Why do we sleep

1. Why do we sleep?
Several theories try to explain why most animals, including humans, have a compelling need for sleep. One theory describes it as a mere a habit, without biological foundation. Creation-based theories attribute the existence of man and all of his needs, including the need for sleep, to a superior being. Another theory refers to sleep as a state of exhaustion, requiringrestoration of bodily functionality.
Whenever we try to determine why human beings do whatever they are doing, we must remember that human beings did not develop overnight. Human beings are the product of billions of years of evolution. Certainly, no superior being created man and then decided that man had to waste half of his life in a state of stupor.
If we search with sufficient persistence, wewill always find an evolutionary explanation for all human behavior. All human physiology and behavior is attributable to the process of evolution. There is no other rational explanation for human behavior.
A search for a plausible explanation of the need for sleep will take us back millions of years, long before humans entered the scene. We need to go back to periods when living organisms firstbecame aware of light and evolved sensors for visually perceiving the difference between night and day, between darkness and light.
Evolution rewarded organisms that had the ability to perceive visual impulses with a greatly enhanced ability to survive. The visual perception of objects greatly enhanced the ability of such organisms to survive by preying on other organisms that lacked thesefaculties.
About 2.5 billion years ago, one billion years after the inception of life on earth, many animals had developed the ability to utilize daylight in order to survive. The competition in the food chain became intense during daylight hours. However, at night when there was no light energy to activate lights sensitive cells, most animals were at a disadvantage.
The most efficient way of copingwith the lack of light was to reduce exposure by lying still and keeping very quiet. Animals that utilized such imposed periods of inactivity to restore their physiological systems, gained a further survival advantage: They were in better condition to pursue prey when the sun rose again.
Another incentive to remain motionless in a safe and secluded place was the difficulty of moving around indarkness. Animals, including the ancestors of humans, who insisted on moving around at night, risked falling off cliffs or into holes. They also exposed themselves to forms of life that had never developed any sensitivity to and dependency on light.
Insomniacs also were in danger from animals that had specialized in hunting at night and had therefore evolved high susceptibility to light. Suchnight-predators, such as the precursors of owls or cats, were able to see when other animals could not. If other animals are stalking you and you cannot even see them, your best course of action is to remain immobile and very quiet: You enter a state of semi-consciousness, you sleep.
2. The Need for Dreams
Over billions of years, the process of evolution favored animals that slept at night. In doingso, they prevented injury to themselves, avoided falling prey to specialized predators and they gained the opportunity to restore their bodily functions. Thus, animals achieved the ability to sleep and rest at night.
However, in the event of a disturbance by predators, this period of semi-consciousness demanded the ability to restore, instantly, full operational control over the body.Therefore, animals benefited from the ability to sleep and rest during the dangerous and unproductive periods of darkness.
While benefiting from sleep, animals also had to develop a mechanism that prevented them from falling into a deep coma while asleep. It was vitally important that some neural systems remained partially active and that the body could be re-activated instantly.
Dreams are the...