An association between male homosexuality and reproductive success

• Published in: Medical hypotheses Vol. 60; no. 2; pp. 225 - 232
• Main Author: Dewar, Colin S
• Format: Journal Article
• Language: English
• Published: United States Elsevier Ltd 01-02-2003
• Subjects: Biological Evolution; Bisexuality; Gender Identity; Heterosexuality; Homosexuality, Male - genetics; Humans; Male; Models, Genetic; Phenotype; Reproduction
• ISSN: 0306-9877; 1532-2777
• DOI: 10.1016/S0306-9877(02)00363-8

The existence of homosexuality in humans poses a problem for evolutionary theory. Exclusive male homosexuality has a catastrophic effect on reproduction and yet inherited factors appear to contribute to it. Previous attempts to resolve this conundrum are inconsistent with aspects of evolutionary theory. Additional limitations are as follows. Until recently, accounts of homosexuality have paid little attention to the probable existence of adaptive bisexuality in ancestral populations, from which further variations in sexual orientation may have evolved. Secondly, previous explanations have concentrated on the ancestral environment of two to three million years ago as the determinant of modern sexuality, when more recent influences are likely to have had considerable impact. I argue in favour of a longitudinal rather than cross-sectional model of the ancestral environment. Thirdly, they have often ignored the possibility of variable phenotypic expression, whereby those individuals with a genetic propensity for homosexuality exhibit different and adaptive qualities on most other occasions. It has been demonstrated in previous studies that homosexual men have superior linguistic skills compared to heterosexual men. This may be the result of an adaptive feminising effect on the male brain and apply to many practising heterosexuals. Other adaptations to the recent ancestral environment may include enhanced empathy, fine motor skills and impulse control. By drawing together these contributing factors an evolutionary basis for homosexuality can be demonstrated.