The perception of sleep
In foraging societies, nearly all adults – many of whom are parents – say they’re very satisfied with their sleep, says evolutionary anthropologist David Samson, director of the University of Toronto’s Sleep and Human Evolution Lab and author of the book The Sleepless Ape: The Strange and Unexpected Story of How Social Sleep Made Us Human.
Samson spent three months living with the Hadza, a foraging society in northern Tanzania, to study their sleep patterns. “When you go to the Hadza and ask them, ‘Is your sleep good or is it bad?’, they say ‘It’s good’,” he says.
In contrast, when parents in modern, industrialized societies are asked about the quality of their sleep, they usually give it low marks. In the German study, for example, mothers rated their satisfaction with their sleep 6.57 on a scale of 0 to 10; fathers, 7.03. In the French study, nearly three-quarters of the mothers of three-month-old’s said they thought they had not had enough sleep.
It’s not that modern parents are waking up more often. Work by Samson and others has found that people in hunter-gatherer societies usually wake more frequently through the night than we do.
Part of this might be because it wasn’t until the Industrial Revolution that we began to focus on the goal of “consolidated” sleep, says Helen Ball, director of the Durham Infancy and Sleep Centre in the UK and author of the book How Babies Sleep: A Factful Guide to the First 365 Days and Nights. The concept still isn’t shared universally around the world. She recently oversaw a research project comparing adolescent sleep in two rural villages in Mexico versus Mexico City. In the rural villages, “this idea of sleeping like a log is unfamiliar”, she says. “It was only in Mexico City that that was a familiar concept.”
Our ancestors may have simply had less practical need to sleep deeply in one continuous stretch. “They would not have had the pressure of having to work a nine-to-five or an eight-to-five job that required them to get a certain amount of sleep during the night to be able to function the next day and to function safely,” Ball says. “They weren’t driving cars. They weren’t operating heavy machinery. The kinds of things that matter to us just simply wouldn’t have been issues.”
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