Evolution of a sleepy species...?

This might be better in a different thread, but I’ll try it here…

Is there any scientific reason why evolution has favoured a species which spends 1/3 of its life unconscious? How could this originally have been considered as advantage?

Or, how long have we (humans) followed this sleep pattern?
Is this sleep pattern normal / common in mammals, or did it ‘evolve’ over time in social groups?
Do any other common species have a longer daily sleep pattern (discounting hibernation)?

The answer to your last question is yes, some “higher” animals sleep even more than humans do. Lions, IIRC, spend at least 12 hours out of every 24 asleep or at least resting. Koalas and sloths spend even more time asleep. In all these cases it is in part an energy conservation strategy. Lions need to chase down their calories, so when they are not actually hunting they waste as little energy as possible by resting. Koalas eat only leaves, which aren’t loaded with calories, so they also take it easy. Sloths have slow metabolic rates so they move very little and therby don’t attract any predators that might be in their area.

I’m not sure, but I think even gorillas sleep more than humans do.

sleep is the time for repair amoung other things - my wag is it’s better to have a species that is fully alert 2/3rds of the day and 1/3 repairing then partially alert and repairing the whole day.

I always wondered why humans slept too. I think that it has to do with the fact of when we sleep too. Night, time when it is most dangerous for us with bad night vision. Those that slept, lived to bear children. Just sort of a guess really. I am not a Biologist. :slight_smile:

Well, I don’t know of any serious testing of hypotheses, but the obvious answer is that daily sleeping is for the same reason as yearly hibernation – it saves energy during a time when food gathering isn’t very efficient (and by ‘food gathering’ I also mean ‘not being eaten while gathering food’, etc.)

A very vision-oriented species like humans will do a lot better during daylight hours at getting food (and avoiding nasties). So much so that it makes sense to not waste energy even trying at night. Just find a safe spot, stop moving around and wait for some light. And if you’re not moving anyway, use the time to do some body & brain repair. Some other species are going to be more efficient at night (bats, for instance), and others at dawn & dusk, so they’ll sleep at different times. Big predators sleep pretty much any time they’re not hungry, since they don’t need to worry much about finding a really safe spot first, so why not save energy?

I imagine if animals had evolved on a planet without defined day/night cycles (or say, at the poles), they wouldn’t have evolved sleep. (if animals evolved originally at the poles, they might easily evolve hibernation, though, which is a fancy word for sleeping on a yearly cycle).

Do you think if humans were individualistic rather than social the idea of sleep would still have evolved due to the day/night movement of the eatrh?
Or, without the social aspect, would we not be here to test that hypotheses?
I guess its safer to sleep in a group where one member can stand guard over many.

Are there ANY species which don’t require any rest / sleep?
(Probably some deep water fish unaffected by day/night?)

Sure. E. coli springs to mind. Or how about oak trees? Or mushrooms? Basically, other than several thousand species of higher vertebrates (which, BTW, get all the good press), the several tens or hundreds of millions of other species of life on this planet don’t sleep. Or at least don’t sleep much. Or at least, don’t sleep in any fashion we recognize. It would help, I suppose, if we had a good definition of “sleep.”

-b