Forging strong social relationships can help mitigate the effects of traumatic childhood events in human adults, but also in baboons. A study published May 17 in the journal Science Advances drew on 36 years of data from almost 200 baboons in southern Kenya and found that even though early adversity can take years of their lifespans, stronger social bonds in adulthood can help get these years back.
[Related: Baboon poop shows how chronic stress shortens lives.]
“It’s like the saying from the King James Apocrypha, ‘a faithful friend is the medicine of life,’” co-author and Duke University biologist and evolutionary anthropologist Susan Alberts said in a statement.
Studies have consistently found that people who go through more bad experiences growing up, such as neglect or abuse, are more likely to die early. However, the mechanisms behind how early adversity leads to a premature death has been harder for researchers to pin down, according to Alberts. Some of the limitations to earlier research is the reliance on self-reported memories which can be imprecise and subjective.
Enter our primate cousins. Baboons share more than 90 percent of their DNA with humans and researchers have followed individual baboons near Amboseli National Park in Kenya since 1971.
In this new study, the researchers analyzed how early life experiences and adult social connections affected long-term survival in 199 female baboons between 1983 and 2019.
Baboon childhood is certainly different from human childhood, but young baboons still face hardships. The team in the study tallied up each female’s exposure to six potential sources of early adversity, including whether she had a low-ranking or socially isolated mother or if her mother died before she reached maturity. It was also noted if she was born in a drought year or into a large group, and if she had a sibling close in age, which could contribute to more competition for both maternal attention and resources.
The team found that stressful experiences are very common for the baboons growing up in the semi-arid and unpredictable landscape of Amboseli. Of the 199 baboons in the study, 75 percent suffered through at least one stressor, and 33 percent had two or more.
Their results confirm previous findings that the more hardship a female baboon faces, the shorter her lifespan. Monkeys who experienced more upheaval at a young age were also more socially isolated as adults.
[Related: Monkeys with close friends have friendlier gut bacteria.]
However, the researchers showed that 90 percent of the dip in survival was due to the direct effects of early adversity, not to the weakened social bonds that continued into adulthood.
No matter how strong their bonds were with other baboons, each additional hardship translated to 1.4 years of life lost. Those who went through four bad experiences growing up died close to 5.6 years earlier than those who didn’t face any. Since the average female baboon lives to age 18, this is a large drop in lost years.
But an unfortunate start in life does not mean that a baboon will absolutely live a short life.
“Females who have bad early lives are not doomed,” co-author and biologist at SUNY Oswego Elizabeth Lange said in a statement. “We found that both early life adversity and adult social interactions affect survival independently. That means that interventions that occur throughout the lifespan could improve survival.”
In baboons, strong social bonds are measured by how often they groom with their closest friends. Those with strong social bonds added 2.2 years to their lives, no matter what adversity they had faced in their earlier years. The baboons whose mothers died before they reached maturity and then forged strong friendships in adulthood showed the best ability to bounce back.
However, the flip side is also true. Weak social bonds can magnify early life adversity, according to the study.
It is not clear yet if these results can be translated to adult humans, but it suggests that early intervention is not the only way to overcome childhood trauma and its lingering effects.
“If you did have early life adversity, whatever you do, try to make friends,” Alberts said.
