How Human Sleep Has Evolved
Humans have long been thought to be the best sleepers in the mammalian world, and now a study published in the journal Evolutionary Anthropology verifies it.
Researchers at Duke University found that we sleep more efficiently than other mammals because we have evolved to sleep for fewer hours, but in deeper sleep stages. They examined sleep patterns across hundreds of mammals, including 21 species of primates such as baboons, lemurs, chimpanzees and humans.
The team found that humans are the shortest sleepers -- averaging seven hours a night -- while other species of primate, such as the southern pig-tailed macaques and gray mouse lemurs, need 14 to 17 hours.
Humans are able to get away with so much less sleep because we spend nearly 25 percent of our sleep time in rapid eye movement (REM) sleep -- which is a deeper stage. Other primates spend only five percent of their time in that state.
While some have suggested that the modern world of gadgets is causing people to sleep less, another study into the sleeping habits of hunter-gatherer societies without electricity in Tanzania, Namibia and Bolivia concluded that they actually get less sleep than people in tech-heavy cultures.
The researchers proposed a "sleep intensity hypothesis," based on the premise that early humans encountered "selective pressure" to get quality sleep in the shortest amount of time possible to shorten their periods of vulnerability.
Don't miss this week's Slice of History: 1st Triple Transplant.