Lights, TV, smartphones and computers are often blamed for depriving modern humans of sleep. But a new study suggests that our prehistoric ancestors didn’t get any more than 7 hours of a sleep a day.

The new study, published in the journal Current Biology, also finds that temperature played a greater role than light in shaping sleeping patterns.

Prof Jerome Siegel, from the University of California, Los Angeles, said: “The issue is: what is the data on how sleep has changed?

Researchers have found that members of three tribes of hunter-gatherers slept, on average, less than 6.5 hours per night. They did not nap and were not necessarily going to bed when the sun set.

In other words, their sleep patterns were not radically different from ours, except that they usually woke before sunrise.

Psychiatrist Jerome Siegel of the University of California at Los Angeles said that the study challenges the notion that our frantic modern life prevents us from enjoying as much sleep as is “natural” and that we must take sleeping pills to maintain balance.

Researchers studied the Hadza of Tanzania, the San of Namibia and the Tsimane of Bolivia, fitting their volunteers with wristwatches that monitor sleep.

The average sleep cycle was 5.7 t0 6.1 hours.

“All three groups have pretty much the same sleep duration and pretty much the same timing of sleep,” said Prof Siegel.

“This gives me reasonable confidence that they reflect the common human biology and they are not a function of their particular situations, which are different.”

Two of these groups are in Africa. The Hazda people live just south of the equator in northern Tanzania, where their food supply depends on hunting and gathering. The San live further south, in Namibia, and are also hunter-gatherers. The third group, the Tsimane, are hunter-horticulturalists in the rainforests of Bolivia.

Besides discovering that the average sleep duration was six hours and 25 minutes, the researchers also found the participants very rarely took naps.

Despite their lack of modern medicine, our ancestors often live well past the age of 60 and sometimes into their 80s. That’s a clear sign that their sleep habits certainly aren’t detrimental to their health.

Two of these groups are in Africa. The Hazda people live just south of the equator in northern Tanzania, where their food supply depends on hunting and gathering. The San live further south, in Namibia, and are also hunter-gatherers. The third group, the Tsimane, are hunter-horticulturalists in the rainforests of Bolivia.

The study was carried out by researchers from US universities, including academics from departments of anthropology, anatomical sciences, neurology and brain research, and psychiatry.

It was funded by US National Institutes for Health grants, the National Research Foundation of South Africa, and the National Science Foundation.