Department of Primatology, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany.
Department of Human Evolutionary Biology, Harvard University, Cambridge, MA, USA.
Proc Biol Sci. 2020 Jun 24;287(1929):20200523. doi: 10.1098/rspb.2020.0523.
Several theories have been generated to understand the socio-cognitive mechanisms underlying the unique cooperative abilities of humans. The 'interdependence hypothesis' posits first, that the cognitive dimension of human cooperation evolved in contexts when several individuals needed to act together to achieve a common goal, like when hunting large prey. Second, the more interdependent individuals are, the more likely they are to provide services to conspecifics in other contexts. Alternatively, the 'social tolerance hypothesis' proposes that higher social tolerance allows conspecifics to cooperate more efficiently and with a wider range of partners. We conducted the first field experimental evaluation of both hypotheses in our closest living relatives by contrasting chimpanzees to the less interdependent but more tolerant bonobos. We compared each species' performance during a cooperative task: informing conspecifics about a danger. We presented Gaboon viper models to 82 individuals from five wild communities. Chimpanzees arriving late at the snake were significantly more likely to have heard a call and less likely to startle, indicating that chimpanzees were better informed about the presence of the threat than bonobos. This stems from clear species differences in how individuals adjusted their calling decisions to the level of information already available. Chimpanzees were more likely to call and produced more alarm calls when they had not yet heard a call, whereas bonobos did so when they already heard a call. Our results confirm the link between interdependence and cooperation performance. These species differences were most likely driven by differences in motivation rather than in cognitive capacities because both species tended to consider audience knowledge in their decision to call. Our results inform theories on the evolution of human cooperation by linking inter-group competition pressure and in-group cooperative motivation and/or capability.
有几种理论被提出以理解人类独特合作能力的社会认知机制。“相互依存假说”首先假定，人类合作的认知维度是在需要多个个体共同行动以实现共同目标的背景下进化的，例如在猎捕大型猎物时。其次，个体之间的相互依存度越高，他们在其他背景下向同种个体提供服务的可能性就越大。或者，“社会宽容假说”则提出，更高的社会宽容度允许同种个体更有效地合作，并与更广泛的伙伴合作。我们通过对比黑猩猩和相对不相互依存但更宽容的倭黑猩猩，在我们最亲近的亲属中首次对这两个假说进行了实地实验评估。我们比较了每个物种在合作任务中的表现：向同种个体通报危险。我们向来自五个野生社区的 82 个个体展示了加蓬蝰蛇模型。当蛇出现时迟到的黑猩猩更有可能听到叫声，并且不太可能受惊，这表明黑猩猩比倭黑猩猩更了解威胁的存在。这源于个体如何根据已经获得的信息来调整叫声决策的明显的物种差异。当黑猩猩还没有听到叫声时，他们更有可能发出叫声并发出更多的警报声，而倭黑猩猩则在已经听到叫声时才这样做。我们的结果证实了相互依存和合作表现之间的联系。这些物种差异很可能是由动机而不是认知能力的差异驱动的，因为这两个物种在做出叫声决策时都倾向于考虑听众的知识。我们的结果通过将群体间竞争压力和群体内合作动机和/或能力联系起来，为人类合作的进化理论提供了信息。
