Short sleep not just modern-day jinx

Busting the 8-hour sleep myth, a new study has revealed that our ancestors probably didn't get 8 hours a night, either.

UCLA-led team of researchers studied sleeping patterns among traditional peoples whose lifestyles closely resemble those of our evolutionary ancestors.

What the team found among the Hadza of Tanzania, the San of Namibia and the Tsimane of Bolivia challenges conventional wisdom about the sleeping habits of pre-industrial humans. The findings suggest that the industrialized world's sleep habits do not differ much from those that humans evolved to have.

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.

"I feel a lot less insecure about my own sleep habits after having found the trends we see here," added lead author Gandhi Yetish.

The findings do validate some common ideas about sleep and health, including the benefits of morning light, a cool bedroom and a consistent wake-up time.

One myth dispelled by the results is that in earlier eras people went to bed at sundown. The subjects of the study stayed awake an average of 3 hours and 20 minutes after sunset.

The fact that we all stay up hours after sunset is absolutely normal and does not appear to be a new development, although electric lights may have further extended this natural waking period, said Siegel.

There is no evidence that these sleep patterns took a toll on people's health. In fact, extensive studies have found that these groups have lower levels of obesity, blood pressure and atherosclerosis than people in industrialized societies, and higher levels of physical fitness.

The study is published in Current Biology.