What is the evidence to support the view that homosexuality has a biological basis? Discuss the criticisms of this view.

There is an ongoing debate on whether homosexuality has a biological basis or not . The search is on for the genetic , chemical neuranatomical and functional evidence that the third sex ' is innate and not just a choice or entirely the product of psychosocial factors There have been several studies supporting this theory . However , they are not without their flaws and even the interpretation of the results leave room for criticism and alternative explanations . This aims to examine the so-called proof of the biological basis of homosexuality

The theory that homosexuality is partly

genetic is based on several twin studies . It was found that there is higher concordance of sexual orientation in identical twins compared to fraternal twins (Bailey et al , 1993 as cited in Byne et al , 1994 . Because identical twins have the exact DNA composition , it was hypothesized that the reason for the high concordance rates for sexual orientation is that it is directly affected by our genes

There are some loopholes in this theory , however , as cited in the book Biology and Human Sexual Orientation (Byne et al , 1994 . One is that the twins used in the studies were not reared apart . Hence , they may have had very similar childhood experiences , possibly causing them to have the same sexual orientation . For studies that did deal with identical twins reared apart , the fact remains that they looked alike and as such people around them may have treated them the same way which again leads them to have the same childhood experiences . Concordance rates only tell us the degree to which homosexuality is associated with genetics and not how genetics actually affect homosexuality Furthermore , it was found that half of the identical twin sets did not have the same sexual orientation , therefore , if genetic does play a role in homosexuality , it is through its interaction with the environment and not direct (Byne et al , 1994

Researchers even went as far as identifying the chromosome responsible for homosexuality . In the controversial study of Hamer , et al ( 1993 as cited in Rice , et al , 1999 , it was claimed that the gene for male homosexuality is localized in the X chromosome , particularly in position Xq28 . This is based on their analysis of chromosomes in families with more than one male homosexual sibling . Their study included an investigation on the sexual orientation of first- , second- , and third-degree relatives as well and found that there are more cases of homosexuality in the mother 's side as compared to the father 's side leading them to think that male homosexuality could be an X-linked trait . Indeed , molecular analysis revealed that there is an excess of allele sharing in the region of Xq28 . These results were replicated in the study of 33 additional homosexual brothers (Hu et al , 1995 as cited in Rice et al , 1999 . However , in the larger-scale study by Rice , et al (1999 , they did not find the shared Xq28 marker . It is unclear why this is so since the sample size differ...