This is too simplistic, and it is inaccurate! Sleep is absolutely not the absence of wake, but a very interesting and complex activity of the brain with important roles in synaptic plasticity, learning, and memory. Indeed, contrary to what the article says, sleep is not primarily for "rest": sleep is an active and necessary function of the brain.
Furthermore, only humans and some new world monkeys such as squirrel monkeys have "consolidated" sleep. Other animals that sleep are "polyphasic" sleeping in shorter bursts during the night (diurnal) the day (nocturnal) or at dawn/dusk (crepuscular) dogs, cats and rodents, to name only a few.
This page needs serious editing, or else it should be removed. It should not provide this simplistic and incorrect information as it stands. The material is simply not correct. -- 00:14, 25 November 2006 188.8.131.52