Apes too suffer from midlife crisis
We should not be surprised that apes have midlife crises when they are like us in so many ways.
THE dreaded feeling usually strikes in the late 40s. A sense of ennui, a life unfulfilled, expectations dashed. A growing suspicion that the best is behind you, that ahead lies only a long, inevitable decline into infirmity, irrelevance and bewilderment. No wonder so many people report that this period is the unhappiest time of their lives.
Many seek a cure – men in particular. They buy an Aston Martin or a flashy racing bike and grow a pair of sideburns to go with it. They can’t be James Bond or (British cyclist) Bradley Wiggins, but they can at least have the wheels.
The midlife crisis is a well-attested phenomenon of the modern age, seemingly a by-product of affluence and the happy fact that so many of us now have the luxury of living well beyond our “middle” years. It is, one would have thought, a quintessentially human trait – and a quintessentially recent one as well. So it is a surprise to find that at least two species of apes suffer this middle-aged downturn, too.
An international team of researchers last week published a study – in the American journal The Proceedings of the National Academy of Sciences – showing that captive chimpanzees and orang-utans display the classic signs of a midlife crisis.
Of course, these primates were not buying sports cars or daft apparel. Instead, they were seen moping around, showing signs of depression, boredom and general dissatisfaction with their lot – at an age that corresponds precisely to the mid- to late 40s in human terms. Like us, it seems, apes experience a “U-shaped” happiness curve in their lives: content when they are young, fine when they are old and, in the words of the study’s authors, “falling to a nadir” in midlife.
The 508 captive apes were studied live in zoos all around the world, in the United States, Singapore, Japan, Canada and Australia. Their keepers maintained a detailed record of their behaviour, answering questions designed to quantify their charges’ mood.
These questions included a subjective assessment of how the apes reacted to social situations and how enthusiastic and successful they were at completing tasks.
Finally, the keepers, all of whom knew the animals well, were asked to put themselves in the ape’s shoes – how happy would they be if they were to be the ape in question for a week?
For both species studied, there was a clear dip in happiness at the midlife stage (from 27 to the early 30s, which is the equivalent in humans of the mid- to late 40s). The effect was seen equally in males and females. So the question is, why does this happen?
If it is a purely social phenomenon in humans (and the midlife crisis, which is linked not only to reported feelings of unhappiness and dissatisfaction but also to increased suicide risk, has been noted in studies in more than 50 countries across all socio-economic and ethnic groups), then how could this explain what happens in apes, which may be biologically similar to us but lead very different lives? And if it has a biological cause, do the same factors affect us as they do our closest cousins?
Professor Andrew Oswald of the University of Warwick, one of the authors of the study, agrees that the U-shaped happiness curve is a major puzzle with no obvious explanations. One possibility is that it has to do with having children around – although this contradicts findings that show children bring positive benefits, and the midlife dip affects the childless equally. The menopause has also been ruled out as a cause, as have differences in sexual roles, because the midlife crisis affects both sexes equally at about the same age.
A socioeconomic theory states that the midlife crisis reflects “hedonic adaptation”, namely that the realisation of impossible aspirations (of financial, sexual, social or professional “stardom”) are first painfully felt around midlife and are then slowly abandoned as reality sinks in.
But can an ape really suffer from a feeling of unfulfilled promise? After all, animals do not seem to have a sense of their own mortality, and even if an ape knows that one day it will die, it is unlikely to have any idea when that will be.
“We ended up showing that (the midlife crisis) cannot be because of mortgages, marital break-up, mobile phones, or any of the other paraphernalia of modern life,” Prof Oswald said.
“Apes also have a pronounced midlife low, and they have none of those things.”
In general, people who are happy tend to live longer, but again this has been found to have no statistical significance in relation to the midlife dip. One persuasive explanation is that the midlife crisis is, in fact, adaptive. Far from being at a biological trough, many people (and perhaps apes, too) are at the top of their game at this “difficult” age.
The “crisis” could act as a motivational mechanism to make sure you do not let things slip, to make the best use of your resources while you still have them.
Alexander Weiss of the University of Edinburgh, the lead author of the study, says that this is a plausible explanation, “but at the moment it is only a hypothesis. This period, middle-age, may be a prime time to improve your situation.”
The fact that the dip is seen in both apes and humans suggests that there is no simple social cause, but that the phenomenon has its roots deep in our evolutionary past, long before our ancestors split from the other apes.
Interestingly, anecdotal evidence suggests that the midlife crisis may not apply to the other great apes – gorillas and bonobos.
Amos Courage, overseas director of the Aspinall Foundation in Kent, has been working with Western Lowland gorillas for years. The foundation is home to the largest population of captive gorillas in the world, more than 100 animals.
“The consensus here is that we have not noticed a dip in middleage,” Courage says.
“In fact, if anything, they just carry on getting grumpier as they get older.”
Courage says that, conversely, bonobos, the chimp-like great ape that sits closest to Homo sapiens on the evolutionary tree, seem to maintain high levels of contentment.
“They are always having sex and seem pretty happy at all ages,” he says.
Should we be surprised that at least two species of ape share this apparently human trait with us? After all, chimps are genetically extremely close cousins of H. sapiens, sharing more than 98% of our DNA.
In terms of ancestry, we only diverged from the lineage that gave rise to bonobos and common chimpanzees around seven million years ago.
Some scientists have argued that such is our biological kinship, the chimps and bonobos should be reclassified as “Hominids”, put in the same group as humans.
And behaviourally we have so much in common with the apes. Like us, chimps and bonobos use tools, sticks to dig termites out of nests, stones for smashing nuts and so on. Apes lack vocal chords but can be taught rudimentary sign language, and on some measures of development, infant chimps and bonobos are actually ahead of their human rivals until the age of five or so.
According to Prof Weiss: “We see so many similarities, not just in behaviour but genetically, too, that we would generally expect humans and apes to have a psychology that is more similar than not.”
We should, perhaps, be cautious with studies like this. Not all psychologists agree that the midlife crisis is real in humans, let alone apes. As they cannot talk, it is impossible to infer what animals are really feeling.
A grumpy-looking chimp may in fact be perfectly content, while a lively and noisy animal could be very anxious. These are intelligent, impressive creatures, very similar to us in many ways. But while they may sit on the next twig to our own on the evolutionary tree, in mental terms they are in a different forest. — The Daily Telegraph