Researchers found that great apes can suffer mid-life crises like humans. This photo shows a chimpanzee (age unknown) at the San Francisco Zool licking gelatin off a pumpkin in October 2009.(Photo: George Nikitin, San Francisco Zoo/AP)
In the middle of life and having a crisis? You've got mates – primates.
Research
out Monday says that apes also experience emotional discontent at
life's midpoint and that it's probably hard-wired into both species by
biology. The "why" needs more study.
Previous studies have found
that humans' emotional health generally follows a U-shape between 20 and
70, with the mid- to late-40s marking the bottom of the big valley.
To
see if great apes followed a similar trajectory, Andrew Oswald, a
professor of economics at the University of Warwick in England, and his
cohorts examined data on the well-being of 508 chimpanzees and orangutans
from zoos and research centers in the United States, Australia, Canada,
Singapore and Japan. Caretakers and scientists were asked about an
ape's mood, the enjoyment the primate gained from socializing, success
at achieving goals -- and how the humans would feel about being the ape
for a week.
"In all three groups we find evidence that well-being
is lowest in chimpanzees and orangutans at an age that roughly
corresponds to midlife in humans," co-author Alex Weiss, a psychologist
at Edinburgh University, told the Guardian.
"On average, well-being scores are lowest when animals are around 30
years old." (An ape's lifespan is about half of a human's.)
"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 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," Oswald said.
Although
they showed signs of depression, "unlike men, great apes are not known
to pursue radical and often disastrous lifestyle changes in middle age,"
the Guardian says. And as the Associated Press noted, they don't buy sports cars or dump their mates" for some cute young bonobos."
Naturally, the findings have attracted skeptics.
"The
judgment of happiness is hard enough in humans, and here we have humans
judging the happiness of apes," Frans de Waal, a primatologist at the
University of Emory who was not involved in the study, told LiveScience. "The study thus scores the well-being of animals through a human filter, perhaps introducing human bias."
The findings were published in the Proceedings of the National Academy of Science.
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