Chapter 6. Evolution of the Brain and Behavior

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Tina Hesman Saey Face-to-face, a human and a chimpanzee are easy to tell apart. The two species share a common primate ancestor, but over millions of years, their characteristics have morphed into easily distinguishable features. Chimps developed prominent brow ridges, flat noses, low-crowned heads and protruding muzzles. Human noses jut from relatively flat faces under high-domed crowns. Those facial features diverged with the help of genetic parasites, mobile bits of genetic material that insert themselves into their hosts’ DNA. These parasites go by many names, including “jumping genes,” “transposable elements” and “transposons.” Some are relics of former viruses assimilated into a host’s genome, or genetic instruction book. Others are self-perpetuating pieces of genetic material whose origins are shrouded in the mists of time. “Transposable elements have been with us since the beginning of evolution. Bacteria have transposable elements,” says evolutionary biologist Josefa González. She doesn’t think of transposons as foreign DNA. They are parts of our genomes — like genes. “You cannot understand the genome without understanding what transposable elements are doing,” says González, of the Institute of Evolutionary Biology in Barcelona. She studies how jumping genes have influenced fruit fly evolution. Genomes of most organisms are littered with the carcasses of transposons, says Cédric Feschotte, an evolutionary geneticist at the University of Utah in Salt Lake City. Fossils of the DNA parasites build up like the remains of ancient algae that formed the white cliffs of Dover. One strain of maize, the organism in which Nobel laureate Barbara McClintock first discovered transposable elements in the 1940s, is nearly 85 percent transposable elements (SN: 12/19/09, p. 9). Corn is an extreme example, but humans have plenty, too: Transposable elements make up nearly half of the human genome. |© Society for Science & the Public 2000 - 2017

Keyword: Development of the Brain; Genes & Behavior
Link ID: 23627 - Posted: 05.17.2017

By FERRIS JABR Con Slobodchikoff and I approached the mountain meadow slowly, obliquely, softening our footfalls and conversing in whispers. It didn’t make much difference. Once we were within 50 feet of the clearing’s edge, the alarm sounded: short, shrill notes in rapid sequence, like rounds of sonic bullets. We had just trespassed on a prairie-dog colony. A North American analogue to Africa’s meerkat, the prairie dog is trepidation incarnate. It lives in subterranean societies of neighboring burrows, surfacing to forage during the day and rarely venturing more than a few hundred feet from the center of town. The moment it detects a hawk, coyote, human or any other threat, it cries out to alert the cohort and takes appropriate evasive action. A prairie dog’s voice has about as much acoustic appeal as a chew toy. French explorers called the rodents petits chiens because they thought they sounded like incessantly yippy versions of their pets back home. On this searing summer morning, Slobodchikoff had taken us to a tract of well-trodden wilderness on the grounds of the Museum of Northern Arizona in Flagstaff. Distressed squeaks flew from the grass, but the vegetation itself remained still; most of the prairie dogs had retreated underground. We continued along a dirt path bisecting the meadow, startling a prairie dog that was peering out of a burrow to our immediate right. It chirped at us a few times, then stared silently. “Hello,” Slobodchikoff said, stooping a bit. A stout bald man with a scraggly white beard and wine-dark lips, Slobodchikoff speaks with a gentler and more lilting voice than you might expect. “Hi, guy. What do you think? Are we worth calling about? Hmm?” Slobodchikoff, an emeritus professor of biology at Northern Arizona University, has been analyzing the sounds of prairie dogs for more than 30 years. Not long after he started, he learned that prairie dogs had distinct alarm calls for different predators. Around the same time, separate researchers found that a few other species had similar vocabularies of danger. What Slobodchikoff claimed to discover in the following decades, however, was extraordinary: Beyond identifying the type of predator, prairie-dog calls also specified its size, shape, color and speed; the animals could even combine the structural elements of their calls in novel ways to describe something they had never seen before. No scientist had ever put forward such a thorough guide to the native tongue of a wild species or discovered one so intricate. Prairie-dog communication is so complex, Slobodchikoff says — so expressive and rich in information — that it constitutes nothing less than language.

Keyword: Language; Evolution
Link ID: 23606 - Posted: 05.12.2017

Shelby Putt How did humans get to be so smart, and when did this happen? To untangle this question, we need to know more about the intelligence of our human ancestors who lived 1.8 million years ago. It was at this point in time that a new type of stone tool hit the scene and the human brain nearly doubled in size. Some researchers have suggested that this more advanced technology, coupled with a bigger brain, implies a higher degree of intelligence and perhaps even the first signs of language. But all that remains from these ancient humans are fossils and stone tools. Without access to a time machine, it’s difficult to know just what cognitive features these early humans possessed, or if they were capable of language. Difficult – but not impossible. Now, thanks to cutting-edge brain imaging technology, my interdisciplinary research team is learning just how intelligent our early tool-making ancestors were. By scanning the brains of modern humans today as they make the same kinds of tools that our very distant ancestors did, we are zeroing in on what kind of brainpower is necessary to complete these tool-making tasks. The stone tools that have survived in the archaeological record can tell us something about the intelligence of the people who made them. Even our earliest human ancestors were no dummies; there is evidence for stone tools as early as 3.3 million years ago, though they were probably making tools from perishable items even earlier. © 2010–2017, The Conversation US, Inc.

Keyword: Evolution; Brain imaging
Link ID: 23594 - Posted: 05.09.2017

Bruce Bower Fossils of a humanlike species with some puzzlingly ancient skeletal quirks are surprisingly young, its discoverers say. It now appears that this hominid, dubbed Homo naledi, inhabited southern Africa close to 300,000 years ago, around the dawn of Homo sapiens. H. naledi achieved worldwide acclaim in 2015 as a possibly pivotal player in the evolution of the human genus, Homo. Retrieved from an underground chamber in South Africa, fossils of this species were thought to be anywhere from 900,000 to at least 1.8 million years old (SN: 8/6/16, p. 12). A younger age for H. naledi resolves one mystery about these cave fossils. It doesn’t, however, answer questions about how long ago the species first appeared and when it died out. What is now known is that H. naledi bodies somehow ended up in Dinaledi Chamber, part of South Africa’s Rising Star cave system, between 236,000 and 335,000 years ago, an international team reports in one of three papers published May 9 in eLife. Paleoanthropologist Lee Berger of the University of the Witwatersrand in Johannesburg headed the team. Geoscientist Paul Dirks of James Cook University in Townsville, Australia, directed the dating effort. In the first paper, two methods of measuring the concentration of natural uranium and other radioactive elements, and damage caused by those elements over time, provided key age estimates for three H. naledi teeth. A thin sheet of rock deposited by flowing water just above the fossils was also dated. |© Society for Science & the Public 2000 - 201

Keyword: Evolution
Link ID: 23591 - Posted: 05.09.2017

By RICHARD O. PRUM In a mossy forest in the western Andes of Ecuador, a small, cocoa-brown bird with a red crown sings from a slim perch. Bip-Bip-WANNGG! It sounds like feedback from an elfin electric guitar. Three rival birds call back in rapid response. These male club-winged manakins are showing off to attract female mates. Their strange songs are associated with an even stranger movement. Instead of opening their beaks, they flick their wings open at their sides to make the Bips, and then snap their wings up over their backs to produce the extraordinary WANNGG. They are singing with their wings, and their potential mates seem to find the sound very alluring. This is an evolutionary innovation — a whole new way to sing. But the evolutionary mechanism behind this novelty is not adaptation by natural selection, in which only those who survive pass on their genes, allowing the species to become better adapted to its environment over time. Rather, it is sexual selection by mate choice, in which individuals pass on their genes only if they’re chosen as mates. From the peacock’s tail to the haunting melodies of the wood thrush, mate choice is responsible for much of the beauty in the natural world. Most biologists believe that these mechanisms always work in concert — that sex appeal is the sign of an objectively better mate, one with better genes or in better condition. But the wing songs of the club-winged manakin provide new insights that contradict this conventional wisdom. Instead of ensuring that organisms are on an inexorable path to self-improvement, mate choice can drive a species into what I call maladaptive decadence — a decline in survival and fecundity of the entire species. It may even lead to extinction. © 2017 The New York Times Company

Keyword: Sexual Behavior; Evolution
Link ID: 23580 - Posted: 05.06.2017

By Sam Wong Six years ago, a chimpanzee had the bright idea to use moss to soak up water, then drink from it, and seven others soon learned the trick. Three years later, researchers returned to the site to see if the practice had persisted to become part of the local chimp culture. They now report that the technique has continued to spread, and it’s mostly been learned by relatives of the original moss-spongers. This adds to earlier evidence that family ties are the most important routes for culture to spread in animals. After the first report of chimps using moss as a sponge in Budongo Forest, Uganda, researchers rarely saw the behaviour again, and wondered whether chimps still knew how to do it. So they set up an experiment, providing moss and leaves at the clay pit where the chimps had demonstrated the technique before. Then they watched to see whether chimpanzees would use leaves – a more common behaviour – or moss to soak up the mineral-rich water from the pit. The eight original moss-spongers all used moss again during the experiment, and so did another 15 chimps, showing the practice had become more widespread. The researchers wondered what factors influenced which individuals adopted it: were they connected socially, or through families, for instance? © Copyright Reed Business Information Ltd.

Keyword: Learning & Memory; Evolution
Link ID: 23543 - Posted: 04.27.2017

Bruce Bower NEW ORLEANS — A relatively small brain can pack a big evolutionary punch. Consider Homo naledi, a famously puzzling fossil species in the human genus. Despite having a brain only slightly larger than a chimpanzee’s, H. naledi displays key humanlike neural features, two anthropologists reported April 20 at the annual meeting of the American Association of Physical Anthropologists. Those brain characteristics include a region corresponding to Broca’s area, which spans parts of the right and left sides of the brain in present-day people. The left side is typically involved in speech and language. “It looks like Homo naledi’s brain evolved a huge amount of shape change that supported social emotions and advanced communication of some type,” said Shawn Hurst of Indiana University Bloomington, who presented the new findings. “We can’t say for sure whether that included language.” Frontal brain locations near Broca’s area contribute to social emotions such as empathy, pride and shame. As interactions within groups became more complex in ancient Homo species, neural capacities for experiencing social emotions and communicating verbally blossomed, Hurst suspects. Scientists don’t know how long ago H. naledi inhabited Africa’s southern tip. If H. naledi lived 2 million or even 900,000 years ago, as some researchers have suggested (SN: 8/6/16, p. 12), humanlike brains with a language-related area would be shocking. A capacity for language is thought to have emerged in Homo over the last few hundred thousand years at most. |© Society for Science & the Public 2000 - 2017.

Keyword: Evolution
Link ID: 23541 - Posted: 04.26.2017

By Virginia Morell Humpback whales are known for their operatic songs that carry across the seas. Their calves, however, whisper, uttering soft squeaks and grunts to their mothers (which you can hear above). Now, a new study suggests that loud calf voices can also attract some unwanted visitors: male humpbacks, who might separate the pair by trying to mate with the mother, and killer whales, who dine on young humpbacks. To record their sounds, scientists placed temporary tagging devices on eight humpback whale mothers and calves in the Exmouth Gulf off Western Australia, where the young whales spend months suckling to gain enough weight for their annual migrations to the Antarctic or Arctic. After listening to the recordings, scientists say the calves’ careful whispers are not cries for food, as previously thought. Instead, they may help them stay in close contact with their mothers when swimming. And, say researchers, writing today in Functional Ecology, the low decibel sounds help keep would-be predators away from the “nursery.” © 2017 American Association for the Advancement of Science

Keyword: Animal Communication
Link ID: 23534 - Posted: 04.26.2017

Amber Dance Biologist Leo Smith held an unusual job while an undergraduate student in San Diego. Twice a year, he tagged along on a chartered boat with elderly passengers. The group needed him to identify two particular species of rockfish, the chilipepper rockfish and the California shortspine thornyhead. Once he’d found the red-orange creatures, the passengers would stab themselves in the arms with the fishes’ spines. Doing so, the seniors believed, would relieve their aching arthritic joints. Smith, now at the University of Kansas in Lawrence, didn’t think much of the practice at the time, but now he wonders if those passengers were on to something. Though there’s no evidence that anything in rockfish venom can alleviate pain — most fish stings are, in fact, quite painful themselves — some scientists suspect fish venom is worth a look. Studying the way venom molecules from diverse fishes inflict pain might help researchers understand how nerve cells sense pain and lead to novel ways to dull the sensation. Smith is one of a handful of scientists who are studying fish venoms, and there’s plenty to investigate. An estimated 7 to 9 percent of fishes, close to 3,000 species, are venomous, Smith’s work suggests. Venomous fishes are found in freshwater and saltwater, including some stingrays, catfishes and stonefishes. Some, such as certain fang blennies, are favorites in home aquariums. Yet stinging fishes haven’t gotten the same attention from scientists as snakes and other venomous creatures. |© Society for Science & the Public 2000 - 2017

Keyword: Pain & Touch; Neurotoxins
Link ID: 23515 - Posted: 04.20.2017

By Elizabeth Pennisi By standing on the shoulders of giants, humans have built the sophisticated high-tech world we live in today. Tapping into the knowledge of previous generations—and those around us—was long thought to be a “humans-only” trait. But homing pigeons can also build collective knowledge banks, behavioral biologists have discovered, at least when it comes to finding their way back to the roost. Like humans, the birds work together and pass on information that lets them get better and better at solving problems. “It is a really exciting development in this field,” says Christine Caldwell, a psychologist at the University of Stirling in the United Kingdom who was not involved with the work. Researchers have admired pigeon intelligence for decades. Previous work has shown the birds are capable of everything from symbolic communication to rudimentary math. They also use a wide range of cues to find their way home, including smell, sight, sound, and magnetism. On its own, a pigeon released multiple times from the same place will even modify its navigation over time for a more optimal route home. The birds also learn specific routes from one another. Because flocks of pigeons tend to take more direct flights home than individuals, scientists have long thought some sort of “collective intelligence” is at work. © 2017 American Association for the Advancement of Science

Keyword: Animal Migration; Evolution
Link ID: 23504 - Posted: 04.18.2017

By Niall Firth The firing of every neuron in an animal’s body has been recorded, live. The breakthrough in imaging the nervous system of a hydra – a tiny, transparent creature related to jellyfish – as it twitches and moves has provided insights into how such simple animals control their behaviour. Similar techniques might one day help us get a deeper understanding of how our own brains work. “This could be important not just for the human brain but for neuroscience in general,” says Rafael Yuste at Columbia University in New York City. Instead of a brain, hydra have the most basic nervous system in nature, a nerve net in which neurons spread throughout its body. Even so, researchers still know almost nothing about how the hydra’s few thousand neurons interact to create behaviour. To find out, Yuste and colleague Christophe Dupre genetically modified hydra so that their neurons glowed in the presence of calcium. Since calcium ions rise in concentration when neurons are active and fire a signal, Yuste and Dupre were able to relate behaviour to activity in glowing circuits of neurons. For example, a circuit that seems to be involved in digestion in the hydra’s stomach-like cavity became active whenever the animal opened its mouth to feed. This circuit may be an ancestor of our gut nervous system, the pair suggest. © Copyright Reed Business Information Ltd.

Keyword: Brain imaging; Evolution
Link ID: 23483 - Posted: 04.12.2017

Nicola Davis Apes are on a par with human infants in being able to tell when people have an accurate belief about a situation or are actually mistaken, researchers say. While previous work has shown that great apes understand the goals, desires and perceptions of others, scientists say the latest finding reveals an important cognitive ability. “For the last 30 or more years people thought that belief understanding is the key marker of humans and really differentiates us from other species – and this does not seem to be the case,” said David Buttelmann, co-author of the research from the Max Planck Institute for Evolutionary Anthropology in Germany. Apes can guess what others are thinking - just like humans, study finds Read more The results follow on the heels of a study published last year which also suggests that apes understand the concept of false beliefs – after research that used eye-tracking technology to monitor the gaze of apes exposed to various pranks carried out by an actor dressed in a King Kong suit. But the new study, says Buttelmann, is an important step forward, showing that apes not only understand false belief in others, but apply that understanding to their own actions. Writing in the journal Plos One, Buttelmann and colleagues described exploring the understanding of false belief in 34 great apes, including bonobos, chimpanzees and orangutans, using a test that can be passed by human infants at one to two years of age. © 2017 Guardian News and Media Limited

Keyword: Attention; Consciousness
Link ID: 23457 - Posted: 04.06.2017

Elle Hunt Inches above the seafloor of Sydney’s Cabbage Tree Bay, with the proximity made possible by several millimetres of neoprene and a scuba diving tank, I’m just about eyeball to eyeball with this creature: an Australian giant cuttlefish. Even allowing for the magnifying effects of the mask snug across my nose, it must be about 60cm (two feet) long, and the peculiarities that abound in the cephalopod family, that includes octopuses and squid, are the more striking writ so large. ADVERTISING Its body – shaped around an internal surfboard-like shell, tailing off into a fistful of tentacles – has the shifting colour of velvet in light, and its W-shaped pupils lend it a stern expression. I don’t think I’m imagining some recognition on its part. The question is, of what? It was an encounter like this one – “at exactly the same place, actually, to the foot” – that first prompted Peter Godfrey-Smith to think about these most other of minds. An Australian academic philosopher, he’d recently been appointed a professor at Harvard. While snorkelling on a visit home to Sydney in about 2007, he came across a giant cuttlefish. The experience had a profound effect on him, establishing an unlikely framework for his own study of philosophy, first at Harvard and then the City University of New York. The cuttlefish hadn’t been afraid – it had seemed as curious about him as he was about it. But to imagine cephalopods’ experience of the world as some iteration of our own may sell them short, given the many millions of years of separation between us – nearly twice as many as with humans and any other vertebrate (mammal, bird or fish)

Keyword: Evolution; Learning & Memory
Link ID: 23429 - Posted: 03.30.2017

Erin Ross The sex of a sea lamprey may be determined by how fast it grows as a larva. Sex is determined by chromosomes in mammals and by temperature in many reptiles. But for sea lampreys — eel-like creatures that dine on blood — the growth rate of their larvae seems to control whether they are male or female. They are the first creatures known to undergo sex determination in this way. Researchers know next to nothing about sex determination in sea lampreys (Petromyzon marinus) and have long been puzzled by the observation that some adult populations are mostly male, and others female. The fish begin their lives as larvae with undifferentiated sexual organs. After a year or so, they develop gonads, and after a few more years — the timing can vary — they metamorphose into adult sucker-mouthed parasites. A team led by biologist Nick Johnson, at the US Geological Survey in Millersburg, Michigan, identified lamprey habitats in and near streams leading to the Great Lakes. Some areas were productive, with lots of food, whereas others were unproductive sites with little food. After taking measures to ensure no wild lamprey were present, they released between 1,500 and 3,000 wire-tagged larval lamprey into each of the study sites. The researchers recaptured the tagged lamprey and checked their sex after the larvae had metamorphosed into adults and migrated upstream. They found that lamprey in productive streams with lots of food were larger, reached maturity earlier and were more likely to be female. But in unproductive sites, smaller, male lamprey dominated, Johnson’s team reports in a paper published on 29 March in Proceedings of the Royal Society B1. © 2017 Macmillan Publishers Limited

Keyword: Sexual Behavior; Evolution
Link ID: 23427 - Posted: 03.30.2017

By Erik Vance The world’s smallest arachnid, the Samoan moss spider, is at a third of a millimeter nearly invisible to the human eye. The largest spider in the world is the goliath birdeater tarantula, which weighs 5 ounces and is about the size of a dinner plate. For reference, that is about the same difference in scale between that same tarantula and a bottlenose dolphin. And yet the bigger spider does not act in more complex ways than its tiny counterpart. “Insects and spiders and the like—in terms of absolute size—have among the tiniest brains we’ve come across,” says William Wcislo, a scientist at the Smithsonian Tropical Research Institute in Panama City. “But their behavior, as far as we can see, is as sophisticated as things that have relatively large brains. So then there’s the question: How do they do that?” No one would argue that a tarantula is as smart as a dolphin or having a really big brain is not an excellent way to perform complicated tasks. But a growing number of scientists are asking the question: Is it the only way? Do you need a big brain to hunt elusive prey, design complicated structures or produce complex social dynamics? For generations scientists have wondered how intelligent creatures developed large brains to perform complicated tasks. But Wcislo is part of a small community of scientists less interested in how brains have grown than how they have shrunk and yet shockingly still perform tasks as well or better than similar species that are much larger in size. In other words, it’s what scientists call brain miniaturization, not unlike the scaling down in size of the transistors in a computer chip. This research, in fact, may hold clues to innovative design strategies that engineers might incorporate in future generations of computers. © 2017 Scientific American

Keyword: Miscellaneous
Link ID: 23418 - Posted: 03.29.2017

By Lizzie Wade Ask any biologist what makes primates special, and they’ll tell you the same thing: big brains. Those impressive noggins make it possible for primates from spider monkeys to humans to use tools, find food, and navigate the complex relationships of group living. But scientists disagree on what drove primates to evolve big brains in the first place. Now, a new study comes to an unexpected conclusion: fruit. “The paper is enormously valuable,” says Richard Wrangham, a biological anthropologist at Harvard University who was not involved in the work. For the last 20 years, many scientists have argued that primates evolved bigger brains to live in bigger groups, an idea known as the “social brain hypothesis.” The new study’s large sample size and robust statistical methods suggest diet and ecology deserve more attention, Wrangham says. But not everyone is convinced. Others say that although a nutrient-rich diet allows for bigger brains, it wouldn’t be enough by itself to serve as a selective evolutionary pressure. When the authors compare diet and social life, “they’re comparing apples and oranges,” says Robin Dunbar, an evolutionary psychologist at the University of Oxford in the United Kingdom and one of the original authors of the social brain hypothesis. Alex DeCasien, the new study’s author, didn’t set out to shake up this decades-long debate. The doctoral student in biological anthropology at New York University in New York City wanted to tease out whether monogamous primates had bigger or smaller brains than more promiscuous species. She collected data about the diets and social lives of more than 140 species across all four primate groups—monkeys, apes, lorises, and lemurs—and calculated which features were more likely to be associated with bigger brains. To her surprise, neither monogamy nor promiscuity predicted anything about a primate’s brain size. Neither did any other measure of social complexity, such as group size. The only factor that seemed to predict which species had larger brains was whether their diets were primarily leaves or fruit, DeCasien and her colleagues report today in Nature Ecology & Evolution. © 2017 American Association for the Advancement of Science

Keyword: Evolution; Genes & Behavior
Link ID: 23416 - Posted: 03.28.2017

If your parrot is feeling glum, it might be tweetable. Wild keas spontaneously burst into playful behaviour when exposed to the parrot equivalent of canned laughter – the first birds known to respond to laughter-like sounds. The parrots soared after one another in aerobatic loops, exchanged foot-kicking high fives in mid-air and tossed objects to each other, in what seems to be emotionally contagious behaviour. And when the recording stops, so does the party, and the birds go back to whatever they had been doing. We already knew that these half-metre-tall parrots engage in playful behaviour, especially when young. What’s new is that a special warbling call they make has been shown to trigger behaviour that seems to be an equivalent of spontaneous, contagious laughter in humans. Moreover, it’s not just the young ones that respond, adults of both sexes join in the fun too. Raoul Schwing of the University of Veterinary Medicine in Vienna, Austria, and his team played 5-minute recordings to gatherings of between two and a dozen wild keas on a mountainside of New Zealand’s Arthur’s Pass National Park, on the southern island. The group played recordings of the warble sound, or other sounds, including two other frequent kea sounds – a screech and a whistle – plus the alarm call of a local robin species and a bland tone. © Copyright Reed Business Information Lt

Keyword: Emotions; Evolution
Link ID: 23400 - Posted: 03.24.2017

By Sam Wong It takes brains to choose a good partner. In one of the first experiments to look at the cognitive demands of choosing a mate, female guppies with big brains showed a preference for more colourful males, while those with smaller brains showed no preference. In guppies, like most animals, females are choosy about who to mate with, since they invest more in their offspring than males, which don’t help care for them. They tend to prefer males with striking colour patterns and big tails, traits that have been linked to good foraging ability and health. By choosing a male with these qualities, female guppies give their offspring a good chance of inheriting the same useful traits. Despite this, females often go on to make different choices. Alberto Corral López and colleagues at Stockholm University wanted to find out if brain size could account for this. Corral López and his team tested 36 females bred to have large brains, 36 bred to have small brains, and 16 females similar to guppies found in the wild. Previous studies have shown that large-brained guppies perform better in cognitive tests, suggesting that they are smarter. Each female was given the opportunity to associate with two males, one more colourful than the other. Females are known to spend more time close to males they would prefer to mate with, so the team timed how long they spent with each male. © Copyright Reed Business Information Ltd

Keyword: Sexual Behavior; Evolution
Link ID: 23394 - Posted: 03.23.2017

by Helen Thompson Aside from being adorable, sea otters and Indo-Pacific bottlenose dolphins share an ecological feat: Both species use tools. Otters crack open snails with rocks, and dolphins carry cone-shaped sponges to protect their snouts while scavenging for rock dwelling fish. Researchers have linked tool use in dolphins to a set of differences in mitochondrial DNA — which passes from mother to offspring — suggesting that tool-use behavior may be inherited. Biologist Katherine Ralls of the Smithsonian Institution in Washington, D.C., and her colleagues looked for a similar pattern in otters off the California coast. The team tracked diet (primarily abalone, crab, mussels, clams, urchins or snails) and tool use in the wild and analyzed DNA from 197 individual otters. Otters that ate lots of hard-shelled snails — and used tools most frequently — rarely shared a common pattern in mitochondrial DNA, nor were they more closely related to other tool-users than any other otter in the population. Unlike dolphins, sea otters may all be predisposed to using tools because their ancestors probably lived off mollusks, which required cracking open. However, modern otters only take up tools when their diet requires them, the researchers report March 21 in Biology Letters. |© Society for Science & the Public 2000 - 2017.

Keyword: Evolution
Link ID: 23386 - Posted: 03.22.2017

Cris Ledón-Rettig Picture a lion: The male has a luxuriant mane, the female doesn’t. This is a classic example of what biologists call sexual dimorphism – the two sexes of the same species exhibit differences in form or behavior. Male and female lions pretty much share the same genetic information, but look quite different. We’re used to thinking of genes as responsible for the traits an organism develops. But different forms of a trait – mane or no mane – can arise from practically identical genetic information. Further, traits are not all equally sexually dimorphic. While the tails of peacocks and peahens are extremely different, their feet, for example, are pretty much the same. Understanding how this variation of form – what geneticists call phenotypic variation – arises is crucial to answering several scientific questions, including how novel traits appear during evolution and how complex diseases emerge during a lifetime. So researchers have taken a closer look at the genome, looking for the genes responsible for differences between sexes and between traits within one sex. The key to these sexually dimorphic traits appears to be a kind of protein called a transcription factor, whose job it is to turn genes “on” and “off.” In our own work with dung beetles, my colleagues and I are untangling how these transcription factors actually lead to the different traits we see in males and females. A lot of it has to do with something called “alternative gene splicing” – a phenomenon that allows a single gene to encode for different proteins, depending on how the building blocks are joined together. © 2010–2017, The Conversation US, Inc.

Keyword: Sexual Behavior; Evolution
Link ID: 23380 - Posted: 03.21.2017