Chimpanzees and orangutans can experience a mid-life crisis just like humans, scientists have found. Their study, in the Proceedings of the National Academy of Sciences, details how they set out to test the theory that the pattern of human well-being over a lifespan might have evolved in our ape ancestors.
The scientists studied more than 500 apes housed in zoos and sanctuaries in the United States, Japan, Canada, Australia and Singapore. The apes' well-being was assessed by keepers, volunteers, researchers and caretakers who knew the apes well. Their happiness was scored with a series of measures adapted from human subjective well-being measures.
The researchers discovered that, as in humans, chimpanzee and orangutan well-being (or happiness) follows a "U" shape and is high in youth, falls in middle age, and rises again in old age.
"We hoped to understand a famous scientific puzzle: why does human happiness follow an approximate U-shape through life?" said researcher Andrew Oswald, from the University of Warwick (UK). "We ended up showing that it cannot be because of mortgages, marital breakup, mobile phones, or any of the other paraphernalia of modern life. Apes also have a pronounced midlife low, and they have none of those."
The study does not rule out the possibility that economic events or social and cultural forces contribute part of the reason for the well-being U shape in humans. However, the researchers contend that evolutionary or biological explanations are part of the answer. "For example, individuals being satisfied at stages of their life where they have fewer resources to improve their lot may be less likely to encounter situations that could be harmful to them or their families," explained Oswald.
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Source: University of Warwick