Links for Keyword: Evolution

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Carl Zimmer You are what you eat, and so were your ancient ancestors. But figuring out what they actually dined on has been no easy task. There are no Pleistocene cookbooks to consult. Instead, scientists must sift through an assortment of clues, from the chemical traces in fossilized bones to the scratch marks on prehistoric digging sticks. Scientists have long recognized that the diets of our ancestors went through a profound shift with the addition of meat. But in the September issue of The Quarterly Review of Biology, researchers argue that another item added to the menu was just as important: carbohydrates, bane of today’s paleo diet enthusiasts. In fact, the scientists propose, by incorporating cooked starches into their diet, our ancestors were able to fuel the evolution of our oversize brains. Roughly seven million years ago, our ancestors split off from the apes. As far as scientists can tell, those so-called hominins ate a diet that included a lot of raw, fiber-rich plants. After several million years, hominins started eating meat. The oldest clues to this shift are 3.3-million-year-old stone tools and 3.4-million-year-old mammal bones scarred with cut marks. The evidence suggests that hominins began by scavenging meat and marrow from dead animals. At some point hominins began to cook meat, but exactly when they invented fire is a question that inspires a lot of debate. Humans were definitely making fires by 300,000 years ago, but some researchers claim to have found campfires dating back as far as 1.8 million years. Cooked meat provided increased protein, fat and energy, helping hominins grow and thrive. But Mark G. Thomas, an evolutionary geneticist at University College London, and his colleagues argue that there was another important food sizzling on the ancient hearth: tubers and other starchy plants. © 2015 The New York Times Company

Related chapters from BP7e: Chapter 13: Homeostasis: Active Regulation of the Internal Environment; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 9: Homeostasis: Active Regulation of the Internal Environment
Link ID: 21299 - Posted: 08.15.2015

By Andrea Alfano Forget the insult “fathead.” We may actually owe our extraordinary smarts to the fat in our brain. A study published in Neuron in February revealed that the variety of fat molecules found in the human neocortex, the brain region responsible for advanced cognitive functions such as language, evolved at an exceptionally fast rate after the human-ape split. The researchers analyzed the concentrations of 5,713 different lipids, or fat molecules and their derivatives, present in samples of brain, kidney and muscle tissues taken from humans, chimpanzees, macaques and mice. Lipids have a variety of critical functions in all cells, including their role as the primary component of a cell's membrane. They are particularly important in the brain because they enable electrical signal transmission among neurons. Yet until this study, it was unknown whether the lipids in the human brain differed significantly from lipids in other mammals. The team discovered that the levels of various lipids found in human brain samples, especially from the neocortex, stood out. Humans and chimps diverged from their common ancestor around the same time, according to much evolutionary evidence. Because the two species have had about the same amount of time to rack up changes to their lipid profiles, the investigators expected them to have roughly the same number of species-specific lipid concentrations, explains computational biologist and study leader Kasia Bozek of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. Indeed, lipid changes in the cerebellum, a primitive part of the brain similar in all vertebrates, were comparable between humans and chimps. But the human neocortex has accumulated about three times more lipid changes than the chimpanzee cortex has since we split from our common ancestor. © 2015 Scientific American

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:None
Link ID: 21260 - Posted: 08.04.2015

Kill, Fido! Docile ants become aggressive guard dogs after a secret signal from their caterpillar overlord. The idea turns on its head the assumption that the two species exchange favours in an even-handed relationship. The caterpillars of the Japanese oakblue butterfly (Narathura japonica) grow up wrapped inside leaves on oak trees. To protect themselves against predators like spiders and wasps, they attract ant bodyguards, Pristomyrmex punctatus, with an offering of sugar droplets. The relationships was thought to be a fair exchange of services in which both parties benefit. But Masaru Hojo from Kobe University in Japan noticed something peculiar: the caterpillars were always attended by the same ant individuals. “It also seemed that the ants never moved away or returned to their nests,” he says. They seemed to abandon searching for food, and were just standing around guarding the caterpillar. Intrigued, Hojo and his colleagues conducted lab experiments in which they allowed some ants to interact with the caterpillars and feed on the secretions, and kept others separate. Ants that ate the caterpillar’s secretions remained close to the caterpillar. They didn’t return to their nest. And whenever the caterpillar everted its tentacles – flipped them so they turned inside out – the ants moved around rapidly, acting aggressively. © Copyright Reed Business Information Ltd.

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior; Chapter 4: The Chemistry of Behavior: Neurotransmitters and Neuropharmacology
Related chapters from MM:Chapter 4: The Chemistry of Behavior: Neurotransmitters and Neuropharmacology
Link ID: 21244 - Posted: 08.01.2015

Ewen Callaway Our ancestors were not a picky bunch. Overwhelming genetic evidence shows that Homo sapiens had sex with Neander­thals, Denisovans and other archaic relatives. Now researchers are using large genomics studies to unravel the decidedly mixed contributions that these ancient romps made to human biology — from the ability of H. sapiens to cope with environments outside Africa, to the tendency of modern humans to get asthma, skin diseases and maybe even depression. The proportion of the human genome that comes from archaic relatives is small. The genomes of most Europeans and Asians are 2–4% Neanderthal1, with Denisovan DNA making up about 5% of the genomes of Mela­nesians2 and Aboriginal Australians3. DNA slivers from other distant relatives probably pepper a variety of human genomes4. But these sequences may have had an outsize effect on human biology. In some cases, they are very different from the corresponding H. sapiens DNA, notes population geneticist David Reich of Harvard Medical School in Boston, Massachusetts — which makes it more likely that they could introduce useful traits. “Even though it’s only a couple or a few per cent of ancestry, that ancestry was sufficiently distant that it punched above its weight,” he says. Last year, Reich co-led one of two teams that catalogued the Neanderthal DNA living on in modern-day humans5, 6. The studies hinted that Neanderthal versions of some genes may have helped Eurasians to reduce heat loss or grow thicker hair. But the evidence that these genes were beneficial was fairly weak. To get a better handle on how Neanderthal DNA shapes human biology, Corinne Simonti and Tony Capra, evolutionary geneticists at Vanderbilt University in Nashville, Tennessee, turned to genome-wide association studies (GWAS) that had already compared thousands of DNA variants in people with and without a certain disease or condition. © 2015 Nature Publishing Group,

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:None
Link ID: 21240 - Posted: 07.30.2015

Carl Zimmer An ant colony is an insect fortress: When enemies invade, soldier ants quickly detect the incursion and rip their foes apart with their oversize mandibles. But some invaders manage to slip in with ease, none more mystifyingly than the ant nest beetle. Adult beetles stride into an ant colony in search of a mate, without being harassed. They lay eggs, from which larva hatch. As far as scientists can tell, workers feed the young beetles as if they were ants. When the beetles grow into adults, the ants swarm around them, grooming their bodies. In exchange for this hospitality, the beetles sink their jaws into ant larvae and freshly moulted adults in order to drink their body fluids. “They’re like vampire beetles wandering in the ant nests,” said Andrea Di Giulio, an entomologist at Roma Tre University in Rome. Dr. Di Giulio and his colleagues have now uncovered a remarkable trick that the beetles use to fool their hosts. It turns out they can perform uncanny impressions, mimicking a range of ant calls. Dr. Di Giulio and his colleagues study a species of ant nest beetle called Paussus favieri, which lives in the Atlas Mountains of Morocco, where it infiltrates the nests of Moroccan ants, known as Pheidole pallidula. Like many ant species, Pheidole pallidula makes noises by rubbing its legs against ridges on its body. The meanings of these signals vary from species to species; leaf-cutting ants summon bodyguards for the march back to the nest; in other species, a queen trills to her workers to attend to her. Scientists have found that Pheidole pallidula ants make three distinct sounds, each produced by a different caste: soldiers, workers and the queen. © 2015 The New York Times Company

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior; Chapter 19: Language and Hemispheric Asymmetry
Related chapters from MM:Chapter 15: Language and Our Divided Brain
Link ID: 21193 - Posted: 07.20.2015

By Michael Balter The human hand is a marvel of dexterity. It can thread a needle, coax intricate melodies from the keys of a piano, and create lasting works of art with a pen or a paintbrush. Many scientists have assumed that our hands evolved their distinctive proportions over millions of years of recent evolution. But a new study suggests a radically different conclusion: Some aspects of the human hand are actually anatomically primitive—more so even than that of many other apes, including our evolutionary cousin the chimpanzee. The findings have important implications for the origins of human toolmaking, as well as for what the ancestor of both humans and chimps might have looked like. Humans and chimps diverged from a common ancestor perhaps about 7 million years ago, and their hands now look very different. We have a relatively long thumb and shorter fingers, which allows us to touch our thumbs to any point along our fingers and thus easily grasp objects. Chimps, on the other hand, have much longer fingers and shorter thumbs, perfect for swinging in trees but much less handy for precision grasping. For decades the dominant view among researchers was that the common ancestor of chimps and humans had chimplike hands, and that the human hand changed in response to the pressures of natural selection to make us better toolmakers. But recently some researchers have begun to challenge the idea that the human hand fundamentally changed its proportions after the evolutionary split with chimps. The earliest humanmade stone tools are thought to date back 3.3 million years, but new evidence has emerged that some of the earliest members of the human line—such as the 4.4-million-year-old Ardipithecus ramidus (“Ardi”)—had hands that resembled those of modern humans rather than chimps, even though it did not make tools. © 2015 American Association for the Advancement of Science

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:None
Link ID: 21170 - Posted: 07.15.2015

by Bob Holmes Bonobos can be just as handy as chimpanzees. In fact, bonobos' tool-using abilities look a lot like those of early humans, suggesting that observing them could teach anthropologists about how our own ancestors evolved such skills. Until now, bonobos have been more renowned for their free and easy sex lives than their abilities with tools. They have never been seen to forage using tools in the wild, although only a handful of wild populations have been studied because of political instability in the Democratic Republic of the Congo, where they live. As for those in captivity, Itai Roffman of Haifa University in Israel and his colleagues previously observed one captive bonobo, called Kanzi, using stone tools to crack a log and extract food. However, it was possible that Kanzi was a lone genius, raised by humans and taught sign language, as well as once being shown how to use tools. To find out if other captive bonobos shared Kanzi's aptitude, Roffman's team looked to animals at a zoo in Germany and a bonobo sanctuary in Iowa. The team gave them a series of problems that required tools to solve – for example, showing the bonobos that food was buried under rocks, then leaving a tray of potential aids such as sticks and antlers nearby. Two of eight zoo animals and four of seven in the sanctuary made use of the tools – in some cases almost immediately. The bonobos used sticks, rocks and antlers to dig, and also used long sticks as levers to move larger rocks out of the way (see video above). Some used different tools in sequence. © Copyright Reed Business Information Ltd

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:None
Link ID: 21147 - Posted: 07.08.2015

By Michael Balter For much of the time dinosaurs were lording over the land, sleek marine reptiles called ichthyosaurs were the masters of the sea. The dolphinlike predators had enormous eyes for hunting and grew as long as 20 meters. But paleontologists have long been baffled by their brain structure, because most fossil specimens have been squished flat by marine sediments. One rare exception—discovered in the 1800s in southern England’s Bristol Channel—is a spectacularly preserved, 180-million-year-old ichthyosaur named Hauffiopteryx. Now, using computerized tomography (CT) scanning, researchers have created a 3D digital reconstruction of Hauffiopteryx’s skull, making a “ghost image” of its brain known as a digital endocast (above). The team, which reported its findings online earlier this month in Palaeontology, found that the brain’s optic lobes were particularly large; so were the cerebellum, which controls motor functions, and the olfactory region, where odors are processed. Taken together, the team concludes these features show ichthyosaurs were highly mobile predators with a keen sense of sight and smell. © 2015 American Association for the Advancement of Science.

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:None
Link ID: 21097 - Posted: 06.27.2015

By David Shultz Not usually lauded for their cuddly appearance, opossums were long thought to have a social inclination to match their looks; the marsupials have mostly been observed lurking alone and hissing at others who encroach on their personal space. However, a new study published online today in Biology Letters suggests that opossums sometimes live in groups and may form pair bonds with mates before the mating season starts. Based on 17,127 observations of 312 artificial nests over 8 years, scientists at the Federal University of Pernambuco in Recife, Brazil, discovered 10 instances of multiple opossums sharing the same den with no signs of hostility or ongoing reproductive activity. An additional observation made on the university campus revealed a group of 13 opossums from three separate age groups all sharing a single den. The researchers speculate that this type of “gregarious denning” may be relatively common in the wild and that males and females may work cooperatively to build a nest—a ritual that could trigger the onset of an estrous cycle in females. Furthermore, the group of 13 animals was discovered in a large concrete box housing electrical equipment, much bigger than the typical artificial dens used by scientists studying opossums. The team suspects that building larger artificial dens may promote more social interactions like the ones they observed. © 2015 American Association for the Advancement of Science

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:None
Link ID: 21059 - Posted: 06.17.2015

James Gorman Chimpanzees have the cognitive ability to cook, according to new research, if only someone would give them ovens. It’s not that the animals are ready to go head-to-head with Gordon Ramsay, but scientists from Harvard and Yale found that chimps have the patience and foresight to resist eating raw food and to place it in a device meant to appear, at least to the chimps, to cook it. That is no small achievement. In a line that could easily apply to human beings, the researchers write, “Many primate species, including chimpanzees, have difficulty giving up food already in their possession and show limitations in their self-control when faced with food.” But they found that chimps would give up a raw slice of sweet potato in the hand for the prospect of a cooked slice of sweet potato a bit later. That kind of foresight and self-control is something any cook who has eaten too much raw cookie dough can admire. The research grew out of the idea that cooking itself may have driven changes in human evolution, a hypothesis put forth by Richard Wrangham, an anthropologist at Harvard and several colleagues about 15 years ago in an article in Current Anthropology, and more recently in his book, “Catching Fire: How Cooking Made Us Human.” He argued that cooking may have begun something like two million years ago, even though hard evidence only dates back about one million years. For that to be true, some early ancestors, perhaps not much more advanced than chimps, had to grasp the whole concept of transforming the raw into the cooked. © 2015 The New York Times Company

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:None
Link ID: 21016 - Posted: 06.03.2015

By Sarah C. P. Williams Bonobos, endangered great apes considered—along with chimpanzees—the closest living relative to humans, spend most of each day climbing through trees, collecting fruit and leaves. Compare that with the lives of early humans who traversed hot, barren landscapes and it begins to make sense why we’re the fattier, less muscular primate. Over the past 3 decades, two researchers analyzed the hard-to-come-by bodies of 13 bonobos that had died in captivity and compared them with already collected data on 49 human bodies donated by means of autopsy to help understand how evolution drove this change. Although some captive bonobos have become obese, the researchers found that, on average, the apes’ body mass—which is thought to resemble that of the closest common ancestor we share with them—is composed of 10% to 13% skin, whereas humans have only 6% skin. This thinner skin, the team hypothesizes, probably arose around the same time that Homo sapiens gained the ability to sweat, allowing more time spent in hot, open areas. The scientists also found that we pack on more fat than our ape relatives: Female and male humans average 36% and 20% body fat, whereas female and male bonobos average 4% and close to 0% body fat, respectively. Increased fat, the researchers hypothesize, allowed our species to survive—and reproduce—during times of low food availability. As for muscle, the team reports online today in the Proceedings of the National Academy of Sciences, bonobos come out on top, especially when it comes to upper body muscles needed for tree climbing and swinging, which became unnecessary when humans went strictly bipedal. The new findings, the researchers say, help illustrate the forces of natural selection that may have affected H. sapiens’s soft tissues even before our brains started expanding in size and tool use shaped the species. © 2015 American Association for the Advancement of Science.

Related chapters from BP7e: Chapter 13: Homeostasis: Active Regulation of the Internal Environment; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 9: Homeostasis: Active Regulation of the Internal Environment
Link ID: 21007 - Posted: 06.02.2015

Carl Zimmer For scientists who study human evolution, the last few months have been a whirlwind. Every couple of weeks, it seems, another team pulls back the curtain on newly discovered bones or stone tools, prompting researchers to rethink what we know about early human history. On Wednesday, it happened again. Yohannes Haile-Selassie of the Cleveland Museum of Natural History and his colleagues reported finding a jaw in Ethiopia that belonged to an ancient human relative that lived some time between 3.3 and 3.5 million years. They argue that the jaw belongs to an entirely new species, which they dubbed Australopithecus deyiremeda. While some experts agree, skeptics argued that the jaw belongs to a familiar hominid species, known as Australopithecus afarensis, that existed from about 3.9 to 3 million years ago. Studies like this one are adding fresh fuel to the debate over the pace of human evolution. Some researchers now believe the human family tree bore exuberant branches early on. “I’m so excited about these discoveries, I’m driving my friends crazy,” said Carol V. Ward, a paleoanthropologist at the University of Missouri. “It makes us stop and rethink everything.” In the 1990s, the broad outlines of human evolution seemed fairly clear. Early human ancestors — known as hominids — evolved from an ancestor shared with chimpanzees about six or seven million years ago. These hominids were short, bipedal apes with small brains and arms and legs still adapted for climbing trees. Until about three million years ago, experts thought, there weren’t a lot of hominid species. In fact, some researchers argued that most hominid fossils represented just a single species. © 2015 The New York Times Company

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:None
Link ID: 20993 - Posted: 05.28.2015

By James Gorman and Robin Lindsay Before human ancestors started making stone tools by chipping off flakes to fashion hand axes and other implements, their ancestors may have used plain old stones, as animals do now. And even that simple step required the intelligence to see that a rock could be used to smash open a nut or an oyster and the muscle control to do it effectively. Researchers have been rigorous in documenting every use of tools they have found find in animals, like crows, chimpanzees and dolphins. And they are now beginning to look at how tools are used by modern primates — part of the scientists’ search for clues about the evolution of the kind of delicate control required to make and use even the simplest hand axes. Monkeys do not exhibit human dexterity with tools, according to Madhur Mangalam of the University of Georgia, one of the authors of a recent study of how capuchin monkeys in Brazil crack open palm nuts. “Monkeys are working as blacksmiths,” he said, “They’re not working as goldsmiths.” But they are not just banging away haphazardly, either. Mr. Mangalam, a graduate student who is interested in “the evolution of precise movement,” reported in a recent issue of Current Biology on how capuchins handle stones. His adviser and co-author was Dorothy M. Fragaszy, the director of the Primate Behavior Laboratory at the university. Using video of the capuchins’ lifting rocks with both hands to slam them down on the hard palm nuts, he analyzed how high a monkey lifted a stone and how fast it brought it down. He found that the capuchins adjusted the force of a strike according to the condition of the nut after the previous strike. © 2015 The New York Times Company

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior; Chapter 17: Learning and Memory
Related chapters from MM:Chapter 13: Memory, Learning, and Development
Link ID: 20952 - Posted: 05.19.2015

By Rachel Feltman Animals didn't always have heads. We know that sometime during the Cambrian Period -- around 500 million years ago, as animals transitioned from the squishy likes of the penis worm to hard-bodied arthropods -- body segments started transitioning into something like the head/body differentiation we see today. But figuring out just how that transition went can be tricky. A study published on Thursday in Current Biology looks to one of the oldest-ever brain fossils for clues. Brains, being all squishy and stuff, aren't commonly found in fossilized form, especially not 500 million years after the fact. But the new study compares two specimens: A trilobite with a squishy body and Odaraia alata, a creature said to resemble a submarine. Cute, yeah? The Cambrian was such a great time. Lead author Javier Ortega-Hernández, a postdoctoral researcher from Cambridge's Department of Earth Sciences, found that the front portions of both creatures' brains had nerve connections to their eye stalks and a hard plate called the anterior sclerite. In modern arthropods, that brain region controls the eyes. Ortega-Hernández believes that this anterior sclerite was a bridge between ancient arthropods and more modern ones. Anomalocaridids, which lived at the same time but looked very different, have a plate that Ortega-Hernández thinks came from the same ancestral anatomy that went on to form anterior sclerites in the animals he examined (and, eventually, a more modern head structure today).

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:None
Link ID: 20899 - Posted: 05.08.2015

By Ann Gibbons Nearly 42,000 years ago, ancient humans began wielding a new kind of Stone Age toolkit in southern Europe—one that included perforated shell ornaments and long, pointed stone bladelets that were thrown long distances atop spears. Now, after decades of speculation about who made the tools, scientists have finally shown that they were crafted by modern humans, rather than Neandertals. The technological breakthrough may have helped our species outcompete Neandertals, who went extinct shortly after the new tools appeared in Europe. The proof comes from a new state-of-the-art analysis of two baby teeth found in 1976 and 1992 at separate archaeological sites in northern Italy. At the time, researchers were unable to tell whether they belonged to modern humans or Neandertals. But in the new study, an international team of researchers led by Stefano Benazzi of the University of Bologna in Italy used three-dimensional digital imaging methods, including computerized tomography scans, to measure the thickness of the enamel of one of the teeth, found at the collapsed rock shelter of Riparo Bombrini in the western Ligurian Alps. The enamel was thick, as in modern humans, rather than relatively thin, as in Neandertals, the authors report online today in Science. And new radiocarbon dates on animal bones and charcoal from the site suggest this modern child lived there approximately 40,710 to 35,640 years ago. The researchers were also able to extract maternally inherited mitochondrial DNA (mtDNA) from the other child’s tooth from Grotta di Fumane, a cave in the western Lessini mountains, which dated between 41,110 and 38,500 years ago. When researchers at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, sequenced the mtDNA and compared it with that of 10 ancient modern humans and 10 Neandertals, they found it belonged to a known lineage of mtDNA, called haplogroup R, which has also been found in a 45,000-year-old modern human bone found in a riverbank near Ust’-Ishim, Siberia. © 2015 American Association for the Advancement of Science

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:None
Link ID: 20843 - Posted: 04.25.2015

By JAMES GORMAN Studies of hunters and gatherers — and of chimpanzees, which are often used as stand-ins for human ancestors — have cast bigger, faster and more powerful males in the hunter role. Now, a 10-year study of chimpanzees in Senegal shows females playing an unexpectedly big role in hunting and males, surprisingly, letting smaller and weaker hunters keep their prey. The results do not overturn the idea of dominant male hunters, said Jill D. Pruetz of Iowa State University, who led the study. But they may offer a new frame of reference on hunting, tools and human evolution. “We need to broaden our perspective,” she said. Among the 30 or so chimps Dr. Pruetz and her colleagues observed, called the Fongoli band, males caught 70 percent of the prey, mostly by chasing and running it down. But these chimps are very unusual in one respect. They are the only apes that regularly hunt other animals with tools — broken tree branches. And females do the majority of that hunting for small primates called bush babies. Craig Stanford, an anthropologist at the University of Southern California who has written extensively on chimp hunting and human evolution, said the research was “really important” because it solidified the evidence for chimps hunting with tools, which Dr. Pruetz had reported in earlier papers. It also clearly shows “the females are more involved than in other places,” he said, adding that it provides new evidence to already documented observations that female chimps are “much more avid tool users than males are.” All chimpanzees eat a variety of plant and animal foods, including insects like termites. And all chimpanzees eat some other animals. The most familiar examples of chimpanzee hunting are bands of the apes chasing red colobus monkeys through the trees in the rain forests of East Africa. © 2015 The New York Times Company

Related chapters from BP7e: 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: 20800 - Posted: 04.15.2015

by Catherine Brahic TRANSLUCENT comb jellies are some of the most primitive animals on Earth, yet they have remarkable nervous systems. Controversial data discussed at a meeting in London last month proposes that their neurons are unlike any others on Earth. This could be evidence that neurons evolved more than once in the history of animal life. The suggestion that neurons evolved in parallel multiple times has divided biologists for over a century. Ultimately, Erich Jarvis of Duke University in North Carolina told a Royal Society conference in March, the question relates to how special we are. If neurons evolved several times on our planet, then it becomes more likely that they could evolve elsewhere in the universe. Until recently, the consensus has leaned towards a very Darwinian story. In this scenario, sometime around 600 million years ago, the common ancestor to all animals gave rise to some organisms with simple neural networks. Central nervous systems arose later, allowing for greater coordination and more complex behaviours. These perhaps started out as tight balls of neurons, but eventually gave rise to the magnificently complex primate brain. This single origin scenario offers a tidy explanation for why some animals, like sponges and flat, simple placozoans, still don't have neurons: they must have branched off before these evolved and are relics of ancestral animals (see diagram). The story was somewhat turned on its head by the recent whole genome sequence of comb jellies. These small marine animals look like jellyfish but in fact seem to be only distantly related. They use a neural network just beneath their skin and a brain-like knot of neurons at one end to catch food, respond to light, sense gravity and escape predators. © Copyright Reed Business Information Ltd.

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:None
Link ID: 20786 - Posted: 04.11.2015

By Jonathan Webb Science reporter, BBC News Living in total darkness, the animals' eyes have disappeared over millions of years A study of blind crustaceans living in deep, dark caves has revealed that evolution is rapidly withering the visual parts of their brain. The findings catch evolution in the act of making this adjustment - as none of the critters have eyes, but some of them still have stumpy eye-stalks. Three different species were studied, each representing a different subgroup within the same class of crustaceans. The research is published in the journal BMC Neuroscience. The class of "malocostracans" also includes much better-known animals like lobsters, shrimps and wood lice, but this study focussed on three tiny and obscure examples that were only discovered in the 20th Century. It is the first investigation of these mysterious animals' brains. "We studied three species. All of them live in caves, and all of them are very rare or hardly accessible," said lead author Dr Martin Stegner, from the University of Rostock in Germany. Specifically, his colleagues retrieved the specimens from the coast of Bermuda, from Table Mountain in South Africa, and from Monte Argentario in Italy. One of the species was retrieved from caves on the coast of Bermuda The animals were preserved rather than living, so the team could not observe their tiny brains in action. But by looking at the physical shape of the brain, and making comparisons with what we know about how the brain works in their evolutionary relatives, the researchers were able to assign jobs to the various lobes, lumps and spindly structures they could see under the microscope. © 2015 BBC.

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior; Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 7: Vision: From Eye to Brain
Link ID: 20769 - Posted: 04.08.2015

by Jan Piotrowski It's not the most charismatic fossil ever found, but it may reveal secrets of our earliest evolution. Unearthed in Ethiopia, the broken jaw with greying teeth suggests that the Homo lineage – of which modern humans are the only surviving member – existed up to 400,000 years earlier than previously thought. The fragment dates from around 2.8 million years ago, and is by far the most ancient specimen to bear the Homo signature. The earliest such fossil was one thought to be up to 2.4 million years ages old. Showing a mixture of traits, the new find pinpoints the time when humans began their transition from primitive, apelike Australopithecus to the big-brained conquerer of the world, says Brian Villmoare from the University of Nevada, Las Vegas, whose student made the find. Geological evidence from the same area, also reported this week in a study led by Erin DiMaggio from Pennsylvania State University, shows that the jaw's owner lived just after a major climate shift in the region: forests and waterways rapidly gave way to arid savannah, leaving only the occasional crocodile-filled lake. Except for the sabre-toothed big cat that once roamed these parts, the environment ended up looking much like it does today. It was probably the pressure to adapt to this new world that jump-started our evolution into what we see looking back at us in the mirror today, according to Villmoare. © Copyright Reed Business Information Ltd.

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:None
Link ID: 20654 - Posted: 03.05.2015

by Catherine Brahic Move over Homo habilis, you're being dethroned. A growing body of evidence – the latest published this week – suggests that our "handy" ancestor was not the first to use stone tools. In fact, the ape-like Australopithecus may have figured out how to be clever with stones before modern humans even evolved. Humans have a way with flint. Sure, other animals use tools. Chimps smash nuts and dip sticks into ant nests to pull out prey. But humans are unique in their ability to apply both precision and strength to their tools. It all began hundreds of thousands of years ago when a distant ancestor began using sharp stone flakes to scrape meat off skin and bones. So who were those first toolmakers? In 2010, German researchers working in Ethiopia discovered markings on two animal bones that were about 3.4 million years old. The cut marks had clearly been made using a sharp stone, and they were at a site that was used by Lucy's species, Australopithecus afarensis. The study, led by Shannon McPherron of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, was controversial. The bones were 800,000 years older than the oldest uncontested stone tools, and at the time few seriously thought that australopithecines had been tool users. Plus, McPherron hadn't found the tool itself. The problem, says McPherron, is that if we just go on tools that have been found, we must conclude that one day somebody made a beautifully flaked Oldowan hand axe, completely out of the blue. That seems unlikely. © Copyright Reed Business Information Ltd.

Related chapters from BP7e: Chapter 6: Evolution of the Brain and Behavior
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Link ID: 20512 - Posted: 01.23.2015