BBC: The amount of time we spend awake and asleep compared to our relatives among the apes, monkeys and lemurs may have played a key role in our evolution.
Research has shown that people in non-industrial societies – the closest thing to the kind of setting our species evolved in – average less than seven hours a night, says evolutionary anthropologist David Samson at the University of Toronto Mississauga. That’s surprising when you consider our closest animal relatives. Humans sleep less than any ape, monkey or lemur that scientists have studied.
Chimpanzees sleep around 9.5 hours out of every 24. Cotton-top tamarins sleep around 13. Three-striped night monkeys are technically nocturnal, though really, they’re hardly ever awake — they sleep for 17 hours a day.
Samson calls this discrepancy the human sleep paradox.
“How is this possible, that we’re sleeping the least out of any primate?” he says. Sleep is known to be important for our memory, immune function and other aspects of health. A predictive model of primate sleep based on factors such as body mass, brain size and diet concluded that humans ought to sleep about 9.5 hours out of every 24, not seven. “Something weird is going on,” Samson says.
Research by Samson and others in primates and non-industrial human populations has revealed the various ways that human sleep is unusual. We spend fewer hours asleep than our nearest relatives, and more of our night in the phase of sleep known as rapid eye movement, or REM. The reasons for our strange sleep habits are still up for debate but can likely be found in the story of how we became human.
