Chimpanzees going through a midlife crisis? It sounds like a setup for a joke.
But there it is, in the title of a report published yesterday in a scientific journal: "Evidence for a midlife crisis in great apes." So what do these apes do? Buy red Ferraris? Leave their mates for some cute young bonobos? Uh, no.
But researchers report that captive chimps and orangutans do show the same low ebb in emotional well-being at midlife that some studies find in people.
That suggests the human tendency toward midlife discontent may have been passed on through evolution, rather than resulting simply from the hassles of modern life, said Andrew Oswald, a study author and a professor of economics at the University of Warwick in England. He presented his work yesterday in the Proceedings of the National Academy of Sciences.
Several studies have concluded that happiness in human adults tends to follow a certain course between ages 20 and 70: It starts high and declines over the years to reach a low point in the late 40s, then turns around and rises to another peak at 70. On a graph, that's a U-shaped pattern.
"This is one of the great patterns of human life. We're all going to slide along this U for good or ill," he said. "So what explains it?"
When he learned that others had been measuring well-being in apes, "it just seemed worth pursuing the hunch that the U might be more general than in humans," he said.
Caretakers and other observers had filled out a four-item questionnaire to assess well-being in the apes. The questions asked such things as the degree to which each animal was in a positive or negative mood, how much pleasure it got from social situations, and how successful it was in achieving goals.
Oswald and his co-authors found that the survey results produced that familiar U-shaped curve, adjusted to an ape's shorter life span.
"We find it for these creatures that don't have a mortgage and don't have to go to work and don't have marriage and all the other stuff," Oswald said. "It's as though the U shape is deep in the biology of humans" rather than a result of uniquely human experiences.