Exchanging food for sex

Wild female chimpanzees will copulate more often with males who regularly bring them meat, according to a study published in the open access journal PLoS One this week.Mate selection by females is a puzzle in chimpanzees as well as in humans, but there is some indication that more successful hunters tend to have more partners and a larger number of offspring.  Male chimpanzees are known to share meat with females, who do not hunt, and so researchers hypothesised that females exchange meat for mating access.

Observing wild chimps in the Taï National Park, on the Ivory Coast, Cristina Gomes and Christophe Boesch recorded meat-sharing and copulation activities over a period of 22 months, and analysed the data to see if their hypothesis held true.  They found that males were more likely to share meat with females during oestrus, when they are at their most fertile and display sexual swellings, but even once these were discounted from the data, the pattern was still present.  Even once they controlled for the effect of male social rank and female gregariousness, females copulated more often with males that share their meat.

The obvious advantage for the females is that they increase their calorific intake without the dangers and energetic costs of hunting.  The males can double their mating success by being generous with the spoils of a hunt.

As their results were collected over 22 months, it also suggests that chimpanzees think of both the past and the future when making decisions about whether or not to share meat, or who to mate with.

Gomes added that "These findings are bound to have an impact on our current knowledge about relationships between men and women; and similar studies will determine if the direct nutritional benefits that women receive from hunters in human hunter-gatherer societies could also be driving the relationship between reproductive success and good hunting skills,".

It also may shed more light of the evolution of compassion and sharing, as there's a clear evolutionary advantage to not being selfish with your food!