Sleep

[The Truth]

What are the evolutionary reasons for sleep?

[theweatherman]

sleep allows your body to rest by running the system on a lower level. A well rested person is far better at cognitive functions than an exhausted person. Hence the people who sleep enough are better ablew to survive.

God willed us to sleep.

[purnell]

At a guess, I would say sleep enhances the likelihood of a young animal's survival to the age of sexual maturity because it makes it harder for predators to find. I googled "sleep evolution" and found this. (http://serendip.brynmawr.edu/bb/neuro/neuro99/web2/Bernstein.html)

edit: That link led me to this (http://serendip.brynmawr.edu/) . Thanks.

[benkahuna]

[ QUOTE ]
sleep allows your body to rest by running the system on a lower level. A well rested person is far better at cognitive functions than an exhausted person. Hence the people who sleep enough are better ablew to survive.

[/ QUOTE ]

Some other animals do not need to sleep and many mammals sleep less than humans.

Sleep actually involves a great deal of activity in the brain (and the human brain uses a large proportion of the body's energy--close to the majority of it). It's a very engaged process. Metabolic rate is only about 15 percent during sleep than wakefulness suggesting that sleep may not be important from an energy perspective. It is a great compromise to have the limited vigilance during sleep when one could rest without sleeping or simply eat a small amount of more food. Additionally, there are only cognitive impairments due to sleep deprivation, not physiological impairments.

Sleep seems to be involved in learning and synthesizing information more than anything else. Making people feel worn out when they haven't slept enough is just a nifty mechanism to get people to sleep enough. Just like pain is a nifty mechanism to get you to not use a part of your body while it has time to repair itself from an injury.

That's just the theory from the latest Principles of Neural Science (and this extraordinary text is always current (with the original research) to within a few months of publication--impressive for a science text) mixed in with some of my own reasoning.

The stats aren't theory, but the proposed role for sleep is. Sleep's function is still not that well understood.