Environment and sexual orientation

Between the 1960s and 2000, many newborn and infant boys were surgically reassigned as females if they were born with malformed penises, or if they lost their penises in accidents.[6]^: 72–73 Many surgeons believed such males would be happier being socially and surgically reassigned female. In all seven published cases that have provided sexual orientation information, the subjects grew up to be strongly attracted to females. In Psychological Science in the Public Interest, six scientists including J. Michael Bailey state this establishes a strong case that male sexual orientation is partly established before birth:

This is the result we would expect if male sexual orientation were entirely due to nature, and it is opposite of the result expected if it were due to nurture, in which case we would expect that none of these individuals would be predominantly attracted to women. They show how difficult it is to derail the development of male sexual orientation by psychosocial means.

They further argue that this raises questions about the significance of the social environment on sexual orientation, stating, "If one cannot reliably make a male human become attracted to other males by cutting off his penis in infancy and rearing him as a girl, then what other psychosocial intervention could plausibly have that effect?" It is further stated that neither cloacal exstrophy (resulting in a malformed penis), nor surgical accidents, are associated with abnormalities of prenatal androgens, thus, the brains of these individuals were male-organized at birth. Six of the seven identified as heterosexual males at follow up, despite being surgically altered and reared as females, with researchers adding: "available evidence indicates that in such instances, parents are deeply committed to raising these children as girls and in as gender-typical a manner as possible." Bailey et al. describe the occurrence of these sex reassignments as "the near-perfect quasi-experiment" in measuring the impact of 'nature' versus 'nurture' with regards to male homosexuality.^[6]

Childhood sexual abuse, molestation or early experiences

The hypothesis that sexual abuse, molestation or early sexual experience, causes homosexuality has been a subject of speculation but does not have scientific support.^{[6][43]: 20} Instead, research has demonstrated that non-heterosexuals, especially men, are more likely to be targeted for childhood sexual abuse due to their gender nonconforming behavior, which is visible from a young age and is a strong predictor of adult homosexuality. As this gender nonconformity often makes them identifiable, they may be especially susceptible to same-sex experiences even at young ages as they may be recognized by older opportunistic individuals, or they may be victimized by others who dislike gender nonconformity. Childhood sexual abuse often includes a variety of different experiences typically before age 18, not simply early childhood. Gay males are more likely to engage in age discrepant relationships during teenage years due to hiding their sexual orientation and a lack of available partners, which may be qualified as sexual abuse, but is not evidence of a "cause" of their sexual orientation.^[6]: 83

Cross-cultural evidence also speaks against the notion that a first sex encounter influences a person’s ultimate sexual orientation. Among the

Additionally, long term studies of British students who attended single-sex boarding schools, where homosexual behavior occurs at elevated rates, found that such students were no more likely to be gay than students who did not attend such schools.[43]^: 20

The hypothesis for females is that sexual abuse would make them averse to males, causing them to seek comfort with women, but that it would somehow make males attracted to the same sex, which has been described as contradictory.^[47] There is evidence that female sexual orientation could be affected by external or social influences. However, there are numerous other confounders that can distort research and that prevent any strong conclusions being made. These include personality traits such as one's level of agreeableness or propensity to risk taking, which have been found to be heightened in studies of lesbians; this may make them more susceptible to being abused.^[6] A 2016 review authored by six experts in the fields of genetics, psychology, biology, neuroscience and endocrinology concluded that they favored biological theories for explaining sexual orientation, and that, compared to males, "it would also be less surprising to us (and to others) to discover that social environment affects female sexual orientation and related behavior", but "that possibility must be scientifically supported rather than assumed".^[6]

A 2013 study "Does Childhood Maltreatment Effect Sexual Orientation?" by Roberts et al. reported that sexual abuse may affect men and not women. According to neuroscientist Simon LeVay, a controversy arose because the conclusion relied on an unusual statistical technique and it is argued she did not apply this correctly.^[43]: 20 This study has been strongly criticized for making unjustified assumptions in the statistical instrumental regression. A criticism by J. Michael Bailey and Drew Bailey says "Not only do Roberts et al.'s results fail to provide support for the idea that childhood maltreatment causes adult homosexuality, the pattern of differences between males and females is opposite what should be expected based on better evidence."^[48] Bailey states that Robert's instrumental regression and analysis were "almost certainly violated" by the confounding factor of genes shared between parents and children (Roberts used parental traits as instruments in her analysis, which are heavily distorted by behavioural genetic effects for depression and neuroticism, which children also inherit).^[48][49] When controlling for genetic confounders, the link between sexual abuse and adult non-heterosexuality in men can be reduced to zero.^[49] Further, Bailey et al. argue that all prior research has demonstrated that it would be the sexual orientation of females, not males, that may be responsive to psychosocial influences, and so it is unlikely that sexual abuse would somehow affect men's sexual orientation and not women's. Bailey concludes that Roberts' conclusion poorly fits the experience of gay men, who usually experience same-sex attraction long before their first sexual experience, that there is "compelling evidence that male sexual orientation is fixed early in development, probably before birth and certainly before childhood adversity could plausibly affect it", and that "previous research is inconsistent with the hypothesis that childhood experiences play a significant causal role in adult sexual orientation, especially in men".^[48][49] Regarding human evolution, no plausible mechanism has been provided for why men would respond to abuse by becoming homosexual.^[47][50]

In 2016, LeVay reported that another research group found evidence "supporting the original idea" that an increased rate of childhood sexual abuse among gay men is entirely due to being targeted for their childhood gender-nonconformist behaviour.^{[43]: 20 [51]} This research found that gay, bisexual, and straight men who were gender nonconforming in childhood were equally as likely to report experiencing childhood sexual abuse, while gay, bi and straight men who were typically masculine in childhood were significantly less likely to report experiencing sexual abuse. Additionally, significant numbers of heterosexuals experience childhood sexual abuse, and yet grew up to be heterosexual. LeVay concludes that "the weight of the evidence does not support the notion that childhood abuse is a causal factor in the development of homosexuality".^[43]: 20

Other confounding factors also distort research, including heterosexuals underreporting abuse, which is a particularly common issue among heterosexual men, while non-heterosexuals may be more likely to be honest about having experienced abuse in coming to terms with their same-sex attraction.^[6]: 83 Sexual minorities can also be victims of corrective rape (or homophobic rape), a hate crime in which someone is sexually assaulted because of their perceived sexual orientation or gender identity. The common intended consequence of the rape, as seen by the perpetrator, is to turn the victim heterosexual or to enforce conformity with gender stereotypes.^[52][53] Additionally, studies relying on convenience samples can result in higher rates of abuse, which have limited validity describing rates of abuse in the wider population.^[54]

Childhood sexual abuse, when defined as "sexual experiences with an adult or any other person younger than 18 years when the individual did not want the sexual experience or was too young to know what was happening", is combining a number of different experiences, likely to have different causes and effects. This may include sexual experiences of children too young to have understood what was happening, and the sexual experiences of late adolescents who understood those experiences but did not want them, as well as abusive experiences with the same sex and with the other sex.^[6]: 83

The American Psychiatric Association states: "...no specific psychosocial or family dynamic cause for homosexuality has been identified, including histories of childhood sexual abuse".^[55] Scientists in sexual orientation research favour biological theories, for which evidence has been building after a long-term failure to demonstrate the influence of the postnatal social environment on sexual orientation, and this is especially so for males.^[6]

Chemical disruptors

Environmental compounds such as plastic softeners (phthalate esters), which are pervasive environmental chemicals with anti-androgenic effects may interfere with sexual differentiation of the human brain during prenatal development.^[56] Researchers are investigating exposure to these endocrine disruptors during pregnancy and later sexual orientation of offspring, although scientists caution that no conclusions can be made yet.^[56][57][58] Historical records indicate homosexual people were present and recognized in many times, cultures and places prior to industrialisation.^[6]

Between 1939 and 1960, around two million expectant mothers in the United States and Europe were prescribed a synthetic estrogen known as diethylstilbestrol (DES) in the belief that it would prevent miscarriages. DES did not prevent miscarriage, but it reportedly increased the likelihood of bisexuality and homosexuality in the daughters of women given the drug.^[17][59]

Other

Data scientist Seth Stephens-Davidowitz reported that the actual prevalence of gay men does not appear to vary between states in the U.S. because the percentage of Internet porn searches that are for gay male porn are nearly the same in all states, about 5%. On this basis he believes migration of gay men to cities is overstated, and says that in states where there is a social stigma against homosexuality so that "many more gay men are in the closet than are out".^{[60][43]: 9}

See also

• Biology and sexual orientation
• Demographics of sexual orientation
• Homosexuality and psychology
• Nature versus nurture
• Sexual fluidity
• Xenoestrogen

References