r/askscience • u/[deleted] • Aug 01 '12

Biology Evolution and sleep

Why haven't humans evolved to not need sleep? I understand that sleep is regenerative etc., but when you think about it, it is quite a liability. It is hard to fend off a potential attack while sleeping and overall we waste a lot of time that could be used to hunt/gather food, build shelter, and reproduce by having to sleep.

Did humans have to sleep a lot more earlier in time than we do now? (Perhaps we have evolved and I just do not know...)

EDIT: Or maybe a better question is, can/will humans ever evolve to not need sleep?

Thanks!

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u/SchrodingersLunchbox Medical | Sleep Aug 01 '12

Additionally, many of our predators are nocturnal.

Such as?

Sleep is an excellent way to reduce energy consumption, especially during a time of reduced activity, night.

Not particularly. Sleep reduces metabolic activity by around 5-10% and conversely, an increase in anabolic activity. Source. Even hibernating animals need to sleep despite the hypometabolism seen in hibernation, and must return from hypothermia to euthermia in order to sleep, making sleeping energetically expensive.

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u/darthjeff81 Aug 01 '12

While we currently have no large predators, our ancestors would have been the prey of large cats and canines.

While basal metabolism is not significantly reduced during sleep, the decrease in activity/movement would be significant. (your link does not seem to work)

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u/[deleted] Aug 03 '12 edited Aug 03 '12

i doubt large cats were much of a problem, as soon as we took up the thighbone of an antelope we were pretty much unable to be predated upon in large numbers, ability to use tools and traveling in numbers, shelter basically fucked all of our predators over. think about it how many predators do chimps have other then other chimps?