Gorillas resilient to early life adversity

Gorillas and humans share a common phenomenon when it comes to adversity in early life: it often leads to long-lasting hardships later on. However, researchers from the Dian Fossey Gorilla Fund and the University of Michigan conducted a study to explore this concept in gorillas, unsure of what they would discover.

Previous studies by the Fossey Fund had already revealed that young gorillas showed surprising resilience in the face of losing their mothers, which differed from findings in many other species. Nonetheless, losing a mother is just one potential negative event that young animals can experience, and there was still a range of potential adverse effects to consider.

The researchers were pleasantly surprised to find that gorillas who survived past the age of six were largely unaffected by the difficulties they encountered in infancy or during their juvenile years. This discovery was published in the journal Current Biology.

In the case of humans, early life adversity can have lasting effects, including a shorter lifespan and health complications. However, it is challenging to determine whether adverse events in early life directly cause these outcomes or if multiple factors, such as behavior, environment, and culture, play a role—or perhaps a combination of all these factors.

Studying how early adverse events affect nonhuman species can provide valuable insights into their impact on humans and potential strategies to mitigate their effects. By examining animals, researchers eliminate many of the variations found in human studies. For instance, animals consume similar diets, engage in daily exercise, and lack the opportunity to engage in behaviors that have negative health outcomes, such as smoking.

Overall, understanding how early life adversity affects various species can enhance our understanding of its impact on humans and inform approaches to minimize its detrimental effects.

According to Robin Morrison, one of the researchers involved in the study, despite the common pattern in most species where early adversity leads to negative effects in adulthood, there seems to be a deeper biological mechanism that is not well understood. The unique findings in gorillas suggest that early life adversities can be overcome, which has significant implications for our own species.

Gorillas, like humans, have long lifespans and invest heavily in a small number of offspring. This similarity makes gorillas an ideal animal model for studying the consequences of early life adverse events. The researchers examined 253 wild mountain gorillas, with data spanning over 55 years, collected in Volcanoes National Park in Rwanda by the Dian Fossey Gorilla Fund.

The study identified six types of early life adversity experienced by the gorillas, including the loss of a father or mother, infanticide by a group member, social group instability, limited age-mates in the group, and having a competing sibling born soon after them. The data included information on the number and timing of these adversities experienced by each gorilla, as well as their lifespans.

The researchers analyzed the outcomes for gorillas who experienced none, one, two, or three or more adverse events. They found that the more adverse events gorillas experienced before the age of 6, the higher the likelihood of dying as juveniles. However, if gorillas survived past the age of 6, there was no evidence that their lifespans were shorter, regardless of the number of adverse events they had encountered.

Interestingly, gorillas that experienced three or more forms of adversity actually lived longer. This increase in longevity was primarily observed in males, and the researchers suspect it may be due to a phenomenon called viability selection. This suggests that the gorillas who were strong enough to survive challenging early life events might be “higher-quality individuals,” thus more likely to have longer lifespans.

The unexpected resilience of mountain gorillas may be attributed to their tightly-knit social groups. Other gorillas in the group provide companionship and support when a young gorilla loses its mother. These strong social networks may act as critical buffers against the consequences of adversity, similar to what has been observed in humans.

Additionally, the resource-rich environment in which mountain gorillas live compared to other primates may contribute to their relative resilience. The availability of abundant food and water could make it easier for gorillas to cope with difficult circumstances without the added stress of scarcity.

These findings indicate that species similar to humans can exhibit significant resilience to early life adversity. They also raise important questions about the biological underpinnings of sensitivity to early experiences and the protective mechanisms that contribute to resilience in gorillas.

Stacy Rosenbaum, another researcher involved in the study, emphasizes that the long-term negative effects of early life adversity should not be assumed as universal. The complexity of data in humans suggests that the impact of early adversity may vary, and the same might be true for other animals. These findings offer hope and challenge the prevailing belief that early life adversity inevitably compromises adulthood.

In conclusion, understanding the resilience observed in gorillas provides valuable insights into mitigating the effects of early life adversity in our own species. By studying animal models, we can unravel the complex interplay of biological, social, and environmental factors, leading to a better understanding of how early life experiences shape our lives.

Source: University of Michigan

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