Factors Associated with Higher Fecundity in Female Maternal Relatives of Homosexual Men

Abstract

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.

Genome-wide scan demonstrates significant linkage for male sexual orientation

“…Speculation has included the possibility that such genes increase sexual attraction to men in both homosexual men and their heterosexual female relatives, leading to increased reproduction in the females (Camperio Ciani et al 2008). An empirical study focusing on female maternal relatives of homosexual men found several personality and self-reported health differences (Camperio Ciani et al 2012); it is unclear if any of the differences were related to increased fecundity. A different possibility, overdominance (male heterozygote advantage) (MacIntyre & Estep, 1993), could conceivably help explain the paradox of autosomal genes for male homosexuality, including our findings of linkage to the pericentromeric region of chromosome 8.…”

Evidence for Heritability of Adult Men's Sexual Interest in Youth Under Age 16 from a Population-Based Extended Twin Design

“…It has been suggested that alleles contributing to sexual interest in individuals of the same sex could simultaneously convey other advantages that outweigh the negative consequences of homosexual interest with regard to producing offspring. For instance, there is some empirical evidence that genes coding for homosexuality could increase fecundity in female carriers of the alleles . Sexual orientation in terms of gender can, to some extent, be compared with pedophilia (as a sexual preference in terms of age).…”

Facial symmetry of the sisters of Thai and Istmo Zapotec androphilic males.

“…Aside from external phenotypic characteristics and hypergyny, there might be psychological and physiological factors that could potentially explain the elevated fertility previously observed among the female relatives of androphilic males. For example, A. S. Camperio Ciani et al (2012) found that the female kin of androphilic males who had increased fecundity also exhibited fewer pregnancy complications and gynecological disorders.…”