baboons that live in close social groups are healthier and have longer-lived children, according to scientists. the research supports the idea that close human groups are good for mental and physical wellbeing and sheds light on when group-living might have evolved among our ancestors.
the conclusions come from a 15-year study of a group of baboons in the moremi game reserve of the okavango delta in botswana. led by robert seyfarth and dorothy cheney of the university of pennsylvania, the observations were carried out for seven hours a day, six days a week between 1992 and 2007. the observers monitored the reproductive lives of 66 adult females during this time.
the analysis, published today in the proceedings of the royal society b, was led by joan silk, an anthropologist at the university of california, los angeles. it shows that the offspring of females with the strongest social bonds were about 1.5 times as likely to be alive at 5 years of age as the offspring of females with the weakest social bonds.
"being sociable means that you spend more time close to others, and this makes you safer from predators," said silk. "females with strong social bonds may be shielded from social conflict and competition, and they might be able to forage more efficiently and nourish their offspring better."
previous work has shown that females with strong social bonds are also better able to cope with stressful events in their lives and it is possible that the short-term benefits are translated into long-term differences in health or evolutionary fitness. "it's also possible that sociable females and their offspring are better protected against predators because there is safety in [numbers]," said silk.
females are the core of any group in baboon society. "females stay in their group their whole lives and inherit their rank from their mother, whereas the males, once they get to adulthood, disperse to a new troop where they are unrelated to all the other individuals," said andrew king, a behavioural ecologist at the university of cambridge and the zoological society of london who studies baboons but was not involved in the latest research.
silk's researchers measured the strength of social bonds within the baboon group using an index of friendshiop that took into account several factors including the frequency and duration of grooming others, how often a baboon requested grooming from others and approaches between animals.
"grooming and proximity are the way baboons build social relationships – females show very strong preferences for close kin, particularly their mothers and daughters," she said. "we do not have many females who don't have any close relatives in the group, so it's hard to tell whether these effects are completely independent of kinship. but we do know that the number of close kin in the group is not as important as the quality of social bonds that females form. and for females whose mothers have died before they reached adulthood and don't have any adult daughters, social bonds with sisters become important predictors of offspring survival."
she said her results paralleled well-established findings in humans demonstrating that social ties have important effects on mental and physical health and welfare. "but we cannot extrapolate directly from baboons to humans – it's possible that different causal processes generate what look like similar outcomes in baboons and humans."
king said the research supported the idea that the role of social bonds for primates goes back millions of years, to at least the common ancestor of baboons and humans. the need to maintain social relationships, he said, may be one of the factors that drove the evolution of big brains in humans. "one way to improve your fitness is to make lots of friends, but then you need to keep tabs on everyone so if you're better at doing that, there will be selection pressure for bigger brains and higher cognitive ability."
据科学家报告，生活在关系密切的社会群体中的狒狒更为健康，而且它们下一代的寿命更长。该研究支持了这种想法：关系密切的人类群体对身心健康是非常有益的。而且也揭示了人类祖先群居生活的进化进程。
一项对博茨瓦纳奥卡万戈三角洲莫瑞米动物保护区的一群狒狒进行的历时15年的研究得出了这一结论。在宾夕法尼亚大学罗伯特·赛法思（robert seyfarth）及多萝西·切尼（dorothy cheney）的领导下，该研究小组在1992年至2007年期间，每周六天、每天七小时进行观察。在此期间，观察人员监视66只成年雌性狒狒的繁殖生活。
今天发表在《英国皇家学会学报：b—生物科学》的这项分析是由加州大学洛杉矶分校人类学家琼·斯克（joan silk）主持的。这项研究表明，社会关系最强的雌性狒狒与社会关系最弱的雌性狒狒相比，前者的后代五岁时的存活率是后者的1.5倍左右。
“善于交际意味着你花费更多的时间接近其他个体，这会使你更为安全，避免落入捕猎者之手，”斯克说，“享有强大社会关系的雌性狒狒可免受社会冲突和竞争，她们也许能更有效地获得食物，给后代更好的营养。”
以往的研究表明，享有强大社会关系的雌性也能更好地应付生活中的紧张事件，这很有可能导致短期利益转变为长期健康的差异或进化性健康。斯克说：“也有可能善于交际的雌性及其后代由于群体在数量上提供了某种安全，以致能得到更好的保护而免遭侵犯。”
雌性狒狒是狒狒社会中任何群体的核心。“雌性狒狒一生都生活在自己的群体中，从她们母亲那里继承群体中的地位，而雄性狒狒一旦成年之后，就会分散到新的群体中，而群体中成员之间毫不相干，”剑桥大学及伦敦动物学会行为生态学家安德鲁·金（andrew king）说。他也研究狒狒，但没有参与该项最新研究。
斯克的研究人员利用一项友谊指数来度量狒狒群体中社会关系的强度，该指数纳入了许多考虑因素，包括给其他个体梳理的次数和时间、要求其他狒狒给自己梳理的频率、以及与其他动物之间的接近。
“梳理和接近是狒狒建立社会关系的主要方式——雌性狒狒对近亲，尤其是自己的母亲和女儿，显示出很强的偏好，”斯克说，“我们观察到绝大多数雌性狒狒在群体中都有自己的近亲，因此很难判断我们得出的结论是否与血缘关系无关。但我们知道，雌性狒狒在群体中的近亲数量不如她自己建立的社会联系质量那么重要。对于那些成年之前母亲已死亡而且也没有成年女儿的雌性狒狒来说，与自己姐妹的社会关系成为预测其后代生存率的重要因素。”
她说，她的研究成果与公认的人类研究相吻合，在人类社会中，社会关系对于身心健康及幸福有着重要的影响。“但是，我们不能将研究结论直接从狒狒延推至人类——有可能在狒狒和人类社会中，不同的因果进程产生出类似的结果。”
金表示，这项研究证明了社会关系在灵长类动物群落中的作用可以追溯到几百万年前，至少可以追溯到狒狒和人类共同祖先的时期。他指出，保持社会关系的需求可能是推动人类大脑进化的因素之一。“改善你健康状况的办法之一就是让交许多朋友，但是，这就需要你记住每个朋友，因此，如果你善于这项任务的话，这样就会产生选择压力，促使人类大脑越来越大，认知能力越来越高。”