Sex differences in genetic influences on childlessness

Previous research found genetic influences on the age at which people have their first child, the total number of children ever born and on childlessness. From an evolutionary perspective one might not expect genetic influences on childlessness to exist since genes that are deleterious for human reproduction would decrease in appearance and in the long run disappear. However, one reason for this counterintuitive finding could be that different genes influence male and female fertility and for that reason these genes will be passed on to the next generation. In this study we examine to what extent genetic factors influence childlessness and if different genes play a role for men and women. Data from the Swedish Twin Register, including genotyped same sex and opposite sex twin pairs is used to answer these questions. Results from the twin method and the extended GREML method indicate that 20% to 48% of the individual differences in childlessness is explained by genetic variation and that different genes influence childlessness in men and in women. These findings provide insight in the causes of why people remain childless, and might explain the evolutionary counterintuitive finding of genes influencing fertility.