Researchers observe sleep-like behavior in jellyfish, a brainless organism :
(T)he revelations about jellyfish sleep are important, he said, because they show how basic sleep is. It appears to be a “conserved” behavior, one that arose relatively early in life’s history and has persisted for millions of years. If the behavior is conserved, then perhaps the biological mechanism is too. Understanding why jellyfish, with their simple nerve nets, need sleep could lead scientists to the function of sleep in humans.