Why boys should be friends with girls

Close friendships can increase the odds of living a long life – not just in humans but also in animals including horses, dolphins, whales, ungulates, rodents and primates.

But in non-human social mammals, studies have focussed on females because they tend to stay in their birth group while males roam around and are thus difficult to keep track of.

Now, researchers have discovered that male baboons who have stronger social bonds with females do live longer, adding to the known benefits of close friendships.

“Male baboons may benefit from forming strong friendships with females in ways that were previously underappreciated,” says Fernando Campos from Duke University, US, first author of a study published in the journal Philosophical Transactions of the Royal Society B.

“We knew that male baboons can benefit from befriending females by protecting their own offspring and by securing future mating opportunities. Our findings show that they can also benefit from extended lifespans.”

There’s a trade-off, though. The researchers found that male baboons with higher rank have shorter lifespans. They suggest this could result from greater reproductive success, which these dominant males achieve through intense competition.

This contrasts with humans, in whom both higher status and social connections can extend the life span. The benefits for us can be quite profound, rivalling that of exercise, healthy weight, healthy drinking and clean air.

The study investigated wild yellow (Papio cynocephalus) and Anubis (P. anubis) baboons in the Amboseli basin, southern Kenya, which researchers have observed for nearly five decades.

It included more than 500 adult baboons – nearly half female – who were individually followed between 1984 and 2018. Baboons bond through regular grooming, so this was used as evidence of social connections.

Male survival was inferred through contextual information, such as the ages at which they typically transfer between groups as well as rare observed deaths, an approach the authors developed previously.

In this study, they extended that by developing a model to show how male survival is influenced by their social environment, including female bonds and social rank.

Results showed that females had similar social bonds with each other as with their male friends and this strongly predicted survival for both sexes. Males with strong female bonds had 28% lower risk of mortality than their mates who had weak connections – particularly important for them given males didn’t show strong bonding with each other.

While there is robust evidence that close social connections can lead to better outcomes in humans, the authors note that their study is correlational and could be explained by other factors; better physical condition could lead to more social connections and lower mortality, for instance.

However, they say several possible mechanisms could explain the benefits of social bonding including greater protection from predators, buffering from stress, lower heart rate and higher immunity.