Sleep has been part of human life since the beginning of evolutionary time. Nevertheless, sleep
patterns have changed over the centuries according to the needs, the environmental factors and
the social life of each new generation. Between 70,000- 40,000 BC Homo sapiens adopted the
monophasic sleep pattern that concentrated sleep at night. Since then, remedies and questions
about sleep have accompanied human evolution. Although ancient civilizations became aware of
the benefits of an adequate sleep, the knowledge about this physiological function in humans has
been limited until recently. Indeed, sleep was considered over the centuries an inactive stage of
the brain caused by a lack of blood flow.