Stereotypically, people experiencing a mid-life crisis desperately seek to justify their lives through superficial means, perhaps by buying an expensive sports car or getting into a relationship with a younger romantic partner. Although their behavior looks rather different, a new study says that chimpanzees and orangutans go through a mid-life nadir in overall well-being and happiness that roughly resembles our own.
A team led by psychologist Alexander Weiss of the University of Edinburgh asked zookeepers and researchers around the world to keep track of the well-being of resident chimpanzees and orangutans—508 animals in total. The results of all that record-keeping, published today in the Proceedings of the National Academy of Sciences, show that, like humans, these great apes generally experience a U-shaped pattern of happiness and well-being, starting off with high ratings for happiness as adolescents, declining gradually during middle age (bottoming out in their late 20s or early 30s), and then rising back up again in their elder years.
Although popular conceptions of human mid-life crises focus on material acquisitions, psychologists believe they’re driven by an underlying decline in satisfaction and happiness as we go through middle age, and reflected by increased antidepressant use and suicide risk. In this sense, the primates studied went through a similar pattern:
Of course, unlike with humans, no one can directly ask chimps and orangutans how they are feeling. Instead, the researchers relied upon surveys, filled out by zookeepers and caretakers, that rated the animals’ mood and how much pleasure they took from certain situations. They acknowledge the ratings are necessarily subjective, but they feel that the size of the dataset and consistency in the trends as reported from the different zoos with different animals suggests that the pattern is legitimate.
Weiss’ group originally embarked on the ape study to answer the question of why mid-life dissatisfaction is so common in humans. “We hoped to understand a famous scientific puzzle: why does human happiness follow an approximate U-shape through life?” Weiss said in a statement.
Although many are apt to blame external cultural factors such as disappointing careers or mounting bills as the cause, Weiss felt it was something more fundamental. By showing that a similar pattern exists in other primates, he argues that his team has dispelled the notion that these types of external factors are solely responsible. “We ended up showing that it cannot be because of mortgages, marital breakup, mobile phones or any of the other paraphernalia of modern life,” he said. “Apes also have a pronounced midlife low, and they have none of those.”
Instead of these cultural factors, Weiss suggests that this pattern is rooted in biological or evolutionary factors. It might have been the case, for example, that the human ancestors who had an innate tendency for happiness and satisfaction at the stages of life when they were most vulnerable (youth and old adulthood) might have been less likely to venture into risky and potentially harmful situations in the pursuit of more resources.