It's common to hear lights, television, smartphone and computers — not to mention the pace of modern life in general — blamed for our inability to get a good night's sleep, but our prehistoric ancestors didn't get any more hours in the sack than we do, a new study suggests.

Researchers looked at three modern hunter-gatherer societies in Africa and South America with lifestyles similar to our paleo-ancestors and found these traditional peoples slept an average 6.5 hours a night — compared with the average of seven to eight hours for people in industrial societies.

"We find that contrary to much conventional wisdom, it is very likely that we do not sleep less than our distant ancestors," says Jerome Siegel, a sleep researcher at the University of California, Los Angeles, and senior author of a study published in Current Biology.

In the traditional societies in the study, the San of Namibia, the Hadza of Tanzania and the Tsimane in Bolivia, people went to sleep several hours after sunset and usually awaken before sunrise, the researchers found.

Tracking people in these groups for more than 1,100 days and nights revealed a surprisingly similarity in the sleep habits among the three groups, they say.

"Despite varying genetics, histories, and environments, we find that all three groups show a similar sleep organization, suggesting that they express core human sleep patterns, probably characteristic of pre-modern-era Homo sapiens," Siegel says.

Sleep time in these societies — and likely in our ancient ancestors as well — may be more dependent on temperature than on light, the study authors suggest.

The onset of sleep seemed linked to a drop in temperature, and the sleep hours spanned the coldest part of the night, they say, with people awakening as sunrise began to warm the day.

That daily cycle of changing temperatures change, largely removed from sleep environments in industrialized society, may be a potent natural regulator of sleep, the researchers suggest.

The study findings challenge the assumption that the particular pressures and stresses of the modern world have greatly reduced sleep, says Siegel, who heads UCLA's Center for Sleep Research.

"This has important implications for the idea that we need to take sleeping pills because sleep has been reduced from its 'natural level' by the widespread use of electricity, TV, the Internet, and so on," he suggests.

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