Modern sleep patterns 'mirror how our ancestors slept'

“Forget eight hours of sleep a night – we only actually need six,” the Daily Mail reports. Research into hunter gatherer tribes suggests getting six to seven hours sleep a night may not be a modern phenomenon and is actually the norm for humans.

An ongoing concern about modern life is our sleep patterns are being adversely affected by the distractions of modern technology, such as smartphones, tablets and TVs. But, as the authors of this research highlight, similar concerns can be found in popular media dating back to the Victorian era.

To get a clearer picture of “pre-industrial” sleep habits, researchers studied three hunter gatherer communities who had no access to any of the trappings of modern life. These people were members of the Hadza (northern Tanzania), San (Namibia), and Tsimane (Bolivia) tribes.

The researchers found the hunter gatherers’ sleep patterns were to a certain extent similar to those of the West – getting an average of 5.7 to 7.1 hours’ sleep a night.

Sleep patterns seemed to mirror the temperature more than light levels. This finding could potentially help people with sleep disorders. The US National Sleep Foundation recommends a bedroom temperature of 18.3C (65F).

Interestingly, chronic insomnia was uncommon among the tribespeople – around 2% of tribespeople, compared with 10-30% in industrial societies. Two of the tribes actually had no word for insomnia in their language. This may suggest an active lifestyle can help prevent insomnia. 

Where did the story come from?

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.

The study was published in the peer-reviewed journal Current Biology on an open-access basis, so it is free to read online or download as a PDF.

Headlines like the Daily Mail’s – “Forget eight hours of sleep a night – we only actually need six” – and a similar headline in The Independent – “Six hours’ sleep a night is enough, say scientists” – are not justified based on the results of this this study alone. The authors only studied sleep patterns. They make no recommendations about what sleep patterns are healthier.

Nonetheless, the Mail’s statement that these “findings challenge [the] eight-hour rule” may be fair – a debate about the right amount of sleep is worth having, given the implications of this research. The next part of the sentence – “modern life is robbing us of sleep” – is largely subjective.  

What kind of research was this?

This was an observational study of the natural sleep cycles in three non-industrial communities. The researchers say it has been argued that the invention of electric lighting, TV, the internet and related gadgetry, along with more caffeine use, has greatly shortened sleep duration from the “natural” levels that occurred before these modern changes.

The authors state this may have health implications. They report sleeping less has been linked to obesity, mood disorders and a “host of other physical and mental health illnesses thought to have increased recently”.

With this in mind, they sought to establish what “natural” sleep patterns might be without the distractions of modern lighting, heating and electronic gadgetry.

In the absence of good data on sleep patterns from the past, they studied three non-industrial societies who live largely as hunter gatherers near the equator: the Hadza (northern Tanzania), the San (Namibia), and the Tsimane (Bolivia).

Studying these modern but non-industrialised groups, they hoped, would give an idea of the type of sleep patterns our ancestors might have had before mass migration to cities and the technological revolution.

Links To The Headlines

Forget eight hours of sleep a night – we only actually need SIX, scientists declare. Daily Mail, October 15 2015

Modern life is rubbish? Sleep is just the same as ever, say scientists. The Guardian, October 15 2015

Six hours’ sleep a night is enough, say scientists. The Independent, October 16 2015

Links To Science

Yetish G, Kaplan H, Gurven M, et al. Natural Sleep and Its Seasonal Variations in Three Pre-industrial Societies. Current Biology. Published online October 15 2015