Chapter 6. Evolution of the Brain and Behavior

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Links 21 - 40 of 1896

By Michael Price Anthropologists have waited decades to find the complete cranium of a Miocene ape from Africa—one that lived in the hazy period before the human lineage split off from the common ancestors we share with chimpanzees some 7 million years ago. Now, scientists in Kenya have found their prize at last: an almost perfectly preserved skull roughly the size of a baseball. The catch? It’s from an infant. That means that although it can give scientists a rough idea of what the common ancestor to all living apes and humans would have looked like, drawing other meaningful conclusions could be challenging. “This is the sort of thing that the fossil record loves to do to us,” says James Rossie, a biological anthropologist at the State University of New York in Stony Brook who wasn’t involved with the study. “The problem is that we learn from fossils by comparing them to others. When there are no other infant Miocene ape skulls to which to make those comparisons, your hands are tied.” The remarkably complete skull was discovered in the Turkana Basin of northern Kenya 3 years ago. As the sun sank behind the Napudet Hills west of Lake Turkana, primate paleontologist Isaiah Nengo of De Anza College in Cupertino, California, and his team started walking back to their jeep. Kenyan fossil hunter John Ekusi raced ahead to smoke a cigarette. Suddenly he began circling in place. When Nengo caught up, he saw a dirt-clogged eye socket staring up at him. “There was this skull just sticking out of the ground,” Nengo recalls. “It was incredible because we had been going up and down that path for weeks and never noticed it.” © 2017 American Association for the Advancement of Science.

Keyword: Evolution
Link ID: 23943 - Posted: 08.10.2017

By Karl Gruber Are you good with faces? So is the Japanese rice fish – at least, it is if the faces are the right way up. Just like humans, the tiny fish has no problem recognising faces orientated the usual way, but, again like us, it struggles when they are inverted. The finding indicates that the fish may have developed a unique brain pathway for face recognition, just as humans have. We have no problem identifying most objects in our environment – say, a chair – no matter what way up they are. But faces are different. It is relatively easy for us to spot the differences between two faces, even if they are physically similar, if we see them in photographs the right way up. But if the images are upside down, telling them apart gets a bit tricky. “This is because we have a specific brain area for processing faces, and when the face is upside down, we process the image through object processing pathways, and not the face-processing pathways any more,” says Mu-Yun Wang at the University of Tokyo, Japan. Until now, this face-inversion effect was considered exclusive to mammals as it has only been observed in primates and sheep. Enter the Japanese rice fish, also known as the medaka (Oryzias latipes), a 3.5-centimetre-long shoaling fish commonly found in rice paddies, marshes, ponds and slow-moving streams in East Asia. These fish are very social, so identifying the right individuals to associate with is important. © Copyright New Scientist Ltd.

Keyword: Attention; Evolution
Link ID: 23891 - Posted: 07.28.2017

By Giorgia Guglielmi Tits amazing are birds Japanese. If you didn’t get that, you wouldn’t be alone: Humans figure out the meaning of sentences like this using grammatical rules such as word order. It turns out that Japanese tits, social birds that live in Japan and the Russian Far East, do it too. These wild birds respond to calls they’ve never heard before only if the chirps are in the right order, researchers report today in Current Biology. When a predator threatens the flock, Japanese tits produce something called a “mobbing call,” with the sequence ABC-D. By itself, the ABC part of the call means “danger.” But the D part of the call—similar to the “recruitment call” of a close relative, the willow tit—attracts flock members when there’s something to share, such as food. When the two parts are produced together, Japanese tits flock together to mob the intruder. To find out if the order of the calls mattered, researchers created a song that Japanese tits had never heard before—an artificial sequence made up of the Japanese tit’s ABC alert, followed by the willow tit’s recruitment call, tӓӓ. (You can listen to them, above.) They then played it from a loudspeaker for a flock of nearby tits. When Japanese tits heard the ABC- tӓӓ call, they turned their heads, looking for a predator, as they approached the loudspeaker. But when the artificial sequence was reversed (tӓӓ-ABC), the birds didn’t react. © 2017 American Association for the Advancement of Science.

Keyword: Animal Communication; Language
Link ID: 23889 - Posted: 07.28.2017

Ryan Kellman The modern Planet of the Apes reboot begins with a research chimpanzee being raised in an American home. It's a pretty plausible premise — that exact scenario has played out in the real world many times. On June 26, 1931, for example, Luella and Winthrop Kellogg pulled a baby female chimpanzee away from her mother and brought her to live in their home in Orange Park, Fla. The Kelloggs were comparative psychologists. Their plan was to raise the chimpanzee, Gua, alongside their own infant son, Donald, and see if she picked up human language. According to the book they wrote about the experiment, Luella wasn't initially on board: ... the enthusiasm of one of us met with so much resistance from the other that it appeared likely we could never come to an agreement upon whether or not we should even attempt such an undertaking. But attempt it they did. The Kelloggs performed a slew of tests on Donald and Gua. How good were their reflexes? How many words did they recognize? How did they react to the sound of a gunshot? What sound did each infant's skull make when tapped by a spoon? (Donald's produced "a dull thud" while Gua's made the sound of a "mallet upon a wooden croquet ball.") Chimpanzees develop faster than humans, so Gua outshone Donald when it came to most tasks. She even learned to respond to English phrases like "Don't touch!" and "Get down!" But unlike the apes in the movies, Gua never learned to speak. © 2017 npr

Keyword: Language; Evolution
Link ID: 23871 - Posted: 07.25.2017

By Becca Cudmore A mother rat’s care for her pup reaches all the way into her offspring’s DNA. A young rat that gets licked and groomed a lot early on in life exhibits diminished responses to stress thanks to epigenetic changes in the hippocampus, a brain region that helps transform emotional information into memory. Specifically, maternal solicitude reduces DNA methylation and changes the structure of DNA-packaging proteins, triggering an uptick in the recycling of the neurotransmitter serotonin and the upregulation of the glucocorticoid receptor. These changes make the nurtured rat’s brain quicker to sense and tamp down the production of stress hormones in response to jarring experiences such as unexpected sound and light. That pup will likely grow into a calm adult, and two studies have shown that female rats who exhibit a dampened stress response are more likely to generously lick, groom, and nurse their own young. Caring for pups is one example of what casual observers of behavior might call an animal’s instinct—generally considered to be an innate, genetically encoded phenomenon. But could such epigenetic changes, when encoded as ancestral learning, also be at the root of maternal care and other seemingly instinctual behaviors we see across the animal kingdom? “We don’t have a general theory for the mechanics of instinct as we do for learning, and this is something that has troubled me for a very long time,” says University of Illinois entomologist Gene Robinson. He studies social evolution in the Western honey bee and recently coauthored a perspective piece in Science together with neurobiologist Andrew Barron of Macquarie University in Sydney, Australia, suggesting methylation as a possible mechanism for the transgenerational transmission of instinctual behavior, rather than those behaviors being hardwired in the genome (356:26-27, 2017). Robinson and Barron suggest that instinctual traits, such as honey bees’ well-known waggle dance or a bird’s in-born ability to sing its species’ songs, are the result of traits first learned by their ancestors and inherited across generations by the process of methylation. This differs from classical thoughts on animal learning, which say that if a behavior is learned, it is not innate, and will not be inherited. © 1986-2017 The Scientist

Keyword: Epigenetics; Evolution
Link ID: 23861 - Posted: 07.22.2017

Ashley Yeager DNA might reveal how dogs became man’s best friend. A new study shows that some of the same genes linked to the behavior of extremely social people can also make dogs friendlier. The result, published July 19 in Science Advances, suggests that dogs’ domestication may be the result of just a few genetic changes rather than hundreds or thousands of them. “It is great to see initial genetic evidence supporting the self-domestication hypothesis or ‘survival of the friendliest,’” says evolutionary anthropologist Brian Hare of Duke University, who studies how dogs think and learn. “This is another piece of the puzzle suggesting that humans did not create dogs intentionally, but instead wolves that were friendliest toward humans were at an evolutionary advantage as our two species began to interact.” Not much is known about the underlying genetics of how dogs became domesticated. In 2010, evolutionary geneticist Bridgett vonHoldt of Princeton University and colleagues published a study comparing dogs’ and wolves’ DNA. The biggest genetic differences gave clues to why dogs and wolves don’t look the same. But major differences were also found in WBSCR17, a gene linked to Williams-Beuren syndrome in humans. Williams-Beuren syndrome leads to delayed development, impaired thinking ability and hypersociability. VonHoldt and colleagues wondered if changes to the same gene in dogs would make the animals more social than wolves, and whether that might have influenced dogs’ domestication. © Society for Science & the Public 2000 - 2017.

Keyword: Aggression; Genes & Behavior
Link ID: 23855 - Posted: 07.20.2017

Susan Milius Ravens have passed what may be their toughest tests yet of powers that, at least on a good day, let people and other apes plan ahead. Lab-dwelling common ravens (Corvus corax) in Sweden at least matched the performance of nonhuman apes and young children in peculiar tests of advanced planning ability. The birds faced such challenges as selecting a rock useless at the moment but likely to be useful for working a puzzle box and getting food later. Ravens also reached apelike levels of self-control, picking a tool instead of a ho-hum treat when the tool would eventually allow them to get a fabulous bit of kibble 17 hours later, Mathias Osvath and Can Kabadayi of Lund University in Sweden report in the July 14 Science. “The insight we get from the experiment is that [ravens] can plan for the future outside behaviors observed in the wild,” Markus Böckle, of the University of Cambridge, said in an e-mail. Böckle, who has studied ravens, coauthored a commentary in the same issue of Science. In the wild, ravens cache some of their food, but that apparent foresight could be more of a specific adaptation that evolved with diet instead of as some broader power of planning. The Lund tests, based on experiments with apes, tried to challenge ravens in less natural ways. The researchers say the birds aren’t considered much of a tool-using species in nature, nor do they trade for food. “The study for the first time in any animal shows that future planning can be used in behaviors it was not originally selected for” in evolution, Böckle says. © Society for Science & the Public 2000 - 2017.

Keyword: Intelligence; Evolution
Link ID: 23835 - Posted: 07.14.2017

By Abby Olena For more than 50 years, scientists have taken for granted that all snakes share a ZW sex determination system, in which males have two Z chromosomes and females have one Z and one W. But a study, published today (July 6) in Current Biology, reveals that the Central American boa (Boa imperator) and the Burmese python (Python bivittatus) use an XY sex determination system, which evolved independently in the two species. “This work is a culmination of a lot of questions that we’ve had about pythons and boas for a long time,” says Jenny Marshall Graves, a geneticist at La Trobe Univeristy in Melbourne, Australia, who did not participate in the study. Some of these questions came up for Warren Booth, a geneticist and ecologist at the University of Tulsa, as he studied parthenogenesis—the growth and development of offspring in the absence of fertilization. He noticed a pattern for organisms undergoing parthenogenesis: animal species that use a ZW system have only male (ZZ) offspring, and the organisms that use an XY system have only female (XX) offspring. Except this pattern doesn’t hold true for boas and pythons, who consistently produce female offspring by parthenogenesis. Booth contacted Tony Gamble, a geneticist at Marquette University in Milwaukee, Wisconsin, who studies sex chromosomes, to begin a collaboration to investigate whether boas and pythons might actually have X and Y chromosomes. Spurred by Booth’s questions, “I went back and reread some of the early papers” on snake sex chromosomes, says Gamble. “What became clear is that they didn’t show that boas and pythons had a ZW sex chromosome system. They just said it without any evidence.” © 1986-2017 The Scientist

Keyword: Sexual Behavior; Evolution
Link ID: 23815 - Posted: 07.09.2017

Carl Zimmer With fossils and DNA, scientists are piecing together a picture of humanity’s beginnings, an origin story with more twists than anything you would find at the movie theater. The expert consensus now is that Homo sapiens evolved at least 300,000 years ago in Africa. Only much later — roughly 70,000 years ago — did a small group of Africans establish themselves on other continents, giving rise to other populations of people today. To Johannes Krause, the director of the Max Planck Institute for Human History in Germany, that gap seems peculiar. “Why did people not leave Africa before?” he asked in an interview. After all, he observed, the continent is physically linked to the Near East. “You could have just walked out.” In a study published Tuesday in Nature Communications, Dr. Krause and his colleagues report that Africans did indeed walk out — over 270,000 years ago. Based on newly discovered DNA in fossils, the researchers conclude that a wave of early Homo sapiens, or close relatives of our species, made their way from Africa to Europe. There, they interbred with Neanderthals. Then the ancient African migrants disappeared. But some of their DNA endured in later generations of Neanderthals. “This is now a comprehensive picture,” Dr. Krause said. “It brings everything together.” Since the 1800s, paleontologists have struggled to understand how Neanderthals are related to us. Fossils show that they were anatomically distinct, with a heavy brow, a stout body and a number of subtler features that we lack. The oldest bones of Neanderthal-like individuals, found in a Spanish cave called Sima de los Huesos, date back 430,000 years. More recent Neanderthal remains, dating to about 100,000 years ago, can be found across Europe and all the way to southern Siberia. © 2017 The New York Times Company

Keyword: Evolution
Link ID: 23809 - Posted: 07.06.2017

By Sandrine Ceurstemont Bird or beast? A cuckoo seems to have learned how to mimic the sounds made by the pig-like peccaries it lives alongside, perhaps to ward off predators. The Neomorphus ground cuckoos live in forests in Central and South America, where they often follow herds of wild peccaries so they can feed on the invertebrates that the peccaries disturb as they plough through the leaf litter. Ecologists have noticed that when the cuckoos clap their beaks together they sound a lot like the tooth clacks the peccaries make to deter large predatory cats. To find out whether this is just coincidence or evidence of mimicry, Cibele Biondo at the Federal University of ABC in Brazil and her team analysed the cuckoo and peccary sounds, and compared them with the beak clapping sounds made by roadrunners – close relatives of the ground cuckoos. Logically, the cuckoos should sound most similar to roadrunners, given that the two are closely related. But the analysis suggested otherwise. “The acoustic characteristics are more similar to the teeth clacking of peccaries,” says Biondo. She suspects that cuckoos have something to gain by imitating the peccaries, particularly in the dark, dense forests where predators rely on hearing as much as vision. “Cuckoos may deceive predators by making it appear that peccaries are present when they are not,” says Biondo. © Copyright New Scientist Ltd.

Keyword: Evolution; Animal Communication
Link ID: 23802 - Posted: 07.04.2017

By Michael Price Contrary to popular lore that portrays chimpanzees as having “super strength,” studies have only found modest differences with humans. But our closest relatives are slightly stronger by several measures, and now a study comparing the muscle fibers of different primates reveals a potential explanation: Humans may have traded strength for endurance, allowing us to travel farther for food. To determine why chimpanzees are stronger than humans—at least on a pound-for-pound basis—Matthew O’Neill, an anatomy and evolution researcher at the University of Arizona College of Medicine in Phoenix, and colleagues biopsied the thigh and calf muscles of three chimps housed at the State University of New York at Stony Brook. They dissected the samples into individual fibers and stimulated them to figure out how much force they could generate. Comparing their measurements to known data from humans, the team found that, at the individual fiber level, muscle output was about the same. Given that different fibers throughout the muscle might make a difference, the researchers conducted a more thorough analysis of tissue samples from pelvic and hind limb muscles of three chimpanzee cadavers from various zoos and research institutes around the United States. Previous studies in mammals have found that muscle composition between trunk, forelimb, and hind limb muscles is largely the same, O’Neill says, so he’s confident the samples are representative across most of the chimp’s musculature. The team used a technique called gel electrophoresis to break down the muscles into individual muscle fibers, and compared this breakdown to human muscle fiber data. © 2017 American Association for the Advancement of Science.

Keyword: Muscles; Evolution
Link ID: 23782 - Posted: 06.27.2017

By Michael Price Whether it’s giving to charity or helping a stranger with directions, we often assist others even when there’s no benefit to us or our family members. Signs of such true altruism have been spotted in some animals, but have been difficult to pin down in our closest evolutionary relatives. Now, in a pair of studies, researchers show that chimpanzees will give up a treat in order to help out an unrelated chimp, and that chimps in the wild go out on risky patrols in order to protect even nonkin at home. The work may give clues to how such cooperation—the foundation of human civilization—evolved in humans. “Both studies provide powerful evidence for forms of cooperation in our closest relatives that have been difficult to demonstrate in other animals besides humans,” says Brian Hare, an evolutionary anthropologist at Duke University in Durham, North Carolina, who was not involved with the research. In the first study, psychologists Martin Schmelz and Sebastian Grüneisen at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, trained six chimps at the Leipzig Zoo to play a sharing game. Each chimp was paired with a partner who was given a choice of four ropes to pull, each with a different outcome: give just herself a banana pellet; give just the subject a pellet; give both of them pellets; or forgo her turn and let her partner make the decision instead. © 2017 American Association for the Advancement of Science.

Keyword: Evolution
Link ID: 23753 - Posted: 06.20.2017

Ian Sample Science editor Fossils recovered from an old mine on a desolate mountain in Morocco have rocked one of the most enduring foundations of the human story: that Homo sapiens arose in a cradle of humankind in East Africa 200,000 years ago. Archaeologists unearthed the bones of at least five people at Jebel Irhoud, a former barite mine 100km west of Marrakesh, in excavations that lasted years. They knew the remains were old, but were stunned when dating tests revealed that a tooth and stone tools found with the bones were about 300,000 years old. Why we're closer than ever to a timeline for human evolution Read more “My reaction was a big ‘wow’,” said Jean-Jacques Hublin, a senior scientist on the team at the Max Planck Institute for Evolutionary Anthropology in Leipzig. “I was expecting them to be old, but not that old.” Hublin said the extreme age of the bones makes them the oldest known specimens of modern humans and poses a major challenge to the idea that the earliest members of our species evolved in a “Garden of Eden” in East Africa one hundred thousand years later. “This gives us a completely different picture of the evolution of our species. It goes much further back in time, but also the very process of evolution is different to what we thought,” Hublin told the Guardian. “It looks like our species was already present probably all over Africa by 300,000 years ago. If there was a Garden of Eden, it might have been the size of the continent.” © 2017 Guardian News and Media Limited

Keyword: Evolution
Link ID: 23723 - Posted: 06.08.2017

By Katie Langin No one likes a con artist. People avoid dealing with characters who have swindled them in the past, and—according to new research—birds avoid those people, too. Ravens, known more for their intelligence, but only slightly less for their love of cheese, were trained by researchers to trade a crust of bread for a morsel of cheese with human partners. When the birds then tried to broker a trade with “fair” and “unfair” partners—some completed the trade as expected, but others took the raven’s bread and kept (and ate) the cheese—the ravens avoided the tricksters in separate trials a month later. This suggests that ravens can not only differentiate between “fair” and “unfair” individuals, but they retain that ability for at least a month, the researchers write this month in Animal Behavior. Ravens have a complex social life involving friendships and rivalries. Their ability to recognize and punish dishonest individuals, even after a single encounter, may help explain how cooperation evolved in this group of birds. For people, though, the moral of the story is simple: Be nice to ravens. © 2017 American Association for the Advancement of Science.

Keyword: Intelligence; Evolution
Link ID: 23709 - Posted: 06.06.2017

By EMILIE LE BEAU LUCCHESI Benjamin Stepp, an Iraq war veteran, sat in his graduate school course trying to focus on the lecture. Neither his classmates nor his professor knew he was silently seething. But his service dog, Arleigh, did. She sensed his agitation and “put herself in my lap,” said Mr. Stepp, 37, of Holly Springs, Miss. “I realized I needed to get out of class. We went outside, I calmed down. We breathed.” During his two deployments to Iraq, Mr. Stepp endured a traumatic brain injury and multiple surgeries on his ankle, and most days he suffers excruciating pain in his legs and lower back. He says he also returned from the war with a lot of anger, which wells up at unexpected times. “Anger kept us alive overseas,” Mr. Stepp said. “You learn that anger keeps you alive.” Now that he is back, though, that anger no longer serves a useful purpose. And Arleigh, a lab and retriever mix who came to Mr. Stepp from K9s For Warriors, a nonprofit organization that trains service dogs, has been helping him to manage it. The dog senses when his agitation and anxiety begin rising, and sends him signals to begin the controlled breathing and other exercises that help to calm him down. Pet owners and trainers have long been aware of a dog’s ability to sense a human’s emotions. In the last 10 years, researchers, too, have begun to explore more deeply the web of emotions, both positive and negative, that can spread between people and animals, said Natalia Albuquerque, an ethologist who studies animal cognition at the University of São Paulo in Brazil and the University of Lincoln in England. The spread of emotions between animals and people, or between animals — what researchers refer to as emotional contagion — is an emerging field of science. But “there are still many unanswered questions we need to address,” Ms. Albuquerque said. © 2017 The New York Times Company

Keyword: Emotions; Evolution
Link ID: 23708 - Posted: 06.05.2017

By Julie Hecht I have been scaring dog lovers for nearly a decade, and Tamas Farago—lead researcher behind a new study on dog growls and cross-species communication—is mostly to blame. I met Farago in 2010 when visiting his research group—the Family Dog Project at Eotvos Lorand University—to conduct my Masters research. By then, Farago was already immersed in the study of dog vocalizations—particularly their barks and growls—so when my study concluded and it was time to leave Budapest, I departed with not only a deep appreciation for paprika and palinka, but also a few audio clips of dogs growling, courtesy of Farago. Since then, whenever I give a talk about canine science, audience members are sure to chuckle, their faces brightening, as recordings of a dog’s breathy, garbled, fast-paced, play growls take over the room. But when I play the low, elongated aggressive growls corresponding to a dog being approached by a threatening stranger or a dog guarding food, even my hair will often stand up. These growls mean business. If a dog happens to be attending the talk—not that I hold lectures for dogs, but if a human brought their dog—I take note before playing the growls. This is because a 2010 study by Farago and colleagues found that dogs not only listen to growls, but extract meaningful information from them. Here’s how they figured this out: In the study, dogs entered a room where they came across a bone. Fine. Normal so far. Just a bone sitting all alone. But unbeknownst to the dogs, a speaker was concealed in a covered crate sitting just behind the bone, and as the dogs approached, one of three growls was played from the speaker (food guarding, threatening stranger, or play). Excellent work sneaky researchers! © 2017 Scientific American

Keyword: Animal Communication; Language
Link ID: 23672 - Posted: 05.29.2017

By STEPH YIN A female and male get together. One thing leads to another, and they have sex. His sperm fuses with her egg, half of his DNA combining with half of her DNA to form an embryo. As humans, this is how we tend to think of reproduction. But there are many other bizarre ways reproduction can take place. For instance, scientists have discovered a fish carrying genes only from its father in the nucleus of its cells. Found in a type of fish called Squalius alburnoides, which normally inhabits rivers in Portugal or Spain, this is the first documented instance in vertebrates of a father producing a near clone of itself through sexual reproduction — a rare phenomenon called androgenesis — the researchers reported in the journal Royal Society Open Science on Wednesday. The possibility of androgenesis is just one of many mysteries about Squalius alburnoides. It’s not a species in the usual sense, but rather something called a hybrid complex, a group of organisms with multiple parental combinations that can mate with one another. The group is thought to have arisen from hybridization between females of one species, Squalius pyrenaicus, and males of another species, now extinct, that belonged to a group of fish called Anaecypris. To sustain its population, Squalius alburnoides mates with several other closely related species belonging to the Squalius lineage. That it can reproduce at all is unusual enough. Most hybrids, like mules, are sterile because the chromosomes from their parents of different species have trouble combining, swapping DNA and dividing — steps required for egg or sperm production. Squalius alburnoides males circumvent this problem by producing sperm cells that do not divide, and therefore contain more than one chromosome set. This is important because most animals, Squalius alburnoides included, need at least two chromosome sets to survive. © 2017 The New York Times Company

Keyword: Sexual Behavior; Evolution
Link ID: 23669 - Posted: 05.27.2017

By Virginia Morell Baby marmosets learn to make their calls by trying to repeat their parents’ vocalizations, scientists report today in Current Biology. Humans were thought to be the only primate with vocal learning—the ability to hear a sound and repeat it, considered essential for speech. When our infants babble, they make apparently random sounds, which adults respond to with words or other sounds; the more this happens, the faster the baby learns to talk. To find out whether marmosets (Callithrix jacchus, pictured) do something similar, scientists played recordings of parental calls during a daily 30-minute session to three sets of newborn marmoset twins until they were 2 months old (roughly equivalent to a 2-year-old human). Baby marmosets make noisy guttural cries; adults respond with soft “phee” contact calls (listen to their calls below). The baby that consistently heard its parents respond to its cries learned to make the adult “phee” sound much faster than did its twin, the team found. It’s not yet known if this ability is limited to the marmosets; if so, the difference may be due to the highly social lives of these animals, where, like us, multiple relatives help care for babies. © 2017 American Association for the Advancement of Science

Keyword: Language; Animal Communication
Link ID: 23662 - Posted: 05.26.2017

James Gorman Darwin’s finches, those little birds in the Galápagos with beaks of different sizes and shapes, were instrumental in the development of the theory of evolution. Similar birds had large and small beaks and beaks in between, all related to what kinds of insects and seeds they ate. From one ancestor, it seemed, different adaptations to the environment had evolved, giving the birds that adapted a survival edge in a particular ecological niche — evolution by natural selection. Biologists who came later went on to identify the genetic changes that had produced different beak shapes. Now another group of finch-like birds has provided a similar example, but of a different kind of evolution, one driven not by the demands of the environment, but by the demands of female birds. Their preferences in color and pattern caused the evolution of different species of seedeater, all with the same behavior and diet, but with males that look different. That’s a process called sexual selection, which Darwin also wrote about. Leonardo Campagna, a researcher at Cornell University and the Cornell Lab of Ornithology, and a group of scientists from the United States and South America investigated nine species of southern capuchino seedeaters, doing full genomes for each one and reported their findings in Science Advances. They found that the DNA of all the species is remarkably similar, as are the birds. All the females look alike and all of the species feed on grass seeds plucked from grass stalks of living plants. Only the males are different. They have a wide variety of colorations and their courting songs are also distinct. Dr. Campagna and the other researchers found that differences between species DNA were all minimal, ranging from as little as 0.03 percent to as great as 0.3 percent. All the species showed variation in the same area, DNA that appeared to have a role in regulating genes for the pigment melanin. © 2017 The New York Times Company

Keyword: Evolution; Sexual Behavior
Link ID: 23660 - Posted: 05.25.2017

Tina Hesman Saey Face-to-face, a human and a chimpanzee are easy to tell apart. The two species share a common primate ancestor, but over millions of years, their characteristics have morphed into easily distinguishable features. Chimps developed prominent brow ridges, flat noses, low-crowned heads and protruding muzzles. Human noses jut from relatively flat faces under high-domed crowns. Those facial features diverged with the help of genetic parasites, mobile bits of genetic material that insert themselves into their hosts’ DNA. These parasites go by many names, including “jumping genes,” “transposable elements” and “transposons.” Some are relics of former viruses assimilated into a host’s genome, or genetic instruction book. Others are self-perpetuating pieces of genetic material whose origins are shrouded in the mists of time. “Transposable elements have been with us since the beginning of evolution. Bacteria have transposable elements,” says evolutionary biologist Josefa González. She doesn’t think of transposons as foreign DNA. They are parts of our genomes — like genes. “You cannot understand the genome without understanding what transposable elements are doing,” says González, of the Institute of Evolutionary Biology in Barcelona. She studies how jumping genes have influenced fruit fly evolution. Genomes of most organisms are littered with the carcasses of transposons, says Cédric Feschotte, an evolutionary geneticist at the University of Utah in Salt Lake City. Fossils of the DNA parasites build up like the remains of ancient algae that formed the white cliffs of Dover. One strain of maize, the organism in which Nobel laureate Barbara McClintock first discovered transposable elements in the 1940s, is nearly 85 percent transposable elements (SN: 12/19/09, p. 9). Corn is an extreme example, but humans have plenty, too: Transposable elements make up nearly half of the human genome. |© Society for Science & the Public 2000 - 2017

Keyword: Development of the Brain; Genes & Behavior
Link ID: 23627 - Posted: 05.17.2017