunting. © Copyright Reed Business Information Ltd.
by Michael Balter CAMBRIDGE, UNITED KINGDOM—Siberia may not be everyone's idea of a tourist destination, but it has been home to humans for tens of thousands of years. Now a new study of indigenous Siberian peoples presented here earlier this month at a meeting on human evolution reveals how natural selection helped people adapt to the frigid north. The findings also show that different living populations adapted in somewhat different ways. Siberia occupies nearly 10% of Earth's land mass, but today it's home to only about 0.5% of the world's population. This is perhaps not surprising, since January temperatures average as low as -25°C. Geneticists have sampled only a few of the region's nearly one dozen indigenous groups; some, such as the 2000-member Teleuts, descendants of a once powerful group of horse and cattle breeders also known for their skill in making leather goods, are in danger of disappearing. Previous research on cold adaptation included two Siberian populations and implicated a couple of related genes. For example, genes called UCP1 and UCP3 tend to be found in more active forms in populations that live in colder climes, according to work published in 2010 by University of Chicago geneticist Anna Di Rienzo and her colleagues. These genes help the body's fat stores directly produce heat rather than producing chemical energy for muscle movements or brain functions, a process called "nonshivering thermogenesis." The new study sampled Siberians much more intensely, including 10 groups that represent nearly all of the region's native populations. © 2010 American Association for the Advancement of Science