NEPOTISM is important in chimpanzee society, but chimps鈥� ability to cooperate extends beyond family connections. This extra level of sophistication is yet another way in which the social behaviour of chimps parallels humans鈥�.
Kevin Langergraber, an anthropologist at the University of Michigan in Ann Arbor, and colleagues recorded alliances, meat sharing and other cooperative behaviour among 41 male chimps in Kibale National Park, Uganda, over a period of seven years. The researchers also genotyped each animal to measure how closely they were related. In 5025 hours of observations, they observed 753 aggressive coalitions and 421 instances of meat sharing.
Chimps who shared a mother were far more likely to cooperate with each other. In contrast, there was no evidence that the same applied to chimps with a shared father. This is probably because fathers do not stay with their offspring, so a chimp has no easy way to recognise his paternal brothers. However, since maternal brothers were rare, most of the cooperating pairs were unrelated or only distantly related (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0611449104).
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Extensive cooperation among non-relatives suggests that chimps do it for selfish reasons, with the expectation that favours will be reciprocated, says Langergraber.
