| Sarah Kaplan |
MILLIONS of years ago, when we were shorter and hairier and, well, let’s just say it, not too far removed from chimps, a night of uninterrupted sleep was impossible to come by.
For one thing, there were the predators – lions and giant hyenas and bears and the killer ancestor of modern kangaroos – who would happily take advantage of any ancient hominid whose eyes were closed too long. For another, there were the sleeping accommodations: the bumpy branch of some uncomfortable tree, where the risk of falling was never more than one bad nightmare away.
“It’s like economy class on a plane,” Duke University evolutionary biologist David R Samson told the New York Times.
Samson is a co-author of a recent study in the journal Evolutionary Anthropology that compared the sleep intensity of humans to that of hundreds of mammals and 21 primate cousins.
Humans, it turns out, are far more efficient: We have evolved to get better quality sleep with just seven or eight hours; some primates need up to 17.
File photo shows people sleeping as they huddle together at a festival near the village of Ozora, 123kms south of Budapest, Hungary, August 7. EPA
The explanation could be as simple as the comfyness of our beds: Once we started sleeping on the ground, around a fire, with plenty of friends nearby to ward off predators, it finally became safe to sleep deeply. So we did.
The key to explaining our unique bedtime habits is in REM, or rapid eye movement, sleep.
The purpose of the REM state remains particularly mystifying to researchers, even by the standards of the rather enigmatic world of sleep science.
It’s thought to be associated with memory, brain development and dreams. Some studies have found that sleep, particularly deep sleep, is associated with the clearing out of molecular waste in the brain.
What is clear is that both REM and non-REM sleep are vitally important – stop a rat from sleeping for two weeks and he’ll simply drop dead, even if nothing else is wrong with him. Presumably the same thing would happen in humans, though no one is likely to test it. – (The Washington Post)
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