• Brain size didn't drive primate evolution, research suggests

    Erin Conway-Smith / AP file

    Chimpanzees sit in an enclosure at the Chimp Eden rehabilitation center, near Nelspruit, South Africa in this February 2011 photo.

    By Tia Ghose
    LiveScience

    Brain organization, not overall size, may be the key evolutionary difference between primate brains, and the key to what gives humans their smarts, new research suggests.

    In the study, researchers looked at 17 species that span 40 million years of evolutionary time, finding changes in the relative size of specific brain regions, rather than changes in brain size, accounted for three-quarters of brain evolution over that time. The study, published Tuesday in the Proceedings of the Royal Society B, also revealed that massive increases in the brain's prefrontal cortex played a critical role in great ape evolution.

    "For the first time, we can really identify what is so special about great ape brain organization," said study co-author Jeroen Smaers, an evolutionary biologist at the University College London.

    Is bigger better?
    Traditionally, scientists have thought humans' superior intelligence derived mostly from the fact that our brains are three times bigger than our nearest living relatives, chimpanzees.

    But bigger isn't always better. Bigger brains take much more energy to power, so scientists have hypothesized that brain reorganization could be a smarter strategy to evolve mental abilities. [10 Odd Facts About the Brain]

    To see how brain organization evolved throughout primates, Smaers and his colleague Christophe Soligo analyzed post-mortem slices of brains from 17 different primates, then mapped changes in brain size onto an evolutionary tree.

    Over evolutionary time, several key brain regions increased in size relative to other regions. Great apes (especially humans) saw a rise in white matter in the prefrontal cortex, which contributes to social cognition, moral judgments, introspection and goal-directed planning. The white matter carries axons, the wires connecting different brain cells, suggesting that that the great apes' brains were evolving for greater neural connections.

    "The prefrontal cortex is a little bit like the CEO of the brain," Smaers told LiveScience. "It takes information from other brain areas and it synthesizes them."

    When great apes diverged from old-world monkeys about 20 million years ago, brain regions tied to motor planning also increased in relative size. That could have helped them orchestrate the complex movements needed to manipulate tools — possibly to get at different food sources, Smaers said.

    Gibbons and howler monkeys showed a different pattern. Even though their bodies and their brains got smaller over time, the hippocampus, which plays a role in spatial tasks, tended to increase in size in relation to the rest of the brain. That may have allowed these monkeys to be spatially adept and inhabit a more diverse range of environments.

    Prefrontal cortex
    The study shows that specific parts of the brain can selectively scale up to meet the demands of new environments, said Chet Sherwood, an anthropologist at George Washington University, who was not involved in the study.

    The finding also drives home the importance of the prefrontal cortex, he said.

    "It's very suggestive that connectivity of prefrontal cortex has been a particularly strong driving force in ape and human brains," Sherwood told LiveScience.

    Follow Tia Ghose on Twitter @tiaghose. Follow LiveScience @livescience, Facebook and Google+. Original article on LiveScience.com.

    Copyright 2013 LiveScience, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

  • Do chimps have a sense of fair play? Study adds to evolutionary debate

    A video from Emory University's Yerkes National Primate Research Center explains how chimpanzees were tested on their preference for fair outcomes when it comes to sharing goodies.

    By Alan Boyle, Science Editor, NBC News


    Primate researchers in Georgia have laid out what they say is the best laboratory evidence yet that chimpanzees have a human-style sense of fairness. Other researchers, however, say the study is flawed — and they're sticking to their view that fairness may be a uniquely human characteristic.

    The debate focuses on a key question about human evolution: How long ago did our ancestors acquire what Abraham Lincoln called the "better angels of our nature"? These angelic traits — such as altruism, empathy and fairness — manifest themselves in behaviors that can run counter to our own self-interest.

    The latest research, published in the Proceedings of the National Academy of Sciences, argues that a sense of fair play may have arisen millions of years ago, before our ancestors split off from the evolutionary line leading to other primates. The study's principal author, Darby Proctor of Emory University's Yerkes National Primate Research Center in Atlanta, told NBC News that the research "opens up the door for exploring the evolutionary roots of fairness in non-human animals."

    "We've concluded that chimpanzees not only get very close to the human sense of fairness, but the animals may actually have exactly the same preferences as our own species," co-author Frans de Waal, director of Emory's Living Links Center, said in a university news release.

    However, the Emory group's findings run counter to what other researchers have found in their own experiments over the past few years. One of the researchers behind those earlier studies, Keith Jensen of the University of Manchester, has said "our sense of fairness is a derived trait and may be unique to the human race."

    Today, Jensen said he and his colleagues had serious reservations about the latest experiment. "I was excited to see a replication of our ultimatum game studies, seven years on, but was disappointed by the results," he told NBC News in an email.

    How the experiment was run
    The "ultimatum game" is a key concept in all these studies: The concept refers to an arrangement in which one player makes a proposal to another player to split up a reward. For example, a parent may offer six stickers to a little girl, on the condition that she divides the treasure with her brother. A researcher may offer six banana slices to a chimp, on the condition that it divides the goodies with another chimp.

    Emory University

    Researchers report that chimpanzees can change their strategy for dividing goodies, based on whether or not the chimps they're sharing with have any say over the deal.

    If the shares are totally determined by the little girl, or the first chimp, their offer to the partner tends to be as low as possible. That's what's known as the "dictator game." But if the other partner has the power to veto a deal, it gets more complex. Make too low of an offer, and the partner might reject the proposition out of spite — even though the result is that no one gets a reward. That's the "ultimatum game."

    The Georgia researchers ran a variety of games using tokens that could be traded for either equal or unequal shares of stickers (for 20 human children, ranging in age from 2 to 7) and bananas (for six adult chimpanzees). The researchers found that the results of the game were similar for the two groups.

    If the one offering the goodies was in full control of the split, that individual kept the lion's share of the goodies. The results were different if the two partners had to agree on the split, however. "Humans typically offer generous portions, such as 50 percent of the reward, to their partners, and that's exactly what we recorded in our study with chimpanzees," Proctor said.

    How the debate is playing out
    Some questions surround the study: The second partner in the ultimatum game always accepted the offer of a split, whether it was equal or unequal. That applied to the kids as well as the chimps. Such behavior might suggest that the recipients would be happy with whatever they got, and didn't care about the fairness of the deal.

    In Jensen's eyes, the fact that none of the chimps turned down an unequal split is a "fatal flaw."

    "The ultimatum game hinges on the responder," Jensen said. "If the responder didn't understand the option of refusing, I would simply say the study did not work." Similarly, the children involved in the study may have been too young to understand that they could turn down an unfair deal — something that Proctor and her colleagues admit in their study.

    They did report, however, that both the chimps and the children occasionally expressed displeasure about an unequal division. For the kids, it was voiced in complaints such as "You got more than me!" For the chimps, it took the form of spitting water at their selfish partner, or hitting a barrier between their cages.

    Proctor and her colleagues cite other studies to back up their claim that chimps are sensitive to unfairness — such as anecdotal, non-experimental reports of chimps negotiating over the division of meat, or leafy branches. But such reports aren't yet rigorous enough to resolve the debate.

    Proctor acknowledged that more research will be required to get a firmer grasp on the better angels of a chimpanzee's nature. "We can't be sure what all was going on between the chimps," Proctor said. "That's something we'd really like to explore in the future — how much communication is necessary to convey something to another chimp."

    More about the better angels of animal nature:

    In addition to Proctor and de Waal, the authors of "Chimpanzees Play the Ultimatum Game" include Rebecca Williamson and Sarah Brosnan.

    Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

  • These 'daytime' primates have active nightlife, too, film shows

    Chia Tan

    "Our camera trap photos showed Guizhou snub-nosed monkeys moving in trees at night," lead author Chia Tan said. "We believe the monkeys were on their way to search for food."

     

    By Jennifer Viegas
    Discovery

    Most primates are active either in the day or night, but camera traps are revealing that some monkey and chimp day dwellers also go out at night for things such as pool soaks and snacks.

    The latest to be snapped unaware is the Guizhou snub-nosed monkey, Rhinopithecus brelichi. Once thought to be exclusively diurnal, this Asian monkey's nightlife is documented in the latest issue of the journal Primates.

    "Our camera trap photos showed Guizhou snub-nosed monkeys moving in trees at night," lead author Chia Tan told Discovery News. "We believe the monkeys were on their way to search for food."

    PHOTOS: Primates at Risk

    Tan, who works at the San Diego Zoo Institute for Conservation Research, and her colleagues Yeqin Yang and Kefeng Niu spied the monkeys after setting out the camera traps. Guizhou snub-nosed monkeys are endangered, with just a single global population of 700-800 individuals restricted to Fanjingshan in southwest China.

    Chia Tan

    Guizhou snub-nosed monkeys are an endangered species.

    The monkeys were active during both day and night all year round, but they went out more at night during the early spring and autumn.

    "We think the monkeys are extending their activity beyond daylight hours to increase feeding, and the highly sought-after food items are young leaves in spring and fruit and seeds in autumn," Tan explained.

    She added, "It makes sense that the monkeys take advantage of these super nutritious foods to maximize their reproduction and survival. Spring and autumn are critical times for the monkeys; they are the birthing and mating seasons, respectively."

    BIG PIC: Gorilla Smiling -- With Reason

    Since their forest home is often foggy, the researchers suspect that the monkeys may have evolved the ability to see under low light conditions. Poor eyesight along with night predators, such as the clouded leopard, would make for a potentially disastrous combination, but the monkeys seem to have mostly overcome it.

    Other primates that are active during the day have been found to have nightlives too. The well-named owl monkey, for example, is known for its nocturnal ways.

    Humans who have swum on a hot summer's night will also appreciate what was discovered about our closest living primate relatives.

    "A recent camera trap study conducted in Fongoli, Senegal, revealed nocturnal behavior -- pool soaking -- in savanna chimpanzees," Tan said.

    Eduardo Fernandez-Duque, an associate professor of anthropology at the University of Pennsylvania, told Discovery News that Tan's team used a "novel approach to the study of primate activity."

    He added, "The article combines the use of some new technology with traditional approaches to learn that the snub-nosed monkeys, traditionally considered diurnal, may show some nocturnal activity under certain circumstances. Their proposition that this flexibility in activity patterns may be associated to the temperate environment is reasonable."

    Humans, of course, fall into the day and/or night-living primate category too. This is often a survival tactic, as people with late shift jobs could attest. It's possible that our distant relatives were 24-7 individuals as well.

    "It is difficult to infer a full range of behavior from fossilized species, but I would not be surprised if some of our earliest human ancestors were regular night owls," Tan said. "They would, under certain environmental conditions, be up at night. Party anyone?"