CHIMPANZEES and orangutans suffer from mid-life crises just as humans do, a study has revealed.
Researchers at the University of Edinburgh and the University of Warwick sought to find out whether the “U-shaped” pattern of human happiness over the course of a lifetime may have been inherited from genetic ancestors.
An international team of scientists discovered that happiness in chimpanzees and orangutans follows a similar pattern to that of humans – a U-shape where wellbeing is high in youth, falls in middle age and rises again in old age.
Researchers, including psychologist Dr Alex Weiss, from the University of Edinburgh, and economist Professor Andrew Oswald, from the University of Warwick, conducted a study of 508 great apes housed in zoos and sanctuaries across four countries – Japan, Canada, Australia and the United States – as well as Singapore.
Apes’ wellbeing was assessed by keepers, volunteers, researchers and caretakers who were familiar with the animals. Happiness was measured with a series of tests adapted from human equivalents.
Professor Oswald said: “We hoped to understand a famous scientific puzzle: why does human happiness follow an approximate U-shape through life?
“We ended up showing that it cannot be because of mortgages, marital break-up, mobile phones or any of the other paraphernalia of modern life. Apes also have a pronounced mid-life low, and they have none of those.”
The study is the first of its kind, and the authors knew their work was unconventional.
Dr Weiss said: “Based on all of the other behavioural and developmental similarities between humans, chimpanzees and orangutans, we predicted that there would be similarities when looking at happiness over the lifespan, too. 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. Researchers pointed out that the findings do not rule out the possibility that economic events or social and cultural forces may contribute towards the wellbeing U-shape in humans.
However, they also highlighted 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 deemed harmful to them or their families.
Chimpanzees, along with bonobo apes, share an estimated 98-99 per cent of their DNA with humans.