Why gorillas are much more resilient than humans

By Alice Clifford via SWNS

Gorillas are much more resilient than humans, a new study reveals.

When most species suffer serious adversity early in life, they are more likely to experience hardship as they get older.

Many animals end up having a shorter lifespan or suffering from health complications, suggesting that there is some kind of deeper biological mechanism at play.

But researchers found that gorillas who survived past the age of six were largely unaffected by difficulties they encountered when they were young.

Their ability to get past these events, such as the death of their mother, reveals that gorillas can overcome adversities much better than humans and other species.

Previous studies by the Dian Fossey Gorilla Fund revealed that young gorillas are surprisingly resilient to losing their mothers in contrast to many other species.

The Dian Fossey Gorilla Fund is a charity that works to protect endangered mountain gorillas.

But losing a mother is only one of many potential bad things that can happen to young animals.

The team identified six different kinds of early life adversity.

These included losing a father or mother, experiencing the death of a group member by infanticide, social group instability, having few age-mates in the social group and having a competing sibling who was born soon after them.

The data included information about how many of these early adversities each gorilla experienced, what age it happened and how long each gorilla lived.

The researchers looked at what happened when a gorilla experienced none, one, two or three or more adverse events.

They found that the more of these adverse events gorillas experienced before age six, the more likely they were to die as juveniles.

But if they managed to reach the age of six, there was no evidence that their lifespans were shorter, no matter how many adverse events the gorillas suffered.

In fact, if a gorilla experienced three or more forms of adversity, it actually lived longer. This group of animals had a 70 percent drop in the risk of death across adulthood.

But this was driven by greater longevity in males specifically and the researchers suspect the trend was due to something called viability selection.

This means that if a gorilla was strong enough to survive difficult early life events, it might just be a "higher-quality individual" and more likely to have a longer life span.

Study author Dr. Stacy Rosenbaum, an anthropologist at the University of Michigan, said. "I was expecting to see that these gorillas would have short lifespans and would not do very well as adults.

"We found that these events are definitely associated with a much higher risk of death when you're young.

“But if you survive to age six there's no evidence that those shorten your lifespan at all. This is quite different from what we see in other species."

The researchers have some theories about why these mountain gorillas were so resilient.

Gorillas have very tight-knit social groups and prior studies have shown that when a young gorilla loses its mother, it doesn't actually become more isolated, as other mother gorillas fill the gap.

Author of the study Dr. Robin Morrison, a researcher with the Dian Fossey Gorilla Fund, said: "The youngster actually increases its time near other gorillas after the loss of its mum and in particular the highest-ranking adult male, even if he isn't their biological father.

"These strong networks might provide critical social buffering, as has been 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 genetics or lifestyle."

Another reason is that mountain gorillas live in a resource-rich environment compared to many other wild primates.

It may be easier for a gorilla to survive difficult circumstances if they are not also constantly dealing with the stress of finding enough food and water.

Rosenbaum said: "For comparison, savanna baboons—who were the inspiration for this analysis—live in this highly seasonal environment where they go through extreme droughts.

“They sometimes will have to walk miles to get to a water hole. They're often struggling for every single calorie they take in.

“That's not the world that mountain gorillas live in. They're often described as living in a giant salad bowl."

The findings suggest that species similar to our own can have significant resilience to early life adversity.

Rosenbaum added: "I don't think we should assume that the long-term negative effects of early life adversity are universal.

"We tend to talk about this as if it's a ubiquitous experience, and a given that your adulthood is going to be compromised if you live through early adversity. But I don't think it's nearly that cut-and-dry, even in the human literature.

“I think the data are a lot more complex for humans and this research would suggest that they might be more complex for other animals, too. And I actually think that that's a hopeful story."

Studying these early adverse events in nonhuman species could help researchers understand how such events affect humans and how to deal with them.

Rosenbaum said: "Assuming that you survive something that we consider early life adversity, it's often still the case that you will be less healthy or you will have fewer kids or your lifespan will be shorter—no matter what species you are.

"There's this whole range of things that happens to you that seems to just make your life worse in adulthood."

Morrison added: "When you look at animals, you remove a lot of the variation that we have in humans.

“For example, they are all eating similar diets, they all get exercise as part of their daily lives, they don't have the opportunity to engage in behaviors with negative health outcomes like smoking,"

Like humans, gorillas live a long time and have a small number of offspring that they heavily invest in.

This makes them a good comparative animal model for understanding the ramifications of early life adverse events.

The researchers looked at 55 years of long-term data collected in 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.

The study is published in the journal Current Biology.