What a nightmare: sleep no more plentiful in primitive cultures

People in all three groups slept an average of just under 6.5 hours a night, the researchers noted.

“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”, says Siegel. The data collected represented 1,165 days in all.

This suggested they were reflecting “core human sleep patterns, most likely characteristic of pre-modern era Homo sapiens”, he said. The hunter-gatherer groups they studied, which slept outside or in crude huts, did not go to sleep when the sun went down.

“There’s this expectation that we should all be sleeping eight or nine hours a night and that if you took away modern technology people would be sleeping more”, said Yetish, who spent 10 months with the Tsimane.

“They do not sleep more than most individuals in industrial societies”, the study authors wrote Thursday in the journal Current Biology.

“Mimicking aspects of the natural environment experienced by these groups might be effective in treating certain modern sleep disorders, particularly insomnia, a disorder affecting more than 20 percent of the United States population”, Siegel says. “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”. “The evidence is that people differ in sleep as they do in height and eye color and there isn’t a magic number”. However, a recent study suggests eight hours of sleep may not be as integral to our health as we have been led to believe.

Despite this, the people studied were healthy, with lower rates of obesity, better blood pressure and healthier hearts than those in industrialised societies.

“In that group they all awakened after sunrise”, Dr Siegel said.

“We’ve been studying sleep in one small slice of humanity living under particular postindustrial conditions and making assumptions”, says Carol Worthman, an anthropologist at Emory University.

“I feel a lot less insecure about my own sleep habits after having found the trends we see here”, says Yetish.

But it’s possible, Siegel says, that sleep researchers could benefit from learning about sleep in more natural environments.

“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, who is also chief of neurobiology research at the Veteran Affairs of Greater Los Angeles Health Care System.

The findings are striking because health authorities have long suggested that poor sleep is rampant in America, and that getting a minimum of seven hours on a consistent basis is a necessity for good health. With the help of contacts at Hunter College, Yale University, UC Santa Barbara, and the University of New Mexico, Siegel was able to accurately measure how long traditional adults slept during summer and winter seasons. The groups did not go sleep at sunset and they did not wake up at sunrise, suggesting that light exposure did not have much influence on their sleep patterns. Light and temperature aren’t the only things dictating how much we sleep. With no central heating, temperatures tended to fall throughout the night. If falling temperatures at night are a signal to our bodies that it is an ideal time to go to sleep, then that could be one reason chronic insomnia is so prevalent in industrialized societies.

Dr Siegel said the study suggested temperature control could be used to treat insomnia and other sleep disorders.

“Today we sleep in environments with fixed temperatures, but none of our ancestors did”, Dr. Siegel said.