If you suffer from any form of insomnia – unable to fall asleep easily, frequent nocturnal wakening, too-early rising – a fascinating study done on a tribal group of hunter-gatherers in Tanzania will come as very welcome information, I think, because this study tells you that, hey, despite the ubiquitous efforts to convince you that you just have to get 7-8 hours of continuous sleep a night, in fact, not sleeping through the night is probably what nature intended for you as you got older.
In this study that tracked the sleep of 33 healthy Hadza adults, the research found that these Hadza varied tremendously in when they were asleep and awake, so that at nearly all times from nightfall on, some were asleep, some were awake.
And this is not a tribe, obviously, that has to account for the fact that some of them are awake simply to watch Jimmy Fallon’s monlogue or to get another video game in.
The reason for why at least one or two Hadza are awake at nearly all hours, the researchers speculate, has to do with watchfulness, so that there is nearly always someone awake to warn the the tribe when a hungry predator might show up to try to eat a Hadza member.
And no surprise to anyone over the age of 50 or so: older members of the Hadza go to bed later, wake up more often, and wake earlier than younger ones.
This varying rhythm of sleep is probably an especially handy evolutionary tool, the speculation goes, for grandparents who might not be able to contribute as much to the hunting and gathering as they used to do but who still have a useful role to play in helping the community byt staying up to watch over things.
So the next time your wife (or husband) is up at 2 AM and complaining that they can’t sleep, just tell them “Relax, that’s just natural,” and you can roll over and go back to sleep yourself.