Chapter 6. Evolution of the Brain and Behavior

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Links 1 - 20 of 2054

Laura Sanders The golf ball–sized chunk of brain is not cooperating. It’s thicker than usual, and bloodier. One side has a swath of tissue that looks, to my untrained eye, like gristle. Nick Dee, the neuroscientist charged with quickly cutting the chunk into neat pieces, confers with his colleagues. “We can trim off that ugliness on the side,” he says. The “ugliness” is the brain’s connective tissue called white matter. To produce useful slices for experiments, the brain tissue must be trimmed, superglued to a lipstick-sized base and then fed into a lab version of a deli slicer. But this difficult chunk isn’t cutting nicely. Dee and colleagues pull it off the base, trim it again and reglue. Half an hour earlier, this piece of neural tissue was tucked inside a 41-year-old woman’s head, on her left side, just above the ear. Surgeons removed the tissue to reach a deeper part of her brain thought to be causing severe seizures. Privacy rules prevent me from knowing much about her; I don’t know her name, much less her first memory, favorite meal or sense of humor. But within this piece of tissue, which the patient generously donated, are clues to how her brain — all of our brains, really — create the mind. Dee’s team is working fast because this piece of brain is alive. Some of the cells can still behave as if they are a part of a person’s brain, which means they hold enormous potential for scientists who want to understand how we remember, plan, behave and feel. After Dee and his team do their part, pieces of the woman’s brain will be whisked into the hands of eager scientists, where the cells will be photographed, zapped with electricity, relieved of their genetic material and even infected with viruses that make them glow green and red. © Society for Science & the Public 2000 - 2019

Keyword: Brain imaging; Evolution
Link ID: 26490 - Posted: 08.12.2019

By Iliana Magra LONDON — On a spring afternoon last year, Neil Fraser was walking down the main shopping street in Aberdeen, a port city in northeastern Scotland, when something strange happened. The bacon-and-chicken sandwich he was halfway through eating suddenly vanished from his hand. The culprit? A hungry bird he hadn’t seen coming. “The sea gull flew in from behind me,” Mr. Fraser, a manager at the Old Schoolhouse pub in the city, said by phone on Wednesday. The bird knocked down his hand and, before he realized what was happening, it was all over: “The sandwich and the sea gull were both gone.” Aggressive gulls trying to snatch people’s food, and at times succeeding, have been a longstanding nuisance in Britain, and various solutions have been proposed over the years, including not feeding the birds, holding a stick or umbrella overhead and installing wires on roofs that they use for nesting. The Old Schoolhouse pub even reportedly offered customers water pistols to deflect the birds. Now, new research proposes a different approach: staring them down. A study published in the journal Biology Letters on Wednesday by the Royal Society, the world’s oldest continuous scientific society, suggested that making eye contact might be key to fending off herring gulls, a familiar sight in British seaside towns. The study, conducted late last year in coastal towns in Cornwall, in southwestern England, focused on that species, which are white-, gray- and black-feathered, with beaks of yellow and red. The researchers tried to test 74 birds by placing potato chips in front of an experimenter. Just 27 of the gulls bit the bait — a factor that the research team attributed to whether the experimenter was facing toward or away from the gull. © 2019 The New York Times Company

Keyword: Aggression; Evolution
Link ID: 26486 - Posted: 08.12.2019

By Knvul Sheikh It’s a myth that black widow female spiders always kill and consume their mates. But courtship remains perilous for males, cannibalism or no. The terrain, navigated in the dark, is challenging. The female’s web releases come-hither pheromones, but only about 12 percent of prospective males manage to reach it. And once there, they can expect to face male rivals competing to pass their genes on to the next generation. Usually, this results in wild displays of machismo. The males slash the female’s webs to make them less enticing to others. They deposit “mating plugs” in the female’s body to block rival sperm. Why not simply avoid the competition and seek out females’ webs empty of other males? But male black widows actually seem to thrive on the competition, according to a study published Wednesday in the Proceedings of the Royal Society B: Biological Sciences. Researchers found that male black widows find potential mates faster by following the silk trails left behind by other males. “Males have to race to find females,” said Catherine Scott, an arachnologist at the University of Toronto Scarborough in Canada and the study’s lead author. “It makes sense for them to try to use all the tricks they can to find females as soon as possible, even if there are other males that have already found her.” If a male arrives an hour or two late at a female’s web, he still has a chance to interrupt the courting rituals of other males, and could still be the first to mate with the female, Ms. Scott said. Males typically make their way to a rendezvous by following female pheromones back to their source. But those signals must be at just the right distance, and uninterrupted by shifting winds and other factors. © 2019 The New York Times Company

Keyword: Sexual Behavior; Evolution
Link ID: 26476 - Posted: 08.01.2019

Bruce Bower Monkeys can keep strings of information in order by using a simple kind of logical thought. Rhesus macaque monkeys learned the order of items in a list with repeated exposure to pairs of items plucked from the list, say psychologist Greg Jensen of Columbia University and colleagues. The animals drew basic logical conclusions about pairs of listed items, akin to assuming that if A comes before B and B comes before C, then A comes before C, the scientists conclude July 30 in Science Advances. Importantly, rewards given to monkeys didn’t provide reliable guidance to the animals about whether they had correctly ordered pairs of items. Monkeys instead worked out the approximate order of images in the list, and used that knowledge to make choices in experiments about which of two images from the list followed the other, Jensen’s group says. Previous studies have suggested that a variety of animals, including monkeys, apes, pigeons, rats and crows, can discern the order of a list of items (SN: 7/5/08, p. 13). But debate persists about whether nonhuman creatures do so only with the prodding of rewards for correct responses or, at least sometimes, by consulting internal knowledge acquired about particular lists. Jensen’s group designed experimental sessions in which four monkeys completed as many as 600 trials to determine the order of seven images in a list. Images included a hot air balloon, an ear of corn and a zebra. Monkeys couldn’t rely on rewards to guide their choices. In some sessions, animals usually received a larger reward for correctly identifying which of two images came later in the list and a smaller reward for an incorrect response. In other sessions, incorrect responses usually yielded a larger reward than correct responses. Rewards consisted of larger or smaller gulps of water delivered through tubes to the moderately thirsty primates. |© Society for Science & the Public 2000 - 2019

Keyword: Attention; Evolution
Link ID: 26475 - Posted: 08.01.2019

Carolyn Wilke Most frogs lay oodles of eggs and quickly hop away. But some poison dart frogs baby their offspring, cleaning and hydrating eggs laid on land and piggybacking hatched tadpoles to water. A peek inside the brains of these nurturing amphibians reveals that in males and females, two regions linked with caring for young are the same — a finding that may provide clues to the neural underpinnings of parental behavior, researchers report online July 17 in Proceedings of the Royal Society B. From humans to crocodiles, many creatures tend to their young. “But we actually understand very little about how the brain makes parental behaviors,” says Eva Fischer, a neuroethologist at Stanford University. To study how such care is wired into the amphibian brain, Fischer and her colleagues looked at neural activity in three poison dart frog species with different parenting strategies: Dendrobates tinctorius, among whom the males take care of the young; Oophaga sylvatica, whose females do the parenting; and Ranitomeya imitator, whose offspring are cared for by a monogamous male and female pair. The researchers collected and quickly killed 25 frogs while the amphibians were toting their tadpoles to water, in order to study the brain while it was still influenced by the parental task. Another 59 brains from non-caregiving frog species or caregivers’ partners were also included in the study. The researchers froze the frog brains and sliced them like loaves of bread. They stained the layers of tissue to pinpoint which nerve cells, or neurons, were turned on. In all three species, a brain region called the preoptic area was lit up with activity in caregiving frogs, but not in those of non-caregiving animals. |© Society for Science & the Public 2000 - 2019.

Keyword: Sexual Behavior; Evolution
Link ID: 26451 - Posted: 07.26.2019

By Virginia Morell A bold claim about gorilla societies is drawing mixed reviews. Great apes, humans’ closest evolutionary relatives, were thought to lack our social complexity. Chimpanzees, for example, form only small bands that are aggressive toward strangers. But based on years of watching gorillas gather in food-rich forest clearings, a team of scientists has concluded the apes have hierarchical societies similar to those of humans, perhaps to help them exploit rich troves of food. The finding, reported in the current issue of the Proceedings of the Royal Society B, challenges the prevailing notion that such sophisticated societies evolved relatively recently, after humans split from chimpanzees. Instead, these researchers say, the origins of such social systems extend at least as far back as the common ancestor of humans and gorillas, but were lost in chimpanzees. The group has presented “a pretty convincing case for a hierarchical social structure in gorillas,” says Richard Connor, a cetacean biologist and expert on dolphin society at the University of Massachusetts in Dartmouth. But because other primates that are not great apes—notably baboons, geladas, and colobine monkeys—show similar hierarchies, he’s not surprised they have turned up in gorillas, too. Gorillas spend most of their time in dense forests, travel great distances to a new home spot daily, and are slow to get used to observers, making their social lives hard to study. But western gorillas in the Republic of Congo gather periodically at swampy clearings in the forests to feed primarily on the highly abundant vegetation, but also on favorite and rare foods such as certain fig trees that produce massive amounts of fruit only every 3 to 5 years, says Robin Morrison, a zoologist at the University of Cambridge in the United Kingdom and the study’s lead author. © 2019 American Association for the Advancement of Science.

Keyword: Evolution
Link ID: 26428 - Posted: 07.18.2019

Ian Sample Science editor A broken skull chiselled from a lump of rock in a cave in Greece is the oldest modern human fossil ever found outside Africa, researchers claim. The partial skull was discovered in the Apidima cave on the Mani peninsula of the southern Peloponnese and has been dated to be at least 210,000 years old. If the claim is verified – and many scientists want more proof – the finding will rewrite a key chapter of the human story, with the skull becoming the oldest known Homo sapiens fossil in Europe by more than 160,000 years. Katerina Harvati, the director of paleoanthropology at the University of Tübingen in Germany, said the skull revealed that at least some modern humans had left Africa far earlier than previously thought and reached further geographically to settle as far away as Europe. Other fossils of early modern humans found in Israel already point to brief excursions out of Africa, where the species evolved, long before the mass exodus during which Homo sapiens spread from the continent about 70,000 years ago and colonised the world. Paleontologists view the excursions as failed dispersals, with the pioneers ultimately dying out and leaving no genetic legacy in people alive today. “Our results indicate that an early dispersal of Homo sapiens out of Africa occurred earlier than previously believed, before 200,000 years ago,” Karvati said. “We’re seeing evidence for human dispersals that are not just limited to one major exodus out of Africa.” © 2019 Guardian News & Media Limited

Keyword: Evolution
Link ID: 26405 - Posted: 07.11.2019

Ian Sample Science editor When Snowball the sulphur-crested cockatoo revealed his first dance moves a decade ago he became an instant sensation. The foot-tapping, head-bobbing bird boogied his way on to TV talkshows and commercials and won an impressive internet audience. Block-rocking beaks: Snowball the cockatoo – reviewed by our dance critic Read more But that was merely the start. A new study of the prancing parrot points to a bird at the peak of his creative powers. In performances conducted from the back of an armchair, Snowball pulled 14 distinct moves – a repertoire that would put many humans to shame. Footage of Snowball in action shows him smashing Another One Bites the Dust by Queen and Cyndi Lauper’s Girls Just Wanna Have Fun with a dazzling routine of head-bobs, foot-lifts, body-rolls, poses and headbanging. In one move, named the Vogue, Snowball moves his head from one side of a lifted foot to another. “We were amazed,” said Aniruddh Patel, a psychology professor at Tufts University in Medford, Massachusetts. “There are moves in there, like the Madonna Vogue move, that I just can’t believe.” Advertisement “It seems that dancing to music isn’t purely a product of human culture. The fact that we see this in another animal suggests that if you have a brain with certain cognitive and neural capacities, you are predisposed to dance,” he added. It all started, as some things must, with the Backstreet Boys. In 2008, Patel, who has long studied the origins of musicality, watched a video on the internet of Snowball dancing in time to the band’s track Everybody. He contacted Irena Schulz, who owned the bird shelter where Snowball lived, and with her soon launched a study of Snowball’s dancing prowess. © 2019 Guardian News & Media Limited

Keyword: Hearing; Evolution
Link ID: 26400 - Posted: 07.09.2019

Bruce Bower South American capuchin monkeys have not only hammered and dug with carefully chosen stones for the last 3,000 years, but also have selected pounding tools of varying sizes and weights along the way. Capuchin stone implements recovered at a site in northeastern Brazil display signs of shifts during the last three millennia between a focus on dealing with either relatively small, soft foods or larger, hard-shelled edibles, researchers report. These discoveries, described online June 24 in Nature Ecology & Evolution, are the first evidence of changing patterns of stone-tool use in a nonhuman primate. “It’s likely that local vegetation changes after 3,000 years ago led to changes in capuchin stone tools,” says archaeologist Tomos Proffitt of University College London. The new findings raise the possibility that chimpanzees and macaque monkeys, which also use stones to pound and dig, have shifted their tool-use styles over the long haul, perhaps in response to climate and habitat changes, Proffitt says. Archaeological sites linked to apes and monkeys are rare, though. Previous excavations in West Africa unearthed nut-cracking stones wielded by chimps around 4,300 years ago (SN: 11/21/09, p. 24). Present-day chimps inhabiting the same part of Africa crack nuts with similar-looking rocks. Evidence of long-term changes in tools used by wild capuchins (Sapajus libidinosus) comes from a site in Brazil’s Serra da Capivara National Park. Excavations there have also yielded ancient human stone tools (SN: 10/18/14, p. 14). But the newly unearthed artifacts more closely resemble stone tools used by modern capuchins at the same site (SN: 11/26/16, p. 16), rather than Stone Age human implements, the researchers say. |© Society for Science & the Public 2000 - 2019

Keyword: Evolution
Link ID: 26356 - Posted: 06.25.2019

Laura Sanders When animals are together, their brain activity aligns. These simpatico signals, described in bats and mice, bring scientists closer to understanding brains as they normally exist — enmeshed in complex social situations. Researchers know that neural synchrony emerges in people who are talking, taking a class together and even watching the same movie. But scientists tend to study human brains in highly constrained scenarios, in part because it’s technologically difficult to capture brain activity as people experience rich social interactions (SN: 5/11/19, p. 4). Now two studies published June 20 in Cell offer more details about how synced brains might influence social behavior. In one study, researchers monitored a pair of Egyptian fruit bats in a dark chamber for more than an hour. Neural implants recorded brain activity as the bats groomed themselves, fought, rested and performed other behaviors. The brain activity of the two bats was highly coordinated. When one bat’s neural activity oscillated in a fast rhythm, for example, the other bat’s brain was likely to do the same thing. This coordination continued even when the bats weren’t directly interacting with each other, the team found. But when the bats were separated into two chambers in the same room, this correlated activity fell away, suggesting that the bats had to be sharing the same social context for their brains to link up. |© Society for Science & the Public 2000 - 2019.

Keyword: Animal Communication; Language
Link ID: 26345 - Posted: 06.22.2019

Ian Sample Science editor In a project that has all the makings of a Roald Dahl classic, scientists have hit on an answer to the mystery of how man’s best friend got its puppy dog eyes. The sad, imploring expression held such power over humans during 33,000 years of canine domestication that the preference for dogs that could pull off the look steered the evolution of their facial muscles, researchers have said. The result is that dogs gradually acquired a new forehead muscle named the levator anguli oculi medialis, or LAOM, and have used it to deploy the doleful look to devastating effect ever since. “They are very powerful animals in how they capture our hearts,” said Prof Bridget Waller, the director of the Centre for Comparative and Evolutionary Psychology at the University of Portsmouth. “We pay a lot of attention to faces, they are meaningful to us, and this expression makes dogs look juvenile and sad. It induces a nurturing response. It’s a cute factor.” Puppy dog eyes are achieved by the LAOM raising the inner eyebrows, in some cases quite dramatically. The movement makes the eyes look larger and the face more babyish. Humans use different muscles to produce a similar expression when they are sad, which may explain why it brings out the caregiver in people. To investigate how the look developed in dogs, the UK-US research team acquired wolf and dog cadavers from taxidermists and US state organisations and dissected their heads to compare the facial muscles. No animals were killed for the research. © 2019 Guardian News & Media Limited

Keyword: Emotions; Evolution
Link ID: 26335 - Posted: 06.18.2019

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