Why do we have to sleep? Well, ok, for humans it is easy to come up with a whole range of reasons why we need a certain budget of sleep - our lives are tiring, our complex brains need rebooting once a day, and sleep does all sorts of good things for us.
However, as research keeps discovering sleep behaviour in more and more primitive animals, including invertebrates that don't even have a brain, the phenomenon is getting harder to explain. If they want a bit of a rest at night, that could be easily regulated in a circadian cycle which most multicellular organisms have anyway. But why did our common animal ancestors, more than half a billion years ago, go to the trouble of evolving a budgeting mechanism of the kind that troubles us when we missed out on sleep and have to catch up?
The short answer is, we don't really know - but the quest to understand this does yield some very interesting insights into the hidden lives of all sorts of animals. My feature on this issue is out now:
The reasons of sleep
Current Biology Volume 29, issue 15, pages R775-R777, August 19, 2019
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Oh, and if I got my maths right, this is the 200th feature in this series - since I took on the challenge to write a feature for every issue, back in February 2011. Since the first one, there have only been three or four issues without one, for one reason or another.
Most mammals are very much like humans in their sleep behaviour. Attempts to explain the evolution of sleep with the mental benefits it has for humans and other mammals are undermined, however, by the findings that some of its features are shared across the animal kingdom. (Photo: RoyBuri/Pixabay.)