People who experience abuse or neglect during childhood are more likely to develop heart disease, diabetes, and other health problems later in life, even after the stressful events have passed.
Now, a new study suggests that wild baboons that experience multiple misfortunes during the first years of life, such as drought or the loss of their mother, grow up to live much shorter adult lives. Their life expectancy is cut short by up to ten years compared with their more fortunate peers.
The findings, published in the journal Nature Communications, are important because they show that early adversity can have long-term negative effects on survival even in the absence of factors commonly evoked to explain similar patterns in humans, such as differences in smoking, drinking, or medical care, says Jenny Tung, assistant professor of evolutionary anthropology and biology at Duke University.
For the study, researchers monitored 196 wild female baboons on a nearly daily basis between 1983 and 2013 near Amboseli National Park in southern Kenya.
Researchers focused on six potential sources of early adversity and discovered that life isn’t easy for a wild baboon. Some, for example, saw very little rainfall in their first year of life, or experienced stiff competition for resources because of sibling spacing or rising numbers within their group.
Others lost their mothers to death or illness, or had moms with lower rank or little social support. More than three-fourths of the baboons in the study had at least one of the six early risk factors; 15 percent had three or more.
Baboons who lost their mothers before age four, or whose next-born sibling arrived before they were fully weaned, were found to be the most vulnerable.
For baboons, like humans, the tougher the childhood, the higher the risks of premature death later in life. Young females that experienced just one or no adverse events—a group the researchers nicknamed the “silver spoon kids”—generally lived into their late teens and early twenties, whereas those that endured three or more often died by age nine.
‘Bad luck’ baby baboons
The “bad luck” babies not only lost more than ten years off their adult lives, they also had fewer surviving offspring. “It’s like a snowball effect,” says coauthor Elizabeth Archie, associate professor at the University of Notre Dame.
Two females named Puma and Mystery, for example, were both born during years of little rainfall, and raised by low-ranking moms who died before their third birthdays. Puma eventually met her end at age seven at the jaws of a leopard. Mystery lived until her disappearance at age 14, presumably to a predator, leaving behind a single infant who died shortly thereafter.
Some researchers studying the effects of childhood stress on adult health in humans pin the blame on differences in medical care or risky behavior. People who had troubled childhoods, the thinking goes, are more likely to turn to drugs, alcohol, or other coping mechanisms that are bad for their health.
But wild baboons don’t smoke or binge on junk food, and they don’t carry health insurance. This supports the idea that differences in lifestyle and medical care are only part of the story, says coauthor Susan Alberts, professor of biology at Duke.
Baboon females that experienced the most misfortune in their early years were also more socially isolated as adults, suggesting that social support may also be at play.
Researchers next plan to investigate how some baboons manage to overcome early adversity. It could be that those who form and maintain supportive relationships as they grow older are better able to survive and thrive, Archie says.
Baboon DNA is 94 percent similar to that of humans, which indicates these patterns could be deep-rooted in primate physiology.
“This suggests that human adult health effects from childhood stresses are not simply products of the modern environment, but have likely been present throughout our evolutionary history,” says George Gilchrist, program director in the National Science Foundation environmental biology division, which funded the research.
Source: Duke University