Great apes have midlife crises too - Study

At middle age, a great ape will neither cheat on a spouse nor buy a red sports car on impulse. However, researchers have found that chimpanzees and orangutans experience midlife crises just as surely as do humans.

That finding, published in the Proceedings of the National Academy of Sciences, could upend firmly held beliefs about the roots of human happiness and the forces that influence its odd trajectory across the life span. If our animal relatives share our propensity for sadness, withdrawal and frustration at life's midpoint, perhaps the midlife crisis is actually driven by biological factors - not the wearing responsibilities of jobs and family and the dawning recognition of our mortality.

"This opens a whole new box in the effort to explain the midlife dip in well-being," said senior author Andrew Oswald, a behavioural economist at University of Warwick in England. "It makes one's head spin."

For men and women alike, social science researchers have located the winter of our discontent somewhere near the 50-year mark, wedged neatly between the vigour and drive of youth and the quest for meaning and happiness that marks the final decades of life. More than just a cultural cliche, the midlife crisis is the well-documented nadir of human well-being on the U-shaped curve of happiness that stretches between birth and death.

As happiness researchers have fanned out around the globe, they have documented this midlife trough in at least 65 countries, suggesting that it is a universal feature of human existence.

Until now, however, the social scientists that have dominated this burgeoning field of study have drawn on economic, psychological and sociological explanations. By midlife, youth's hot-blooded drive to mastery has driven off. Responsibilities abound. Decades of striving - to raise a family, to establish oneself in the community, to climb the professional ziggurat - have shown us the mountaintop and, with it, the limits of our reach and usefulness. A recognition of our mortality settles in.

In the years after midlife, the theory goes, humans shoulder fewer burdens for the care of others. Their time horizons are shorter, prompting them to focus on people and activities that give pleasure and meaning to their lives. They regret less.

Oswald had a hunch that these explanations were overlooking the fundamental role of biology in influencing mood. So he reached out to Alexander Weiss, a primatologist and evolutionary psychologist at the University of Edinburgh in Scotland who studies well-being in great apes.

The pair put together an international team of primatologists from Scotland, Japan and Arizona and devised an unprecedented census of well-being among 336 chimpanzees and 172 orangutans of all ages living in two research centres, one sanctuary and nine zoos across five countries.

To gauge the animals' well-being, the researchers turned to the keepers that knew them best and asked them a series of questions that might stymie even the most devoted dog or cat owner. Designed to capture the mood, sense of effectiveness and pleasure-seeking drive of apes across the life span, the questions were based on established methods of measuring human well-being, but modified for this population.

Keepers were asked to rate the positive or negative mood of each subject and to gauge the degree of pleasure the animal derived from social situations. A third question was how successful each great ape was in achieving its goals - whether winning a mate, commanding the attention of a fellow member of its social group or gaining hold of an out-of-reach toy. Finally, the study authors asked keepers to consider how happy they would be if they had to live as their chimpanzees or orangutans for a week.

- Los Angeles Times