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Bruce Bower A nearly complete hominid skeleton known as Little Foot has finally been largely freed from the stony shell in which it was discovered in a South African cave more than 20 years ago. And in the first formal analyses of the fossils, researchers say the 3.67-million-year-old Little Foot belonged to its own species. In four papers posted online at bioRxiv.org between November 29 and December 5, paleoanthropologist Ronald Clarke of the University of the Witwatersrand in Johannesburg and colleagues assign Little Foot to a previously proposed species, Australopithecus prometheus, that has failed to gain traction among many researchers. Clarke has held that controversial view for more than a decade (SN: 5/2/15, p. 8). He found the first of Little Foot’s remains in a storage box of fossils from a site called Sterkfontein in 1994. Excavations of the rest of the skeleton began in 1997. Many other researchers, however, regard Little Foot as an early member of a hominid species called Australopithecus africanus. Anthropologist Raymond Dart first identified A. africanus in 1924 from an ancient youngster’s skull called the Taung Child. Hundreds of A. africanus fossils have since been found in South African caves, including Sterkfontein. One of those caves, Makapansgat, produced a partial braincase that Dart assigned to A. prometheus in 1948. But Dart dropped that label after 1955, assigning the braincase and another Makapansgat fossil to A. africanus. |© Society for Science & the Public 2000 - 2018.

Related chapters from BN8e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:None
Link ID: 25778 - Posted: 12.12.2018

One of the animals that's thought to give creatures like apes, dolphins and crows a run for their money when it comes to intelligence is the octopus. For those other animals, there's a pattern to how they evolved to be so smart — they live long, socially complex lives. But that's not the case for octopuses that live solitary lives for the year or two they usually survive. Now scientists think they've figured out how the octopus became so so smart, and it has to do with the loss of their shell through evolution. "Octopuses, unlike many other molluscs, they do not have a protective shell," said Piero Amodio, the lead author on the new study published in the journal Trends in Ecology & Evolution about how cephalopods (octopuses and their relatives) gained their intelligence. "So [octopuses] are very, very vulnerable to many kinds of predators — from fishes to marine mammals to birds — and the idea is that by becoming quite smart, this is a kind of weapon they can use to avoid being eaten." Amodio, a PhD student at the University of Cambridge, told Quirks & Quarks host Bob McDonald that this evolutionary process differs from those that led to intelligence in other groups of vertebrates. Intelligence in other vertebrates is thought to have arisen because they live long and socially complex lives. Building a brain is a metabolically labour intensive process, so it's a big investment for an animal to develop a big brain like in apes, dolphins, and crows — an investment they get a return on when they live a long time. ©2018 CBC/Radio-Canada.

Related chapters from BN8e: Chapter 17: Learning and Memory; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 13: Memory, Learning, and Development
Link ID: 25763 - Posted: 12.08.2018

Bruce Bower Neandertals are shaking off their reputation as head bangers. Our close evolutionary cousins experienced plenty of head injuries, but no more so than late Stone Age humans did, a study suggests. Rates of fractures and other bone damage in a large sample of Neandertal and ancient Homo sapiens skulls roughly match rates previously reported for human foragers and farmers who have lived within the past 10,000 years, concludes a team led by paleoanthropologist Katerina Harvati of the University of Tübingen in Germany. Males suffered the bulk of harmful head knocks, whether they were Neandertals or ancient humans, the scientists report online November 14 in Nature. “Our results suggest that Neandertal lifestyles were not more dangerous than those of early modern Europeans,” Harvati says. Until recently, researchers depicted Neandertals, who inhabited Europe and Asia between around 400,000 and 40,000 years ago, as especially prone to head injuries. Serious damage to small numbers of Neandertal skulls fueled a view that these hominids led dangerous lives. Proposed causes of Neandertal noggin wounds have included fighting, attacks by cave bears and other carnivores and close-range hunting of large prey animals. Paleoanthropologist Erik Trinkaus of Washington University in St. Louis coauthored an influential 1995 paper arguing that Neandertals incurred an unusually large number of head and upper-body injuries. Trinkaus recanted that conclusion in 2012, though. All sorts of causes, including accidents and fossilization, could have resulted in Neandertal skull damage observed in relatively small fossil samples, he contended (SN: 5/27/17, p. 13). |© Society for Science & the Public 2000 - 2018.

Related chapters from BN8e: Chapter 6: Evolution of the Brain and Behavior; Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 11: Emotions, Aggression, and Stress
Link ID: 25686 - Posted: 11.15.2018

By Virginia Morell When wild orangutans spot a predator, they let out a loud “kiss-squeak,” a call that sounds like a human smooching. That noise tells tigers and other enemies, “I’ve seen you,” scientists believe, and it also lets other orangutans know danger is near. Now, researchers report having heard orangutans making this call long after predators have passed—the first evidence that primates other than humans can “talk” about the past. “The results are quite surprising,” says Carel van Schaik, a primatologist at the University of Zurich in Switzerland who was not involved in the work. The ability to talk about the past or the future “is one of the things that makes language so effective,” he says. That suggests, he adds, that the new findings could provide clues to the evolution of language itself. Many mammals and birds have alarm calls, some of which include information on the type and size of a predator, its location and distance, and what level of danger it poses. But until now, researchers have never heard wild animals announcing danger after the fact. Adriano Reis e Lameira, a postdoctoral student at the University of St. Andrews in the United Kingdom, was examining alarm calls in orangutans in Sumatra’s dense Ketambe forest, where the primates have been observed for nearly 40 years. He set up a simple experiment to investigate their alarm calls: A scientist draped in a tiger-striped, spotted, or plain sheet walked on all fours along the forest floor, right underneath lone female orangutans sitting in trees at heights of 5 to 20 meters above the ground. © 2018 American Association for the Advancement of Science

Related chapters from BN8e: Chapter 6: Evolution of the Brain and Behavior; Chapter 19: Language and Lateralization
Related chapters from MM:Chapter 15: Brain Asymmetry, Spatial Cognition, and Language
Link ID: 25685 - Posted: 11.15.2018

By Neil Genzlinger Dorothy L. Cheney, whose careful research into how primates live and communicate revealed the surprising complexity of their thought processes and social structures, died on Friday at her home in Devon, Pa. She was 68. Her husband and research partner, Robert M. Seyfarth, said the cause was breast cancer. “Cheney was a spectacular scientist,” Robert M. Sapolsky, a professor of biology and neurology at Stanford University and the author of books like “A Primate’s Memoir,” said by email. “Along with Robert Seyfarth, she did wonderfully clever, elegant field experiments that revealed how other primates think about the world — showing that they think in far more sophisticated and interesting ways than people anticipated.” Rather than doing their research in laboratories, Dr. Cheney and Dr. Seyfarth spent long stretches in the wilds of Africa and elsewhere, studying gorillas, baboons, vervet monkeys and other animals. One of their best-known experiments, conducted in Kenya in 1977, showed that vervets made distress sounds not just involuntarily, out of fear, but to convey a specific message about a given threat. They hid loudspeakers in bushes, played recorded sounds of vervets and watched the reaction. A particular bark sent the animals scurrying up trees because it was a warning about leopards; a low-pitched staccato noise had them looking skyward for predatory eagles. They summarized their research in their first book, “How Monkeys See the World: Inside the Mind of Another Species” (1990). Later research in Botswana included insights into the hierarchical nature of baboon societies and its possible evolutionary effects. “Because Western scientists learned about primates by examining corpses or observing single animals brought home as pets,” they wrote in their 2007 book, “Baboon Metaphysics: The Evolution of a Social Mind,” “few if any ever learned what can be discovered only through long, patient observation: that the most human features of monkeys and apes lie not in their physical appearance but in their social relationships.” © 2018 The New York Times Company

Related chapters from BN8e: Chapter 6: Evolution of the Brain and Behavior; Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 25683 - Posted: 11.15.2018

David Sington Aubrey Manning’s hugely popular 1998 BBC series Earth Story, about the evolution and shaping of the planet Earth, inspired a generation and led to a noticeable increase in students applying to read earth sciences. Yet, Aubrey, who has died aged 88, was not a geologist, but an ethologist, whose work made an important contribution to the understanding of how animal behaviour plays a role in the evolution of new species. In a series of experiments at Oxford and Edinburgh universities – he was professor of natural history (1973-97) at the latter – Aubrey showed how mutations in genes that affect the behaviour of fruit flies could lead to reproductive isolation, a key mechanism in the creation of new species. This work laid the foundation for the modern study of the evolutionary genetics of behaviour. His 1967 publication An Introduction to Animal Behaviour, now in its sixth edition, is still the standard textbook in its field, and his lectures were so popular – packed with students from many other courses – that the university took to scheduling them for 9am on Mondays as the most effective way to get undergraduates out of bed. It was this reputation as a superb communicator of science that led the BBC to his door. When as its producer I approached him in 1997 to present Earth Story, Aubrey, with typical modesty, protested that I had the wrong man and insisted on introducing me to his geological colleagues. However, it was the very fact that the subject was new to him that was the secret of the ventures success. © 2018 Guardian News and Media Limited

Related chapters from BN8e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:None
Link ID: 25667 - Posted: 11.12.2018

By Carl Zimmer People of Asian and European descent — almost anyone with origins outside of Africa — have inherited a sliver of DNA from some unusual ancestors: the Neanderthals. These genes are the result of repeated interbreeding long ago between Neanderthals and modern humans. But why are those genes still there 40,000 years after Neanderthals became extinct? As it turns out, some of them may protect humans against infections. In a study published on Thursday, scientists reported new evidence that modern humans encountered new viruses — including some related to influenza, herpes and H.I.V. — as they expanded out of Africa roughly 70,000 years ago. Some of those infections may have been picked up directly from Neanderthals. Without immunity to pathogens they had never encountered, modern humans were particularly vulnerable. “We were actually able to not only say, ‘Yes, modern humans and Neanderthals exchanged viruses,’” said David Enard, an evolutionary biologist at the University of Arizona and co-author of the new paper, published in the journal Cell. “We are able to start saying something about which types of viruses were involved.” But if Neanderthals made us sick, they also helped keep us well. Some of the genes inherited from them through interbreeding also protected our ancestors from these infections, just as they protected the Neanderthals. Lluis Quintana-Murci, a geneticist at the Pasteur Institute in Paris who was not involved in the new research, said that until now, scientists had not dreamed of getting such a glimpse at the distant medical history of our species. “Five years ago, we would never have imagined that,” he said. © 2018 The New York Times Company

Related chapters from BN8e: Chapter 6: Evolution of the Brain and Behavior; Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 13: Memory, Learning, and Development
Link ID: 25533 - Posted: 10.05.2018

By JoAnna Klein Plants have no eyes, no ears, no mouth and no hands. They do not have a brain or a nervous system. Muscles? Forget them. They’re stuck where they started, soaking up the sun and sucking up nutrients from the soil. And yet, when something comes around to eat them, they sense it. And they fight back. How is this possible? “You’ve got to think like a vegetable now,” says Simon Gilroy, a botanist who studies how plants sense and respond to their environments at the University of Wisconsin-Madison. “Plants are not green animals,” Dr. Gilroy says. “Plants are different, but sometimes they’re remarkably similar to how animals operate.” To reveal the secret workings of a plant’s threat communication system for a study published Thursday in Science, Masatsugu Toyota (now a professor at Saitama University in Japan) and other researchers in Dr. Gilroy’s lab sent in munching caterpillars like in the video above. They also slashed leaves with scissors. They applied glutamate, an important neurotransmitter that helps neurons communicate in animals. In these and about a dozen other videos, they used a glowing, green protein to trace calcium and accompanying chemical and electrical messages in the plant. And they watched beneath a microscope as warnings transited through the leafy green appendages, revealing that plants aren’t as passive as they seem. The messages start at the point of attack, where glutamate initiates a wave of calcium that propagates through the plant’s veins, or plumbing system. The deluge turns on stress hormones and genetic switches that open plant arsenals and prepare the plant to ward off attackers — with no thought or movement. © 2018 The New York Times Company

Related chapters from BN8e: Chapter 6: Evolution of the Brain and Behavior; Chapter 3: Neurophysiology: The Generation, Transmission, and Integration of Neural Signals
Related chapters from MM:Chapter 3: Neurophysiology: The Generation, Transmission, and Integration of Neural Signals
Link ID: 25450 - Posted: 09.14.2018

By Jake Buehler Whether it’s avoiding the slap of a flyswatter or shooting a tongue out at just the right moment to capture prey, fast reflexes can mean the difference between life and death in the animal kingdom. But a new study finds that not all reflexes are created equal: Larger animals are slower on the draw than smaller ones and because of that, they can’t move nearly as fast as they should be able to. When it comes to reflexes, there’s no doubt that bigger animals are a little slower. Big animals have longer neurons, and that means more time for a signal to travel from the spine to a leg muscle, for example. But nerve speed isn’t the only thing that slows down reflexes. So in the new study, researchers decided to look at myriad factors, like how fast muscles can generate force. They combed through data from other studies on electrically stimulated nerves and muscles in animals as small as shrews to as large as elephants. They also looked at the gaits of these mammals to calculate how long their stride and foot-down positions were in relation to their body size, which allowed researchers to look at how relatively quick their reflexes are. As size scales up, so does the total time it takes for muscles to respond, the team reported yesterday in the Proceedings of the Royal Society B. Large mammals experience a delay between nerve firing and muscle movement that is more than 15 times longer than small mammals. But, relative to the speed of their body movements, that delay is only twice as long—which means to compensate for slow signals, they’re moving more slowly. If this didn’t happen, a running 250-kilogram elk would be a cartoonish blur of legs, taking steps far faster than its reflexes could ever respond to. Call it a biological speed limit. © 2018 American Association for the Advancement of Science

Related chapters from BN8e: Chapter 3: Neurophysiology: The Generation, Transmission, and Integration of Neural Signals; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 3: Neurophysiology: The Generation, Transmission, and Integration of Neural Signals
Link ID: 25398 - Posted: 08.31.2018

By Carl Zimmer In a limestone cave nestled high above the Anuy River in Siberia, scientists have discovered the fossil of an extraordinary human hybrid. The 90,000-year-old bone fragment came from a female whose mother was Neanderthal, according to an analysis of DNA discovered inside it. But her father was not: He belonged to another branch of ancient humanity known as the Denisovans. Scientists have been recovering genomes from ancient human fossils for just over a decade. Now, with the discovery of a Neanderthal-Denisovan hybrid, the world as it was tens of thousands of years ago is coming into remarkable new focus: home to a marvelous range of human diversity. In 2010, researchers working in the Siberian cave, called Denisova, announced they had found DNA from a scrap of bone representing an unknown group of humans. Subsequent discoveries in the cave confirmed that the Denisovans were a lineage distinct from modern humans. Scientists can’t yet say what Denisovans looked like or how they behaved, but it’s clear they were separated from Neanderthals and modern humans by hundreds of thousands of years of evolution. Until now, scientists had indirect clues that Neanderthals, Denisovans and modern humans interbred, at least a few times. But the new study, published on Wednesday in the journal Nature, offers clear evidence. “They managed to catch it in the act — it’s an amazing discovery,” said Sharon Browning, a statistical geneticist at the University of Washington who was not involved in the new study. © 2018 The New York Times Company

Related chapters from BN8e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:None
Link ID: 25367 - Posted: 08.23.2018

James R. Howe VI In May 2007, Wim Hof went on a short hike in well-worn summer clothes, a pair of shorts and open-toed sandals. But it may have been a poor choice: his foot started to hurt and he had to turn back after four and a half miles. There are two crucial details to this story: Hof began his hike at Base Camp on Mount Everest, and the pain in his foot was caused by severe frostbite. He had reason to think he could withstand the extreme conditions; Wim Hof is also known as “The Iceman,” holder of 26 world records and one of the most successful extreme athletes of all time. He attributes his success to a breathing method that he thinks exploits his “reptilian brain,” helping him acquire a superhuman tolerance to punishing cold. According to some, tricks like these fool the lizard part of your brain – the more primitive, unconscious mind – and can be used to make us vulnerable to marketing, lose us money, or maybe even elect Donald Trump. Paul MacLean first proposed the idea of the “lizard brain” in 1957 as part of his triune brain concept, theorizing that the human brain supposedly consists of three sections, nested based on their evolutionary age. He believed the neocortex, which he thought arose in primates, is the largest, outermost, and newest part of the human brain: It houses our conscious mind and handles learning, language, and abstract thought. MacLean thought the older, deeper limbic system – which mediates emotion and motivation – began in mammals. Finally, he traced the brainstem and basal ganglia back to primordial reptiles, theorizing that they controlled our reflexes, as well as our four major instincts: to fight, flee, feed, and fornicate.

Related chapters from BN8e: Chapter 6: Evolution of the Brain and Behavior; Chapter 2: Functional Neuroanatomy: The Nervous System and Behavior
Related chapters from MM:Chapter 2: Cells and Structures: The Anatomy of the Nervous System
Link ID: 25356 - Posted: 08.21.2018

By Carl Zimmer In 2003, researchers digging in a mountain cave on the Indonesian island of Flores discovered astonishing fossils of a tiny, humanlike individual with a small, chimp-sized brain. They called the species Homo floresiensis. These relatives of modern humans stood just over three feet tall. Several villages in the area, scientists noted, are inhabited by people whose average height is 4 feet 9 inches. Was this the result of interbreeding long ago between taller modern humans and shorter Homo floresiensis? Fifteen years after the bones’ discovery, a study of the DNA of living people on Flores has delivered a verdict. “It’s rare in science that you set about to answer a question and you get something of a definitive answer and it’s the end,” said Richard E. Green, a geneticist at the University of California, Santa Cruz, and a co-author of the study, published on Thursday in Science. “The answer is a clear enough ‘no’ that I’m done with it.” But as often happens in science, the answer to one question raises new ones. The study shows that at least twice in ancient history, humans and their relatives (known as hominins) arrived on Flores and then grew shorter. And not just humans: Other research has shown that elephants also arrived on Flores twice, and both times the species evolved into dwarves. So what mysterious power does this island have to shrink the body? When the fossils of Homo floresiensis first came to light, many researchers hoped they might still hold fragments of DNA. They were encouraged by the initial dating of the fossils — an estimated age of perhaps just 13,000 years. © 2018 The New York Times Company

Related chapters from BN8e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:None
Link ID: 25288 - Posted: 08.03.2018

by Sarah Kaplan For years, scientists at the Smithsonian Tropical Research Institute in Panama had whispered about the remote island where monkeys used stone tools. A botanist had witnessed the phenomenon during a long-ago survey — but, being more interested in flora than fauna at the time, she couldn't linger to investigate. A return to the site would require new funds, good weather for a treacherous 35-mile boat ride, and days of swimming, hiking and camping amid rocky, wave-pounded shorelines and dense tropical forest. “For while, it kind of just stayed a rumor,” said Brendan Barrett, a behavioral ecologist at the Max Planck Institute in Germany and a visiting researcher at STRI. But when Barrett and his colleagues finally arrived at Jicarón Island in Panama's Coiba National Park last year, what they found was well-worth the effort: Tiny white-faced capuchin monkeys were using stones almost half their body weight as hammers to smash open shellfish, nuts and other foods. “We were stunned,” said Barrett, the lead author of a new paper on the discovery posted on the preprint website bioRxiv. The capuchins are the first animals of their genus observed using stone tools, and only the fourth group of nonhuman primates known to do so. Sophisticated, social, and tolerant of observation, they also provide scientists with an ideal system for studying what causes a species to venture into the stone age — and could help researchers understand how and why our own ancestors first picked up stone tools more than 2 million years ago. © 1996-2018 The Washington Post

Related chapters from BN8e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:None
Link ID: 25175 - Posted: 07.06.2018

By Elizabeth Gamillo Why does a wild rabbit flee when a person approaches it, but a domestic rabbit sticks around for a treat? A new study finds that domestication may have triggered changes in the brains of these—and perhaps other—animals that have helped them adapt to their new, human-dominated environment. The new study provides “specific and new insights” into the ongoing debate over the physiological factors shaping domestication and evolution, says Marcelo Sánchez-Villagra, a professor of paleobiology at the University of Zurich in Switzerland who was not involved with the work. The leader of the research team, animal geneticist Leif Andersson of Uppsala University in Sweden and Texas A&M University in College Station, thinks the process of domestication has led to changes in brain structure that allow the rabbit to be less nervous around humans. To find out, he and colleagues took MRI scans of the brains of eight wild and eight domestic rabbits and compared the results. The team found that the amygdala, a region of the brain that processes fear and anxiety, is 10% smaller in domesticated rabbits than in wild rabbits. Meanwhile, the medial prefrontal cortex, which controls responses to aggressive behavior and fear, is 11% larger in domesticated rabbits. The researchers also found that the brains of domesticated rabbits are less able to process information related to fight-or-flight responses because they have less white matter than their feral cousins do. White matter handles information processing. When a wild rabbit is in danger, more white matter is needed for faster reflexes and for learning what to be afraid of. © 2018 American Association for the Advancement of Science.

Related chapters from BN8e: Chapter 15: Emotions, Aggression, and Stress; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 11: Emotions, Aggression, and Stress
Link ID: 25142 - Posted: 06.26.2018

By Maggie Koerth-Baker If an animal is smart enough, should we treat it like a human? An abstract question, but one that found its way into a courtroom recently. A case bidding for consideration by the New York State Court of Appeals sought to extend the legal concept of habeas corpus — which allows a person to petition a court for freedom from unlawful imprisonment — to cover two privately-owned chimpanzees. The case for giving the chimps a human right like freedom from unlawful incarceration is based on their similarity to humans — they can think, feel and plan, argue the people bringing the case on behalf of the chimpanzees, so shouldn’t they have some guarantees of liberty? The court declined to hear the case, but one judge did say that some highly intelligent animals probably should be treated more like people and less like property. It’s just one judge, but you hear this kind of thing a lot from animal rights activists. The Nonhuman Rights Project, the nonprofit behind the habeas corpus lawsuit, has a stated goal of securing increased, human-like rights for great apes, elephants, dolphins and whales — highly intelligent, charismatic mammals. So, does a chimpanzee deserve more rights than, say, a pigeon? The logic that leads to “yes” is clear enough, but putting it into practice would be tough, scientists say. Because when it comes to measuring intelligence, we’re actually a little dumb. One of the problems: Animals don’t stack up the way you’d expect. “[Pigeons have] knocked our socks off in our own lab and other people’s labs in terms of what they can do,” said Edward Wasserman, a professor of experimental psychology at the University of Iowa. “Pigeons can blow the doors off monkeys in some tasks.” Experts who study animal intelligence across species say we can’t rank animals by their smarts — scientists don’t even try anymore — which means there’s no objective way to determine which animals would deserve more human-like rights.

Related chapters from BN8e: Chapter 6: Evolution of the Brain and Behavior; Chapter 1: Biological Psychology: Scope and Outlook
Related chapters from MM:Chapter 1: An Introduction to Brain and Behavior
Link ID: 25047 - Posted: 06.01.2018

By Elizabeth Pennisi Three nearly identical genes could help explain how 0.5 liters of gray matter in early human ancestors became the 1.4-liter organ that has made our species so successful and distinctive. The newly identified genes could also help explain how brain development sometimes goes wrong, leading to neurological disorders. The genes, descendants of an ancient developmental gene that multiplied and changed in the course of evolution, add to a growing list of DNA implicated in human brain expansion. But they stand out because so much has been learned about how they work their magic, says James Noonan, an evolutionary genomicist at Yale University. Researchers have shown that this trio boosts the number of potential nerve cells in brain tissue, and one team even pinned down the protein interactions likely responsible. “These are new proteins that are potentially modifying a very important pathway in brain development in a very powerful way,” Noonan adds. Until now, the four genes were thought to be one, NOTCH2NL, itself a spinoff of the NOTCH gene family, which controls the timing of development in everything from fruit flies to whales. But two studies in the 31 May issue of Cell trace a series of genetic accidents in recent evolutionary history that have yielded four very closely related NOTCH2NL genes in humans (see graphic, below). David Haussler, a bioinformatician at the University of California, Santa Cruz, and his colleagues got on the trail of the genes after they discovered that the NOTCH pathway works differently in human and macaque brain organoids—test tube models of the developing brain. NOTCH2NL was missing in the macaque organoid and, later analyses showed, in other nonhuman apes as well. That suggested NOTCH2NL might have played a unique role in human evolution. © 2018 American Association for the Advancement of Science.

Related chapters from BN8e: Chapter 7: Life-Span Development of the Brain and Behavior; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 13: Memory, Learning, and Development
Link ID: 25046 - Posted: 06.01.2018

By Carl Zimmer Early inhabitants of the Americas split into two populations over 13,000 years ago, according to a new study of ancient DNA, and remained separated for thousands of years. Eventually, somewhere, the two groups met again and began commingling. Today, their descendants inhabit a vast region stretching from Mexico to the southern tip of South America. The research, published on Thursday in the journal Science, paints a complex picture of human migrations through the Americas. When people arrived in the Western Hemisphere from Asia, they didn’t just move to new territories and settle down. “This study is important because it begins to move us away from overly simplistic models of how people first spread throughout the Americas,” said Deborah A. Bolnick, a geneticist at the University of Texas at Austin, who was not involved in the study. The findings emerged from a study of 91 ancient genomes of people who lived as long as 4,800 years ago in what are now Alaska, California and Ontario. They represent a major addition to the catalog of ancient DNA in the Western Hemisphere. Until the 1990s, archaeological sites provided much of the evidence for the spread of people across the Americas. There’s firm archaeological evidence that people had reached southern Chile by 14,500 years ago, for example; some researchers even argue that people arrived several thousand years earlier. Yet archaeology alone has left many questions unanswered, such as who exactly lived in those early sites and how they were related to each other. Geneticists are seeking to answer some of those questions by looking at the DNA of living Native Americans. Early studies on small fragments of genes suggested that all Native Americans south of the Arctic descended from the same group of migrants, who may have traveled across the Bering Land Bridge connecting Asia to what is now Alaska at the end of the last ice age. © 2018 The New York Times Company

Related chapters from BN8e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:None
Link ID: 25044 - Posted: 06.01.2018

By Ashley Yeager Finding food and lighting fires might explain why humans have such big brains, researchers report yesterday (May 23) in Nature. Humans’ brains are six times as large as those of similarly sized mammals, an observation that has led scientists to ponder for decades what led to such big noodles. Studies suggest social challenges, such as cooperating to hunt, or sharing cultural knowledge spurred the expansion, but a mathematical model to explain human brain evolution finds the environment had a stronger influence. Study coauthors Mauricio González-Forero and Andy Gardner of the University of St. Andrews developed a computer model to simulate the effects of social, environmental, and cultural challenges on brain size over time. “We were expecting social challenges to be a strong promoter of brain size,” González-Forero tells New Scientist. Surprisingly, environmental challenges won out. About 60 percent of the increase in brain size over our ape ancestors came as a result of surviving in the environment, finding and caching food, for example. Another 30 percent came from banding together to survive, and the final 10 percent came from competing with other human groups, the researchers report. If left alone to survive, humans’ brains would be even bigger, according to the model, González-Forero tells The Los Angeles Times. Increasing the cooperative challenges in the model to greater than 30 percent decreased brain size, the team found. “Cooperation decreases brain size because you can rely on the brain of other individuals and you don’t need to invest in such a large and expensive brain,” González-Forero says. The Scientist

Related chapters from BN8e: Chapter 6: Evolution of the Brain and Behavior; Chapter 1: Biological Psychology: Scope and Outlook
Related chapters from MM:Chapter 1: An Introduction to Brain and Behavior
Link ID: 25019 - Posted: 05.25.2018

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

Related chapters from BN8e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:None
Link ID: 25000 - Posted: 05.21.2018

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

Related chapters from BN8e: Chapter 6: Evolution of the Brain and Behavior
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Link ID: 24977 - Posted: 05.15.2018