Check out this new study done at Lola!!
Human men may look similar to male bonobos before competition, but status striving males probably look more like chimpanzees.
A new study published today in Proceedings of the National Academy of Sciences reveals differing hormone levels in our two closest relatives, bonobos and chimpanzees, in anticipation of competition.
Chimpanzees live in male dominated societies where status is paramount and aggression can be severe. In bonobos, a female is always the most dominant and tolerance can allow for more flexible cooperation and food sharing. Scientists have frequently questioned whether differences in behavior could in part be explained by differing physiological responses to competition.
Researchers from Harvard and Duke University collected saliva from the apes using cotton wads dipped in Sweet Tart candy, then measured hormone levels before and after pairs from each species were presented with a pile of food. Males of both species who were intolerant and could not share with their partners had the strongest hormonal reaction in anticipation of competition – but bonobos and chimpanzees were completely different in the type of hormonal response.
Male chimpanzees showed an increase in testosterone, which is thought to prime animals before competition or aggressive interactions. Male bonobos showed an increase in cortisol, which is associated with stress and more passive coping strategies in other animals.
“Chimpanzee males reacted to the competition as if it was a threat to their status” says Victoria Wobber, Harvard graduate student. “While bonobos reacted as if a potential competition is stressful showing changes in their cortisol levels.”
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.
“These results suggest that the steroid hormone shifts that are correlated with the competitive drive of men are shared through descent with other apes,” says Wobber.
While some men may seem more bonobo-like before competition and others more chimpanzee-like, something unique about human males is that after competition they experience an increase in testosterone if they win or a decrease in testosterone if they lose (which accounts for all the giddy or depressed sports fans following a win or a loss). This variation in hormones post-competition was not observed in either chimpanzees or bonobos.
‘It’s exciting because we can see that in some ways we’re similar to bonobos, in others we’re similar to chimpanzees,” says Brian Hare of Duke University. “But then there’s also a part of our biology that seems to be entirely unique.”