Whatever sleep does, it's something nature has had a tough time optimizing out despite the extreme vulnerability it creates and the sacrifice of a little under half an organism's waking time.

That should tell us it's something incredibly important that's hard to do any other way.

Edit: on the other hand... if Earth had two suns and rarely had periods of darkness, you wonder if maybe there would have been more evolutionary pressure to find another way.

Alternately, sleep is the optimal ultra-high-efficiency survival state and wakefulness only exists to give creatures enough time to get their affairs in order so that they can safely return to dormancy.

It's easy to think of sleep as a compromise to be defeated because we're culturally preoccupied with the achievements and pleasures of wakefulness, but that's really just us claiming personal preference for one narrow part of a holistic system that's just doing its own survival and propagation thing.

Consider trees, mushrooms, cicadas, snakes, or cats. Chilling out in low power mode as much is possible is maybe not a error to be fixed so much as it is an outcome of efficient design.

I wonder if we looked at really basic life forms like bacteria, would we find things akin to sleep at that level? What about next up in sophistication?

> if Earth had two suns and rarely had periods of darkness, you wonder if maybe there would have been more evolutionary pressure to find another way.

Cats sleep during the day without any issues. So the amount of light seems to not matter.

By the way I wonder do their ear sleep or not because they still wake up easily if there is some suspicious sound.

Yeah. Nature is the ultimate form of science. At any moment, it's incorporating an infinite amount of science, most of which we likely haven't discovered yet, and may not discover for millions of years - if ever.

Nature developed over millions of years of trial and error.

Seems likely like the need for sleep then selects for many social/group behaviors. “Solo self-found” is not really an option unless you’re really good at hiding or have some other tricks

Sleep is vulnerable, but it also keeps you curled up and hidden somewhere rather than out in the open walking around and taking risks.