Which came first, sleep or the brain?

(Kyushu University) In work that could help unravel the origin of sleep, an international team of researchers led by Kyushu University has shown that tiny, water-dwelling hydras not only show signs of a sleep-like state despite lacking central nervous systems but also respond to molecules associated with sleep in more evolved animals. The new results suggest that many sleep-related mechanisms developed before the brain and may have been conserved during the evolution of central nervous systems.
Source: EurekAlert! - Biology - Category: Biology Source Type: news