Chapter 6. Evolution of the Brain and Behavior

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Links 1 - 20 of 2043

By Joshua Sokol For half the year, a little brown bird on the northernmost islands of the Galápagos uses its wickedly sharp beak to pick at seeds, nectar and insects. But when the climate dries out, it drinks blood. Yes, there is such a thing as a vampire finch. Yes, it is what it sounds like. Galápagos finches have been used since Darwin’s time to illustrate evolution in action. Even among them, Geospiza septentrionalis is an outlier, one of the few birds in the world to intentionally draw and drink blood. And the species is only found on Wolf and Darwin islands, two of the most remote and off-limits places in the entire archipelago. The vampire finch has a method. First, one bird hops on the back of a resting Nazca booby, pecks at the base of the seabird’s wing, and drinks. Blood stains the booby’s white feathers. Other finches crowd around to wait their turn, or to watch and learn. Because adult boobies can fly away, the attacks are almost never fatal. The only casualties are chicks that flee from the finches on foot and, unable to find their way back, starve. Drinking blood is an unusual diet, and research published last year showed that vampire finches have evolved specialized bacteria in their guts to aid digestion. Even more surprising, according to a paper this week in the journal Philosophical Transactions of the Royal Society B, is that some of these bacteria are similar to ones found in the vampire bats of Central and South America. Se Jin Song, a biologist at the University of California San Diego and the study’s lead author, had previously studied the convergent evolution of gut bacteria. Do disparate animals with the equivalent of fad diets — eating only ants and termites, for instance — develop similar gut microbiota over evolutionary time? © 2019 The New York Times Company

Keyword: Evolution; Obesity
Link ID: 26312 - Posted: 06.10.2019

Nell Greenfieldboyce At the Marine Biological Laboratory in Woods Hole, Mass., there's a room filled with burbling aquariums. A lot of them have lids weighed down with big rocks. "Octopuses are notorious for being able to, kind of, escape out of their enclosures," says Bret Grasse, whose official title at MBL is "manager of cephalopod operations" — cephalopods being squid, cuttlefish and octopuses. He's part of a team that's trying to figure out the best ways to raise these sea creatures in captivity, so that scientists can investigate their genes and learn the secrets of their strange, almost alien ways. For decades, much of the basic research in biology has focused on just a few, well-studied model organisms like mice, fruit flies, worms and zebrafish. That's because these critters are easy to keep in the laboratory, and scientists have worked out how to routinely alter their genes, leading to all kinds of insights into behavior, diseases and possible treatments. "With these organisms, you could understand what genes did by manipulating them," says Josh Rosenthal, another biologist at MBL. "And that really became an indispensable part of biology." But it's also meant that basic biology has ignored much of the animal kingdom, especially its more exotic denizens. "We're really missing out on, I would say, the diversity of biology's solutions to problems," Rosenthal notes. © 2019 npr

Keyword: Learning & Memory; Evolution
Link ID: 26295 - Posted: 06.04.2019

By Gian Gastone Mascetti One of the most striking features of living organisms, both animals and plants, is the way their physiology and behavior have adapted to follow the fluctuations of daily light and nocturnal darkness. A clock in the brain synchronized to environmental cues generates biological changes that vary over a 24-hour cycle—circadian rhythms (from the Latin words circa and diem, meaning “about” and “a day,” respectively). In this way, the earth’s rotation is reproduced in the dynamics of our neuronal circuits. The sleep-wakefulness cycle is a typical circadian rhythm. Wakefulness is characterized by sensory activity and movement; during sleep the senses lose touch with their surroundings, and movements subside. This periodic loss of consciousness appears on electroencephalogram (EEG) recordings as a clear signature: deep sleep consists of slow oscillations of high amplitude. Wakefulness, in contrast, is made up of fast, low-amplitude oscillations. Much about sleep remains a mystery, however. Why would an animal shut down basic sensory and motor activity for hours on end, leaving itself a target for predators? This question becomes more acute in aquatic mammals, which need to regulate breathing and body temperature while they sleep. Remarkably, some animals have solved this problem by developing the ability to sleep with one half their brain while remaining vigilant with the other—a behavior known as unihemispheric slow-wave sleep (USWS). Still others engage in USWS under some circumstances but put both hemispheres to bed when necessary. Marine mammals, bird species and possibly reptiles enter a half-on/half-off state, sometimes keeping one eye open during these intervals. Recently researchers have even discovered a vestigial form of unihemispheric sleep in humans. © 2019 Scientific American

Keyword: Sleep; Laterality
Link ID: 26290 - Posted: 06.03.2019

Carolyn Wilke Here’s a downer: Pessimism seems contagious among ravens. But positivity? Not so much. When ravens saw fellow birds’ responses to a disliked food, but not the food itself, their interest in their own food options waned, researchers report May 20 in the Proceedings of the National Academy of Sciences. The study suggests that the birds pick up on and even share negative emotions, the researchers say. Ravens are “very good problem solvers … but this paper’s really highlighting their social intelligence as well,” says Andrew Gallup, a psychologist at SUNY Polytechnic Institute in Utica, N.Y., who was not involved in the study. The work paints a richer picture of how the birds’ brains work, he says. Known for their smarts, ravens act in ways that suggest a capacity for empathy, such as by appearing to console a distressed comrade. Thomas Bugnyar, a cognitive ethologist at the University of Vienna, and his colleagues wanted to look into one building block of empathy — whether animals share emotions. To be able to feel for others, an animal needs to be able to feel like others, he says. But sizing up an animal’s mood is tricky. Scientists generally rely on behavioral or physiological cues to clue into a creature’s emotional state. More challenging is assessing how one animal’s mood might influence another’s: Similar actions appearing to stem from kindred emotions may just be mimicry. |© Society for Science & the Public 2000 - 2019

Keyword: Emotions; Evolution
Link ID: 26259 - Posted: 05.22.2019

Ian Sample Science editor Male bonobos living with their mothers are three times more likely to father offspring, research suggests. Their mothers are so keen for them to father children that they usher them in front of promising partners, shield them from violent competitors and dash the chances of other males by charging them while they are at it. For a bonobo mother, it is all part of the parenting day, and analysis finds the hard work pays off. Males of the species that live with their mothers are three times more likely to father offspring than those whose mothers are absent. Martin Surbeck, a primatologist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, said: “We wanted to see if the mothers’ behaviour changes the odds of their sons’ success, and it does. The mothers have a strong influence on the number of grandchildren they get.” Bonobo mothers seize every opportunity to give their sons a leg-up. In bonobo society, the lower ranks tend to be gender balanced, but females dominate the top ranks. Many mothers have social clout and chaperone their sons to huddles with fertile females, ensuring them better chances to mate. “The mothers tend to be a social passport for their sons,” said Surbeck. © 2019 Guardian News & Media Limited

Keyword: Sexual Behavior; Evolution
Link ID: 26256 - Posted: 05.21.2019

By John Horgan In a previous post I summarized my remarks at “Souls or Selfish Genes,” a conversation at Stevens Institute of Technology about religious versus scientific views of humanity. I represented the agnostic position and David Lahti, a biologist and philosopher at the City University of New York, a position more friendly to theism. Below is Lahti’s summary of his opening comments. –John Horgan I’ve been asked to deal with the question of “Souls vs. Selfish Genes”. And whereas I am sure this is a false dichotomy, I’m not quite sure how exactly to fit the two parts of the truth together. But I’ll give you a few thoughts I’ve had about it, which can at least start us off. First, selfish genes. This of course is a reference to Richard Dawkins’ 1976 book of the same name, which is a popular and sensational description of a revolution in our understanding of the way evolution by natural selection operates. Briefly, we discovered in the 1960s-70s that the organismic individual was generally the most important level at which natural selection operates, meaning that evolution by natural selection proceeds primarily via certain individuals in a population reproducing more successfully than others. In fact, this is too simplistic. Hamilton’s theory of kin selection showed that it’s actually below the level of the individual where we really have to concentrate in order to explain certain traits, such as the self-sacrificial stinging of bees and the fact that some young male birds help their mother raise her next brood instead of looking for a mate. Those individuals are not being as selfish as we might predict. © 2019 Scientific American

Keyword: Consciousness; Genes & Behavior
Link ID: 26250 - Posted: 05.20.2019

Bruce Bower People and Neandertals separated from a common ancestor more than 800,000 years ago — much earlier than many researchers had thought. That conclusion, published online May 15 in Science Advances, stems from an analysis of early fossilized Neandertal teeth found at a Spanish site called Sima de los Huesos. During hominid evolution, tooth crowns changed in size and shape at a steady rate, says Aida Gómez-Robles, a paleoanthropologist at University College London. The Neandertal teeth, which date to around 430,000 years ago, could have evolved their distinctive shapes at a pace typical of other hominids only if Neandertals originated between 800,000 and 1.2 million years ago, she finds. Gómez-Robles’ study indicates that, if a common ancestor of present-day humans and Neandertals existed after around 1 million years ago, “there wasn’t enough time for Neandertal teeth to change at the rate [teeth] do in other parts of the human family tree” in order to end up looking like the Spanish finds, says palaeoanthropologist Bernard Wood of George Washington University in Washington, D.C. Many researchers have presumed that a species dubbed Homo heidelbergensis, thought to have inhabited Africa and Europe, originated around 700,000 years ago and gave rise to an ancestor of both Neandertals and Homo sapiens by roughly 400,000 years ago. Genetic evidence that Sima de los Huesos fossils came from Neandertals raised suspicions that a common ancestor with H. sapiens existed well before that (SN Online: 3/14/16). Recent Neandertal DNA studies place that common ancestor at between 550,000 and 765,000 years old. But those results rest on contested estimates of how fast and how consistently genetic changes accumulated over time. |© Society for Science & the Public 2000 - 2019.

Keyword: Evolution
Link ID: 26239 - Posted: 05.17.2019

Mitchel Daniel If you’re looking for love, it pays to stand out from the crowd. Or at least that’s how it works in some parts of the animal kingdom. Scientists have found that in several species – green swordtail fish, Trinidadian guppies, fruit flies, Poecilia parae fish – ladies overwhelmingly go for the guy that looks different from the rest. But the reason for this attraction to novelty has remained a mystery. So my colleagues and I used the Trinidadian guppy to investigate the psychology behind why many females have an affinity for the unusual. Male features that attract females The guppy has long been a workhorse for biologists like me who are interested in understanding the mating decisions that animals make and the evolutionary forces behind those decisions. Male guppies attempt to woo females using courtship dances that show off the elaborate color patterns adorning their bodies. The females of the species are color pattern connoisseurs, carefully choosing among their suitors based, in large part, on their visual appeal. This tendency has made the guppy an excellent model for studying mate choice. Male guppies showcase their colors during their courtship dances. Many types of animals exhibit what evolutionary biologists call directional preferences, an attraction to more of a certain thing – think bigger antlers, a longer tail or brighter color spots. And there are evolutionary theories that help make sense of these preferences. If a male can grow more extreme features, that can be a sign that he is in good physical condition, has good genes, or would make a good parent. What’s less clear, though, is why females should value unusualness in a mate. © 2010–2019,

Keyword: Sexual Behavior; Evolution
Link ID: 26233 - Posted: 05.15.2019

By Cara Giaimo Here’s a pop quiz for you. Tom is taller than Dick. Dick is taller than Harry. Who’s taller, Harry or Tom? If you said Tom, congratulations! You just demonstrated what’s called “transitive inference” — the ability to compare things indirectly, based on previous juxtapositions. But before you pat yourself on the back too much, you should know that this skill was recently demonstrated by another creature: the humble paper wasp that might be living in your backyard right now. In the summer of 2017, researchers at the University of Michigan put two species of paper wasps through a transitive inference test. A statistically significant portion of the time, the wasps passed. Other animals — including rats, geese and cichlid fish — have also exhibited this capacity. But this study, which was published Tuesday in Biology Letters, is the first to successfully showcase it in an invertebrate (honeybees failed a similar test in 2004). Paper wasps are found on every continent except Antarctica. You might be near some right now. “They tend to nest in the eaves of houses, or inside barbecue grills,” said Elizabeth Tibbetts, the study’s lead author. In a previous study, Dr. Tibbetts showed that individual female wasps can identify one another by their distinct facial patterns, which resemble Rorschach ink blots. “When two wasps meet, they learn, ‘Oh, that’s what Suzy looks like,’” she said. “And the next time they meet, they remember who Suzy is.” In the spring, the females spend a lot of time brawling, getting in each other’s faces and trading slaps with their appendages. These matchups look like schoolyard tussles. “Some wasps will be fighting; some wasps will be watching the fights,” said Dr. Tibbetts. “It’s a very exciting time.” The wasps remember the winners and losers, and use them to establish a social hierarchy: the strongest reproduce, while the weaker ones do all the work. © 2019 The New York Times Company

Keyword: Evolution; Learning & Memory
Link ID: 26229 - Posted: 05.11.2019

By David Grimm CORVALLIS, OREGON—Carl the cat was born to beat the odds. Abandoned on the side of the road in a Rubbermaid container, the scrawny black kitten—with white paws, white chest, and a white, skunklike stripe down his nose—was rescued by Kristyn Vitale, a postdoc at Oregon State University here who just happens to study the feline mind. Now, Vitale hopes Carl will pull off another coup, by performing a feat of social smarts researchers once thought was impossible. In a stark white laboratory room, Vitale sits against the back wall, flanked by two overturned cardboard bowls. An undergraduate research assistant kneels a couple of meters away, holding Carl firmly. "Carl!" Vitale calls, and then points to one of the bowls. The assistant lets go. Toddlers pass this test easily. They know that when we point at something, we're telling them to look at it—an insight into the intentions of others that will become essential as children learn to interact with people around them. Most other animals, including our closest living relative, chimpanzees, fail the experiment. But about 20 years ago, researchers discovered something surprising: Dogs pass the test with flying colors. The finding shook the scientific community and led to an explosion of studies into the canine mind. Cats like Carl were supposed to be a contrast. Like dogs, cats have lived with us in close quarters for thousands of years. But unlike our canine pals, cats descend from antisocial ancestors, and humans have spent far less time aggressively molding them into companions. So researchers thought cats couldn't possibly share our brain waves the way dogs do. © 2019 American Association for the Advancement of Science

Keyword: Learning & Memory; Evolution
Link ID: 26226 - Posted: 05.10.2019

Matthew Warren Scientists have uncovered the most complete remains yet from the mysterious ancient-hominin group known as the Denisovans. The jawbone, discovered high on the Tibetan Plateau and dated to more than 160,000 years ago, is also the first Denisovan specimen found outside the Siberian cave in which the hominin was uncovered a decade ago — confirming suspicions that Denisovans were more widespread than the fossil record currently suggests. The research marks the first time an ancient human has been identified solely through the analysis of proteins. With no usable DNA, scientists examined proteins in the specimen’s teeth, raising hopes that more fossils could be identified even when DNA is not preserved. “This is fantastic work,” says Katerina Douka, an archaeologist at the Max Planck Institute for the Science of Human History in Jena, Germany, who runs a separate project aiming to uncover Denisovan fossils in Asia. “It tells us that we are looking at the right area.” Until now, everything scientists have learnt about Denisovans has come from a handful of teeth and bone fragments from Denisova Cave in Russia’s Altai Mountains. DNA from these remains revealed that the Denisovans were a sister group to Neanderthals, both descending from a population that split away from modern humans about 550,00–765,000 years ago. And at Denisova Cave, the two groups seem to have met and interbred: a bone fragment described last year belonged an ancient-human hybrid individual who had a Denisovan father and Neanderthal mother.

Keyword: Evolution
Link ID: 26198 - Posted: 05.02.2019

By Sam Roberts Ralph Solecki, an archaeologist whose research helped debunk the view of Neanderthals as heartless and brutish half-wits and inspired a popular series of novels about prehistoric life, died on March 20 in Livingston, N.J. He was 101. The cause was pneumonia, his son William said. Starting in the mid-1950s, leading teams from Columbia University, Dr. Solecki discovered the fossilized skeletons of eight adult and two infant Neanderthals who had lived tens of thousands of years ago in what is now northern Iraq. Dr. Solecki, who was also a Smithsonian Institution anthropologist at the time, said physical evidence at Shanidar Cave, where the skeletons were found, suggested that Neanderthals had tended to the weak and the wounded, and that they had also buried their dead with flowers, which were placed ornamentally and possibly selected for their therapeutic benefits. The exhumed bones of a man, named Shanidar 3, who had been blind in one eye and missing his right arm but who had survived for years after he was hurt, indicated that fellow Neanderthals had helped provide him with sustenance and other support. “Although the body was archaic, the spirit was modern,” Dr. Solecki wrote in the magazine Science in 1975. Large amounts of pollen found in the soil at a grave site suggested that bodies might have been ceremonially entombed with bluebonnet, hollyhock, grape hyacinth and other flowers — a theory that is still being explored and amplified. (Some researchers hypothesized that the pollen might have been carried by rodents or bees, but Dr. Solecki’s theory has become widely accepted.) “The association of flowers with Neanderthals adds a whole new dimension to our knowledge of his humanness, indicating he had a ‘soul,’ ” Dr. Solecki wrote. © 2019 The New York Times Company

Keyword: Evolution
Link ID: 26131 - Posted: 04.12.2019

By Carl Zimmer In a cave in the Philippines, scientists have discovered a new branch of the human family tree. At least 50,000 years ago, an extinct human species lived on what is now the island of Luzon, researchers reported on Wednesday. It’s possible that Homo luzonensis, as they’re calling the species, stood less than three feet tall. The discovery adds growing complexity to the story of human evolution. It was not a simple march forward, as it once seemed. Instead, our lineage assumed an exuberant burst of strange forms along the way. Our species, Homo sapiens, now inhabits a comparatively lonely world. “The more fossils that people pull out of the ground, the more we realize that the variation that was present in the past far exceeds what we see in us today,” said Matthew Tocheri, a paleoanthropologist at Lakehead University in Canada, who was not involved in the new discovery. In the early 2000s, Armand Salvador Mijares, a graduate student at the University of the Philippines, was digging at Callao Cave, on Luzon, for traces of the first farmers on the Philippines. Soon, he decided to dig a little deeper. Researchers on the Indonesian island of Flores had discovered the bones of an extraordinary humanlike species about 60,000 years old. The scientists named it Homo floresiensis. Some features were similar to ours, but in other ways Homo floresiensis more closely resembled other hominins (the term scientists use for modern humans and other species in our lineage). © 2019 The New York Times Company

Keyword: Evolution
Link ID: 26126 - Posted: 04.11.2019

/ By Richard Kemeny Northern Ethiopia was once home to a vast, ancient lake. Saber-toothed cats prowled around it, giant crocodiles swam within. The streams and rivers that fed it — over 3 million years ago, during the Pliocene — left behind trails of sediment that have now hardened into sandstone. Deposited within these layers are fossils: some of early hominins, along with the bones of hippos, antelope, and elephants. Anthropologist Jessica Thompson encountered two of these specimens, from an area named Dikika, in 2010. At the time, she was a visiting researcher at the Institute of Human Origins at Arizona State University. Given no explanation as to their history, she analyzed the bones and found signs of butchery. Percussion marks suggested someone may have accessed the marrow; cut marks hinted that flesh was stripped from bone. To her surprise, the specimens were 3.4 million years old, putting the butcher’s behaviors back 800,000 years earlier than conventional estimates would suggest. That fact got Thompson, now an assistant professor in the Department of Anthropology at Yale University, thinking there might be more traces of tool use from those early times. In a wide-ranging review published in February’s issue of Current Anthropology, Thompson joins a team of researchers to weave together several strands of recent evidence and propose a new theory about the transition to large animal consumption by our ancestors. The prevailing view, supported by a confluence of fossil evidence from sites in Ethiopia, is that the emergence of flaked tool use and meat consumption led to the cerebral expansion that kickstarted human evolution more than 2 million years ago. Thompson and her colleagues disagree: Rather than using sharpened stones to hunt and scrape meat from animals, they suggest, earlier hominins may have first bashed bones to harvest fatty nutrients from marrow and brains. Copyright 2019 Undark

Keyword: Evolution
Link ID: 26107 - Posted: 04.03.2019

By Veronique Greenwood The sun bears were making faces at each other. And that was a bit of a surprise. Comparative psychologists have been studying the facial expressions of primates like orangutans and gorillas for years. They have evolved in complex societies and thus need to be able to convey their joy, anger, and other emotions to their companions. But nobody had thought to look at creatures like sun bears, who live mostly solitary lives. Marina Davila-Ross, a primatologist at the University of Portsmouth in England, and her colleagues learned that a handful of the Southeast Asian bears, which primarily live alone in the wild, were in a rehabilitation center near the orangutan center in Malaysia where Dr. Davila-Ross was doing research. Curious about whether facial communication was more common in the animal kingdom that people thought, they deployed cameras to capture hours of footage of the bears interacting with each other. In a study published Thursday in Scientific Reports, they say that sun bears do use facial expressions to communicate, suggesting that the capacity to do so may be widespread, and that social creatures do not have a monopoly on expressing themselves this way. Sun bears are exceedingly solitary. A female’s one or two cubs will live with her for about two years, and then set off for lives on their own. Adults seem to rarely meet, except for mating. At the center, bears that cannot be released back into the wild live in enclosures in groups of five or six. For the bears, it was an unnatural setup — but it was perfect for the scientists. In their footage of 22 bears going about their daily lives, the scientists zeroed in on moments when the animals were playing, batting at each other and grappling good-humoredly. They watched for moments where the playing bears were looking into each other’s faces, and then they looked for certain facial expressions, like opening one’s mouth wide and showing teeth. © 2019 The New York Times Company

Keyword: Emotions; Evolution
Link ID: 26067 - Posted: 03.23.2019

Terry Gross When Frans de Waal started studying nonhuman primates, in the Netherlands more than 40 years ago, he was told not to consider the emotions of the animals he was observing. "Thoughts and feelings — the mental processes basically — were off limits," he says. "We were told not to talk about them, because they were considered by many scientists as 'inner states' and you only were allowed to talk about 'outer states.' " But over the course of his career, de Waal became convinced that primates and other animals express emotions similar to human emotions. He's now the director of the Living Links Center at the Yerkes National Primate Research Center in Atlanta, where his office window looks out on a colony of chimps. "I am now at the point that I think emotions are more like organs," he says. "All my organs are present in a rat's body, and the same way, I think, all my emotions are probably present in the rat." De Waal writes about primate empathy, rivalry, bonding, sex and murder in his new book, Mama's Last Hug. The title of the book was inspired by a tender interaction between a dying 59-year-old chimp named Mama and de Waal's mentor, Jan van Hooff, who had known Mama for more than 40 years. "People were surprised [by] how humanlike the expression of Mama was and how humanlike her gestures were," de Waal says of the interaction. "I thought, 'Well, everyone knows that chimps are our closest relative, so why wouldn't the way they express their emotions be extremely similar to ours?' But people were surprised by that." © 2019 npr

Keyword: Emotions; Evolution
Link ID: 26054 - Posted: 03.20.2019

Bruce Bower Humankind’s gift of gab is not set in stone, and farming could help to explain why. Over the last 6,000 years or so, farming societies increasingly have substituted processed dairy and grain products for tougher-to-chew game meat and wild plants common in hunter-gatherer diets. Switching to those diets of softer, processed foods altered people’s jaw structure over time, rendering certain sounds like “f” and “v” easier to utter, and changing languages worldwide, scientists contend. People who regularly chew tough foods such as game meat experience a jaw shift that removes a slight overbite from childhood. But individuals who grow up eating softer foods retain that overbite into adulthood, say comparative linguist Damián Blasi of the University of Zurich and his colleagues. Computer simulations suggest that adults with an overbite are better able to produce certain sounds that require touching the lower lip to the upper teeth, the researchers report in the March 15 Science. Linguists classify those speech sounds, found in about half of the world’s languages, as labiodentals. And when Blasi and his team reconstructed language change over time among Indo-European tongues (SN: 11/25/17, p. 16), currently spoken from Iceland to India, the researchers found that the likelihood of using labiodentals in those languages rose substantially over the past 6,000 to 7,000 years. That was especially true when foods such as milled grains and dairy products started appearing (SN: 2/1/03, p. 67). “Labiodental sounds emerged recently in our species, and appear more frequently in populations with long traditions of eating soft foods,” Blasi said at a March 12 telephone news conference. |© Society for Science & the Public 2000 - 2019

Keyword: Language; Evolution
Link ID: 26037 - Posted: 03.15.2019

By Elizabeth Pennisi Cowbirds are the quintessential deadbeat parents. They, and about 90 other bird species, abandon their eggs in other birds’ nests, leaving the burden of chick care to others. An arms race is the result: Cuckolded foster parents keep evolving ways to fight back, and deadbeats evolve countermeasures. Now, researchers have discovered how spots on an egg play a crucial role in a parent’s decision to keep an egg—or boot it from the nest. One of the shiny cowbird’s (Molothrus bonariensis) most common victims is the chalk-browed mockingbird (Mimus saturninus). The mockingbird’s eggs are blue-green and spotted, whereas the cowbird’s eggs vary from pure white to brown and spotted. Researchers had assumed mockingbirds reject cowbird eggs that don't look like their own, in pattern and color. But the new study finds it’s not that simple. To get a better sense of how mockingbirds decide which eggs to boot, evolutionary ecologist Daniel Hanley at Long Island University in Brookville, New York, and colleagues painted 70 3D-printed eggs a range of colors and put spots on half of them. They distributed these eggs among 85 mockingbird nests and checked several days later to see which eggs were still there. Spots tended to make the mockingbirds hedge their bets and keep an egg, even if the color wasn’t “right,” Hanley and his colleagues report in the April issue of the Philosophical Transactions of the Royal Society B. For example, the mockingbirds removed unspotted brown eggs—a “wrong” color and pattern—90% of the time. But the birds were less sure when the egg had spots. They removed brown eggs with spots just 60% of the time, for example. In general, mockingbirds were more accepting of very blue eggs, even those that were much bluer than their own eggs. And when these blue eggs had spots, parents kept them more than 90% of the time. © 2019 American Association for the Advancement of Science

Keyword: Sexual Behavior; Evolution
Link ID: 26014 - Posted: 03.07.2019

Carolyn Wilke Over the course of human evolution, our brains expanded massively. One of the areas that ballooned over the past few million years is the cerebral cortex, the wrinkly outer layer of the brain. It processes sensory information, coordinates our motion, and is in charge of our higher order functions, such as language processing and problem solving. Scientists are scrutinizing the structure of the cortex for clues about its development throughout our lives and our evolution as a species and to understand where heredity intersects with intelligence. A new study of hundreds of developing brains reveals a trifecta of overlap in regions of the cortical surface that develop from childhood to adulthood, expanded during evolution, and are connected to genetics. The scientists also found genetically mediated links between IQ test scores and surface area in regions related to intelligence, they report today (March 4) in the Journal of Neuroscience. “I think it’s a very, very strong work,” says Rachel Brouwer, a neuroscientist at University Medical Center Utrecht in the Netherlands who was not part of the study. The authors pick up which regions of the brain where variability is most explained by genes, but by looking for connections with evolutionary expansion and neurodevelopment, “it is an attempt to link [heritability] to what it actually means in a broader picture,” she says. © 1986 - 2019 The Scientist

Keyword: Intelligence; Evolution
Link ID: 26010 - Posted: 03.06.2019

Susan Milius Cheating pays, sort of. But for a glossy blue-black bird with a bright yellow eye, cheating doesn’t outdo regular honest parenting. The greater ani, a type of cuckoo found from Panama to the Amazon Basin, usually starts out as a dutiful parent. Two or three male-female pairs typically build and fill a communal nest “like a big basket of eggs,” says behavioral ecologist Christina Riehl of Princeton University. But if a snake or some other disaster kills the young, a bereft female sometimes gets sneaky. She slips into neighboring ani nests and leaves an egg here and there that she won’t care for, but the rightful nest owners might. Not all females from trashed nests do that. Some just wait for the next breeding season, when all the birds get a fresh start building another nest. Greater anis’ sporadic cheating offers a rare chance to compare the success of egg-sneaks with honest mothers in the same species. Over 11 breeding seasons, Riehl and colleagues determined the parentage of more than 1,700 eggs and found 65 eggs in foster nests. Mothers that parasitize other nests in this way seem to lay more eggs a year, on average, Riehl says. “It’s actually kind of hard to be a parasite,” she says. But the average number of chicks that survived to flutter out of the nest on their own frantic wing power was about the same for all females, Riehl and Princeton colleague Meghan Strong report online February 27 in Nature. The mothers that always cooperated averaged about one fledgling a year, and so did the females that laid stealth eggs. |© Society for Science & the Public 2000 - 2019

Keyword: Sexual Behavior; Evolution
Link ID: 25991 - Posted: 02.28.2019