Dario Maestripieri: University of Chicago, Department of Comparative Human Development; Institute for Mind and Biology

Several lines of evidence suggest that eveningness is associated with traits that favor short-term mating such as higher extraversion, novelty-seeking, risk-taking, and short-term relationship orientation in both males and females. Night owl men also report a higher number of sexual partners than early-morning men, who instead, show personality and behavioral traits typically associated with slow life histories. Evidence also exists that autistic-like and schizotypal personality traits reflect opposite sides of a continuum of variation in personality and cognition that are best understood in reference to other slow and fast life history adaptations. Cortisol and testosterone may be some the physiological mechanisms underlying psychological and behavioral traits associated with slow and fast life histories. Both cortisol and testosterone levels differ between individuals who are single and in relationships, with cortisol being associated with some aspects of personality and stress, while men’s testosterone is more directly linked to variation in courtship activity and sexual promiscuity.