Adult humans average about seven hours of sleep per day. By contrast, chimpanzee, one of our closest relatives, sleep 9.5 hours a day, and other primates sleep even longer. Why is that? Common sense might tell you that it's because of television, the internet, stress, artificial schedules, and lights. But studies show that non-industrial communities, even those without electricity, sleep about the same amount. There's something about being human that causes us to get less sleep than other primates. Some new studies give us a hypothesis and some caveats.
It's possible that we evolved to operate on less sleep when we stopped living in trees. Animals that sleep on the ground are at a higher risk from predators, so our ancestors began sleeping in groups with someone keeping watch in shifts. That would also explain why humans have more flexible sleep patterns than other primates.
The caveat is that we might not know as much about animal sleep patterns as we think we do. Some studies show that creatures who live in zoos and laboratories sleep more than those in the wild, although studies of how long wild animals sleep in their own environment are rather scarce. Read a lot more about the research into why humans sleep less than other primates at Smithsonian.
(Image credit: Daniel Ramirez)
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