Thursday, September 13, 2007

Are chimpanzees going biblical on us?

Well, not quite, thought the headline of this PLoS One article makes it sound that way.

Chimpanzees Share Forbidden Fruit by Kimberley J. Hockings, Tatyana Humle, James R. Anderson, Dora Biro, Claudia Sousa, Gaku Ohashi, and Tetsuro Matsuzawa.

However, there are no snakes involved. Rather, we are talking about high-risk food here, such as meat, or cultivated plant foods. Cultivated by Humans, that is, not Chimpanzees. It is the later food type that Hockings et al focus on.

The sharing of wild plant foods is infrequent in chimpanzees, but in chimpanzee communities that engage in hunting, meat is frequently used as a ‘social tool’ for nurturing alliances and social bonds. Here we report the only recorded example of regular sharing of plant foods by unrelated, non-provisioned wild chimpanzees, and the contexts in which these sharing behaviours occur. From direct observations, adult chimpanzees at Bossou (Republic of Guinea, West Africa) very rarely transferred wild plant foods. In contrast, they shared cultivated plant foods much more frequently (58 out of 59 food sharing events). Sharing primarily consists of adult males allowing reproductively cycling females to take food that they possess. We propose that hypotheses focussing on ‘food-for-sex and -grooming’ and ‘showing-off’ strategies plausibly account for observed sharing behaviours. A changing human-dominated landscape presents chimpanzees with fresh challenges, and our observations suggest that crop-raiding provides adult male chimpanzees at Bossou with highly desirable food commodities that may be traded for other currencies.

Quite interesting. And I must admit it's a bit surprising to me that such things haven't been well documented in the past - either with sharing of crops or with meat sharing, though there is some knowledge about the later. From the article, it would seem that the behavior differs quite a bit from chimpanzee group to chimpanzee group, at least when it comes to meat sharing, but there seems to be a common tendency for males to share meat with females.

Food sharing is observed throughout the animal kingdom, albeit at varying levels and complexities. Hypotheses proposed to explain food sharing behaviours in chimpanzees [for reviews], [see 1,2] range from cognitively simple explanations, such as begging intensity [3], to more complex sharing strategies, such as reciprocity [4]. Within chimpanzee communities that engage in hunting, meat is reportedly used as a ‘social tool’ [5]; alliances and affiliative relationships are cemented by gifts of meat. Long-term data from Mahale in Tanzania suggest that alpha males use meat sharing as a coalition strategy, never sharing with potential rivals such as beta or younger adult males [6]. However in Taï, Ivory Coast, hunters receive a share of meat if they participated in the hunt, regardless of the identity of the possessor [7]. The ‘meat-for-sex’ hypothesis suggests that males share meat with females either to gain immediate access to swollen females [8], [9] or to establish or strengthen an affiliative relationship and thus increase future mating opportunities [10]. Additionally, as meat is typically energetically costly and risky to acquire for chimpanzees, sharing with others may advertise an individual's strength and prowess [11]; simply possessing a desirable item may draw positive attention to an individual, enhancing the latter's social status [12], [13].

The article suggests that if we learn to understand the behaviors and motivations for chimpanzees, we could also learn something of our own kind's behavior.

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