Though they’re separated by 25 million years of evolution, monkeys and humans share at least one common fact of life: both choose to have a less engaged social life at old age.
The conclusion was made by researchers at the German Primate Center in Goettingen, Germany, who followed a group of Barbary macaques at a French wildlife park. The monkeys varied from age 4 to age 29 (that’s equivalent to age 105 in humans).
During the course of several weeks, the team recorded how the monkeys interacted with objects like novel toys baited with food, how often they groomed friends or fought and how they responded to social cues like photos and haul recordings from friends or strangers.
As the monkeys aged past their childhoods and began lives as adults — essentially when they reached sexual maturity — their interest in toys waned. The pensioner monkeys, or those older than 20, had the fewest “friends” and engaged in social contact rarely, akin to how our elderly prefer to stick to themselves and the few ‘true’ friendships they have left.
It’s important to note that while the old monkeys got quite grumpy with old age, they still were very much aware of their surroundings. They responded to photos and audio recordings of other monkeys and hissed during fights. And while they groomed other monkeys far less frequently, the elderly were often groomed by younger monkeys.
Psychologists say that humans become more choosy with how they decided to spend their time once with old age. When you realize you have little time to spend, you choose to use that time more wisely. You visit the same restaurant and are less inclined to engage socially with mere acquaintances. But a monkey, we suspect, is not aware of its own mortality. Yet, the pattern of similarities between old monkeys and humans is striking.
Dr. Julia Fischer, one of the lead authors of the study, says we might just be rationalizing an inherent biological construct. Both monkeys and humans might simply have too little energy left once they hit their golden years, and thus unable to reserve resources for new relationships. There’s also a tendency to become more risk adverse with old age, which might also explain social withdrawal.
“Our behaviors that seem very much the result of our deliberation and choice,” said Dr. Freund, “might be more similar to our primate ancestors than we might think.”