According to a new study, a restless sleep may be tied to more than just biological or environmental factors. It could also be a throwback to our early ancestors which had to be more than careful when sleeping.
The research team considers that the sleeping pattern differences in between the older population and teenagers could be explained by the ancient need of having someone awake at all times. This would have ensured protection to those sleeping. It could have also transformed sleep disturbances into an evolutionary survival tool.
Previous studies looked at outside factors that might be disrupting sleep, at methods of improving it or reasons for avoiding oversleeping. Still, this is the first research to cast a look so far back into the human history and its relation to sleep.
A Restless Sleep Tied to the Grandparents’ Theory
The new study conclusions are based on an analysis of data gathered while monitoring the Hadza. These are a hunters and gatherers tribe living in the bushlands of northern Tanzania. They also still have a very similar lifestyle to that of our earlier ancestors. The Hadza live in groups of some 20 to 30 people, which usually gather in smaller units before going to sleep.
The researchers asked for help from 33 healthy women of men, which agreed to wear motion-sensor devices on their wrists. These helped monitor their nighttime motions, without being intrusive.
According to the resulting data, synchronized sleep in all the adults is a sporadic event. Namely, throughout the monitoring, which lasted some 20 days, there were only 18 minutes in which all the adults were simultaneously asleep.
At least one person had a restless sleep, with others either sleeping lightly and at least one being fully awake at any given time. Additional research seems to suggest that these sleeping patterns might also depend on the age mixture in the group.
“We’re calling it the ‘poorly sleeping grandparent’ hypothesis. Having a mixed-age demographic increases the sentinel-like behavior within a group,” stated David Samson, who is now a Duke University researcher and study lead.
This was tied to the grandmother hypothesis, which states that grandparents could help look out after the children of the group. In turn, this was seen as an advantage to growing old.
More research on the matter is still needed, but the current study results are already available in the Proceedings of the Royal Society B.
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