Thursday, December 08, 2011
Chimps 'Trade' Like Humans - Some Even Indulge In 'The Oldest Profession'
Primatologists are reassessing the complexity of chimpanzee society in the light of new findings that also suggest answers to a long-standing question: why share things with non-relatives?
For the first time wild chimps in Senegal have been observed taking plant foods and tools from other chimps, who don't react to the intrusion. The chimps donating their stuff don't get paid, but neither do they protest. Instead, the trade appears to help build social cohesion.
What's more, in another west African study, this time in Ivory Coast, a "market" has been described where chimps exchange commodities in the shape of both social behaviours including grooming and sex, and resources such as meat.
Christophe Boesch of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, says we have only recently begun to appreciate the time and energy chimps invest in reciprocal relationships, and he compares chimp relationships to friendship. "These findings have prompted primatologists to use some terms that have in the past been reserved for humans."
Jill Pruetz of Iowa State University in Ames and colleague Stacy Lindshield documented a kind of proto-trade in savannah chimps (Pan troglodytes verus) living in the Fongoli area of south-east Senegal. They witnessed 41 transfers of plant foods and tools. Chimps are known to share meat, but this is the first study to document them sharing other types of goods.
Food or tools were transferred from males to females 27 times. In most cases this was the result of a female simply taking the item and the male doing nothing to stop her. In other chimp populations males may lash out in this situation but at Fongoli males outnumber females and have to be nice to them if they want to have sex later.
Pruetz suspects that item transfer is a social lubricant. "It seems like the ulterior motive is social group harmony on some level," she says.
If a male is transferring goods to another male, then Pruetz predicts that the male will expect support from the recipient of his largesse in any future aggressive encounter with other males. If a male shares with a female he is likely to expect sexual benefits from her. "But other age-sex classes were also involved," says Pruetz, "and I think this reflects the cohesive nature of this chimp community."
Full story here.