Discover Magazine: Compared to other primates, human slumber is exceptionally short.

Human sleep is an anomaly among primates. Our closest relatives, the chimpanzees, sleep three hours more than the average person — on a mattress made of branches suspended in the canopy. Then there’s the mouse lemur, a pint-sized primate with gleaming saucers for eyes that’s so skilled at sleeping it lies unconscious for 17 hours each day.

David Samson, an assistant professor of anthropology at the University of Toronto Mississauga, has used sleep prediction analyses to estimate the sleep time of different primates. After accounting for factors such as brain size, degree of predation and metabolism, Samson and his colleagues can accurately predict how much sleep each species needs … just not for humans.

“Our models predict that humans should sleep 10.5 to 11 hours,” Samson says. But this is three to four hours more than the seven hours an average person clocks per night. Not only do we sleep far less than the average ape, we also spend a larger portion of that time in rapid eye movement (REM) sleep, the deepest sleep stage. Humans spend 22 percent of sleep in REM, the most of any primate, according to Samson.

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