Before the invention of boxed chocolates, Corvettes and bling-bling, all a man had to do for sweet lovin' was provide his special ladies with meat.  Studies of extant hunter-gatherer societies show that literally bringing home the bacon leads to greater reproductive success.  Highly skilled hunters also partake in more extra-marital affairs and in polygamous societies, have more wives. 

In order to explain the correlation between hunting skill and reproductive success observed in societies that are reminiscent of our ancestor's culture, anthropologists have proposed the “meat-for-sex” hypothesis which states that females consent to sex in exchange for meat.

However, as with all human behaviors, culture convolutes biological undertones; greater reproductive success observed in skilled hunters could be attributed to kin selection (familial meat provisioning improves fitness) and also that males who are good hunters often are associated with higher status which makes them more desirable to females.

To further investigate the relationship between meat exchange for sex in humans, researchers at the Max Planck Institute for Evolutionary Anthropology studied chimpanzees.  The sex-for-meat scenario is more easily observed and quantifiable in our promiscuous relatives.  Overall, their research shows that females copulate more frequently with males who share meat with them on at least one occasion, compared with males who never share meat with them.  This indicates that sharing meat with females improves a males' mating success.

It is well known that male chimpanzees often trade meat in exchange for sex with unrelated females, however, the researcher’s article states that, “the mechanisms driving the transfers of meat from males to females, which occur less frequently, is still poorly understood.”


Photo: Cristina Gomes

Max Planck researcher Cristina Gomes explains, “Previous studies might not have found a relationship between mating success and meat sharing because they focused on short-term exchanges; or perhaps because in those groups access to females was driven by male coercion so females rarely chose their mating partners.”

Copulation as the outcome of meat sharing was quantified over a twenty-two month period in a wild chimpanzee population located at the Taï National Park in West Africa. 

Although chimpanzee culture is less complex than our own, variables including; “rank of the male, the rank or age of the female, the association patterns of the dyad, the level of gregariousness of the female, and the begging tendencies of each females towards each male” had to be taken into consideration during statistical analysis in order to ensure that female chimpanzees were consenting to sex in exchange for meat and for no other "reason."

According to Gomes, “Our results strongly suggest that wild chimpanzees exchange meat for sex, and do so on a long-term basis.  Males who shared meat with females doubled their mating success, whereas females, who had difficulty obtaining meat on their own, increased their caloric intake, without suffering the energetic costs and potential risk of injury related to hunting.”

The researchers propose that this scenario occurs in chimpanzee populations where females have mate choice freedom and males are able to control how they share their meat. 

Furthermore, males preferentially mated with females that were in estrous.  However, males
also gave meat to anestrous females which indicates that males make long-term investments.  This type of interaction further exemplifies the cognitive capacity of chimpanzees.

“Our findings add to the ever-growing evidence suggesting that chimpanzees can think in past and the future and that this influences their present behavior,” Christophe Boesch, co-author of the study said.

Gomes concludes, “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.”

As for the relevance of these findings in Western society—ladies, you might want to consider accompanying your mate on his next hunting excursion so he doesn’t share his meat with other females and fellas, if your woman returns home smelling like a BBQ you should be suspicious.

References:

Gomes, C. M. and Boesch, C. (2009).  Wild chimpanzees exchange meat for sex on a long-term basis.  PLoS ONE 4(4): e5116.