WASHINGTON - Perhaps we cannot blame late-night TV, endless Internet surfing, midnight snacks, good books, bothersome work deadlines and other distractions of modern life for encroaching on our sleep.
Research unveiled on Thursday shows that people in isolated and technologically primitive African and South American cultures get no more slumber than the rest of us.
Scientists tracked 94 adults from the Tsimane people of Bolivia, the Hadza people of Tanzania and the San people of Namibia for a combined 1,165 days in the first study on the sleep patterns of people in primitive foraging and hunting cultures.
Even without electricity or other modern trappings, they logged an average of six hours and 25 minutes of sleep daily, a figure near the low end of averages in industrialised societies.
"The bigger conclusion is not that they sleep less but that they very clearly do not sleep more, contrary to what has been assumed," said UCLA psychiatry professor Jerome Siegel.
He said there had been a notion that people used to sleep more than they do now and that modern life reduced sleep time, but the new findings suggest this is a myth.
University of New Mexico anthropologist Gandhi Yetish said the research suggested that eight hours of sleep, long touted as the ideal total, "may be a longer sleep duration than can be realistically expected".
"These findings challenge many of the traditional beliefs about 'normal' sleep," he said.
The Hadza and San are hunter-gatherers and the Tsimane are hunter-horticulturalists, growing some food.
Their lifestyles are seen as analogous to ancient human societies.
Despite having no electric lights, they did not go to sleep at sundown, remaining awake more than three hours after sunset and awakening before sunrise. They rarely napped.
Their sleep durations were seasonal, with about six hours during summer and just under seven hours in winter.
Study participants wore wristband devices that tracked sleeping and waking times along with light exposure.
"I visited study participants in their homes each morning to conduct short, 10-minute interviews on their pre-bedtime activities, fatigue, dreams and other sleep-related issues," said Professor Yetish, who spent time with the Tsimane. The research was published in the journal Current Biology.