Genetic Influences on Male Homosexuality

Sexual orientation, identity and desire is the final product of complex interactions between factors such as genetic influences, epigenetic, developmental pathways, both prenatal such as sex hormones, including the maternal factors acting on the foetus, and postnatal factors including shared environmental influences such as family education, social and cultural influences, and nonshared environmental influence such as unique personal experiences. Male homosexuality poses an evolutionary dilemma as it entails reduced fitness but is nevertheless, in part, influenced by genetic factors. Examining the causes of homosexuality the author investigates the Darwinian dilemma as to why genetic factors that influence homosexual nonreproductive behaviour can be maintained in the population without disappearing as expected. Sexually antagonistic selection can explain male homosexuality. A sexually antagonistic model with genetic factors partially linked to X chromosome by increasing fecundity in females and influencing homosexuality in males could be selectively balanced in the population and explain all the peculiarity of male homosexuality.