Chapter 6. Evolution of the Brain and Behavior

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Dolphins are known to use physical contact like petting and rubbing to bond with their closest allies. But for more distant contacts, male dolphins bond by trading whistles instead. KELSEY SNELL, HOST: You know those friends who live far away, but you still stay in touch? You can't really hug, so you call or text them instead. Well, dolphins do something sort of similar. AILSA CHANG, HOST: That, my friends, is whistling. A new study found that the male bottlenose dolphins in Western Australia whistle to the other male dolphins they don't have strong bonds with. SNELL: University of Bristol marine biologist Emma Chereskin is the lead author of the study. She explains that male bottlenose dolphins have an alliance structure. They have their closest circle where the bonds are strong. EMMA CHERESKIN: They often use physical touch, so rubbing their fins together, swimming side by side. CHANG: Then there is another circle where the bonds are weaker and they don't use as much physical touch, but they do whistle to identify themselves and to keep alliances intact. In other words, they bond at a distance. Sound familiar? SNELL: That was a whistle exchange between three dolphins. The researchers gave them names - Kooks (ph), Spirit and Guppy. CHERESKIN: They're saying, hi, I'm Kooks. I'm right here. And then Spirit would reply, hi, I'm Spirit. I'm also right here. And then Guppy gets in on it towards the end. He's saying, hi, I'm Guppy. I'm also here. CHANG: The study tests the social bonding hypothesis of Robin Dunbar. He proposed that animal vocalizations evolved as a form of vocal grooming to replace physical grooming. Karl Berg from the University of Texas Rio Grande Valley says this study advances that hypothesis. KARL BERG: These dolphin groups can be in really large groups in the dark ocean where visual communication isn't going to be possible. It makes sense that this vocal communication system is very important to them. © 2022 npr

Keyword: Animal Communication; Evolution
Link ID: 28262 - Posted: 04.02.2022

By Bruce Bower Human language, in its many current forms, may owe an evolutionary debt to our distant ape ancestors who sounded off in groups of scattered individuals. Wild orangutans’ social worlds mold how they communicate vocally, much as local communities shape the way people speak, researchers report March 21 in Nature Ecology & Evolution. This finding suggests that social forces began engineering an expanding inventory of communication sounds among ancient ancestors of apes and humans, laying a foundation for the evolution of language, say evolutionary psychologist Adriano Lameira, of the University of Warwick in England, and his colleagues. Lameira’s group recorded predator-warning calls known as “kiss-squeaks” — which typically involve drawing in breath through pursed lips — of 76 orangutans from six populations living on the islands of Borneo and Sumatra, where they face survival threats (SN: 2/15/18). The team tracked the animals and estimated their population densities from 2005 through 2010, with at least five consecutive months of observations and recordings in each population. Analyses of recordings then revealed how much individuals’ kiss-squeaks changed or remained the same over time. Orangutans in high-density populations, which up the odds of frequent social encounters, concoct many variations of kiss-squeaks, the researchers report. Novel reworkings of kiss-squeaks usually get modified further by other orangutans or drop out of use in crowded settings, they say. © Society for Science & the Public 2000–2022.

Keyword: Language; Evolution
Link ID: 28258 - Posted: 03.30.2022

Dave Davies Did Stone Age people conduct brain surgery? Medical historian Ira Rutkow points to evidence that suggests they did. "There have been many instances of skulls that have been found dating back to Neolithic times that have grooves in them where portions of the skull have been removed. And it's evident if you look at these skulls, that this was all done by hand," Rutkow says. There's no written record of Stone Age neurosurgery, but Rutkow theorizes it may have been conducted by a shaman on patients who were comatose or who had been otherwise injured. What's more, he says, physical evidence indicates that some patients likely survived: "With many of these older skulls, new bone growth had already formed, and bone in the skull can only form if the patient is alive," he says. Rutkow is a surgeon himself. His new book, Empire of the Scalpel, traces the history of surgery, from the days when barbers did most operations and patients died in great numbers, to today's high tech operations that use robots with artificial intelligence. He says that when looking back, it's important to keep in mind the body of knowledge that existed at a particular point in history — and to not judge surgeons of yore too harshly. "People write about medical history and they say, 'Oh, it was barbaric,' or 'The doctors were maltreating,'" he says. "We have to remember at all times that whatever I write about in the past was considered state of the art at the time. ... I would hate to think that 200 years from now, somebody is looking at what we are doing today and saying, 'Boy, that treatment that they were doing was just barbaric. How do they do that to people?'" © 2022 npr

Keyword: Brain Injury/Concussion; Evolution
Link ID: 28257 - Posted: 03.30.2022

By Veronique Greenwood Sharks are celebrated for their apparently ceaseless motion — a small handful of species such as great white sharks must even swim to breathe, keeping water washing over their gills. Still, all that moving doesn’t preclude sharks from having a rest. Sleep across the animal kingdom manifests itself in many peculiar ways, like the birds whose brains sleep one half at a time or the bats that spend almost every hour of their day snoozing. And in a paper published in Current Biology on Wednesday, researchers confirmed that the draughtsboard shark, a small nocturnal shark native to New Zealand, appears to be sleeping during periods of calm, reporting that their metabolism and posture change significantly during these bouts of repose. They do, however, in a creepy touch, keep their eyes open for a lot of it. Further research will be required to demonstrate that other kinds of sharks catch underwater z’s like the draughtsboard shark. But the new study supports the hypothesis that one reason organisms might have evolved sleep is as a tool for conserving energy. Draughtsboard sharks were identified last year as sleepers by this same group of researchers based in New Zealand and Australia. They watched captured sharks carefully in tanks and tested their responses to disturbances during their restful periods. (These sharks are not among those that swim to breathe; they hang out on the ocean floor and pump water over their gills.) The team found that it was more difficult to prompt the sharks into movement if they had been still for a long time, suggesting they were in fact sleeping. This time, said Craig Radford, a professor of marine science at the University of Auckland and an author of the new paper, the researchers were looking to compare the sharks’ metabolisms during these periods of calm, defined as being still for longer than five minutes, with when they were resting for shorter periods and when they were actively swimming. They used a specially built tank with instruments that let them monitor how much oxygen the sharks were using, a way to indirectly measure metabolism. Seven sharks each spent 24 hours in the tank, and the researchers found that these states were indeed quite different. © 2022 The New York Times Company

Keyword: Sleep; Evolution
Link ID: 28234 - Posted: 03.11.2022

Dominique Potvin When we attached tiny, backpack-like tracking devices to five Australian magpies for a pilot study, we didn’t expect to discover an entirely new social behaviour rarely seen in birds. Our goal was to learn more about the movement and social dynamics of these highly intelligent birds, and to test these new, durable and reusable devices. Instead, the birds outsmarted us. As our new research paper explains, the magpies began showing evidence of cooperative “rescue” behaviour to help each other remove the tracker. While we’re familiar with magpies being intelligent and social creatures, this was the first instance we knew of that showed this type of seemingly altruistic behaviour: helping another member of the group without getting an immediate, tangible reward. As academic scientists, we’re accustomed to experiments going awry in one way or another. Expired substances, failing equipment, contaminated samples, an unplanned power outage—these can all set back months (or even years) of carefully planned research. For those of us who study animals, and especially behaviour, unpredictability is part of the job description. This is the reason we often require pilot studies. Our pilot study was one of the first of its kind—most trackers are too big to fit on medium to small birds, and those that do tend to have very limited capacity for data storage or battery life. They also tend to be single-use only. A novel aspect of our research was the design of the harness that held the tracker. We devised a method that didn’t require birds to be caught again to download precious data or reuse the small devices. © 1986–2022 The Scientist.

Keyword: Evolution; Learning & Memory
Link ID: 28218 - Posted: 02.26.2022

ByTess Joosse Bite into a lemon and you’ll likely experience a clashing rush of sensations: crushing sharpness, mouth-watering tanginess, and pleasant brightness. But despite its assertiveness—and its role as one of the five main taste profiles (along with sweet, salty, savory, and bitter)—scientists don’t know much about how our acidic taste evolved. Enter Rob Dunn. The North Carolina State University ecologist and his collaborators have spent years scanning the scientific literature in search of an answer. In a paper published this week in the Proceedings of the Royal Society B, the team reports some clues. Science chatted with Dunn about how, and why, humans like to pucker up. This interview has been edited for clarity and length. Rob Dunn Ecologist Rob DunnAmanda Ward Q: Do other animals like sour foods? A: With almost all the other tastes, species have lost them through evolution. Dolphins appear to have no taste receptors other than salty, and cats don’t have sweet taste receptors. That’s what we expected to see with sour. What we see instead is all the species that have been tested [about 60 so far] are able to detect acidity in their food. Of those animals, pigs and primates seem to really like acidic foods. For example, wild pigs (Sus scrofa) are really attracted to fermented corn, and gorillas (Gorilla gorilla) have shown a preference for acidic fruits in the ginger family. Q: Sweet taste gives us a reward for energy, and bitter alerts us to potential poisons. Why might we have evolved a taste for sour? A: Sour taste was likely present in ancient fish—they’re the earliest vertebrate animals that we know can sense sour. The origin in fish was likely not to taste food with their mouths, but to sense acidity in the ocean—basically fish “tasting” with the outside of their body. Variations in dissolved carbon dioxide can create acidity gradients in the water, which can be dangerous for fish. Being able to sense acidity would have been important. © 2022 American Association for the Advancement of Science.

Keyword: Chemical Senses (Smell & Taste); Evolution
Link ID: 28198 - Posted: 02.12.2022

ByMichael Price When it comes to killing and eating other creatures, chimpanzees—our closest relatives—have nothing on us. Animal flesh makes up much more of the average human’s diet than a chimp’s. Many scientists have long suggested our blood lust ramped up about 2 million years ago, based on the number of butchery marks found at ancient archaeological sites. The spike in calories from meat, the story goes, allowed one of our early ancestors, Homo erectus, to grow bigger bodies and brains. But a new study argues the evidence behind this hypothesis is statistically flawed because it fails to account for the fact that researchers have focused most of their time and attention on later sites. As a result of this unequal “sampling effort” over time at different sites, the authors say, it’s impossible to know how big a role meat eating played in human evolution. Even before the study, many experts suspected the link between carnivory and bigger brains and bodies in early humans might be complex, says Rachel Carmody, an evolutionary biologist at Harvard University who wasn’t involved in the work. The new results, though, “take the important step of demonstrating empirically that controlling for sampling effort actually changes the interpretation.” To conduct the study, W. Andrew Barr, a paleoanthropologist at George Washington University, and colleagues reviewed previously reported data on the appearance of butchery marks at nine archaeological hotbeds of early human activity across eastern Africa spanning 2.6 million to 1.2 million years ago. As expected, the scientist found an increase in the number of cutmarks on animal bones beginning about 2 million years ago. However, the researchers noticed that archaeologists tended to find more cutmarks at the sites that have received the most research attention. In other words, the more time and effort researchers poured into a site, the more likely they were to discover evidence of meat eating. © 2022 American Association for the Advancement of Science.

Keyword: Evolution
Link ID: 28169 - Posted: 01.26.2022

By Christina Caron For the entirety of my adult life I have tried to avoid driving. I could claim all sorts of noble reasons for this: concern about the environment, a desire to save money, the health benefits gained from walking or biking. But the main reason is that I’m anxious. What if I did something stupid and accidentally pressed the gas pedal instead of the brake? What if a small child suddenly darted into the middle of the road? What if another driver was distracted or full of rage? By 2020 I had managed to avoid driving for eight years, even though I’d gotten my license in high school. Then came the pandemic. After more than a year of hunkering down in our Manhattan neighborhood, my little family of three was yearning for new surroundings. So, I booked lodging in the Adirondacks, about a three-hour drive from New York City, and — for the first time in my life — signed up for formal driving lessons. On that first day, I arrived queasy and full of impending doom, muscles tensed and brain on high alert. But my instructor assured me that we would not meet our demise — we wouldn’t be driving fast enough for that, he explained — and then he told me something that nobody ever had: “The fear never leaves you.” You have to learn to harness it, he said. Have just enough fear to stay alert and be aware of your surroundings, but not so much that it is making you overly hesitant. The idea that I didn’t need to completely erase my anxiety was freeing. Having some anxiety — especially when faced with a stressful situation — isn’t necessarily bad and can actually be helpful, experts say. Anxiety is an uncomfortable emotion, often fueled by uncertainty. It can create intense, excessive and persistent worry and fear, not just about stressful events but also about everyday situations. There are usually physical symptoms too, like fast heart rate, muscle tension, rapid breathing, sweating and fatigue. Too much anxiety can be debilitating. But a normal amount is meant to help keep us safe, experts say. © 2022 The New York Times Company

Keyword: Emotions; Evolution
Link ID: 28168 - Posted: 01.22.2022

Chloe Tenn Whether they’re predicting the outcomes of sports games or opening jars, the intelligence of octopuses and their cephalopod kin has fascinated avid sports fans and scientists alike (not that the two groups are mutually exclusive). However, insights into the animals’ brains have been limited, as structural data has come from low-tech methods such as dissection. Wen-Sung Chung, a University of Queensland Brain Institute neurobiologist who focuses on marine species, explains that octopuses have “probably the biggest centralized brain in invertebrates,” with multiple layers and lobes. Some species have more than 500 million neurons, he adds—compared to around 70 million in lab mice—making cephalopods especially intriguing as models for neuroscience. Chung and his colleagues decided to bring cephalopod neuroscience into the 21st century: using cutting-edge MRI, they probed the brains of four cephalopod species. They were especially interested in exploring whether cephalopod brain structures reflect the environments they live in. Indeed, the team reports numerous structural differences between species that live on reefs and those that dwell in deeper waters in a November 18 Current Biology paper. Giovanna Ponte, an evolutionary marine biologist at Stazione Zoologica Anton Dohrn Napoli in Italy who was not involved with the work, tells The Scientist that while this isn’t the first study to look for neurological correlates underlying ecological differences in cephalopods, it offers a new technological approach to investigating these animals’ brain morphology and diversity, and most importantly, “is the first time that there is . . . a comparative approach between different species.” © 1986–2022 The Scientist.

Keyword: Evolution; Brain imaging
Link ID: 28166 - Posted: 01.22.2022

Nicola Davis It’s a cold winter’s day, and I’m standing in a room watching my dog stare fixedly at two flower pots. I’m about to get an answer to a burning question: is my puppy a clever girl? Dogs have been our companions for millennia, domesticated sometime between 15,000 and 30,000 years ago. And the bond endures: according to the latest figures from the Pet Food Manufacturers Association 33% of households in the UK have a dog. But as well as fulfilling roles from Covid detection to lovable family rogue, scientists investigating how dogs think, express themselves and communicate with humans say dogs can also teach us about ourselves. And so I am here at the dog cognition centre at the University of Portsmouth with Calisto, the flat-coated retriever, and a pocket full of frankfurter sausage to find out how. We begin with a task superficially reminiscent of the cup and ballgame favoured by small-time conmen. Amy West, a PhD student at the centre, places two flower pots a few metres in front of Calisto, and appears to pop something under each. However, only one actually contains a tasty morsel. West points at the pot under which the sausage lurks, and I drop Calisto’s lead. The puppy makes a beeline for the correct pot. But according to Dr Juliane Kaminski, reader in comparative psychology at the University of Portsmouth, this was not unexpected. “A chimpanzee is our closest living relative – they ignore gestures like these coming from humans entirely,” she says. “But dogs don’t.” © 2022 Guardian News & Media Limited

Keyword: Learning & Memory; Evolution
Link ID: 28162 - Posted: 01.19.2022

By Sabrina Imbler Common bottlenose dolphins have sex frequently — very likely multiple times in a day. Copulation lasts only a few seconds, but social sex, which is used to maintain social bonds, can last much longer, happen more frequently and involve myriad heterosexual and homosexual pairings of dolphins and their body parts. Anything is possible, and, as new research suggests, probably pleasurable for swimmers of both sexes. According to a paper published on Monday in the journal Current Biology, female bottlenose dolphins most likely experience pleasure through their clitorises. The findings come as little surprise to scientists who research these dolphins. “The only thing that surprises me is how long it has taken us as scientists to look at the basic reproductive anatomy,” Sarah Mesnick, an ecologist at NOAA Fisheries who was not involved with the research, said, speaking of the clitoris. She added, “It took a team of brilliant women,” referring to two of the authors. “A lot of people assume that humans are unique in having sex for pleasure,” Justa Heinen-Kay, a researcher at the University of Minnesota who was not involved with the paper, wrote in an email. “This research challenges that notion.” And learning more about the anatomy of marine mammals’ genitalia has clear implications for their survival, Dr. Mesnick said: “The more we know about the social behavior of these animals, the better we’re able to understand their evolution and help use that to manage and conserve them.” Historically, researchers have focused on male genitalia, driven by prejudice toward male subjects, prejudice against female choice in sexual selection and the fact that it can be easier to study something that sticks out. “Female genitalia were assumed to be simple and uninteresting,” Dr. Heinen-Kay said. “But the more that researchers study female genitalia, the more we’re learning that this isn’t the case at all.” She added that this shift may be driven in part by the increasing number of women researchers. © 2022 The New York Times Company

Keyword: Sexual Behavior; Evolution
Link ID: 28147 - Posted: 01.12.2022

Stephen Wooding The sweetness of sugar is one of life’s great pleasures. People’s love for sweet is so visceral, food companies lure consumers to their products by adding sugar to almost everything they make: yogurt, ketchup, fruit snacks, breakfast cereals and even supposed health foods like granola bars. Schoolchildren learn as early as kindergarten that sweet treats belong in the smallest tip of the food pyramid, and adults learn from the media about sugar’s role in unwanted weight gain. It’s hard to imagine a greater disconnect between a powerful attraction to something and a rational disdain for it. How did people end up in this predicament? I’m an anthropologist who studies the evolution of taste perception. I believe insights into our species’ evolutionary history can provide important clues about why it’s so hard to say no to sweet. The basic activities of day-to-day life, such as raising the young, finding shelter and securing enough food, all required energy in the form of calories. Individuals more proficient at garnering calories tended to be more successful at all these tasks. They survived longer and had more surviving children – they had greater fitness, in evolutionary terms. One contributor to success was how good they were at foraging. Being able to detect sweet things – sugars – could give someone a big leg up. In nature, sweetness signals the presence of sugars, an excellent source of calories. So foragers able to perceive sweetness could detect whether sugar was present in potential foods, especially plants, and how much. © 2010–2022, The Conversation US, Inc.

Keyword: Chemical Senses (Smell & Taste); Evolution
Link ID: 28146 - Posted: 01.12.2022

Alejandra Marquez Janse & Christopher Intagliata Imagine you're moving to a new country on the other side of the world. Besides the geographical and cultural changes, you will find a key difference will be the language. But will your pets notice the difference? It was a question that nagged at Laura Cuaya, a brain researcher at the Neuroethology of Communication Lab at at Eötvös Loránd University in Budapest. "When I moved from Mexico to Hungary to start my post-doc research, all was new for me. Obviously, here, people in Budapest speak Hungarian. So you've had a different language, completely different for me," she said. The language was also new to her two dogs: Kun Kun and Odín. "People are super friendly with their dogs [in Budapest]. And my dogs, they are interested in interacting with people," Cuaya said. "But I wonder, did they also notice people here ... spoke a different language?" Cuaya set out to find the answer. She and her colleagues designed an experiment with 18 volunteer dogs — including her two border collies — to see if they could differentiate between two languages. Kun Kun and Odín were used to hearing Spanish; the other dogs Hungarian. The dogs sat still within an MRI machine, while listening to an excerpt from the story The Little Prince. They heard one version in Spanish, and another in Hungarian. Then the scientists analyzed the dogs' brain activity. © 2022 npr

Keyword: Language; Evolution
Link ID: 28145 - Posted: 01.08.2022

By Carl Zimmer Edward O. Wilson, a biologist and author who conducted pioneering work on biodiversity, insects and human nature — and won two Pulitzer Prizes along the way — died on Sunday in Burlington, Mass. He was 92. His death was announced on Monday by the E.O. Wilson Biodiversity Foundation. When Dr. Wilson began his career in evolutionary biology in the 1950s, the study of animals and plants seemed to many scientists like a quaint, obsolete hobby. Molecular biologists were getting their first glimpses of DNA, proteins and other invisible foundations of life. Dr. Wilson made it his life’s work to put evolution on an equal footing. “How could our seemingly old-fashioned subjects achieve new intellectual rigor and originality compared to molecular biology?” he recalled in 2009. He answered his own question by pioneering new fields of research. As an expert on insects, Dr. Wilson studied the evolution of behavior, exploring how natural selection and other forces could produce something as extraordinarily complex as an ant colony. He then championed this kind of research as a way of making sense of all behavior — including our own. As part of his campaign, Dr. Wilson wrote a string of books that influenced his fellow scientists while also gaining a broad public audience. “On Human Nature” won the Pulitzer Prize for general nonfiction in 1979; “The Ants,” which Dr. Wilson wrote with his longtime colleague Bert Hölldobler, won him his second Pulitzer, in 1991. © 2021 The New York Times Company

Keyword: Evolution
Link ID: 28125 - Posted: 12.29.2021

By Cara Giaimo Sign up for Science Times Get stories that capture the wonders of nature, the cosmos and the human body. Get it sent to your inbox. It’s tough out there for a mouse. Outdoors, its enemies lurk on all sides: owls above, snakes below, weasels around the bend. Indoors, a mouse may find itself targeted by broom-wielding humans or bored cats. Mice compensate with sharp senses of sight, hearing and smell. But they may have another set of tools we’ve overlooked. A paper published last week in Royal Society Open Science details striking similarities between the internal structures of certain small mammal and marsupial hairs and those of man-made optical instruments. In this paper as well as other unpublished experiments, the author, Ian Baker, a physicist who works in private industry, posits that these hairs may act as heat-sensing “infrared antennae” — further cluing the animals into the presence of warm-blooded predators. Although much more work is necessary to connect the structure of these hairs to this potential function, the study paints an “intriguing picture,” said Tim Caro, a professor of evolutionary ecology at the University of Bristol in England who was not involved. Dr. Baker has spent decades working with thermal imaging cameras, which visualize infrared radiation produced by heat. For his employer, the British defense company Leonardo UK Ltd., he researches and designs infrared sensors. But in his spare time he often takes the cameras to fields and forests near his home in Southampton, England, to film wildlife. Over the years, he has developed an appreciation for “how comfortable animals are in complete darkness,” he said. That led him to wonder about the extent of their sensory powers. © 2021 The New York Times Company

Keyword: Pain & Touch; Evolution
Link ID: 28120 - Posted: 12.18.2021

Rafael Yuste Michael Levin In the middle of his landmark book On the Origin of Species, Darwin had a crisis of faith. In a bout of honesty, he wrote, “To suppose that the eye with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I confess, absurd in the highest degree.” While scientists are still working out the details of how the eye evolved, we are also still stuck on the question of how intelligence emerges in biology. How can a biological system ever generate coherent and goal-oriented behavior from the bottom up when there is no external designer? In fact, intelligence—a purposeful response to available information, often anticipating the future—is not restricted to the minds of some privileged species. It is distributed throughout biology, at many different spatial and temporal scales. There are not just intelligent people, mammals, birds and cephalopods. Intelligent, purposeful problem-solving behavior can be found in parts of all living things: single cells and tissues, individual neurons and networks of neurons, viruses, ribosomes and RNA fragments, down to motor proteins and molecular networks. Arguably, understanding the origin of intelligence is the central problem in biology—one that is still wide open. In this piece, we argue that progress in developmental biology and neuroscience is now providing a promising path to show how the architecture of modular systems underlies evolutionary and organismal intelligence. © 2021 Scientific American

Keyword: Evolution; Development of the Brain
Link ID: 28118 - Posted: 12.18.2021

By Bruce Bower Evidence that cross-continental Stone Age networking events powered human evolution ramped up in 2021. A long-standing argument that Homo sapiens originated in East Africa before moving elsewhere and replacing Eurasian Homo species such as Neandertals has come under increasing fire over the last decade. Research this year supported an alternative scenario in which H. sapiens evolved across vast geographic expanses, first within Africa and later outside it. The process would have worked as follows: Many Homo groups lived during a period known as the Middle Pleistocene, about 789,000 to 130,000 years ago, and were too closely related to have been distinct species. These groups would have occasionally mated with each other while traveling through Africa, Asia and Europe. A variety of skeletal variations on a human theme emerged among far-flung communities. Human anatomy and DNA today include remnants of that complex networking legacy, proponents of this scenario say. It’s not clear precisely how often or when during this period groups may have mixed and mingled. But in this framework, no clear genetic or physical dividing line separated Middle Pleistocene folks usually classed as H. sapiens from Neandertals, Denisovans and other ancient Homo populations. “Middle Pleistocene Homo groups were humans,” says paleoanthropologist John Hawks of the University of Wisconsin–Madison. “Today’s humans are a remix of those ancient ancestors.” © Society for Science & the Public 2000–2021.

Keyword: Evolution; Sexual Behavior
Link ID: 28111 - Posted: 12.15.2021

By Sabrina Imbler The male Bornean rock frog cannot scream over the sound of a waterfall. Instead, he threatens other frogs with his feet. The frog intimidates his male competitors with a can-can-like gesture: kicking his leg up into the air, fully extending his splayed foot, and dragging it down toward the ground. This foot-flagging display may not sound threatening to a human, but its effect has to do with a frog’s visual perception. To a frog, the world contains two kinds of objects: things that are worms, and things that are not worms. If a frog sees a skinny object moving parallel to its long axis — like how a worm travels along the ground — it sees dinner. But if a frog sees a similar shape moving perpendicular its long axis — very unlike a worm — it sees a threat to flee from. Scientists call this latter movement the anti-worm stimulus, and it strikes fear into the hearts of frogs. Frogs likely evolved this visual system to hunt worms and stay safe from larger predators. Now, researchers suggest some male frogs have evolved to take advantage of their froggy brethren’s fears by kicking and lowering their legs in a gesture that looks a lot like an anti-worm signal, as a way to frighten their competition. In a paper published Wednesday in Proceedings of the Royal Society B, researchers reveal that they could amplify the foot-flagging behavior of Bornean rock frogs by giving the frogs a dose of testosterone. The hormone acts on the muscles in the frog’s leg to exaggerate the gesture, meaning the more testosterone coursing through the frog, the bigger the foot-flagging display. This flamboyant foot display, intensified by the sex hormone, suggests the frogs evolved a way to exploit their competitors’ unusual visual system to appear more dangerous to other frogs. © 2021 The New York Times Company

Keyword: Aggression; Hormones & Behavior
Link ID: 28087 - Posted: 11.20.2021

By Bruce Bower A child’s partial skull found in a remote section of a South African cave system has fueled suspicion that an ancient hominid known as Homo naledi deliberately disposed of its dead in caves. An international team led by paleoanthropologist Lee Berger of University of the Witwatersrand, Johannesburg pieced together 28 skull fragments and six teeth from a child’s skull discovered in a narrow opening located about 12 meters from an underground chamber where cave explorers first found H. naledi fossils (SN: 9/10/15). Features of the child’s skull qualify it as H. naledi, a species with an orange-sized brain and skeletal characteristics of both present-day people and Homo species from around 2 million years ago. “The case is building for deliberate, ritualized body disposal in caves by Homo naledi,” Berger said at a November 4 news conference held in Johannesburg. While that argument is controversial, there is no evidence that the child’s skull was washed into the tiny space or dragged there by predators or scavengers (SN: 4/19/16). Berger’s group describes the find in two papers published November 4 in PaleoAnthropology. In one, Juliet Brophy, a paleoanthropologist at Louisiana State University in Baton Rouge and colleagues describe the youngster’s skull. In the other, paleoanthropologist Marina Elliott of Canada’s Simon Fraser University in Burnaby and colleagues detail new explorations in South Africa’s Rising Star cave system. © Society for Science & the Public 2000–2021.

Keyword: Evolution
Link ID: 28068 - Posted: 11.09.2021

By Laura Sanders Brains are like sponges, slurping up new information. But sponges may also be a little bit like brains. Sponges, which are humans’ very distant evolutionary relatives, don’t have nervous systems. But a detailed analysis of sponge cells turns up what might just be an echo of our own brains: cells called neuroids that crawl around the animal’s digestive chambers and send out messages, researchers report in the Nov. 5 Science. The finding not only gives clues about the early evolution of more complicated nervous systems, but also raises many questions, says evolutionary biologist Thibaut Brunet of the Pasteur Institute in Paris, who wasn’t involved in the study. “This is just the beginning,” he says. “There’s a lot more to explore.” The cells were lurking in Spongilla lacustris, a freshwater sponge that grows in lakes in the Northern Hemisphere. “We jokingly call it the Godzilla of sponges” because of the rhyme with Spongilla, say Jacob Musser, an evolutionary biologist in Detlev Arendt’s group at the European Molecular Biology Laboratory in Heidelberg, Germany. Simple as they are, these sponges have a surprising amount of complexity, says Musser, who helped pry the sponges off a metal ferry dock using paint scrapers. “They’re such fascinating creatures.” © Society for Science & the Public 2000–2021.

Keyword: Evolution; Development of the Brain
Link ID: 28065 - Posted: 11.06.2021