How and why did sleep evolve? Which forms of life require sleep and which don't? What does this tell us about sleep and how it evolved? Is it possible for complex life to evolve that doesn't require sleep?
It has just occurred to me what a strange thing sleep is in a evolutionary context. A state of high vulnerability that has evolved. Why? Is there no way round it?
I have no answers or strong opinions of my own. I am just intrigued as to the purpose, need and hence evolution of sleep.