Homosexuality is a term which invokes a response that is colored by various opinions, be it social, political or personal. Sexual orientation refers to as the sexual affinity for men or women or both. Normally people who are sexually attracted to members of the same sex are called homosexuals. Being an uncommon trait homosexuality is not well-received by society. However, statistically homosexuality is a surprisingly common trait in human populations (e.g. a prevalence of about 8% in both sexes was reported in a large and systematic sample in Australia (1)). To some extent some homosexual people in Australia have demonstrated saying that they should be given their rights to act as homosexuals.
When analyzing homosexual origin it can be said that an individual’s attitude towards sexual orientation influences one’s notion of the causes of sexual orientation. Therefore determining the cause behind homosexual behavior plays a crucial role in changing the social and political perceptions of ‘gay’, ‘lesbian’ or ‘bisexual’ individuals. People have tried to come up with scientific explanations to pin point the cause of this anomaly in sexual development but with limited success. In 1993 a team that was led by geneticist Dean Hamer of the National Cancer Institute reported in Science that one or more genes for homosexuality (“gay genes”) had to reside on Xq28, a subtelomeric region of the long arm of the X chromosome (2). The discovery generated ripples worldwide but some teams were unable to replicate the findings (3) and the actual genes were not found by a team that supported Hamer’s identification of Xq28 in a sample size 10 times larger than his. Homosexual orientation not being a simple Mendelian trait, it is safe to assume that simple gene sequences cannot totally account for homosexuality.
Twin studies also suggested that the identical twin of a gay man despite having the same genome only has a 20% to 50% probability of being gay himself. Other independent studies have revealed the influence of neuroanatomical differences and prenatal androgens in determining partner preference. Three brain regions have been implicated in influencing sexual orientation in males. The anterior hypothalamus anterior plays a role in the regulation of male-typical sexual behavior. Volumes of Four cell groups in this region [interstitial nuclei of the anterior hypothalamus (INAH) 1, 2, 3, and 4 from three distinct groups; heterosexual men and women and homosexual men were measured in postmortem tissues. While there were no differences between the groups in the volumes of INAH 1, 2, or 4; INAH 3 was found to be smaller in gay men and more similar in size to heterosexual females (4). The arginine vasopressin neuronal population of the suprachiasmatic nucleus and the anterior commissure in gay men (5) is larger than those in heterosexual males and females. However the findings were not fully backed up because there was some information that showed that genetic information cannot determine or be the cause of homosexuality.
In addition Epigenetics is a relatively new sub-discipline of genetics that is gaining an increasingly important role in evolution and heritability. Changes in chromatin structure that alter the transcription rates of genes, such as nucleosome repositioning, DNA methylation, and/or modification of histone tails but (no changes in DNA sequence) are called epi-marks. A parent’s epi-marks sometimes are transferred across generations and determines the phenotypes of off springs (8). Since the genes responsible for androgen sensitivity reside on autosomes it is conceivable that sex chromosome epi-marks can regulate these autosomal genes independent of circulating sex hormones (7,8). The role of imprinted genes in sexual orientation was corroborated by a genome-wide linkage analysis on gay-brother pairs that showed the presence of a maternally-expressed, paternally-silenced imprinted gene for sexual orientation in chromosome location 10 (9). Researchers from the genomic company 23andMe completed a genome wide association study of sexual orientation by screening 24000 individuals (self-report on sexual orientation) for genetic markers and found one close to the pericentromeric region of chromosome 8 (10). Conclusively these molecular genetics studies indicate that sexual orientation genes have small effects individually and non-social environmental influences can shape male sexual orientation. More studies with large sample sizes are needed to identify the genes that determine the sexual orientation (11,12).
Further it is clear that non-genetic factors can influence the development of homosexual behavior! A female embryo randomly inactivates one X chromosome early in development to create dosage compensation. A study published in 2006 showed that mothers of two or more gay sons demonstrated extreme skewing of X-chromosome inactivation (nonrandom pattern of X-inactivation) highlighting the role of X chromosome in regulating sexual orientation in males (13). Thus the origins of sexual orientation need a lot more investigation before we can arrive at a conclusive result. However years of efforts from scientists all around the world has led us to understand that homosexuality is not the exclusive result of social environment or a sickness. Sometimes people are born different (for several biological and environmental causes) and accepting them without doubt or caution is the best we can do to be better humans.
Additionally it is clear that homosexuality is not regarded as an inherited thing and it has nothing to do with family hereditary. In most cases it is someone’s choice which is mostly contributed by the society and the group of people that person interacts with. Thus it is true that gene sequence has nothing to do with homosexuality. However it is also not true to say that hypothalamus plays a role in homosexuality because the acts of homosexual displays are usually shaped by one’s characters that develop into behaviors. Additionally some research and human opinions such as that of Boston psychiatrist Richard Pillard who argued that homosexuality is kind of a biological diversity with some genes diversity, however the nature denied that notion saying that genes do not make one become homosexual. For example, it is clear that no evidence of the family sharing common ancestors are all homosexual hence indicating that genes are not in any way related to homosexuality.
Moreover only a few cases that can be reported that women with some form of congenital adrenal hyperplasia might be having masculinized genitalia that may make them develop heterosexuality, however there is no clear evidence that it has led to issues of gay or lesbianism, therefore it is clear that even though there is such a case it is mostly related to the brain, however no clear evidence is built on it. Additionally from the issue on the homosexual MZ and DZ twins indicates that there is no clear evidence nor significant reason that one can take to show what causes homosexuality. Indications that to some extent homosexuality is brought on by unhealthy child upbringing such as allowing children to have relationship with people of the opposite sex that ends up becoming a frustrating one hence making individuals think that the opposite sex is bad and consequently opting for homosexuality. Moreover distorted concepts of another gender affects one’s view towards the other gender hence making one lack any interest towards the opposite sex. Moreover sexual abuse and peer pressure can also contribute to cases of homosexuality.
However it can be concluded that there is no exact or known fact that brings about homosexuality because genetics, hormonal or even one’s cultures may not fully dictate the issue of homosexuality but in most research one’s care and nature might trigger one in becoming a homosexual. Thus concluding that there is no research that shows one hundred per cent that homosexuality is related to any form of genes disorder, therefore it is said to be a habit due to one’s peer group, upbringing and the environment in which one grows. Besides, the relationship that one has with the opposite sex may lead one to become a homosexual.
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