Notwithstanding these limitations, this study provides empirical findings that bolster our understanding of the evolutionary genetics of personality, suggesting that genetic variation is maintained primarily by a balance between an influx of deleterious mutations and selection against them. While this study focuses on human personality, the results may help guide theory and empirical research in other species and other traits; indeed, the methodology used here can in principle be used to investigate maintenance of variation in any trait in any species, providing sufficiently large samples can be obtained. Furthermore, methodological developments in the near future (e.g. low-cost genome sequencing) may allow more direct assessment of the effect of mutation load on personality and other traits, opening rich new avenues for exploration.
