Apes get mid-life crises too
They don't buy a sports car or get Botox - but it appears that chimpanzees and orangutans can experience a mid-life crisis just as humans do.
Their well-being, or happiness, follows exactly the same U shape: high in youth, falling in middle age, and rising again in old age.
The authors studied 508 great apes housed in zoos and sanctuaries in the US, Japan, Canada, Australia and Singapore. Their well-being was assessed by keepers, volunteers, researchers and caretakers who knew them well, and scored with a series of measures adapted from tests designed for humans.
"We hoped to understand a famous scientific puzzle: why does human happiness follow an approximate U-shape through life?" says Professor Andrew Oswald from the University of Warwick.
"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 researchers point out that their findings don't mean that economic events or social and cultural forces are irrelevant. However, they say they do show a need to consider evolutionary or biological explanations.
For example, if individuals are satisfied at stages of their life where they have fewer resources to improve their lot, they may be less likely to encounter situations that could be harmful to them or their families.
"Based on all of the other behavioural and developmental similarities between humans, chimpanzees, and orang-utans, we predicted that there would be similarities when looking at happiness over the lifespan, too," says Dr Alex Weiss from the University of Edinburgh.
"However, one never knows how these things will turn out, so it's wonderful when they are consistent with findings from so many other areas."