The debate surrounding the Darwinian paradox of male homosexuality remains unresolved. It suggests that if male homosexuality has a genetic component, its survival in the population runs counter to the negative impact it has on reproductive potential. However, as there is so far no convincing evidence for a genetic basis to male homosexuality, the Darwinian paradox may well prove to be illusory. Moreover, we are only looking at half of the equation for homosexuality as our knowledge of the mechanisms underlying human sexuality is still rudimentary. Male and female homosexuality may not be single conditions but multifaceted syndromes that are affected by a variety of genetic and environmental factors. There may also be strong anthropological or psychological dimensions. If this is the case, we should avoid the quest for so-called ‘gay genes’ or evolutionary theories that attempt to justify male homosexuality, and accept that the survival of human societies depends on a variety of highly complex interactions, such as same sex alliances, which are not directly associated with reproduction.  

SUMMARY

Investigations into a genetic basis to male homosexuality were prompted initially by studies that revealed that male homosexuality was familial in nature (Pillard and Weinrich, 1986; Bailey and Pillard, 1991). By the early 1990s, genome probing techniques had revealed a region on the X chromosome that fitted the pattern of maternal inheritance for male homosexuality (Hamer , 1993), however this finding was hotly disputed (Rice , 1999). By 2005, a genomewide scan for genes linked to homosexuality located three regions on non-sex chromosomes that could be assigned functions of relevance to sexual orientation (Mustanski , 2005). However these results have yet to be replicated and the debate over a genetic basis remains inconclusive. Meanwhile, evolutionary biologists have sought to explain why male homosexuality might persist in populations despite its being detrimental to reproductive fitness. The kin selection hypothesis was first applied to human sexual orientation by Wilson in 1975. However, this is now widely rejected as an explanation for male homosexuality. Instead, contemporary theories are examining the role of homosexual behaviour as a reinforcement of homosocial behaviour which could provide reproductive advantages and can thus be selected for (Kirkpatrick, 2000).