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Female baboons that had a harder life as youngsters tend to end up struggling in social situations as adults.

These individuals often fail to give the friendly grunt that usually precedes social interactions between baboons, which might make them “socially awkward” and could lead to them being approached and groomed less by peers, says at New York University.

“Basically, if a female approaches another baboon and grunts, she’s saying, ‘Hey, I’m going to be friendly and not attack you; everything’s good’,” says Patterson. “But if the female approaches and doesn’t grunt, that’s stressful [for the other baboon] because it’s unpredictable.”

Patterson and their fellow researchers in the US and Kenya investigated 50 years’ worth of historical data on three groups of wild female olive baboons (Papio anubis) in Kenya, all part of the . The team also recorded more than 2600 hours of observations of 31 female olive baboons from the three groups, noting their activity, social interactions, social partners and their vocalisations.

The researchers rated the levels of early life adversity on a scale from 0 to 5 for each of these 31 animals. To do so, they considered a number of factors relating to each individual’s early life.

For instance, they looked at food availability – based on grassland condition – for the year of the baboon’s birth; competition the individual might have experienced based on the group size at the time of her birth; personal trauma based on whether or not the individual lost her mother early in life; the mother’s health condition based on number of years since she had previously given birth; and the mother’s parenting experience – essentially whether the individual was the mother’s firstborn or not.

The researchers found that baboons with a higher early life adversity score were less sociable, meaning they had fewer interactions with other baboons, says Patterson. In particular, they were less likely to receive social attention, like grooming, from fellow baboons compared to those with lower early life adversity scores.

The team’s observations of the 31 baboons offered a potential explanation. The female baboons with a harder start in life were less likely to grunt when approaching another baboon, suggesting they were less adept at social communication. And that, the researchers write, could make the baboon “less attractive” in a social environment.

“Social partners want someone who’s reliable and predictable – which I think humans can relate to as well,” says Patterson.

Individuals who had a more difficult start in life might be less social as adults because they needed to prioritise their own survival needs as youngsters, or possibly because they simply missed the opportunity to develop social skills during the social development “window” of infancy and adolescence because they had to focus on survival instead, says Patterson.

“We now know that early life adversity isn’t affecting [adult interactions] just due to energy availability and body condition, but also how individuals are socialising and their attractiveness,” says Patterson.

“I think getting a better understanding of that early social development and how it gets ‘under the skin’ and influences later adult outcomes will shed a lot of light on human experience… We need a lot more research on baboons, humans and other species to really disentangle all these pathways.”

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