Chimps Give Away Meat to Secure Future Mating Partners

It has long been known that successful hunters in the chimpanzee world are also successful maters, but it wasn’t known how the two were directly connected. Humans and chimpanzees are the only primates that regularly participate in group hunts for mammals, and then share the spoils with others. Because chimpanzees are genetically the closest living animal to humans, it is thought that shedding light on why chimps share meat might provide insight into early hunter-gatherer societies.

Fifteen years ago, Craig Stanford, an anthropologist, suggested that perhaps chimps traded meat for sex. But all previous studies found that, over a period of a few months, there did not appear to be an immediate correlation between males giving females meat and receiving sex, as it was noted that the males gave away meat to both estrous (ovulating) and anestrous (non-ovulating) females, and that male chimps only mate with estrous females.

In a recent study by Cristina Gomes and Christophe Boesch of the Max Planck Institute for Evolutionary Anthropology, the meat-for-sex theory was given a new life. This study was conducted between 2003 and 2006 in a group of chimps on the Ivory Coast, and seems to show that previous studies had not taken into account the idea that the meat-for-sex trade might be a long-term arrangement.

In their study, Gomes and Boesch found that a male’s mating success was twice as great if he gave away meat to a female than if he did not. Each male chimp gave away more meat to certain females than others, and in turn those females had sex more often with the males who gave them meat.

Only male chimps hunt for meat, so females can only acquire meat if they are given it from males, or if they steal it. For the males, this means that the more successful they are at hunting, the more meat they will have to give away in the long term, and the greater the potential for sex. For the females, the benefit of this exchange is the meat, which is an uncommon treat for chimps, as they mostly eat fruits and vegetables.  

Until recently, it was thought that only humans could plan for future events. If the long-term meat-for-sex theory continues to hold up, it will be another piece of evidence demonstrating that chimps have that same ability.

In 1997, zookeepers discovered that Santino, one of the chimps in their Swedish zoo, had been collecting stones in the morning so that he could later throw them at zoo visitors. Earlier this year a study of Santino’s behavior by cognitive scientist Mathias Osvath seemed to prove that Santino was “anticipating a future mental state” each morning as he calmly collected his stones, knowing he would later want to throw them at visitors.

Osvath pointed out that for wild chimpanzees, the ability to plan for the future could be much more beneficial than it could be fore Santino, as wild chimps might be able to plan for food shortages or potential dangers.

It continues to be debated whether chimps may share additional traits once thought to belong only to humans, such as the idea of fairness, or the need to conform to social norms.