What were “owls” doing in our ancestral photoperiodic environment? Chronobiological account for the evolutionary advantage of nocturnal lifestyle

Abstract

Since evolutionary process is slow, the human brain was adapted to the ancestral rather than today’s environment. Therefore, genetic predisposition of young people to nocturnal lifestyle requires explanation. The pattern of age- and sex-associated differences revealed from self-reports of 2054 native and non-native residents of Turkmenia, Siberia, Yakutia, Chukotka and Alaska suggested that late bedtime preference might has evolved under sexual selection pressure. Moreover, simulation of experimental data on prolonged wakefulness indicated that differences between people preferring early, late and extremely late bedtimes (n = 39, 53 and 38, respectively) on wave-forms of their alertness rhythm can be explained by a relatively small circadian phase delay. It was hypothesized that, due to sexual division of daytime labour in ancestral societies, the late bedtime preference evolved to solve an adaptive problem of creation of early night lek for displaying throughout courtship various human-specific behaviours advertising high cognitive, music, gymnastic, artistic, language and humour abilities.