The Sleeping Grandmother hypothesis
Senile insomnia was called an adaptation important for survival
Sergey Vasiliev, Naked Science
A new study confirms the importance of age-related changes in sleep patterns: "poorly sleeping grandmothers" increased the safety of a tribe living in the wild.
Anthropologists and psychologists have long suggested that sleep time in humans (as in some other eusocial animals living in close groups) should be distributed among members of the community so that while some rested, others could stay awake and stay alert, looking out for all possible dangers. This is what is often explained by different "chronotypes" peculiar to people of different ages, including the love of teenagers for long night "gatherings" and, conversely, the usual early sleep and early rise in the morning for older people.
However, according to David Samson and his colleagues from Canada and the USA, so far this hypothesis has not been properly tested in field studies. They have done this work, and the corresponding article will be published by the journal Proceedings of the Royal Society B. Duke University's Live-in grandparents helped human ancestors get a safer night's sleep tells briefly about the study.
As an object, the scientists chose representatives of the Hadza people, the indigenous inhabitants of Tanzania, many of whom continue to maintain an isolated, traditional way of life.
The Hadza live in tribes of about 30 adults, in grass huts, each of which accommodates 1-2 adults, plus several children and teenagers. Scientists have agreed with 33 adults (from 22 different huts) that for 20 days they will wear motion sensors that will allow them to monitor their sleep and wakefulness. Indeed, simultaneous sleep in adults from the same hut was extremely rare: in 99.8 percent of cases, while one of the adults was asleep, the second was awake or dozing, remaining alert. Of the entire experimental group, an average of eight people were awake at any random moment of the night. Further analysis of the collected data showed that the difference in sleep periods correlates with a person's age.
In general, old age in our species lasts noticeably longer than in our closest relatives. It is assumed that this makes it possible to transfer the accumulated experience to the next generations more efficiently. In addition, there is a hypothesis that by looking after children "in the camp", the elderly free up the resources of adult mature and strong men and women, allowing them to get more food – the "grandmother's hypothesis". Now old age has found another benefit. "We call it the 'sleeping grandmother hypothesis,'" he says. David Samson. "Having people of different ages increases safety for the whole group."
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12.07.2017