If you're someone who stays up late, only gets about six hours of sleep and rarely takes naps, you're actually living like a caveman, according to a small October 2015 study published in Current Biology.
For a little over three years, researchers from UCLA looked at the sleeping behaviors of 94 adults who live much like early humans did — in isolated, hunter-gatherer communities. The study included people living among the Hadza of Tanzania, the San of Namibia and the Tsimane of Bolivia.
With the help of modern technology — special watch-sized devices that measure sleeping and waking times, as well as light exposure — the researchers discovered that not only do these "pre-industrial" people live on an average of six hours and 25 minutes of shut-eye each night, they also have lower levels of obesity, blood pressure and atherosclerosis than people in industrialized societies. They also rarely nap, and insomnia is practically unheard of.
"The argument has always been that modern life has reduced our sleep time below the amount our ancestors got, but our data indicates that this is a myth," said Jerome Siegel, leader of the research team and professor of psychiatry at UCLA's Semel Institute of Neuroscience and Human Behavior, in a statement.
So What's All This About Needing Eight Hours?
"One thing I believe is that everyone's sleep need is individual," says Michael "The Sleep Doctor" Breus, PhD, clinical psychologist with a specialty in sleep disorders and author of The Sleep Doctor's Diet Plan: Lose Weight Through Better Sleep. He explains that sleep requirements are determined by our DNA, "and if [the study participants are] a small group, they are likely genetically homogeneous — meaning they are all pretty similar from a genetic standpoint."
So have our sleep needs changed over the years or not? "I am not convinced we need more or less sleep than our ancestors… What we need to remember is that sleep itself is in a constant state of evolution," Dr. Breus says.
He adds that current stressors have also affected our sleep. "It is how we, as a society, deal with stress that is the issue," Breus says. "And it is how we view the importance of sleep that has likely changed some of our habits."
What's more important, says Nathaniel F. Watson, MD, president of the American Academy of Sleep Medicine, is to look at why we face so many health problems associated with sleep deprivation if our ancestors got about the same amount of sleep as we do.
"There is a very strong amount of evidence in adults sleeping less than seven hours — and certainly less than six — is associated with a number of [negative] health outcomes, such as cardiovascular disease, diabetes, mood disorders, and so on," he says. "And many people feel tired and fatigued during the day and have problems with insomnia. These are all facts."
So even though our ancestors may have lived on fewer hours of snoozing, don't give up on that eight-hour goal just yet. "Our recommendation of seven or more hours of sleep is based on the careful consideration of a massive body of research," Dr. Watson says. "I think that it would be a disservice for us to cast that aside based on the results of this one study."