Why do all vertebrates need sleep? Rat's deprived of sleep eventually die (Rechtschaffen, et al. 1983, Science).
What does sleep do? It must be something important, even dolphins sleep. Since they have no breathing reflex,
they have developed the unusual capacit to sleep one hemisphere at a time (Mukhmetov et al. Sleep Mechanisms 1984).
Only warm blooded animals (Birds and Mammals) exhibit REM sleep patterns. Thus REM is of recent phylogenetic origin and
may have a different function than that which sleep originally evolved for.
If anybody knows anything about what sleep is, why it evolved, its evolutionary implications, or what it does, please let me know.
What I really need are good, relevant journal articles.