Battling predators, hunger, and often each other, chimpanzees tend to forge a harsh existence in the forests of Central Africa. So much so, it has long been thought that they have a shockingly low life expectancy at around 17 years in the wild. But a long-term study of one population has found that chimps living in Uganda tend to live to a ripe old age.
The chimpanzees in question live in the Ngogo community in Kibale National Park, which contains a large group of relatively undisturbed apes that have been studied continuously since 1995. Using this data, the researchers were able to build a detailed picture of the life histories of the chimps and calculate the average life expectancy for individuals born into the community during this time.
They found that the total demographic of 306 chimpanzees had an average life expectancy of a stunning 33 years. While captive chimps have been known to reach ages of up to 78, the maximum age in the wild is estimated to be over 60 years, although this is far from the norm. What is more, this 33-year figure even sits within the life expectancy range generally given for human hunter-gatherer communities of around 27 to 37 years.
“It has long been proposed that there are extreme differences in the life expectancies of human hunter-gatherers and chimpanzees,” explains Yale University’s David Watts, co-author of the study published in the Journal of Human Evolution, in a statement. “Our study finds that while maximum lifespan differs a great deal, the differences in average lifespan are not as dramatic as typically thought, especially when chimpanzees are not subjected to major negative impacts caused by humans.”
The researchers suspect that the previously low averages for chimp life expectancies may be down to which communities were being studied and the level of disease outbreak and anthropogenic disturbances they are facing. The apes found in the Ngogo community have a relatively untouched life, with abundant food, no natural predators, and little human influences. There has also been no recorded disease outbreak, whether of natural or human origin, within the forest.
“Our findings show how ecological factors, including variation in food supplies and predation levels, drive variation in life expectancy among wild chimpanzee populations,” says lead author Brian Wood. It seems that this population of apes more closely resembles that of hunter-gatherers rather than chimpanzees.
The study may also help inform what our ancestors’ life histories may have looked like. It can, for example, give us an idea of how changing ecosystems can lead to dramatic changes in life expectancy, which could then have significant impacts on whether or not certain populations are more likely to survive or not.
