Chapter 6. Evolution of the Brain and Behavior

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By Jason Bittel Elaborate poses, tufts of feathers, flamboyant shuffles along an immaculate forest floor — male birds-of-paradise have many ways to woo a potential mate. But now, by examining prepared specimens at the American Museum of Natural History in New York, scientists have discovered what could be yet another tool in the kit of the tropical birds — a visual effect known as photoluminescence. Sometimes called biofluorescence in living things, this phenomenon occurs when an object absorbs high-energy wavelengths of light and re-emits them as lower energy wavelengths. Biofluorescence has already been found in various species of fishes, amphibians and even mammals, from bats to wombats. Interestingly, birds remain woefully understudied when it comes to the optical extras. Until now, no one had looked for the glowing property in birds-of-paradise, which are native to Australia, Indonesia and New Guinea and are famous for their elaborate mating displays. In a study published on Tuesday in the journal Royal Society Open Science, researchers examined prepared specimens housed at the American Museum of Natural History and found evidence of biofluorescence in 37 of 45 birds-of-paradise species. “What they’re doing is taking this UV color, which they can’t see, and re-emitting it at a wavelength that is actually visible to their eyes,” said Rene Martin, the lead author of the study and a biologist at the University of Nebraska-Lincoln. “In their case, it’s kind of a bright green and green-yellow color.” In short, biofluorescence supercharges a bright color to make it even brighter. © 2025 The New York Times Company

Keyword: Sexual Behavior; Evolution
Link ID: 29666 - Posted: 02.12.2025

By Laura Sanders Ancient ear-wiggling muscles kick on when people strain to hear. That auricular activity, described January 30 in Frontiers in Neuroscience, probably doesn’t do much, if anything. But these small muscles are at least present, and more active than anyone knew. You’ve probably seen a cat or dog swing their ears toward a sound, like satellite dishes orienting to a signal. We can’t move our relatively rigid human ears this dramatically. And yet, humans still possess ear-moving muscles, as those of us who can wiggle our ears on demand know. Neuroscientist Andreas Schröer and colleagues asked 20 people with normal hearing to listen to a recorded voice while distracting podcasts played in the background. All the while, electrodes around the ears recorded muscle activity. An ear muscle called the superior auricular muscle, which sits just above the ear and lifts it up, fired up when the listening conditions were difficult, the researchers found. Millions of years ago, these muscles may have helped human ancestors collect sounds. Today, it’s doubtful that this tiny wisp of muscle activity helps a person hear better, though scientists haven’t tested that. “It does its best, but it probably doesn’t work,” says Schröer, of Saarland University in Saarbrücken, Germany. These vestigial muscles may not help us hear, but their activity could provide a measurement of a person’s hearing efforts. That information may be useful to hearing aid technology, telling the device to change its behavior when a person is struggling, for instance. © Society for Science & the Public 2000–2025.

Keyword: Hearing; Evolution
Link ID: 29665 - Posted: 02.12.2025

By Emily Anthes The English language is full of wonderful words, from “anemone” and “aurora” to “zenith” and “zodiac.” But these are special occasion words, sprinkled sparingly into writing and conversation. The words in heaviest rotation are short and mundane. And they follow a remarkable statistical rule, which is universal across human languages: The most common word, which in English is “the,” is used about twice as frequently as the second most common word (“of,” in English), three times as frequently as the third most common word (“and”), continuing in that pattern. Now, an international, interdisciplinary team of scientists has found that the intricate songs of humpback whales, which can spread rapidly from one population to another, follow the same rule, which is known as Zipf’s law. The scientists are careful to note that whale song is not equivalent to human language. But the findings, they argue, suggest that forms of vocal communication that are complex and culturally transmitted may have shared structural properties. “We expect them to evolve to be easy to learn,” said Simon Kirby, an expert on language evolution at the University of Edinburgh and an author of the new study. The results were published on Thursday in the journal Science. “We think of language as this culturally evolving system that has to essentially be passed on by its hosts, which are humans,” Dr. Kirby added. “What’s so gratifying for me is to see that same logic seems to also potentially apply to whale song.” Zipf’s law, which was named for the linguist George Kingsley Zipf, holds that in any given language the frequency of a word is inversely proportional to its rank. There is still considerable debate over why this pattern exists and how meaningful it is. But some research suggests that this kind of skewed word distribution can make language easier to learn. © 2025 The New York Times Company

Keyword: Language; Evolution
Link ID: 29662 - Posted: 02.08.2025

By Avery Schuyler Nunn Migratory songbirds may talk to one another more than we thought as they wing through the night. Each fall, hundreds of millions of birds from dozens of species co-migrate, some of them making dangerous journeys across continents. Come spring, they return home. Scientists have long believed that these songbirds rely on instinct and experience alone to make the trek. But new research from a team of ornithologists at the University of Illinois suggests they may help one another out—even across species—through their nocturnal calls. “They broadcast vocal pings into the sky, potentially sharing information about who they are and what lies ahead,” says ornithologist Benjamin Van Doren of the University of Illinois, Urbana-Champaign and a co-author of the study, published in Current Biology. Using ground-based microphones across 26 sites in eastern North America, Van Doren and his team recorded over 18,300 hours of nocturnal flight calls from 27 different species of birds—brief, high-pitched vocalizations that some warblers, thrushes, and sparrows emit while flying. To process the enormous dataset of calls, they used machine-learning tools, including a customized version of Merlin, the Cornell Lab of Ornithology’s bird-call identification app. The analysis revealed that birds of different species were flying in close proximity and calling to one another in repeated patterns that suggested a kind of code. Flight proximity was closest between migrating songbirds species that made similar calls in pitch and rhythm, traveled at similar speeds, and had similar wing shapes. © 2025 NautilusNext Inc.,

Keyword: Language; Evolution
Link ID: 29661 - Posted: 02.08.2025

Nell Greenfieldboyce People are constantly looking at the behavior of others and coming up with ideas about what might be going on in their heads. Now, a new study of bonobos adds to evidence that they might do the same thing. Specifically, some bonobos were more likely to point to the location of a treat when they knew that a human companion was not aware of where it had been hidden, according to a study which appears in the Proceedings of the National Academy of Sciences. The findings add to a long-running debate about whether humans have a unique ability to imagine and understand the mental states of others. Some researchers say this kind of "theory of mind" may be practiced more widely in the animal kingdom, and potentially watching it in action was quite the experience. "It's quite surreal. I mean, I've worked with primates for quite some years now and you never get used to it," says Luke Townrow, a PhD student at Johns Hopkins University. "We found evidence that they are tailoring their communication based on what I know." Hmmm, where is the grape? To see what bonobos might know about what humans around them know, Townrow worked with Chris Krupenye of Johns Hopkins University to devise a simple experiment. "It's always a challenge for us, that animals don't speak, so we can't just ask them what they're thinking. We have to come up with creative, experimental designs that allow them to express their knowledge," says Krupenye. © 2025 npr

Keyword: Attention; Consciousness
Link ID: 29658 - Posted: 02.05.2025

By Bethany Brookshire Self-awareness may be beyond primates in the wild. Chimps, organutans and other species faced with a mirror react to a dot on their face in the lab, a widely used measure of self-awareness. But while baboons in Namibia exposed to mirrors find the reflective glass fascinating, they don’t respond to dots placed on their faces, researchers report in the January Proceedings of the Royal Society B: Biological Sciences. The result could indicate that lab responses to mirrors are a result of training — and that self-awareness might exist on a spectrum. Support Science Today. Thank you for being a subscriber to Science News! Interested in more ways to support STEM? Consider making a gift to our nonprofit publisher, the Society for Science, an organization dedicated to expanding scientific literacy and ensuring that every young person can strive to become an engineer or scientist. Donate Now “Psychological self-awareness is this idea that you as an individual can become an object of your own attention,” says Alecia Carter, an evolutionary anthropologist at University College London. It’s a hard concept to measure in other species, in part, she notes, because “it’s also difficult to imagine not having that kind of self-awareness.” One measure of self-awareness is the mark test. An animal sits in front of a mirror, and a mark is placed somewhere they normally cannot see, such as on the face. If the animal recognizes themselves in the mirror, and the mark as out of place, the animal will respond to the mark. Chimps, orangutans and bonobos have “passed” the mark test in the lab, while primates that are not great apes, such as rhesus macaques, have mastered it only after training. Other species, such as Asian elephants, dolphins and even a fish called the cleaner wrasse, have also responded to the mark test. © Society for Science & the Public 2000–2025.

Keyword: Chemical Senses (Smell & Taste); Evolution
Link ID: 29654 - Posted: 02.01.2025

Nicola Davis Science correspondent Wiggling your ears might be more of a pub party piece than a survival skill, but humans still try to prick up their ears when listening hard, researchers have found. Ear movement is crucial in many animals, not least in helping them focus their attention on particular noises and work out which direction they are coming from. But while the human ear is far more static, traces of our ancestors’ ear-orienting system remain in what has been called a “neural fossil”. “It is believed that our ancestors lost their ability to move their ears about 25m years ago. Why, exactly, is difficult to say,” said Andreas Schröer, the lead author of the research from Saarland University in Germany. “However, we have been able to demonstrate that the neural circuits still seem to be present in some state, [that is] our brain retained some of the structures to move the ears, even though they apparently are not useful any more.” The team previously found the movement of these muscles in humans is related to the direction of the sounds they are paying attention to. Now, they have found that some of these muscles become activated when humans listen hard to a sound. Writing in the journal Frontiers in Neuroscience, the team reported how they asked 20 adults without hearing problems to listen to an audiobook played through a speaker at the same time as a podcast was played from the same location. The team created three different scenarios: in the “easiest” scenario the podcast was quieter than the audiobook, with a large difference in pitch between the voices. In the “hardest” scenario, two podcasts were played which, taken together, were louder than the audiobook, with one of the podcasts spoken at a similar pitch to the audiobook. © 2025 Guardian News & Media Limited

Keyword: Hearing; Evolution
Link ID: 29649 - Posted: 02.01.2025

By Tina Hesman Saey After nearly 350 years, a depiction of a bee’s brain is getting some buzz. A manuscript created in the mid-1670s contains the oldest known depiction of an insect’s brain, historian of science Andrea Strazzoni of the University of Turin in Italy reports January 29 in Royal Society Notes and Records. Handwritten by Dutch biologist and microscopist Johannes Swammerdam, the manuscript contains a detailed description and drawing of a honeybee drone’s brain. The illustration, based on his own dissections, was just one of Swammerdam’s firsts. In 1658, he was also the first to see and describe red blood cells. Since no one had previously reported dissecting a bee brain, Swammerdam based his descriptions on what was known about the brain anatomy of humans and other mammals. “He knew what to expect from or to imagine in his observations: in particular, the pineal gland and the cerebellum,” Strazzoni writes. Bees have neither of those parts but have brain structures that the 17th century scientist mistook for them. But Swammerdam deserves some slack, Strazzoni suggests. He was working with single-lens microscopes and developing new techniques for dissecting and observing insects’ internal organs. Even with those crude instruments, he was able to identify some nerves and describe how parts of the brain connected. © Society for Science & the Public 2000–2025.

Keyword: Brain imaging; Evolution
Link ID: 29644 - Posted: 01.29.2025

By Shaena Montanari For evolutionary neuroanatomists who compare diverse animal brains, access to a gold mine of 500,000 histological sections and whole mounts is now only a mouse-click away. The R. Glenn Northcutt Collection of Comparative Vertebrate Neuroanatomy and Embryology at Harvard University—which comprises 33,000 slides of tissue samples from more than 240 vertebrate genera—is one of the world’s largest and most diverse collections of its kind. Northcutt, a prolific comparative vertebrate neuroanatomist and emeritus professor of neurosciences at the University of California, San Diego, amassed the collection over the course of five decades. Since 2021, James Hanken, research professor of biology at Harvard University and curator at the Museum of Comparative Zoology, has led an effort to digitize it. The scanning process is still ongoing and may take another two years to complete, Hanken says, but more than 8,000 slides are already publicly available in two online data repositories: MCZBase and MorphoSource. A comprehensive inventory of the entire collection appears in a paper Hanken and his colleagues published last week in the Bulletin of the Museum of Comparative Zoology. It provides researchers with an in-depth guide for using the collection, Hanken says. Few other resources of this type are available online to researchers interested in evolutionary biology and brain anatomy, says Andrew Iwaniuk, professor of neuroscience at the University of Lethbridge. For example, neither the Welker Comparative Anatomy Collection nor the Starr Collection, both housed at the U.S. National Museum of Health and Medicine in Silver Spring, Maryland, are available online. To access slide collections such as these, scientists have had to travel to see them in person, which can be difficult for those outside the United States, Iwaniuk adds. © 2025 Simons Foundation

Keyword: Brain imaging; Evolution
Link ID: 29642 - Posted: 01.25.2025

By Calli McMurray, Angie Voyles Askham, Claudia López Lloreda, Shaena Montanari Neuroscience can sometimes feel like an old mouse club—but it wasn’t always that way. In the 1960s and ’70s, neuroscientists routinely put on their field boots to search for the “animal that was expert at doing the task that you were interested in studying,” says Eve Marder, university professor of biology at Brandeis University. “People studied insects and annelids and mollusks and every kind of animal imaginable. And if they could have studied elephants, they would have.” Many fundamental—and Nobel-prize-winning—discoveries emerged from this approach. Recording from the squid’s giant axon, for example, revealed how action potentials work; experiments in sea slugs illuminated the molecular changes that drive learning and memory; work in barn owls unraveled sound localization; and studies in horseshoe crabs first exposed lateral inhibition in photoreceptors. But by the end of the 20th century, model diversity had fallen out of vogue. A small band of neuroethologists continued to explore animals off the beaten path, but the majority of neuroscientists soon jumped over to standard animal models, Marder says. Many of today’s common model organisms—including the mouse, zebrafish, roundworm and fruit fly—soared in popularity because they are cheap, easy to work with and quick to raise in a lab. The invention of molecular and genetic tools tailored to these species only increased their appeal, as did attention from the U.S. federal government. In 1999, the National Institutes of Health (NIH) published a list of 13 canonical model organisms for biomedical research, and in 2004 the organization’s “road map” encouraged the use of research animals for which genetic tools were available. Now, two decades later, a non-model organism “renaissance” is underway, says Ishmail Abdus-Saboor, associate professor of biological sciences at Columbia University, as a growing number of neuroscientists step outside of the model organism box. This shift is largely due to cost reductions and technological advances in “species-neutral” techniques, says Sam Reiter, assistant professor of computational neuroethology at the Okinawa Institute of Science and Technology, such as high-throughput extracellular recordings, machine-learning-based behavioral tracking, genome and transcriptome sequencing, and gene-editing tools. “This lets researchers quickly reach close to the cutting edge, even if working on an animal where little is known.” © 2024 Simons Foundation

Keyword: Evolution
Link ID: 29605 - Posted: 12.21.2024

By Sofia Quaglia It’s amazing what chimpanzees will do for a snack. In Congolese rainforests, the apes have been known to poke a hole into the ground with a stout stick, then grab a long stem and strip it through their teeth, making a brush-like end. Into the hole that lure goes, helping the chimps fish out a meal of termites. How did the chimps figure out this sophisticated foraging technique and others? “It’s difficult to imagine that it can just have appeared out of the blue,” said Andrew Whiten, a cultural evolution expert from the University of St. Andrews in Scotland who has studied tool use and foraging in chimpanzees. Now Dr. Whiten’s team has set out to demonstrate that advanced uses of tools are an example of humanlike cultural transmission that has accumulated over time. Where bands of apes in Central and East Africa exhibit such complex behaviors, they say, there are also signs of genes flowing between groups. They describe this as evidence that such foraging techniques have been passed from generation to generation, and innovated over time across different interconnected communities. In a study published on Thursday in the journal Science, Dr. Whiten and colleagues go as far as arguing that chimpanzees have a “tiny degree of cumulative culture,” a capability long thought unique to humans. From mammals to birds to reptiles and even insects, many animals exhibit some evidence of culture, when individuals can socially learn something from a nearby individual and then start doing it. But culture becomes cumulative over time when individuals learn from others, each building on the technique so much that a single animal wouldn’t have been able to learn all of it on its own. For instance, some researchers interpret using rocks as a hammer and anvil to open a nut as something chimpanzees would not do spontaneously without learning it socially. Humans excel at this, with individual doctors practicing medicine each day, but medicine is no one single person’s endeavor. Instead, it is an accumulation of knowledge over time. Most chimpanzee populations do not use a complex set of tools, in a specific sequence, to extract food. © 2024 The New York Times Company

Keyword: Evolution; Learning & Memory
Link ID: 29573 - Posted: 11.23.2024

By Janna Levin It’s fair to say that enjoyment of a podcast would be severely limited without the human capacity to create and understand speech. That capacity has often been cited as a defining characteristic of our species, and one that sets us apart in the long history of life on Earth. Yet we know that other species communicate in complex ways. Studies of the neurological foundations of language suggest that birdsong, or communication among bats or elephants, originates with brain structures similar to our own. So why do some species vocalize while others don’t? In this episode, Erich Jarvis, who studies behavior and neurogenetics at the Rockefeller University, chats with Janna Levin about the surprising connections between human speech, birdsong and dance. JANNA LEVIN: All animals exhibit some form of communication, from the primitive hiss of a lizard to the complex gestures natural to chimps, or the songs shared by whales. But human language does seem exceptional, a vast and discrete cognitive leap. Yet recent research is finding surprising neurological connections between our expressive speech and the types of communication innate to other animals, giving us new ideas about the biological and developmental origins of language. Erich is a professor at the Rockefeller University and a Howard Hughes Medical Institute investigator. At Rockefeller, he directs the Field Research Center of Ethology and Ecology. He also directs the Neurogenetics Lab of Language and codirects the Vertebrate Genome Lab, where he studies song-learning birds and other species to gain insight into the mechanism’s underlying language and vocal learning. ERICH JARVIS: So, the first part: Language is built-in genetically in us humans. We’re born with the capacity to learn how to produce and how to understand language, and pass it on culturally from one generation to the next. The actual detail is learned, but the actual plan in the brain is there. Second part of your question: Is it, you know, special or unique to humans? It is specialized in humans, but certainly many components of what gives rise to language is not unique to humans. There’s a spectrum of abilities out there in other species that we share some aspects of with other species. © 2024 Simons Foundation

Keyword: Language; Evolution
Link ID: 29572 - Posted: 11.23.2024

By Ann Gibbons As the parent of any teenager knows, humans need a long time to grow up: We take about twice as long as chimpanzees to reach adulthood. Anthropologists theorize that our long childhood and adolescence allow us to build comparatively bigger brains or learn skills that help us survive and reproduce. Now, a study of an ancient youth’s teeth suggests a slow pattern of growth appeared at least 1.8 million years ago, half a million years earlier than any previous evidence for delayed dental development. Researchers used state-of-the art x-ray imaging methods to count growth lines in the molars of a member of our genus, Homo, who lived 1.77 million years ago in what today is Dmanisi, Georgia. Although the youth developed much faster than children today, its molars grew as slowly as a modern human’s during the first 5 years of life, the researchers report today in Nature. The finding, in a group whose brains are hardly larger than chimpanzees, could provide clues to why humans evolved such long childhoods. “One of the main questions in paleoanthropology is to understand when this pattern of slow development evolves in [our genus] Homo,” says Alessia Nava, a bioarchaeologist at the Sapienza University of Rome who is not part of the study. “Now, we have an important hint.” Others caution that although the teeth of this youngster grew slowly, other individuals, including our direct ancestors, might have developed faster. Researchers have known since the 1930s that humans stay immature longer than other apes. Some posit our ancestors evolved slow growth to allow more time and energy to build bigger brains, or to learn how to adapt to complex social interactions and environments before they had children. To pin down when this slow pattern of growth arose, researchers often turn to teeth, especially permanent molars, because they persist in the fossil record and contain growth lines like tree rings. What’s more, the dental growth rate in humans and other primates correlates with the development of the brain and body.

Keyword: Evolution; Sexual Behavior
Link ID: 29562 - Posted: 11.16.2024

Ari Daniel The birds of today descended from the dinosaurs of yore. Researchers have known relatively little, however, about how the bird's brain took shape over tens of millions of years. "Birds are one of the most intelligent groups of living vertebrate animals," says Daniel Field, a vertebrate biologist at the University of Cambridge. "They really rival mammals in terms of their relative brain size and the complexity of their behaviors, social interactions, breeding displays." Now, a newly discovered fossil provides the most complete glimpse to date of the brains of the ancestral birds that once flew above the dinosaurs. The species was named Navaornis hestiae, and it's described in the journal Nature. Piecing together how bird brains evolved has been a challenge. First, most of the fossil evidence dates back to tens of millions of years before the end of the Cretaceous period when dinosaurs went extinct and birds diversified. In addition, the fossils of feathered dinosaurs that have turned up often have a key problem. "They're beautiful, but they're all like roadkill," says Luis Chiappe, a paleontologist and curator at the Natural History Museum of Los Angeles County. "They're all flattened and there are aspects that you're never going to be able to recover from those fossils." The shape and three-dimensional structure of the brain are among those missing aspects. But in 2016, Brazilian paleontologist William Nava discovered a remarkably well-preserved fossil in São Paulo state. It came from a prehistoric bird that fills in a crucial gap in understanding of how modern bird brains evolved. © 2024 npr

Keyword: Evolution; Development of the Brain
Link ID: 29561 - Posted: 11.16.2024

By Miryam Naddaf When a dog shakes water off its fur, the action is not just a random flurry of movements — nor a deliberate effort to drench anyone standing nearby. This instinctive reflex is shared by many furry mammals including mice, cats, squirrels, lions, tigers and bears. The move helps animals to remove water, insects or other irritants from hard-to-reach places. But underlying the shakes is a complex — and previously mysterious — neurological mechanism. Now, researchers have identified the neural circuit that triggers characteristic ‘wet dog’ shaking behaviour in mice — which involves a specific class of touch receptors, and neurons that connect the spinal cord to the brain. Their findings were published in Science on 7 November1. “The touch system is so complex and rich that [it] can distinguish a water droplet from a crawling insect from the gentle touch of a loved one,” says Kara Marshall, a neuroscientist at Baylor College of Medicine in Houston, Texas. “It’s really remarkable to be able to link a very specific subset of touch receptors to this familiar and understandable behaviour.” The hairy skin of mammals is packed with more than 12 types of sensory neuron, each with a unique function to detect and interpret various sensations. Study co-author Dawei Zhang, a neuroscientist then at Harvard Medical School in Boston, Massachusetts, and his colleagues focused on a type of ultra-sensitive touch detecting receptors called C-fibre low-threshold mechanoreceptors (C-LTMRs), which wrap around hair follicles. In humans, these receptors are associated with pleasant touch sensations, such as a soft hug or a soothing stroke. But in mice and other animals, they serve a protective role: alerting them to the presence of something on their skin, whether it’s water, dirt or a parasite. When these stimuli cause hairs on the skin to bend it activates the C-LTMRs, says Marshall, “extending the sensibility of the skin beyond just the surface”. © 2024 Springer Nature Limited

Keyword: Pain & Touch; Evolution
Link ID: 29551 - Posted: 11.09.2024

By Sara Reardon Elephants love showering to cool off, and most do so by sucking water into their trunks and spitting it over their bodies. But an elderly pachyderm named Mary has perfected the technique by using a hose as a showerhead, much in the way humans do. The behavior is a remarkable example of sophisticated tool use in the animal kingdom. But the story doesn’t end there. Mary’s long, luxurious baths have drawn so much attention that an envious elephant at the Berlin Zoo has figured out how to shut the water off on her supersoaking rival—a type of sabotage rarely seen among animals. Both behaviors, reported today in Current Biology, further cement elephants as complex thinkers, says Lucy Bates, a behavioral ecologist at the University of Portsmouth not involved in the study. The work, she says, “suggests problem solving or even ‘insight.’” Many elephants enjoy playing with hoses, probably because they remind them of trunks, says Michael Brecht, a computational neuroscientist at Humboldt University of Berlin. But Mary takes the activity to another level. Using her trunk, the 54-year-old Asian elephant (Elephas maximus)—a senior citizen, given the average captive life span of her species of 48 years—holds a hose over her head and waves it back and forth. She also changes her grip on the hose to spray different parts of her body and swings it like a lasso to throw water over her back. Brecht’s graduate student, Lena Kaufmann, noticed Mary’s hose use while studying other types of behavior in the zoo’s elephants; the zookeepers told her Mary did this frequently. So Kaufman and her colleagues started to record the showering on video over the course of a year, testing how Mary reacted to changes in the setup.

Keyword: Learning & Memory; Evolution
Link ID: 29547 - Posted: 11.09.2024

By Kerri Smith Infographics by Nik Spencer There must be something about the human brain that’s different from the brains of other animals — something that enables humans to plan, imagine the future, solve crossword puzzles, tell sarcastic jokes and do the many other things that together make our species unique. And something that explains why humans get devastating conditions that other animals don’t — such as bipolar disorder and schizophrenia. Brain size is tightly correlated with body size in most animals. But humans break the mould. Our brains are much larger than expected given our body size. Here are some animals’ brains ranked according to size. Researchers often use a ratio called the encephalization quotient (EQ) to get an idea of how much larger or smaller an animal’s brain is compared with what would be expected given its body size. The EQ is 1.0 if the brain to body mass ratio meets expectations. Here are their brains scaled according to their EQ, with the actual brain sizes represented by dotted lines. The mouse brain is half as big as expected for its body size. The human brain is more than seven times the expected size. Although evolution has enlarged the human brain, it hasn’t done so uniformly: some brain areas have ballooned more than others. One particularly enlarged region is the cortex, an area that carries out planning, reasoning, language and many other behaviours that humans excel at. Other areas, such as the cerebellum — an area at the back of the brain that is densely populated with neurons, and which helps to conduct movement and planning — have expanded too. The prefrontal cortex has a similar structure in both chimps and humans, although it takes up much more real estate in the human brain than in the chimp brain.

Keyword: Evolution
Link ID: 29539 - Posted: 11.02.2024

Ian Sample Science editor Humans may have turned drinking into something of an art form but when it comes to animals putting alcohol away, Homo sapiens are not such an outlier, researchers say. A review of published evidence shows that alcohol occurs naturally in nearly every ecosystem on Earth, making it likely that most animals that feast on sugary fruits and nectar regularly imbibe the intoxicating substance. Although many creatures have evolved to tolerate a tipple and gain little more than calories from their consumption, some species have learned to protect themselves with alcohol. Others, however, seem less able to handle its effects. “We’re moving away from this anthropocentric view that alcohol is used by just humans and that actually ethanol is quite abundant in the natural world,” said Anna Bowland, a researcher in the team at the University of Exeter. After trawling research papers on animals and alcohol, the scientists arrived at a “diverse coterie” of species that have embraced and adapted to ethanol in their diets, normally arising through fermented fruits, sap and nectar. Ethanol became plentiful on Earth about 100m years ago when flowering plants began to produce sugary fruits and nectar that yeast could ferment. The alcohol content is typically low, at around 1% to 2% alcohol by volume (ABV), but in over-ripe palm fruit the concentration can reach 10% ABV. In one study, wild chimpanzees in south eastern Guinea were caught on camera bingeing on the alcoholic sap of raffia palms. Meanwhile, spider monkeys on Barro Colorado Island, Panama, are partial to ethanol-laden yellow mombin fruit, revealed to contain between 1% and 2.5% alcohol. “Evidence is growing that humans are not drinking alone,” the authors write in Trends in Ecology and Evolution. © 2024 Guardian News & Media Limited

Keyword: Drug Abuse; Evolution
Link ID: 29537 - Posted: 11.02.2024

By Thomas Fuller Over and over, the crows attacked Lisa Joyce as she ran screaming down a Vancouver street. They dive bombed, landing on her head and taking off again eight times by Ms. Joyce’s count. With hundreds of people gathered outdoors to watch fireworks that July evening, Ms. Joyce wondered why she had been singled out. “I’m not a fraidy-cat, I’m not generally nervous of wildlife,” said Ms. Joyce, whose crow encounters grew so frequent this past summer that she changed her commute to work to avoid the birds. “But it was so relentless,” she said, “and quite terrifying.” Ms. Joyce is far from alone in fearing the wrath of the crow. CrowTrax, a website started eight years ago by Jim O’Leary, a Vancouver resident, has since received more than 8,000 reports of crow attacks in the leafy city, where crows are relatively abundant. And such encounters stretch well beyond the Pacific Northwest. A Los Angeles resident, Neil Dave, described crows attacking his house, slamming their beaks against his glass door to the point where he was afraid it would shatter. Jim Ru, an artist in Brunswick, Maine, said crows destroyed the wiper blades of dozens of cars in the parking lot of his senior living apartment complex. Nothing seemed to dissuade them. Renowned for their intelligence, crows can mimic human speech, use tools and gather for what seem to be funeral rites when a member of their murder, as groups of crows are known, dies or is killed. They can identify and remember faces, even among large crowds. They also tenaciously hold grudges. When a murder of crows singles out a person as dangerous, its wrath can be alarming, and can be passed along beyond an individual crow’s life span of up to a dozen or so years, creating multigenerational grudges. © 2024 The New York Times Company

Keyword: Intelligence; Learning & Memory
Link ID: 29534 - Posted: 10.30.2024

By Phie Jacobs Whether it’s two newlyweds going in for a smooch after saying “I do” or a parent soothing their child’s scraped knee, kissing is one of humanity’s most recognizable symbols of affection. Clay tablets from ancient Mesopotamia dating to 2500 B.C.E. provide the earliest archaeological evidence of romantic kissing. But the behavior may be older than civilization itself, with some studies suggesting Neanderthals swapped spit with modern humans—and shared each other’s oral microbes—more than 100,000 years ago. Some researchers have suggested kissing evolved from behaviors such as sniffing, nursing babies, or even parents passing chewed-up food to their offspring. But in an article published this month in Evolutionary Anthropology, evolutionary psychologist Adriano Lameira of the University of Warwick offers another hypothesis. Drawing on his knowledge of great ape behavior, Lameira suggests kissing got its start as a fur grooming ritual still observed in modern-day chimpanzees and other great apes. Science sat down with Lameira to learn more about his work. This interview has been edited for length and clarity. Q: What made you want to study kissing? A: It’s a behavior that is charged with so much meaning and symbolism, perhaps the most iconic way of how we show affection on an individual and societal level. I was surprised to find that we know so little about its evolution and nature. In our lab, we’re mostly intrigued by the evolution of language, dance, and imagination. But in the largest sense we’re interested in behaviors and rituals that are evolutionary heirlooms from our apelike ancestors—things our ancestors did that set us on course towards who we are today. Q: Do other animals kiss, or is the behavior unique to humans? © 2024 American Association for the Advancement of Science.

Keyword: Sexual Behavior; Evolution
Link ID: 29532 - Posted: 10.30.2024