Chapter 6. Evolution of the Brain and Behavior

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By Matthew Hutson Parents tend to favor children of one gender in certain situations—or so evolutionary biologists tell us. A new study used data on colored backpack sales to show that parental wealth may influence spending on sons versus daughters. In 1973 biologist Robert Trivers and computer scientist Dan Willard published a paper suggesting that parents invest more resources, such as food and effort, in male offspring when times are good and in female offspring when times are bad. According to the Trivers-Willard hypothesis, a son given lots of resources can outcompete others for mates—but when parents have few resources, they are more inclined to invest them in daughters, who generally find it easier to attract reproductive partners. Trivers and Willard further posited that parental circumstances could even influence the likelihood of having a boy or girl, a concept widely supported by research across vertebrate species. Studying parental investment after birth is difficult, however, and has produced conflicting results. The new study looked for a metric of such investment that met several criteria: it should be immune to inherent sex differences in the need for resources; it should measure investment rather than outcomes; and it should be objective rather than rely on self-reporting. Study author Shige Song, a sociologist at Queens College, City University of New York, examined spending on pink and blue backpacks purchased in China in 2015 from a large retailer, JD.com. He narrowed the data to about 5,000 bags: blue backpacks bought by households known to have at least one boy and pink ones bought by households known to have at least one girl. The results showed that wealthier families spent more on blue versus pink backpacks—suggesting greater investment in sons. Poorer families spent more on pink packs than blue ones. The findings were published online in February in Evolution and Human Behavior. © 2018 Scientific American

Keyword: Evolution
Link ID: 25000 - Posted: 05.21.2018

By Jeremy Rehm A man may be attractive because of his curly, blond hair or slick pin-striped suit, but strip everything away and one luring—maybe evolutionary—piece remains, a new study finds: how proportional his body is, especially his legs. Women prefer a man with legs that are about half his height, according to previous research; scientists believe that is an evolutionary result of women wanting to choose only healthy men. Legs that are too short, for example, have been linked to type 2 diabetes. But other proportions, such as arm length to body height or whether the elbow and knee divide a limb in half, can also relate to a person’s health. Do they influence women’s views as well? To answer this, researchers collected average body proportions from roughly 9000 men in the U.S. military and used them to create computer-generated images of male models (pictured). The scientists made the model’s arms and legs slightly longer or shorter, and then asked more than 800 heterosexual U.S. women to rank each model’s attractiveness. © 2018 American Association for the Advancement of Science.

Keyword: Sexual Behavior; Evolution
Link ID: 24986 - Posted: 05.17.2018

By Nicholas St. Fleur What makes humans so smart? For a long time the answer was simple: our big brains. But new research into the tiny noggins of a recently discovered human relative called Homo naledi may challenge that notion. The findings, published Monday, suggest that when it comes to developing complex brains, size isn’t all that matters. In 2013 scientists excavating a cave in South Africa found remains of Homo naledi, an extinct hominin now thought to have lived 236,000 to 335,000 years ago. Based on the cranial remains, the researchers concluded it had a small brain only about the size of an orange or your fist. Recently, they took another look at the skull fragments and found imprints left behind by the brain. The impressions suggest that despite its tiny size, Homo naledi’s brain shared a similar shape and structure with that of modern human brains, which are three times as large. “We’ve now seen that you can package the complexity of a large brain in a tiny packet,” said Lee Berger, a paleoanthropologist at Wits University in South Africa and an author of the paper published in the journal Proceedings of the National Academy of Sciences. “Almost in one fell swoop we slayed the sacred cow that complexity in the hominid brain was directly associated with increasing brain size.” Not every scientist agrees with their interpretation. Since its remains were first retrieved, Homo naledi has puzzled scientists. From head to toe the ancient hominin displays a medley of primitive, apelike features and more advanced, humanlike characteristics. © 2018 The New York Times Company

Keyword: Evolution
Link ID: 24977 - Posted: 05.15.2018

Hannah Devlin Scientists are preparing to create “miniature brains” that have been genetically engineered to contain Neanderthal DNA, in an unprecedented attempt to understand how humans differ from our closest relatives. In the next few months the small blobs of tissue, known as brain organoids, will be grown from human stem cells that have been edited to contain “Neanderthalised” versions of several genes. The lentil-sized organoids, which are incapable of thoughts or feelings, replicate some of the basic structures of an adult brain. They could demonstrate for the first time if there were meaningful differences between human and Neanderthal brain biology. “Neanderthals are the closest relatives to everyday humans, so if we should define ourselves as a group or a species it is really them that we should compare ourselves to,” said Prof Svante Pääbo, director of the genetics department at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, where the experiments are being performed. Pääbo previously led the successful international effort to crack the Neanderthal genome, and his lab is now focused on bringing Neanderthal traits back to life in the laboratory through sophisticated gene-editing techniques. The lab has already inserted Neanderthal genes for craniofacial development into mice (heavy-browed rodents are not anticipated), and Neanderthal pain perception genes into frogs’ eggs, which could hint at whether they had a different pain threshold to humans. Now the lab is turning its attention to the brain.

Keyword: Development of the Brain; Evolution
Link ID: 24971 - Posted: 05.13.2018

/ By David Dobbs If you think of beauty as something absolute — if you think Beyoncé or George Clooney is just beautiful, simple as that — Michael J. Ryan is here to tell you you’re wrong. Beauty, he asserts in this lovely and learned new book, exists only as a value-laden, capricious, and sometimes fleeting perception generated by the brain. Sexual selection is a counterintuitive theory that tries to explain bizarre forms and behavior. Even Darwin couldn’t quite wrap his mind around it. Beauty is literally in the eye of the beholder: It reveals itself only where and when the beholder thinks it does. In effect, then, to perceive beauty is to create it. And virtually all sexual species have evolved both the neural systems to perceive beauty and the traits that are or become so perceived. If you’re thinking this sounds circular and suspiciously chicken-and-egg, I’m here to tell you you’re right. Sexual selection is a complex, counterintuitive, three-pronged theory that seeks to explain both everyday sexual attraction and some of nature’s most bizarre forms, phenomena, and behavior. Even Darwin, who conceived the theory a century and a half ago, couldn’t quite wrap his mind around it, and the mature version that Ryan explores here is much and savagely disputed. The difficulty of explaining how sexual selection creates beauty is only Ryan’s first challenge. His second is that at least two notable books have already explained it memorably. The first, of course, was “The Descent of Man, and Selection in Relation to Sex” (Darwin’s “second most famous book,” notes Ryan), which explained it memorably but incompletely. Copyright 2018 Undark

Keyword: Emotions; Evolution
Link ID: 24966 - Posted: 05.12.2018

By Viviane Callier A human genetic variant in a gene involved in sensing cold temperatures became more common when early humans migrated out of Africa into colder climates between 20,000 and 30,000 years ago, a study published today (May 3) in PLOS Genetics shows. The advantage conferred by this variant isn’t definitively known, but the researchers suspect that it influences the gene’s expression levels, which in turn affect the degree of cold sensation. The observed pattern of positive selection strongly indicates that the allele was beneficial, but that benefit had a tradeoff—bringing with it a higher risk of getting migraines. “This paper is the latest in a series of papers showing that humans really have adapted to different environments after some of our ancestors migrated out of Africa,” explains evolutionary geneticist Rasmus Nieslen of the University of California, Berkeley, who was not involved in the study. “There are a number of adaptations associated with moving into an artic climate, but none with as clear a connection to cold as this one,” he adds. Although studies have demonstrated some striking examples of recent human adaptation, for instance, warding off infectious diseases such as malaria or having the ability to digest milk, relatively little was known about the evolutionary responses to fundamental features of the environment, namely, temperature and climate. “Obviously, humans lived in Africa for a long time, and one of the main environmental factors that changed as humans migrated north was temperature,” explains population geneticist Aida Andres. So she and Felix Key the Max Planck Institute in Leipzig homed in on a gene, TRPM8, that encodes a cation channel in the neurons that innervate the skin. It is activated by cold temperatures and necessary for sensing cold and for thermoregulation. If there was a place to look for human adaptation, this gene looked like a good candidate. © 1986-2018 The Scientist

Keyword: Pain & Touch; Evolution
Link ID: 24940 - Posted: 05.05.2018

Carl Zimmer Nine years later, Erin Wessling can still remember the first time she visited Fongoli, a savanna in southeast Senegal. “You feel like you walk into an oven,” she said. Temperatures at Fongoli can reach 110 degrees Fahrenheit or more. During every dry season, brush fires sweep across the parched landscape, leaving behind leafless trees and baked, orange soil. “It’s really nuts,” said Ms. Wessling, now a graduate student at the Max Planck Institute for Evolutionary Anthropology. Yet Ms. Wessling and her colleagues keep coming back to Fongoli, despite the harsh conditions. That’s because it’s home to some remarkable residents: chimpanzees. To study them, scientists have mostly traveled to African rain forests and woodlands, where the apes live in dense groups. The sparse populations of chimpanzees that live on savannas in western and central Africa are far less understood. Ms. Wessling and her colleagues think there are important lessons to be learned from chimps like the ones at Fongoli. Because they are our closest living relatives, they may even tell us something about our own deep history. Millions of years ago, our apelike ancestors gradually moved from woodlands to savannas and began walking upright at some point. The Fongoli chimpanzees demonstrate just how difficult that transition would have been — and how that challenge may have driven some major changes in our evolution, from evolving sweat glands to losing fur and walking upright. The savanna became the subject of long-term research in 2000, when Ms. Wessling’s undergraduate adviser at Iowa State University, Jill D. Pruetz, first paid a visit. Surveying Fongoli, Dr. Pruetz decided it would be a good place to observe the differences between chimpanzee life on a savanna compared to forests. In forests, for example, chimpanzees typically thrive on a diet of ripe fruit. That’s a rare treat on a savanna. © 2018 The New York Times Company

Keyword: Evolution
Link ID: 24920 - Posted: 04.28.2018

Jason Bittel In most North American hummingbirds, males court females by diving at them head on — but Costa’s hummingbirds (Calypte costae) perform their courtship dives off to the side. Researchers now find that this strategy allows the males to aim sounds at potential mates as if they were using a megaphone. During high-speed courtship dives, males fan their tails at the last second to create a high-pitched chirp. The faster the dive, the more those tail feathers vibrate and the higher the pitch created by the would-be Romeos. Researchers suspect that females prefer higher-pitched dives, which results in various strategies to boost the frequency of the noise a male makes. A study1 published on 12 April in Current Biology finds that male Costa’s hummingbirds can twist half of their tail feathers in the direction of the female, manipulating the volume and pitch of their chirps (see video). The researchers suspect that the targeted noise also masks audio cues that the females can use to judge how fast the males are diving. “You can think of the feather as being like a flashlight,” says Chris Clark, an ornithologist at the University of California, Riverside. “If you point the flashlight straight at something, the light is much brighter. And if you look at it from the side, at a 90-degree angle, there’s still some light but not nearly as much.” © 2018 Macmillan Publishers Limited

Keyword: Sexual Behavior; Evolution
Link ID: 24866 - Posted: 04.14.2018

Ian Sample Science editor Modern humans might never have raised a quizzical eyebrow had Homo sapiens not lost the thick, bony brows of its ancient ancestors in favour of smoother facial features, a new study suggests. Researchers at the University of York believe early humans bore prominent brow ridges as a mark of physical dominance, and as the human face evolved to become smaller and flatter, it became a canvas on which the eyebrows could portray a much richer range of emotions. “We traded dominance or aggression for a wider palette of expression,” said Paul O’Higgins, a professor of anatomy and lead author on the study. “As the face became smaller and the forehead flattened, the muscles in the face could move the eyebrows up and down and we could express all these subtler feelings.” The York team stress their conclusions are speculative, but if they are right, the evolution of smaller, flatter faces may have unleashed the social power of the eyebrow, allowing humans to communicate at a distance in more complex and nuanced ways. “We moved from a position where we wanted to compete, where looking more intimidating was an advantage, to one where it was better to get on with people, to recognise each other from afar with an eyebrow flash, and to sympathise and so on,” said Penny Spikins, a palaeolithic archaeologist at York and co-author on the study, published in Nature Ecology & Evolution. © 2018 Guardian News and Media Limited

Keyword: Emotions; Evolution
Link ID: 24845 - Posted: 04.10.2018

By Knvul Sheikh In the bare winter woods across North America, you can hear the clear whistles of Black-capped and Carolina Chickadees as they forage for food. The insects they normally love to eat are gone, so the birds must find seeds and stash them among the trees for later. The Black-capped Chickadee and its southern lookalike, the Carolina Chickadee, are like squirrels in this sense: well-known for their food-caching behavior. They’ve evolved sharp brains, with some parts that grow bigger in the winter, specifically so they can remember the location of hundreds to thousands of seeds. But in the narrow strip of land from Kansas to New Jersey where the two species overlap and mate, their offspring have a weaker memory, according to a new study published in Evolution last week. In a set of experiments, only 62.5 percent of hybrid chickadees were able to solve a puzzle to uncover their food, as opposed to 95 percent of normal chickadees. More importantly, the hybrids’ poor recall could hurt their ability to survive harsh winters. “These birds don’t migrate; they stay in their regions throughout the year, so winter survival is pretty important,” says Michael McQuillan, a biologist at Lehigh University who was the lead author of the research. “If the hybrids are less able to do this, or if they have worse memories, that could be really bad for them.” The trend could also explain why the blended birds haven’t evolved into a distinct species over time. Black-capped and Carolina Chickadees hybridize extensively—often to the chagrin of birders, who already have a hard time telling them apart. In general, hybridization is common: It occurs in about 10 percent of animal and 25 percent of plant species, McQuillan says. Many hybrids thrive, and in rare cases like the Golden-crowned Manakin and the Galapagos “Bird Bird” finch, they can form stable new lineages.

Keyword: Learning & Memory; Evolution
Link ID: 24832 - Posted: 04.07.2018

James Gorman The snow monkeys of Japan are famous, as monkeys go. This troop of Japanese macaques lives in the north, near Nagano, the mountainous, snowy site of the 1998 Winter Olympics. Others of their species live even farther north, farther than any other nonhuman primate, so they are able to adapt to winter weather. But the source of this troop’s fame is an adaptation that only they exhibit: soaking in hot spring bathing pools. Their habitat is full of natural hot springs that tend to be over 140 degrees Fahrenheit, a temperature that is apparently uncomfortable for the monkeys. It wasn’t until 1963 that a young female macaque was first observed bathing in a pool built by a hotel, with the water cooled to a temperature comfortable enough for humans and monkeys. At first, one or two monkeys joining human visitors were a curiosity , but eventually they became a nuisance and health hazard, and a park was built with hot spring pools at a comfortable 104 degrees Fahrenheit, for monkeys only. The monkeys have been a long time tourist attraction and favorite of photographers, and it looked like they were trying to stay warm. Only recently have scientists investigated this behavior by measuring levels of stress hormones and observing the effects of social structure. © 2018 The New York Times Company

Keyword: Stress; Evolution
Link ID: 24821 - Posted: 04.04.2018

Kas Roussy · You think you have a dysfunctional clan? Check out the family feud involving Humphrey, Charlie and Hugh. In the early '70s, the trio was part of a tight-knit community of wild chimpanzees in Gombe National Park, Tanzania. These are some of the same chimps that British primatologist Jane Goodall was studying at the time, looking at social and family dynamics. "Jane and other researchers who came to Gombe initially had this idea that chimpanzees were these idyllic forest-dwelling species that could provide this model for what humanity could be like," says Duke University researcher Joseph Feldblum. "They thought they were peaceful and egalitarian." They were about to get a reality check of the wild kingdom variety. According to a new study, the same things that fuel deadly clashes in humans — like power, ambition, and jealousy — can also tear apart chimpanzees. You'll recall from all those wildlife documentaries that chimps are our closest animal relatives. In Gombe, Goodall and her colleagues watched a once-unified group of chimps disintegrate into two rival factions. "There's still a bit of uncertainty, even with people who were there at the time, about exactly what happened," Feldblum tells CBC News. But thanks to new digitized data taken from Goodall's own field notes from that period, Feldblum and a team of scientists were able to get a clearer, more detailed picture of what they call "the seeds of the conflict." "We were able to examine the course of the split in more detail and pinpoint when it became obvious more precisely," says co-author and Duke anthropologist Anne Pusey. ©2018 CBC/Radio-Canada

Keyword: Aggression; Evolution
Link ID: 24820 - Posted: 04.04.2018

By Ann Gibbons With their opposable toes and flat feet, early human ancestors have often been portrayed as weird walkers, swaying from side to side or rolling off the outside edges of their feet. Now, a new study finds that this picture of awkward upright locomotion is wrong: Early members of the human family, or hominins, were already walking upright with an efficient, straight-legged gait some 4.4 million years ago. The study helps settle a long-standing debate about how quickly our ancestors developed a humanlike gait, and shows that ancient hominins didn’t have to sacrifice climbing agility to walk upright efficiently. For years, some paleoanthropologists argued that hominins like the famous 3.1-million-year-old Lucy weren’t graceful on the ground because they retained traits for climbing trees, such as long fingers and toes. In one famous experiment, researchers donned extra-long shoes—one critic called them clown shoes—to mimic walking with longer toes. The scientists stumbled over their long feet and concluded that early hominins would have been just as clumsy. But other researchers argued that natural selection would have quickly favored adaptations for efficient walking given the dangers on the ground, even while hominins were still scurrying up trees. To test these hypotheses, evolutionary anthropologist Herman Pontzer of the City University of New York (CUNY) in New York City and his team compared how humans, living apes, and monkeys use their hips, leg bones, and muscles when they walk and climb. CUNY graduate student Elaine Kozma filmed chimps, bonobos, gorillas, gibbons, and other primates in zoos so she could measure the precise angles of their legs and hips when they walked upright. She then calculated the stresses on their bones during maximum extension and found that apes put a lot of force on their massive thighs, hamstrings, and knees—forces that also help them power up trees. © 2018 American Association for the Advancement of Science.

Keyword: Evolution
Link ID: 24816 - Posted: 04.03.2018

Bruce Bower Groove patterns on the surface of modern chimpanzee brains throw a monkey wrench into proposals that some ancient southern African hominids evolved humanlike brain characteristics, a new study suggests. MRIs of eight living chimps reveal substantial variability in the shape and location of certain features on the brain surface. Some of these brains showed surface creases similar to ones that were thought to have signaled a turn toward humanlike brain organization in ancient hominids hundreds of thousands, if not millions, of years ago. Paleoanthropologist Dean Falk of Florida State University in Tallahassee and colleagues report their findings online March 13 in Brain, Behavior and Evolution. The study casts doubt on a 2014 paper by Falk that was based on casts of the inside of fossil braincases, called endocasts, which preserve impressions of these surface features. At the time, Falk argued that four endocasts from southern African hominids — three Australopithecus africanus and one Australopithecus sediba — showed folding patterns that suggested that brain reorganization was underway as early as 3 million years ago in a frontal area involved in human speech production. But MRIs of three of the chimp brains reveal comparable creases, the researchers found. Two other chimps display other frontal tissue furrows that Falk had also previously described as distinctly humanlike. |© Society for Science & the Public 2000 - 2018

Keyword: Evolution
Link ID: 24786 - Posted: 03.27.2018

Jeff Tollefson Early humans in eastern Africa crafted advanced tools and displayed other complex behaviours tens of thousands of years earlier than previously thought, according to a trio of papers published on 15 March in Science1,2,3. Those advances coincided with — and may have been driven by — major climate and landscape changes. The latest evidence comes from the Olorgesailie Basin in Southern Kenya, where researchers have previously found traces of ancient relatives of modern human as far back as 1.2 million years ago. Evidence collected at sites in the basin suggests that early humans underwent a series of profound changes at some point before roughly 320,000 years ago. They abandoned simple hand axes in favour of smaller and more advanced blades made from obsidian and other materials obtained from distant sources. That shift suggests the early people living there had developed a trade network — evidence of growing sophistication in behaviour. The researchers also found gouges on black and red rocks and minerals, which indicate that early Olorgesailie residents used those materials to create pigments and possibly communicate ideas. All of these changes in human behaviour occurred during an extended period of environmental upheaval, punctuated by strong earthquakes and a shift towards a more variable and arid climate. These changes occurred at the same time as larger animals disappeared from the site and were replaced by smaller creatures. “It’s a one-two punch combining tectonic shifts and climate shifts,” says Rick Potts, who led the work as director of the human origins programme at the Smithsonian Institution in Washington DC. “That’s the kind of stuff out of which evolution arises.” Researchers from the Smithsonian Institution digging in the Olorgesailie Basin in Kenya. © 2018 Macmillan Publishers Limited

Keyword: Evolution
Link ID: 24759 - Posted: 03.16.2018

By Elizabeth Pennisi Although it’s hard to believe that delicate nervous tissues could persist for hundreds of millions of years, that’s exactly what happened to the brains and eyes of some 15 ancestors of modern-day spiders and lobsters, called Kerygmachela kierkegaardi (after the famous philosopher Søren Kierkegaard). Found along the coast of north Greenland, the 518-million-year-old fossils contained enough preserved brains and eyes to help researchers write a brand-new history of the arthropod nervous system. Until now, many biologists had argued that ancient arthropods—which gave rise to today’s insects, spiders, and crustaceans—had a three-part brain and very simple eyes. Compound eyes, in which the “eye” is really a cluster of many smaller eyes, supposedly evolved later from a pair of legs that moved into the head and was modified to sense light. But these new fossils, which range from a few centimeters to 30 centimeters long, had a tiny, unsegmented brain, akin to what’s seen in modern velvet worms, researchers report today in Nature Communications. Despite the simple brain, Kerygmachela’s eyes were probably complex, perhaps enough to form rudimentary images. The eyes, indicated by shiny spots in the fossil’s small head, appear to be duplicated versions of the small, simple eyes seen today in soft, primitive arthropods called water bears and velvet worms. © 2018 American Association for the Advancement of Science.

Keyword: Evolution
Link ID: 24734 - Posted: 03.10.2018

Bruce Bower People have evolved to sleep much less than chimps, baboons or any other primate studied so far. A large comparison of primate sleep patterns finds that most species get somewhere between nine and 15 hours of shut-eye daily, while humans average just seven. An analysis of several lifestyle and biological factors, however, predicts people should get 9.55 hours, researchers report online February 14 in the American Journal of Physical Anthropology. Most other primates in the study typically sleep as much as the scientists’ statistical models predict they should. Two long-standing features of human life have contributed to unusually short sleep times, argue evolutionary anthropologists Charles Nunn of Duke University and David Samson of the University of Toronto Mississauga. First, when humans’ ancestors descended from the trees to sleep on the ground, individuals probably had to spend more time awake to guard against predator attacks. Second, humans have faced intense pressure to learn and teach new skills and to make social connections at the expense of sleep. As sleep declined, rapid-eye movement, or REM — sleep linked to learning and memory (SN: 6/11/16, p. 15) — came to play an outsize role in human slumber, the researchers propose. Non-REM sleep accounts for an unexpectedly small share of human sleep, although it may also aid memory (SN: 7/12/14, p. 8), the scientists contend. “It’s pretty surprising that non-REM sleep time is so low in humans, but something had to give as we slept less,” Nunn says. |© Society for Science & the Public 2000 - 2018.

Keyword: Sleep; Evolution
Link ID: 24728 - Posted: 03.07.2018

By Virginia Morell Want to say “Hello,” but don’t know the local language? Try waving your hand. Such gestures, common among humans, are also surprisingly similar among chimpanzees and bonobos, our closest great ape relatives. Now, a new study has identified numerous gestures that mean the same thing to both species. That suggests these signals have biological underpinnings and could be inherited from our last common ancestor. Gestures, signals often used to get someone’s attention or ask for or stop something, are not technically languages. They don’t have specific linguistic and grammatical rules or accepted vocabularies. But gestures still have meaning: Among chimpanzees, for example, scientists have documented that many of their movements—from mouth stroking to request food or arm raising to request grooming—are used to elicit specific responses from other chimpanzees. Researchers have now found something similar in bonobos, great apes closely related to chimpanzees but with longer legs, pink lips, and long hair that’s parted in the middle on their heads. Scientists started by shooting and analyzing videos of wild bonobos in the Democratic Republic of the Congo. When a bonobo made a common gesture that brought a consistent, satisfying response from others, it was added to the list. For example, when one bonobo looked at another while loudly scratching one arm, the second often responded by grooming the first. Because the first bonobo was almost always satisfied by this response, the researchers concluded that a “big, loud scratch” is a request for grooming. The scientists next compared the bonobo gestures to those of chimpanzees, and found that their repertoires overlapped by about 90%, significantly more than “would be expected by chance,” says lead author Kirsty Graham, a comparative psychologist at the University of York in the United Kingdom. © 2018 American Association for the Advancement of Science

Keyword: Animal Communication; Evolution
Link ID: 24709 - Posted: 02.28.2018

Lauren Smith As a shark biologist, I enjoy nothing more than going scuba diving with sharks in the wild. However, I realise it’s an immense privilege to do this as part of my work – and that for the vast majority of people experiencing the underwater world in such a way is simply not possible. Nevertheless, even without the aid of an air tank humans interact with fish on many levels and in greater numbers than they do with mammals and birds. A review published by the journal Animal Cognition in 2014 by Culum Brown, an associate professor at Macquarie University, Sydney, explains that fish are one of the vertebrate taxa most highly utilised by humans. But despite the fact that they are harvested from wild stocks as part of global fishing industries, grown under intensive aquaculture conditions, are the most common pet and are widely used for scientific research, fish are seldom afforded the same level of compassion or welfare as warm-blooded vertebrates. As Brown highlights in his review, part of the problem is the large gap between people’s perception of fish intelligence and the scientific reality. This is an important issue because public perception guides government policy. The perception of an animal’s intelligence often drives our decision on whether or not to include them in our moral circle. From a welfare perspective, most researchers would suggest that if an animal is sentient, then it can most likely suffer and should therefore be offered some form of formal protection.

Keyword: Consciousness; Evolution
Link ID: 24702 - Posted: 02.27.2018

By Alexandra Rosati The shift to a cooked-food diet was a decisive point in human history. The main topic of debate is when, exactly, this change occurred. All known human societies eat cooked foods, and biologists generally agree cooking could have had major effects on how the human body evolved. For example, cooked foods tend to be softer than raw ones, so humans can eat them with smaller teeth and weaker jaws. Cooking also increases the energy they can get from the food they eat. Starchy potatoes and other tubers, eaten by people across the world, are barely digestible when raw. Moreover, when humans try to eat more like chimpanzees and other primates, we cannot extract enough calories to live healthily. Up to 50 percent of women who exclusively eat raw foods develop amenorrhea, or lack of menstruation, a sign the body does not have enough energy to support a pregnancy—a big problem from an evolutionary perspective. Such evidence suggests modern humans are biologically dependent on cooking. But at what point in our evolutionary history was this strange new practice adopted? Some researchers think cooking is a relatively recent innovation—at most 500,000 years old. Cooking requires control of fire, and there is not much archaeological evidence for hearths and purposefully built fires before this time. The archaeological record becomes increasingly fragile farther back in time, however, so others think fire may have been controlled much earlier. Anthropologist Richard Wrangham has proposed cooking arose before 1.8 million years ago, an invention of our evolutionary ancestors. If the custom emerged this early, it could explain a defining feature of our species: the increase in brain size that occurred around this time. © 2018 Scientific American,

Keyword: Evolution
Link ID: 24698 - Posted: 02.26.2018