Published in Proceedings of the National Academy of Sciences, a new study shows that, as in humans, chimpanzee and orangutan well-being (or happiness) follows a U shape that is high in youth, falls in middle age, and rises again into old age.
The authors studied 508 great 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.
“We hoped to understand a famous scientific puzzle: why does human happiness follow an approximate U-shape through life?” says Andrew Oswald, professor at 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 study is the first of its kind and the authors knew their work was likely to be unconventional.
“Based on all of the other behavioral and developmental similarities between humans, chimpanzees, and orangutans, we predicted that there would be similarities when looking at happiness over the lifespan, too,” says Alex Weiss of 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.”
The team included primatologists and psychologists from Japan and the United States. In the paper, the team points out that their findings do 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, they highlight the need to consider evolutionary or biological explanations. 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.