Personality and occupational markers of ‘solid citizenship’ are associated with having fewer children

•We found low conscientiousness is associated with high reproductive fitness.•We found occupational failure is associated with high reproductive fitness.•Historical data show an opposite relationship between personality and reproductive fitness.•This reversal may reflect the less diligent use of contraception by less conscientious people.•The advent of welfare provisioning may boost reproductive fitness of less conscientious people.

Investigating associations between personality and reproductive fitness may reveal the adaptive significance of human behavioural traits. What we dub ‘solid-citizenship’ personality characteristics such as self-control, diligence and responsibility may repay study from an evolutionary perspective as they protect against negative life-outcomes. We explored associations between reproductive fitness and personality questionnaire markers of solid citizenship in 4981 women from four Australian samples. We also examined relations between reproductive fitness and army discharge status, an applied measure of solid citizenship, in 15,283 Vietnam War-era military veterans. In two Australian samples there were significant negative associations between reproductive fitness and personality measures of solid citizenship. Similarly, in the US study honourably discharged servicemen on average fathered significantly fewer children than non-honourably discharged servicemen. Since personality is genetically influenced, our results suggest that genetic variants for solid citizenship may be decreasing in frequency in some populations, in line with other modern findings but in contrast to historical analyses. Causes for this change may include relatively more conscientious women using contraception to prioritise their careers over reproduction and the availability of systematic welfare provisioning.