Social bonds, considered so important for humans, are also vital for baboons, say researchers who've found such bonds make a difference when it comes to survival.
That's the outcome of an analysis of a massive amount of data on social relationships among wild baboons, collected almost daily for 30 years by researchers observing individual baboons, their activities and the other baboons they interacted with.
"We can tell individual baboons apart by distinct features of their appearance, such as their fur color, the shape of their tail, or how they move," says Elizabeth Archie, a biologist at the University of Notre Dame who helps direct the baboon observation project.
"We especially focused on grooming interactions, which are a sign of social support in baboons," she says. "Baboons spend more time grooming their 'friends', and baboons with stronger grooming connections seem to live longer."
Female baboons with strong social connections to both other females and males enjoyed longer lives than did females with weaker ties to either or both of the sexes, the researchers report in the journal Proceeding of the Royal Society B.
Previous studies have suggested that's true in many species, including humans, Archie says.
"I think the results are applicable to humans," she says. "Our results help confirm this phenomenon in mammals and suggest it might be widely shared across several social species."
There is ample evidence that human lifespan can be predicted, or at least estimated, based on social relationships, she says.
"Across a range of circumstances, people who receive more social support tend to live longer than people who are socially isolated," she explains. "Our results suggest that this phenomenon might be part of our shared biological history with other mammals."
Archie did note that their findings applied almost exclusively to female baboons, who spend their whole lives in the same social group.
"When they disappear from the group, we can be pretty certain that they died," allowing an accurate measure of their life spans.
Male baboons, on the other hand, will repeatedly move from one social group to another, so if they suddenly disappear that's not conclusive evidence that they've died, Archie says.
That makes accurate determination of male baboons' life span difficult, she says.
It was the long-term character of the study that allowed them to make definite assumptions about baboon life span and its association with social connections, the researchers said.
Baboons in the wild can live for 25 years, so the 30-year collection of data was needed to confirm what was suspected about the effect of close social connections, Archie says.