Findings on Human Sexuality
Some say that a “gay” gene will never be found. This reasoning could be accurate. Pinpointing an exact gene for homosexuality would be nearly impossible. There is the possibility of a combination of genes relating to human sexuality, but there is still no definite proof, as “the mechanisms by which sexually dimorphic structures are formed in the brain remains poorly understood.”
Rather than just searching for the exact DNA behind human sexuality, some scientists have investigated the overall effect of brain development on sexual orientation. A large fraction of the population (40%-90%), depending on the society considered, believe that sexual orientation is a choice or the consequence of events in early childhood. This is mostly due to Sigmund Freud’s original notions on homosexuality. However, Jacques Balthazart provides evidence in “Brain Development and Sexual Orientation” that hormones before birth and in early life play a role in sexuality. In the book many case studies are investigated to support that nature is the main influence in human sexual orientation, not CHOICE.
Like humans, animals are sexually differentiated and show preference almost exclusively to one sex. But also like humans, this is not always the case with animals, which is why many tests have been run and observations have been made on mammals to examine parallels in sexuality.
Rather than just searching for the exact DNA behind human sexuality, some scientists have investigated the overall effect of brain development on sexual orientation. A large fraction of the population (40%-90%), depending on the society considered, believe that sexual orientation is a choice or the consequence of events in early childhood. This is mostly due to Sigmund Freud’s original notions on homosexuality. However, Jacques Balthazart provides evidence in “Brain Development and Sexual Orientation” that hormones before birth and in early life play a role in sexuality. In the book many case studies are investigated to support that nature is the main influence in human sexual orientation, not CHOICE.
Like humans, animals are sexually differentiated and show preference almost exclusively to one sex. But also like humans, this is not always the case with animals, which is why many tests have been run and observations have been made on mammals to examine parallels in sexuality.
Nature...?
The Critical Period
This case study explores the period of development in which the brain differentiates into male or female. This development is irreversible. With the presence of testosterone, the male sex is differentiated and with the absence of the hormone, female differentiated. This is called “the critical period” because the brain is still very plastic and can be changed with exposure to steroids or hormones. If testosterone is injected into a female rat while in the last week of gestation or in the first week post birth, the female will show masculinized behaviors and qualities for the rest of her life. The female will not show the behavior of lordosis and will behave more similar to a male sexually. If estradiol is injected, the subject is feminized. With the appropriate adjustments made, these principles appear to be applicable to humans. Günter Dörner, a German endocrinologist, was the first to propose that hormonal imprinting could be linked to homosexuality. His theory states that sexual differentiation in the presence of low testosterone in boys or high testosterone in girls will cause atypical sexual differentiation. As influential as prenatal hormones may be, they can only predispose sexual orientation but not fully determine it in humans.
Stress During Pregnancy
Maternal stress could affect the sexual orientation of embryos. Initially performed on rats, the study stressed pregnant females by immobilizing them and exposing them to uncomfortably bright areas. The male offspring of the stressed mothers showed female sexual behaviors, like lordosis, partial lack of masculinization and defeminization, lower blood levels of testosterone, and inhibited aromatase activity (conversion of testosterone to estradiol). This incomplete sexual differentiation was directly related to the stress induced on the mothers. The experiment performed on rats sparked the investigation of the possibility of an effect of stress on sexual orientation in humans. Günter Dörner, a German scientist, studied the significant rise in homosexual males born between 1942 and 1946. The peak of homosexuality went back to baseline in the year 1948. It is easy to assume that these mothers in Berlin at the time were under a large amount of stress due to World War II. A questionnaire given to the mothers who remember significantly stressful events during pregnancy found that stress was linked to the likelihood that the child born would be homosexual. Overall, the data collected on stressful pregnancies suggest that the disruption of androgen production could affect homosexuality in males.
Morphological Indicators
This study aims to connect the morphological feature of index finger length with sexuality. Different finger lengths relate to different levels of embryonic androgens in the body during development since testosterone modulates growth in long bones. The ratio of the index finger (D2) to the ring finger (D4) in men is lower than that of women. Females exposed to more testosterone have a masculinized, lower D2:D4 ratio. When this study was performed on monozygotic twins (one being homosexual and the other heterosexual), the lesbian twin had a smaller ratio than that of the heterosexual sister. This would suggest that sexual orientation is not genetic, since the twins would share the same genetic heritage, but due to hormonal exposure during development. This would also suggest that sexual orientation is not a lifestyle choice because it would be hard to change the relative size of fingers.
Above: Ratio of lengths of the index finger (D2) and ring finer (D4) compared to sexual orientation. In women, the D2:D4 ratio is greater than in men, which is probably caused by exposure to testosterone by males as an embryo. In homosexual women, this ratio is much closer to that of a male, suggesting greater exposure to testosterone as an embryo. There is no marked difference between homosexual and heterosexual males.
Above: Ratio of lengths of the index finger (D2) and ring finer (D4) compared to sexual orientation. In women, the D2:D4 ratio is greater than in men, which is probably caused by exposure to testosterone by males as an embryo. In homosexual women, this ratio is much closer to that of a male, suggesting greater exposure to testosterone as an embryo. There is no marked difference between homosexual and heterosexual males.
The Older Brother Effect
Scientists Ray Blanchard and Anthony Bogaert have found a correlation between the number of older brothers a man has and his probably of being homosexual. The study suggests that the likelihood of homosexuality is 33% higher than in the general population for each older brother a man has. The certain mechanism is still being investigated but current data suggest that a postulated immune response of the pregnant mother towards the male embryo causes an increased chance of homosexuality. Over successive male pregnancies, the mother develops an immune response and attacks the embryo with unknown foreign proteins and maternal antibodies. This affects brain development and thus the sexual orientation of the child. The identity of these foreign proteins is still unknown but being investigated. Scientists know that the proteins have to be male-specific, they must enter the maternal circulation; they should be expressed in the brain and should play a role in differentiation.
Right: The relationship between percent homosexual men and the number of older brothers he has born from the same woman in a population of 50% gay men and 50% control straight men. Also shows probabilities associated with other predictors of homosexuality in men as well and number of subjects in each category along the regression.
Right: The relationship between percent homosexual men and the number of older brothers he has born from the same woman in a population of 50% gay men and 50% control straight men. Also shows probabilities associated with other predictors of homosexuality in men as well and number of subjects in each category along the regression.
Homosexual Sheep
It is common in sheep to perform bisexual actions. However, in studying sheep of the Northwestern USA, 8% of rams were not stimulated in the presence of female sheep at all. In these male-oriented males, the oSDN, normally three times larger, was much smaller than in female-oriented males. The nucleus contained fewer neurons and showed a reduced level of aromatase. Since the oSDN is located in the center of the Preoptic area, which determines sexual orientation in males, the smaller size of the nucleus appears to be a cause of their atypical sexual orientation due to an inadequate masculinization by testosterone in the embryonic stage.
or Nurture...?
The Effects of Religion on Sexuality
Many religions in Western cultures do not acknowledge homosexuality. Homosexual members of these religions are likely to internalize their sexual orientation for fear of being rejected by family and their Church community. Researchers have done studies that suggest internalizing sexual orientation results in negative psychological consequences. The lack of affirmation by their religion leads to higher rates of depression and psychological disorders in homosexual individuals and increase rates of homophobia.
Sexuality and the Family
Family formation could possible play an influential role on human sexuality. Different types of family units exist today that are not what monotheistic religions would consider the norm – the traditional heterosexual family, with two heterosexual parents, one female, one male, who reproduce to have their own biological children. Monotheistic religions and cultures derived from these have considered the main focus of sex to be reproduction. With the introduction of contraceptives, it is evident that reproduction is not the only reasoning for sexuality; it has become much more of a recreational activity. With this in mind, the “normal” family cannot be seen as a “norm” since human sexuality cannot be classified as strictly for procreation. Homosexuality should thus not be frowned upon by these religions since family formations of this nature also deserve acceptance. Although human sexuality has moved away from having a purely reproductive function, it remains a powerful bonding force keeping families together, regardless of the gender identity and biological links of family members. Some cultures believe that the influence of these homosexual parents will create homosexual children, but this is simply not true. Due to technological developments, parenthood is possible for many who haven’t had the opportunity for parenthood in the past. Even among traditional societies, other types of families can exist besides the “normal” heterosexual interpretation.
Sex determination before birth
Determining the sex of a fetus before birth can influence the child’s sexual identity. These issues arise in gender identification while children are still in the womb and developing. As soon as gender identification is made in the womb, a specific environment develops for the child, pink with the pronoun she or blue with the pronoun he. The child may identify with a different gender than that they were told they were beginning in the womb and during early development. This can be too much pressure on the fetus and developing child and thus complicate and confuse the development of the child’s sexual identity.
Masculine Ideals
The pressure to be masculine in today’s society is hard for both heterosexual and homosexual men. Many of the characteristics that are associated with masculinity and femininity are socially constructed and thus, social groups define what is and is not masculine and feminine. There may be specific ideals associated with traditional masculinity, but there is no singular type of masculinity, as different groups of individuals define masculinity very differently and hold their own standards for men. Homosexual males hold a distinct masculine ideology. The stereotype of gay males is seen to break from traditional masculinity ideology because of their affectional and sexual orientation. Consequently, the general perception is that gay men are not masculine. This perception affects homosexual relationships and gay men’s self-image. Living up to the ideals of masculine men is a lot of pressure for gay males aside from being rejected because of sexual orientation. Masculine men are seen as guys with large muscles, high pain tolerance, no fashion sense, and dominant. Thompson and Pleck (1995) proposed that a lot stress comes from gender role strain due to beliefs that one has failed to live up to an internalized notion of masculinity, the stress due to the tendency to persist in dysfunctional behavior because of traditional masculine ideals (e.g., denying physical pain and neglecting to see a doctor), and the strain due to trauma experienced during early gender role socialization. Living up to the social standard is difficult for all and the masculine aspect may be even more influential on the gay community. Masculinity may be in the eye of the beholder, but it does play a role in the gay community.
Prior Heterosexual Experiences
The choice of homosexuality is a big question. Many studies suggest choice is not the reasoning behind homosexuality, but in some women, choice could be the case. This choice is influenced by the past heterosexual encounters they have had with males. In a study, past heterosexual experiences were examined: dating histories, sexual experiences, and physical and sexual abuse, and it seems negative heterosexual experiences may play a role in the expression of same-sex sexual orientation in women.
...Or sOmething in Between?
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