Introduction. Recent evidence suggests that sexually antagonistic genetic factors in the maternal line promote homosexuality in men and fecundity in female relatives. However, it is not clear if and how these genetic factors are phenotypically expressed to simultaneously induce homosexuality in men and increased fecundity in their mothers and maternal aunts.
Aims. The aim of the present study was to investigate the phenotypic expression of genetic factors that could explain increased fecundity in the putative female carriers.
Methods. Using a questionnaire-based approach, which included also the Big Five Questionnaire personality inventory based on the Big Five theory, we investigated fecundity in 161 female European subjects and scrutinized possible influences, including physiological, behavioral, and personality factors. We compared 61 female probands who were either mothers or maternal aunts of homosexual men. One hundred females who were mothers or aunts of heterosexual men were used as controls.
Main Outcome Measures. Personality traits, retrospective physiological and clinical data, behavior and opinions on fecundity-related issues were assessed and analyzed to illustrate possible effects on fecundity between probands and control females.
Results. Our analysis showed that both mothers and maternal aunts of homosexual men show increased fecundity compared with corresponding maternal female relatives of heterosexual men. A two-step statistical analysis, which was based on t-tests and multiple logistic regression analysis, showed that mothers and maternal aunts of homosexual men (i) had fewer gynecological disorders; (ii) had fewer complicated pregnancies; (iii) had less interest in having children; (iv) placed less emphasis on romantic love within couples; (v) placed less importance on their social life; (vi) showed reduced family stability; (vii) were more extraverted; and (viii) had divorced or separated from their spouses more frequently.
Conclusions. Our findings are based on a small sample and would benefit from a larger replication, however they suggest that if sexually antagonistic genetic factors that induce homosexuality in males exist, the factors might be maintained in the population by contributing to increased fecundity greater reproductive health, extraversion, and a generally relaxed attitude toward family and social values in females of the maternal line of homosexual men. Camperio Ciani AS, Fontanesi L, Iemmola F, Giannella E, Ferron C, and Lombardi L. Factors associated with higher fecundity in female maternal relatives of homosexual men. J Sex Med 2012;9:2878–2887.