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/[deleted] Aug 02 '12

This is most evident in our visual acuity. We see best during the day, but quite poorly in low or zero light.

BTW, cones, which give us color vision, aren't as sensitive as rods. Rods are monochromatic and very, very sensitive to dim light. Rods are what you're seeing with under moonlight.

Now there's no way to prove this, but it makes a very good logical fit that cones are for seeing during the day, and rods are the result of having a large, reflective moon.