There are many theories suggesting why as humans we sleep:
Inactive theory
The inactive theory is also known as the evolutionary theory, it suggests that our behaviour of sleep was deprived from natural selection. Animals who were able to be quiet and hidden at night prevented them from being hunted by predators. Therefor animals who did not move at night stayed safe during nightfall and through natural selection the behaviour soon evolved to become sleep.
Energy Conservation theory
The next theory suggests we sleep to preserve our energy demand. When we are sleeping our bodies conserve energy and we save more energy for the day ahead. This was proved by research showing that at night our metabolism significantly reduces.
Restorative Sleep
Inactive theory
The inactive theory is also known as the evolutionary theory, it suggests that our behaviour of sleep was deprived from natural selection. Animals who were able to be quiet and hidden at night prevented them from being hunted by predators. Therefor animals who did not move at night stayed safe during nightfall and through natural selection the behaviour soon evolved to become sleep.
Energy Conservation theory
The next theory suggests we sleep to preserve our energy demand. When we are sleeping our bodies conserve energy and we save more energy for the day ahead. This was proved by research showing that at night our metabolism significantly reduces.
Restorative Sleep