In terms of sleep duration, a person is not a "record holder" among animals, and yet he spends in this state a very significant part of the time - on average 8-9 hours, which is about a third of the day.
Sleep duration is an individual indicator, some people sleep less, others more. But what unites most of humanity is the habit of sleeping at night. This can be explained by the established tradition: from infancy, a child is taught to go to bed at night, an adult is forced to sleep at night because public life at this time stops - neither shops, nor any institutions, nor public transport are working. But for such a tradition to develop in ancient times, it had to have some origins rooted in human nature.
Causes of night sleep
Man is not the only living creature whose period of activity falls on the daytime, and sleep during the dark. Birds wake up at dawn, and among mammals there are much more daytime animals than nocturnal ones.
In the regulation of the circadian rhythm - the daily cycle of wakefulness and sleep, the leading role is played by the hormone melatonin, produced by the pineal gland. It is produced only in the dark, and this explains the night's sleep. Such a mechanism was entrenched in the course of evolution because it was the key to survival for human ancestors.
The leading sensation for humans and other primates is vision, through which a person receives about 80% of the information. When it enters the human eye, light is scattered. It does not have special cells that focus light - as, for example, in a cat, so a person sees extremely poorly in the dark.
Before the invention of artificial lighting, man was helpless at night: it was difficult for him to get food and escape from predators. Consequently, individuals whose period of activity fell on the night time quickly died. Those whose circadian rhythm made it possible to stay awake during the day and leave the night for sleep survived and left offspring.
A night in culture
If during the day the ancient man could feel himself “master of the situation”, at night he felt insecure, as in “foreign territory”, where he could not orient himself well. For this reason, the opposition of day and night, which is characteristic of many cultures, is a variant of the binary opposition "friend or foe", projected not on space, but on time.
Since ancient times, the night seemed to be something frightening. Until the 18th century, it was believed that the night air contains fumes that are harmful to health. The legends associated the activity of sorcerers and fantastic creatures hostile to man with the dark time of day.
Man saw something dangerous, demonic, and in nocturnal animals. That is why legends were made about werewolves, cats were considered helpers of witches, and demons in paintings and frescoes were often depicted with webbed wings like bats.
The shadow of the ancient fear generated by night lives in the soul of modern man. True, at present, this fear is more often determined by real reasons. And yet, at night, a person is much more afraid of becoming a victim of criminals, although this can happen during the day.