There is something that most species—from baboons to humans to horses—have in common: when they experience serious adversity early in life, they are more likely to experience hardship later in life.
When researchers from the Dian Fossey Gorilla Fund and the University of Michigan decided to look at this question in gorillas, they weren’t sure what to find.
Previous studies by the Fossey Fund revealed that baby gorillas are surprisingly resilient to the loss of their mothers, in contrast to what has been found in many other species. But losing your mom is just one of the many potentially bad things that can happen to young animals.
“Assuming you survive something we consider an early life adversity, it often remains the case that you will be less healthy or have fewer children or have a shorter lifespan — no matter what your type is,” said UM anthropologist Stacy Stacy Rosenbaum, senior author in the study. “There are a whole bunch of things that happen to you that seem to make your life worse in adulthood.”
But instead, the researchers found that gorillas who survived to the age of 6 were largely unaffected by the difficulties they faced as infants or juveniles. The study was published in the journal Current Biology.
Like other species, humans also deal with early life adversities, Rosenbaum said, and the effects of that can follow us into adulthood, such as shorter lives or health complications. But in humans, it’s hard to underestimate whether, for example, we get cancer or die early as adults because of an adverse event early in life in and of itself, or whether it’s due to a multitude of behavioral, environmental, and cultural factors—or a combination of all. what mentioned before.
Studying these early adverse events in non-human species can help researchers understand how such events affect humans, and how to mitigate them.
“When you look at animals, you remove a lot of the differences that we have in humans. For example, they all eat similar diets, they all get exercise as part of their daily lives, and they don’t have the opportunity to participate,” said Robin Morrison, researcher at the Dian Fossey Gorilla Fund and author. In the main study, behaviors with negative health outcomes such as smoking.
But even so, in most species, it’s still the case that early adversity can have negative effects in adulthood, suggesting some kind of deep biological mechanism that we don’t understand very well, Morrison said. The gorilla’s display of a different pattern suggests that these early life adversities can be overcome. She said understanding why and how this happened could have major implications for our species.
Like humans, gorillas live a long time and have few offspring in which they are very invested. This makes it a good comparative animal model for understanding the repercussions of negative events in early life. The researchers examined 55 years of long-term data collected on 253 wild mountain gorillas, 135 of which were male and 118 female. These gorillas live in Volcanoes National Park in Rwanda and have been monitored for more than five decades by the Dian Fossey Gorilla Fund.
Researchers have identified six different types of early life adversity: loss of a father or mother, death of a group member via infanticide, social group instability, having few peers in the social group, and having a rival sibling born soon. after them. The data included information on how many of these early ordeals each gorilla went through and at what age, as well as how long each gorilla had lived.
The researchers looked at what happened when the gorillas experienced none, two, three, or more negative events. They found that the more of these adverse events gorillas experienced before the age of six, the more likely they were to die young. But, despite their exposure to early adversity, they survived to the age of 6 – after the juvenile stage – the researchers found no evidence that their lifespan was shorter, no matter how many negative events the gorillas experienced.
In fact, if gorillas suffer three or more forms of misfortune, they actually live longer; This group of animals has a 70% reduction in the risk of death across adulthood. But this was specifically driven by longer lifespans in males, and the researchers suspect the trend was due to something called viability selection. This means that if a gorilla is strong enough to withstand difficult early life events, it may just be a “higher quality personality” and thus more likely to have a longer lifespan.
“I was expecting to see that these gorillas had short lifespans and wouldn’t do as well as adults,” Rosenbaum said. “We found that these events are definitely associated with a much higher risk of death when you are young. But if you survive until the age of 6, there is no evidence that these events shorten life at all. This is very different from what we see in other species.”
Researchers have a few theories as to why these mountain gorillas are so resilient. Gorillas have very tight-knit social groups and previous studies have shown that when baby gorillas lose their mother, they don’t actually become more isolated: other gorillas fill the gap in social companionship.
“The youngster increases his time near other gorillas after losing his mother and especially the first-order adult male, even if he is not their biological father,” Morrison said. “These strong networks may provide important social protection, as shown in humans. The quality of our social relationships is a very important predictor of our health and longevity—in some cases, more important than genes or lifestyle.”
Another reason they may be relatively protected from the consequences of adversity is that mountain gorillas live in an environment that is richer in resources than many other wild primates. Rosenbaum said it might be easier for gorillas to survive difficult conditions if they weren’t constantly dealing with the stress of finding enough food and water.
“For comparison, the savannah monkey—which was the inspiration for this analysis—lives in this very seasonal environment where they go through extreme drought. And they’ll sometimes have to walk miles to get to the water hole. They often struggle for every calorie they take in,” she said. Not the world where mountain gorillas live. She is often described as living in a giant salad bowl.”
The researchers’ findings suggest that species like ours can have great resilience to early life adversities. The findings also raise important questions about the biological roots of sensitivity to early experiments, and the protective mechanisms that contribute to resilience in gorillas.
“I don’t think we should assume that the negative long-term effects of early life adversity are universal,” Rosenbaum said. “We tend to talk about this as if it’s an omnipresent experience, and it’s a given that your adulthood will be compromised if you live through early misfortune.
“But I don’t think it’s nearly cut and dry, even in the human literature. I think the data is much more complex for humans, and this research might suggest that it might be more complex for other animals as well. And I actually think that’s a hopeful story.” .