Too often the argument is made that homosexuality is a lifestyle choice and that anyone can overcome this “disability” with will power, therapy, etc. While I am not a homosexual myself, I have a fetish and I know what it is like to be inclined to like something and know that it is not necessarily by choice.
In this article, I want to look at the evidence showing that homosexuality is a physical determinant, not psychological. Also, I want to show that homosexuality exists in other animals, not just humans. Finally, I want to look at the actual evidence of homosexuality’s prevalence statistics compared to common perceptions of it.
Furthermore, while homosexuality is a heated debate, I think it is commonly agreed upon that the central reasons are backed by religious justifications. I do not want to delve into that. I simple want to look at the evidence of the matter and leave the rest of the religious implications up for debate. Maybe in another post I will cover my philosophical position on the matter, but for now, I just want to look at the evidence.
➡ Evidence for Biological Causation of Homosexuality in Humans
As per my usual approach, I am not going to offer conjecture like it is objective truth. Instead, I will reference and highlight scientific journals with real evidence and provide links so you can see the rest for yourself. If I do not highlight anything (like the one below), it’s because I’m keeping it short and to the point of the important information it has to offer.
Morphometric analysis of the human hypothalamus revealed that the volume of the suprachiasmatic nucleus (SCN) in homosexual men is 1.7 times as large as that of a reference group of male subjects and contains 2.1 times as many cells. In another hypothalamic nucleus which is located in the immediate vicinity of the SCN, the sexually dimorphic nucleus (SDN), no such differences in either volume or cell number were found. The SDN data indicate the selectivity of the enlarged SCN in homosexual men, but do not support the hypothesis that homosexual men have a ‘female hypothalamus’.
The anterior commissure, a fiber tract that is larger in its midsagittal area in women than in men, was examined in 90 postmortem brains from homosexual men, heterosexual men, and heterosexual women. The midsagittal plane of the anterior commissure in homosexual men was 18% larger than in heterosexual women and 34% larger than in heterosexual men. This anatomical difference, which correlates with gender and sexual orientation, may, in part, underlie differences in cognitive function and cerebral lateralization among homosexual men, heterosexual men, and heterosexual women. Moreover, this rinding of a difference in a structure not known to be related to reproductive functions supports the hypothesis that factors operating early in development differentiate sexually dimorphic structures and functions of the brain, including the anterior commissure and sexual orientation, in a global fashion.
Later fraternal birth order (FBO) is a well-established correlate of homosexuality in human males and may implicate a maternal immunization response in the feminization of male sexuality. This has led to the suggestion that FBO may relate to other markers of male sexual orientation which are robustly sexually dimorphic. If so, among homosexual males the number of older brothers should strongly correlate with traits such as spatial ability and psychological gender, indicative of greater behavioural feminization, compared to heterosexual males. The present study failed to find significant associations between number of older brothers and these traits.
Gonadal steroids have remarkable developmental effects on sex-dependent brain organization and behavior in animals. Presumably, fetal or neonatal gonadal steroids are also responsible for sexual differentiation of the human brain. A limbic structure of special interest in this regard is the sexually dimorphic central subdivision of the bed nucleus of the stria terminalis (BSTc), because its size has been related to the gender identity disorder transsexuality. To determine at what age the BSTc becomes sexually dimorphic, the BSTc volume in males and females was studied from midgestation into adulthood. Using vasoactive intestinal polypeptide and somatostatin immunocytochemical staining as markers, we found that the BSTc was larger and contains more neurons in men than in women. However, this difference became significant only in adulthood, showing that sexual differentiation of the human brain may extend into the adulthood. The unexpectedly late sexual differentiation of the BSTc is discussed in relation to sex differences in developmental, adolescent, and adult gonadal steroid levels.
Cerebral responses to putative pheromones and objects of sexual attraction were recently found to differ between homo- and heterosexual subjects. Although this observation may merely mirror perceptional differences, it raises the intriguing question as to whether certain sexually dimorphic features in the brain may differ between individuals of the same sex but different sexual orientation. We addressed this issue by studying hemispheric asymmetry and functional connectivity, two parameters that in previous publications have shown specific sex differences. Ninety subjects [25 heterosexual men (HeM) and women (HeW), and 20 homosexual men (HoM) and women (HoW)] were investigated with magnetic resonance volumetry of cerebral and cerebellar hemispheres. Fifty of them also participated in PET measurements of cerebral blood flow, used for analyses of functional connections from the right and left amygdalae. HeM and HoW showed a rightward cerebral asymmetry, whereas volumes of the cerebral hemispheres were symmetrical in HoM and HeW. No cerebellar asymmetries were found. Homosexual subjects also showed sex-atypical amygdala connections. In HoM, as in HeW, the connections were more widespread from the left amygdala; in HoW and HeM, on the other hand, from the right amygdala. Furthermore, in HoM and HeW the connections were primarily displayed with the contralateral amygdala and the anterior cingulate, in HeM and HoW with the caudate, putamen, and the prefrontal cortex. The present study shows sex-atypical cerebral asymmetry and functional connections in homosexual subjects. The results cannot be primarily ascribed to learned effects, and they suggest a linkage to neurobiological entities.
From the above studies, we can conclude that homosexuality has varying biological causation. We know from the above that:
* The suprachiasmatic nucleus is a variable in sexual orientation depending on size
* The anterior commisure is a determining factor in sexual orientation; it is significantly larger than those of the opposing sexual orientation of the same sex.
* Birth order does not seem to play a role in homosexuality
* Sexuality maturates through adulthood and is affected by gonadal steroidal levels
* The amygdala plays a significant role in differing sexual orientations
➡ Homosexuality in Animals
In male rats, androgen deficiency during a critical hypothalamic organizational period was shown to give rise to a predominantly female-differentiated brain, homosexual behavior, and demonstration of a positive estrogen feedback effect. A positive estrogen feedback effect was also induced in intact homosexual men in contrast to intact heterosexual and bisexual men. Thus in 21 homosexual men an intravenous injection of 20 mg Presomen (Premarin) produced a significant decrease of serum LH levels followed by an increase above initial LH values. In 20 heterosexual and in five bisexual men, by contrast, intravenous estrogen administration, while producing a significant decrease of the serum LH level, was not followed by an increase above the initial LH values. Using a radioimmunoassay, plasma testosterone levels and 24-hr urinary excretions of unconjugated testosterone of adult homosexual men were found to be in the normal range as observed in heterosexual men. This finding suggests that homosexual men possess a predominantly female-differentiated brain which may be activated to homosexual behavior by normal or approximately normal androgen levels in adulthood.
While this article demonstrates biological sexual determinism in humans, it also has implications for animal homosexuality.
This study examined endocrine components of sexual orientation of male sheep. Sexual orientation of adult rams was identified through standardized sexual performance tests. Four rams that copulated with ewes, four rams that never mounted females and copulated with males, and eight ewes were used in the experiments. Exogenous estradiol benzoate (50 μg, i.m.) stimulated (P < .05) a preovulatory-like LH surge 16-22 hr after administration to females. Estradiol did not (P > .05) affect LH release of heterosexual or homosexual rams. Thirty days after the estradiol challenge, sheep were euthanized and areas of the amygdala (AMY), hypothalamus (HYP), anterior pituitary (AP), and preoptic area (POA) of the hypothalamus were collected. Occupied and unoccupied content of estradiol receptors (ER) was determined. The content of ER in the amygdala of both homosexual rams and ewes was similar, but less than (P < .05) the content of ER in heterosexual rams. The ER content measured in other brain regions did not differ by sex or orientation. In summary, results from these data show that the preovulatory LH surge mechanism that is a characteristic of the female does not occur in either homosexual or heterosexual rams. Conversely, the ER content of the AMY of homosexual rams is similar to that of ewes and differs from the heterosexual male. Differences in ER content between heterosexual and homosexual rams imply that the amygdala serves as a link for input from potential mates. These data suggest that the amygdala not only plays a role in sexual behavior but may be involved in sexual orientation of rams.
It is evident that homosexuality is not exclusive to humans.
➡ Prevalence of Homosexuality
In this section, I just want to look at some prevalence statistics and evidence of homosexuality in the face of commonly held views of it. For example, if you took the media for granted, it would seem that there are more gay women than men. Also, some people seem to underestimate how common it is. While I do not want to delve into the dynamics of sexual orientation (ie. the Kinsey sexual orientation scale), I want to look at some statistics from the DSM. I must note now that it was at this point I looked into the DSM to search for homosexuality and found that it has been removed since the DSM-III. It is difficult to find statistics on homosexuality because the very definitions is debated let alone people coming out to report it. However, I want to share some interesting evidence on their prevalence.
Although homosexual activity is prevalent among US teenagers, adolescent homosexuality per se has been a poorly understood phenomenon. The purpose of this investigation is to describe the meaning and experience of homosexuality from the adolescent’s perspective. Twenty-nine male teenagers, self-described as gay (79%) or bisexual (21%), volunteered to participate in a structured interview, the purpose of which was to examine the definition of homosexuality, the acquisition of a gay identity, and the impact of sexuality on family, peers, and community. The youths demonstrated well-established sexual identities by the consistency of their sexual fantasies, interests, and behaviors over time. Homosexuality was more frequently described as a general attraction to men (48%) and an indicator of positive personal attributes (33%) than as an isolated sexual behavior. The subjects reported strong negative attitudes from parents (43%) and friends (41%) toward their sexualities. Discrimination (37%), verbal abuse from peers (55%), and physical assaults (30%) were frequently cited problems. These stressors may place the boys at high risk for physical and psychosocial dysfunction.
This study above shows some differing perspectives that teens have about homosexuality. I’d elaborate, but I think the abstract is well said.
A nationally representative study of the sexual behavior of men aged 20-39 in the United States shows that the prevalence and frequency of sexual acts (vaginal, anal and oral) and sexual orientation vary by social and demographic characteristics. Analysis of data from 3,321 respondents to the 1991 National Survey of Men reveals that 95% of men have had vaginal intercourse; among them, 23% have had 20 or more vaginal sex partners in their lifetime. About one-fifth of never-married and formerly married men had had four or more partners over a recent 18-month period. However, 41% of never-married men and 32% of formerly married men did not have coitus during the four weeks preceding the interview. Only 20% of men have ever engaged in anal intercourse. Among these, 51% had not done so during the previous 18 months, and 90% had not done so during the previous four weeks. Seventy-five percent of men have performed oral sex and 79% have received oral sex, although 53% of men who ever performed oral sex had not done so during the four weeks prior to interview, and only 11% had done so six or more times. The frequency of receiving oral sex is similar. Only 2% of sexually active men aged 20-39 have had any same-gender sexual activity during the last 10 years, and only 1% reported being exclusively homosexual during this interval
While this above article only quotes 2% of men reporting homosexuality, we can find conflicting evidence in other sources, like the one below:
Researchers determining the prevalence of homosexuality in nationally representative samples have focused upon determining the prevalence of homosexual behavior, ignoring those individuals whose sexual attraction to the same sex had not resulted in sexual behavior. We examine the use of sexual attraction as well as sexual behavior to estimate the prevalence of homosexuality in the United States, the United Kingdom, and France using the Project HOPE International Survey of AIDS-Risk Behaviors. We find that 8.7, 7.9, and 8.5% of males and 11.1, 8.6, and 11.7% of females in the United States, the United Kingdom, and France, respectively, report some homosexual attraction but no homosexual behavior since age 15. Further, considering homosexual behavior and homosexual attraction as different but overlapping dimensions of homosexuality, we find 20.8, 16.3, and 18.5% of males, and 17.8, 18.6, and 18.5% of females in the United States, the United Kingdom, and France report either homosexual behavior or homosexual attraction since age 15. Examination of homosexual behavior separately finds that 6.2, 4.5, and 10.7% of males and 3.6, 2.1, and 3.3% of females in the United States, the United Kingdom, and France, respectively, report having had sexual contact with someone of the same sex in the previous 5 years. Our findings highlight the importance of using more than just homosexual behavior to examine the prevalence of homosexuality.
It is clear that there is conflicting evidence in the prevalence. However, it is consistent that that are more gay men than gay women.
On another note, some people claim that legalizing gay marriage would lead to higher divorce rates. However, the study below shows the contrary.
According to provisional data from the Census Bureau and the Centers for Disease Control’s National Vital Statistics System, 5 of the 10 states, plus the District of Columbia, with the lowest divorce rates per thousand people (of the 44 states, plus D.C., that had available data) are also among the nine jurisdictions (a group that includes eight states and the District of Columbia) that currently perform or recognize gay marriages. Of course, states with more marriages naturally have more chances for divorce. But the trend also holds up when one looks at divorces as a share of marriages. In states that recognize or perform gay marriages, the number of divorces in 2009 was 41.2 percent of the number of marriages. In the 36 other states for which 2009 data are available, it was 50.3 percent. Remove the outlier Nevada, the state with by far the lowest divorce rate by this metric (16.3 percent), likely due in part to Las Vegas’s status as a wedding hotspot for out-of-state couples who may get married there but divorced elsewhere, and the figure jumps to 53.2 percent.
My intent of this article was simply looking at the evidence of biological homosexuality. I ought to note here the Kinsey sexual orientation scale. This scale was used in Kinsey’s extensive research on sexuality because it was evident that people are not truly on extremes as imagined. It is not the case there there it is simply gay, straight, and bi. There is a plethora of evidence supporting this dynamic because it is a reflection of the dynamic of the human mind:
This dynamic scale also illustrates the diversity in the biological homosexuality. While it is evident that biological properties cause homosexuality, it is obvious that these biological properties are not clear cut and do vary in size, degree, potency, etc. I imagine the differences in these biological constructs are reflected in this scale.
At length, homosexuality is not a choice deliberately made by humans. While we can willfully deter this behavior and it’s manifestation in our everyday life, it is clear that it is not something arbitrarily chosen. Furthermore, I liked to point out that there are more gay men than women. Furthermore, embracing same-sex rights is related to lower divorce rates, something which many people imagined would be contradictory.
I am glad to see people are more accepting of the dynamic nature of the human mind. We are not a simple coin that has only two sides with the rare middle. Humans are a powerfully diverse and broad being. We need to respect that. We need to also respect that somethings are not within our choice, we are our biology. You cannot will a sixth finger. You cannot will a second head. You cannot will additional arteries. You cannot will lesions in the brain to remove characteristics. I embrace this about ourselves. Enjoy what you do have and respect others for who they are.
Edit: I found a great video with the same title