Low Honesty & Openness & high Emotionality predicted the number of children; low Openness & high Conscientiousness predicted number of grandchildren; Extraversion was negatively related to the age at first birth; seems that personality is related to biological fitness in contemporary human populations

Revealing complex relations between personality and fitness: HEXACO personality traits, life-time reproductive success and the age at first birth. Janko Mededovic et al. Personality and Individual Differences, Volume 129, 15 July 2018, Pages 143-148, https://doi.org/10.1016/j.paid.2018.03.014

Highlights
•    We explored the relations between HEXACO personality traits and evolutionary fitness.
•    Low Honesty and Openness and high Emotionality predicted the number of children.
•    Low Openness and high Conscientiousness predicted the number of grandchildren.
•    Extraversion was negatively related to the age at first birth.
•    Findings suggest that HEXACO traits are likely under current natural selection.

Abstract: HEXACO personality framework represents one of the most prominent models of human personality traits. Despite of this, there are no empirical studies that estimate the fitness outcomes of HEXACO traits, although this topic represents a basic foundation for the study of the contemporary evolution of personality. In the present research we explored the relations between HEXACO personality traits, and three fitness indicators: the number of children, the number of grandchildren and the age at first birth. Participants were selected from the community population of individuals in a post-reproductive stage (N = 255; Mage = 64.9 years). Results from the regression analyses showed that the number of children was associated with lower scores on Honesty and Openness and higher scores on Emotionality; Agreeableness was positively associated with this criterion but only in males. The number of grandchildren was predicted by low Openness and marginally by high Conscientiousness, while Honesty had positive zero-order correlation with the criterion measure. Individuals with higher Extraversion tended to reproduce earlier in their lifetime. Findings contribute to the empirical data which suggest that personality is related to biological fitness in contemporary human populations: this means that personality is likely under natural selection and hence, it continues to evolve.