Category Archives: Sleep

What Are Our Ancestral Sleep Patterns?


He got up before sunrise

Here are some answers in the summary of an article in Current Biology:

How did humans sleep before the modern era? Because the tools to measure sleep under natural conditions were developed long after the invention of the electric devices suspected of delaying and reducing sleep, we investigated sleep in three preindustrial societies. We find that all three show similar sleep organization, suggesting that they express core human sleep patterns, most likely characteristic of pre-modern era Homo sapiens. Sleep periods, the times from onset to offset, averaged 6.9–8.5 hr, with sleep durations of 5.7–7.1 hr, amounts near the low end of those industrial societies. There was a difference of nearly 1 hr between summer and winter sleep. Daily variation in sleep duration was strongly linked to time of onset, rather than offset. None of these groups began sleep near sunset, onset occurring, on average, 3.3 hr after sunset. Awakening was usually before sunrise. The sleep period consistently occurred during the nighttime period of falling environmental temperature, was not interrupted by extended periods of waking, and terminated, with vasoconstriction, near the nadir of daily ambient temperature. The daily cycle of tem- perature change, largely eliminated from modern sleep environments, may be a potent natural regulator of sleep. Light exposure was maximal in the morning and greatly decreased at noon, indicating that all three groups seek shade at midday and that light activation of the suprachiasmatic nucleus is maximal in the morning. Napping occurred on <7% of days in winter and <22% of days in summer. Mimicking aspects of the natural environment might be effective in treating certain modern sleep disorders.


How Much Exercise Does It Take To Improve Insomnia?

Paleobetic diet

Better to exercise than take a sleeping pill

It doesn’t take much exercise: 30 minutes of aerobic exercise thrice weekly.

The Well blog at the New York Times has details. The study at hand involved only 11 women with insomnia, mostly in their 60s. A key take-away is that it took as long as four months for some  to see an improvement. So don’t get discouraged and stop exercising too soon.

Read the whole thing (it’s brief).

Why Do Young Children Protest at Bedtime?

Parents in hunter-gatherer societies know why kids don’t like to retire alone to a dark room at night, writes Peter Gray, a psychologist:

Until a mere 10,000 years ago we were all hunter-gatherers.  We all lived in a world where any young child, alone, in the dark, would have been a tasty snack for nighttime predators.  The monsters under the bed or in the closet were real ones, prowling in the jungle or savannah, sniffing around, not far from the band’s encampment. A grass hut was not protection, but the close proximity of an adult, preferably many adults, was protection.  In the history of our species, infants and young children who grew frightened and cried out to elicit adult attention when left alone at night were more likely to survive to pass on their genes to future generations than were children who placidly accepted their fate. In a hunter-gatherer culture only a crazy person or an extremely negligent person would leave a small child alone at night, and at the slightest protest from the child, some adult would come to the rescue.

Safer than sleeping alone on the ground

I gotta confess I’d never thought about it this way before.  Makes sense. Read the rest of Dr. Gray’s post.

Steve Parker, M.D.

h/t to Amy Alkon