Cause
The American Psychological Association, American Psychiatric Association, and National Association of Social Workers stated in 2006:
| “ | Currently, there is no scientific consensus about the specific factors that cause an individual to become heterosexual, homosexual, or bisexual—including possible biological, psychological, or social effects of the parents' sexual orientation. However, the available evidence indicates that the vast majority of lesbian and gay adults were raised by heterosexual parents and the vast majority of children raised by lesbian and gay parents eventually grow up to be heterosexual. | ” |
The Royal College of Psychiatrists stated in 2007:
| “ | Despite almost a century of psychoanalytic and psychological speculation, there is no substantive evidence to support the suggestion that the nature of parenting or early childhood experiences play any role in the formation of a person's fundamental heterosexual or homosexual orientation. It would appear that sexual orientation is biological in nature, determined by a complex interplay of genetic factors and the early uterine environment. Sexual orientation is therefore not a choice. | ” |
The American Academy of Pediatrics stated in Pediatrics in 2004:
| “ | Sexual orientation probably is not determined by any one factor but by a combination of genetic, hormonal, and environmental influences. In recent decades, biologically based theories have been favored by experts. Although there continues to be controversy and uncertainty as to the genesis of the variety of human sexual orientations, there is no scientific evidence that abnormal parenting, sexual abuse, or other adverse life events influence sexual orientation. Current knowledge suggests that sexual orientation is usually established during early childhood. | ” |
The American Psychological Association states "there are probably many reasons for a person's sexual orientation and the reasons may be different for different people", and says most people's sexual orientation is determined at an early age. Research into how sexual orientation in males may be determined by genetic or other prenatal factors plays a role in political and social debates about homosexuality, and also raises fears about genetic profiling and prenatal testing.
Professor Michael King states: "The conclusion reached by scientists who have investigated the origins and stability of sexual orientation is that it is a human characteristic that is formed early in life, and is resistant to change. Scientific evidence on the origins of homosexuality is considered relevant to theological and social debate because it undermines suggestions that sexual orientation is a choice."
Innate bisexuality (or predisposition to bisexuality) is a term introduced by Sigmund Freud, based on work by his associate Wilhelm Fliess, that expounds that all humans are born bisexual but through psychological development—which includes both external and internal factors—become monosexual, while the bisexuality remains in a latent state.
The authors of a 2008 study stated "there is considerable evidence that human sexual orientation is genetically influenced, so it is not known how homosexuality, which tends to lower reproductive success, is maintained in the population at a relatively high frequency". They hypothesized that "while genes predisposing to homosexuality reduce homosexuals' reproductive success, they may confer some advantage in heterosexuals who carry them". Their results suggested that "genes predisposing to homosexuality may confer a mating advantage in heterosexuals, which could help explain the evolution and maintenance of homosexuality in the population". A 2009 study also suggested a significant increase in fecundity in the females related to the homosexual people from the maternal line (but not in those related from the paternal one).
Garcia-Falgueras and Swaab state in the abstract of their 2010 study, "The fetal brain develops during the intrauterine period in the male direction through a direct action of testosterone on the developing nerve cells, or in the female direction through the absence of this hormone surge. In this way, our gender identity (the conviction of belonging to the male or female gender) and sexual orientation are programmed or organized into our brain structures when we are still in the womb. There is no indication that social environment after birth has an effect on gender identity or sexual orientation."
Read more about this topic: Homosexuality