Quote Originally Posted by ericwd View Post
I had heard a theory that there is no physical need for sleep

Experimentally, rats have died when subjected to extreme sleep dep:

However. these profoundly sleep-deprived rats did exhibit a unique syndrome consisting of a progressive increase in energy expenditure, a debilitated appearance (Figs. 3 and 4), the development of distinctive skin lesions (Figs. 5 and 6), and thermoregulatory changes, and eventual death - which had never been documented in any conventionally stressed rats in an experimental setting (4).
See Sleep Deprivation: Basic Science, Physiology, and Behavior By Clete Anthony Kushida for some good info.