Links for Keyword: Evolution

Follow us on Facebook and Twitter, or subscribe to our mailing list, to receive news updates. Learn more.


Links 1 - 20 of 795

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
Related chapters from MM:None
Link ID: 24977 - Posted: 05.15.2018

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

Related chapters from BN8e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:None
Link ID: 24920 - Posted: 04.28.2018

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.

Related chapters from BN8e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:None
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

Related chapters from BN8e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:None
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

Related chapters from BN8e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:None
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.

Related chapters from BN8e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:None
Link ID: 24734 - Posted: 03.10.2018

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,

Related chapters from BN8e: Chapter 6: Evolution of the Brain and Behavior; Chapter 13: Homeostasis: Active Regulation of the Internal Environment
Related chapters from MM:Chapter 9: Homeostasis: Active Regulation of the Internal Environment
Link ID: 24698 - Posted: 02.26.2018