Unravel the mystery of why humans, the most advanced primates, sleep less than their relatives in the animal kingdom. Delve into the evolutionary, biological, and societal factors that have shaped our unique sleep patterns.
A sloth snoozes in Costa Rica
One study in wild sloths found they slept for about 9.5 hours per day, whereas people typically sleep for only about seven
- The human sleep paradox is the result of our evolutionary history
- 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 nine hours out of every 24, not seven
Fireside chats
Our ancestors may have compressed their sleep into a shorter period because they had more important things to do in the evenings than rest.
- A typical evening with the Tsimane: After spending the day working on various tasks, a group comes together around a fire while food is cooked, then linger by the fire in the dark.
Unsatisfied sleepers
Our sleep problems may have to do with stress or out-of-whack circadian rhythms
- When we struggle to get sleep, we could be experiencing a mismatch between how we evolved and how we live now
- A better understanding of how human sleep evolved could help people rest better
From canopy bed to snail’s shell
To learn about how ancient humans slept, anthropologists study the best proxy they have: contemporary non-industrial societies
- Brief, flexibly timed REM-dense sleep likely evolved because of the threat of predation when humans began sleeping on the ground
- Another key to sleeping safely on land was snoozing in a group
Republish
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
- This is a surprising number when you consider our closest animal relatives, such as monkeys and apes, sleep less than 9.5 hours out of every 24.
- Samson calls this the human sleep paradox
- A predictive model of human sleep based on factors such as body mass, brain size, and diet concluded that humans ought to sleep about nine hours every night, not seven
- 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
- From canopy bed to snail’s shell
- Millions of years ago, our ancestors slept in trees, and today’s chimpanzees and other great apes sleep in temporary tree beds or platforms
- Our ancestors transitioned out of trees to live on the ground, and at some point started sleeping there too, giving up all the perks of arboreal sleep
As special as we seem?
It makes sense that the threat of predators may have led humans to sleep less than tree-living primates
- But Capellini isn’t sure that human sleep is as different from that of other primates as it seems
- Most of the existing data about sleep in primates comes from captive animals
- In a zoo or lab, animals might sleep less because of stress
- Or they might sleep more because they are bored
- The standard laboratory conditions might not match what an animal experiences in nature
