A new study suggest apes have midlife crises, too. (Image credit: Emily Wabitsch/AFP/Getty Images)

Reported by Dr. Nisha Nathan:

Sure, they may not be able to ditch their wives, buy a shiny red Ferrari, or pick up a 21-year-old at a bar. But apes have midlife crises too - at least according to a new study.

"The midlife crisis is real," said Dr. Andrew Oswald, co-author of the study of 500 chimpanzees and orangutans published Monday in the Proceedings of the National Academy of Sciences. "Great apes go through it also, so it is inescapable for the average person."

The term "midlife crisis" was coined in 1965 by psychologist Elliot Jacques to describe the time when adults realize their own mortality, recognize that their existence is halfway over, and rush to make significant changes in core aspects of their day-to-day lives. And since the human species evolved from ancestors of modern apes, it would be reasonable to suspect that they have mood swings just as we do.

To see if this was actually the case, researchers asked zookeepers who had close relationships with their apes a series of questions to see whether the animals were happy or sad, if they enjoyed socializing, and how successful they were in achieving their "personal goals."

As for what a personal goal might be for an orangutan or chimp, study coauthor Alexander Weiss of the University of Edinburgh said this included such lofty ambitions as climbing a rope, staking out territory, getting prized figs or bananas - or even hunting down and eating their distant monkey cousins.

Before you knock it, understand that these questions have been used before to assess ape aspiration.

"This questionnaire is a well-established method for assessing positive affect in captive nonhuman primates. There is considerable evidence for this measure's objective validity," the study says.

Finally, researchers asked the zookeepers the ultimate question: How happy would you be to switch roles with the apes for a week?

In other words, Weiss said, "How happy would the rater be to walk a week in the chimp's shoes - even though chimps don't have shoes?"

Looking at the zookeepers' answers and the ages of the apes, the authors concluded that great apes have age and well-being highs and lows similar to those of humans - according to Oswald, a pattern that can best be described as a "U-shape," with the high points early and late in life, and the nadir of existence in the middle. This U-shaped curve of human well-being as compared to age, in fact, has been well understood the world over.

As for exactly why this happens to be the case, who knows?

Oswald admits the study has limitations.

"It would be great if we could ask apes to fill out a questionnaire," he said. "However this is a human's assessment of an ape's well-being and that's what we are stuck with, being human."

Despite the apes' silence on the matter, psychological experts who were not involved with the research described the findings as "fascinating."

"This is one more example showing that we may be more related to our non-human primates than we think," said Dr. Nadine Kaslow, vice chair of the department of psychiatry at Emory University in Atlanta. "It's quite fascinating that this U-shaped curve is across species."

For years, researchers have speculated that this U-shape is secondary to social, psychological, or economic explanation. Dr. Redford Williams, director of the Behavioral Medicine Research Center at Duke University Medical Center in Durham, N.C., said this study seems to point at something much more inherent.

"It's got to be biological," he said. "It's not just that you're depressed because your earning capacity goes down in mid-life, because I don't imagine that apes living in the zoo would have to worry about those matters."

Williams said the study shows there is hope for us humans.

"Don't worry if you are having a mid-life slump," he said. "Don't feel too guilty; it has to have a genetic basis. It's not that you screwed up to cause it, because apes are having it too."