full story: http://news.nationalgeographic.com/news/2009/04/090407-chimps-meat-sex.html
Chimps Trade Meat for Sex -- And It Works
Nick Wadhams in Nairobi, Kenya
for National Geographic News
April 7, 2009
The time-honored tradition of the dinner date may be just one more example of evolution at work.
Wild male chimps that share meat with females double their chances of having sex with those females, a new study says. The findings support a long-held hypothesis that food sharing improves male chimpanzees' chances of mating.
Studies had long shown that male chimpanzees shared meat with females, which don't typically hunt. The reason for the meat sharing, however, was a mystery—though perhaps not too tough to guess.
Males observed in the West African nation of Côte d'Ivoire (Ivory Coast) shared monkey meat with females that exhibited the pink swellings on their rear ends that indicate ovulation and sexual availability.
More surprising was that males shared meat with females that didn't have sexual swellings, perhaps in hopes of future success, the researchers say.
The sex "may not necessarily occur immediately—it could occur sometime in the future," said study co-author Cristina M. Gomes, a researcher at the Max Planck Institute for Evolutionary Anthropology in Germany.
Meat is generally a rare treat for chimps, whose diet consists mainly of fruits and vegetables.
Evolution at Work?
The findings could shed light on our own evolutionary origins, researchers said.
Studies of human hunter-gatherer societies have long shown that skillful hunters have more offspring and wives. But scientists are divided on how, or whether, hunting skills and mating success were connected.
The fact that the chimp males also shared meat with females not in heat could also add new fire to the debate about chimpanzees' cognitive abilities, experts add. That's because the research might suggest that chimps can anticipate future interactions or remember interactions they had in the past.