Circadian Preference and Sexual Selection: A Novel Evolutionary Approach

Davide Piffer

doi:10.1038/npre.2009.2964

Abstract

Human sleep patterns differ across age groups and between males and females, and their association with age and gender suggest that they might have been the target of sexual selection during human evolutionary history. In this study, I will test the hypothesis that a phase-delayed circadian phase is a sexually selected trait in humans. A short version of the Horne and Ostberg questionnaire and a questionnaire on sexual behaviour were administered to 134 males and 140 females. A significant negative relationship was found between the MEQ score and the number of sexual partners among males, with evening types reporting more sexual partners than morning types. No significant relationship between females MEQ and number of sexual partners was found. Findings support the hypothesis that evening preference in males is a sexually selected trait.

Highlights

Every living animal species, including humans, has a biological clock that responds to environmental cues like light/dark cycles
Human sleep patterns differ across age groups and between males and females, and their association with age and gender suggest that they might have been the target of sexual selection during human evolutionary history
My study on sleep patterns suggests that a phase delayed circadian type 15

Summary

Introduction

Every living animal species, including humans, has a biological clock that responds to environmental cues like light/dark cycles. This property is called ‘chronobiosis’ and regulates the secretion of the hormone melatonin from the pineal gland. Melatonin is a hormone secreted mainly at night and it reaches its nadir in the early morning. The circadian pacemaker, is contained in the suprachiasmatic nucleus (SCN). Strikes the retina and reaches the SCN via the retinohypothalamic pathway or the RHT. The SCN sends signals via a series of nerve fibers in the hypothalamus, up to the pineal gland to stimulate melatonin secretion, which in turn, induces sleep (Gibb 2007)

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