Some males react to competition like chimps

LONDON - Prior to competition, an average man experiences hormonal changes similar to a passive bonobo, a dwarf chimp species, and a “status-striving” man undergoes changes similar to a chimpanzee, says a study.

Researchers from Duke and Harvard universities revealed differing hormone levels in two closest relatives of humans, bonobos and chimpanzees, in anticipation of competition.

Chimpanzees live in male-dominated societies where status is paramount and aggression can be severe.

In bonobos, the female is always the most dominant and tolerance can allow for more cooperation and food-sharing.

Scientists have frequently questioned whether differences in competitive behaviour could in part be explained by differing physiological responses to competition.

Researchers collected saliva from the apes using cotton wads dipped in Sweet Tarts candy, then measured hormone levels before and after pairs from each species were presented with a pile of food.

They found that males of both species showed hormonal changes in anticipation of competing for food.

Male chimpanzees showed an increase in testosterone, which is thought to prepare animals for competition or aggressive interactions.

By contrast, male bonobos showed an increase in cortisol, which is associated with stress and more passive social strategies in other animals.

“Chimpanzee males reacted to the competition as if it was a threat to their status, while bonobos reacted as if a potential competition is stressful by showing changes in their cortisol levels,” said Victoria Wobber, Harvard graduate student, who led the study.

Human males usually experience an increase in cortisol before many types of competition in a similar way as seen in the bonobos.

However, if men have what is called a “high power motive,” or a strong desire to achieve high status, they experience an increase in testosterone before a competition, said a release of Duke and Harvard Universities.

“These results suggest that the steroid hormone shifts that are correlated with the competitive drive of men are shared through descent with other apes,” Wobber said.

These findings were published on in Proceedings of the National Academy of Sciences