Is there a homosexual gene?

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I have never put much thought into this topic but since we had a class on animals being gay, it has intrigued me and I want to find out if there is an accepted answer. Before I get into studies that have been done I want to share my thoughts on this topic. My thinking is that homosexuality is not linked to genes because of basic evolutionary thinking. The reason why I think that is because in order for humans to pass on their genes they have to have a child and it is not very easy for homosexuals to do this, even though it is possible today it is not very common due to high prices and small number of participants. This leads me to think that if genes caused homosexuality, the gene would eventually become extinct because they are not being passed onto their offspring. This is an article that further explains evolutionary thinking of homosexuality. The reason why I became interested in this topic is because I am a twin and there have been studies done to try to sort out this debate by doing studies on identical twins since we share a lot of similarities in terms of genes.

In the first half 1900's there was a theory that homosexuality was caused by genes because they were studied in mental hospitals where people had mental and physical defects which led psychologists to believe that homosexuality was a defect. In the early 1950's a geneticist Franz Kallman put together a study of 85 pairs identical and fraternal twins where at least one of the twins claimed to be homosexual. The reason why he chose to study identical and fraternal twins is because identical twins share a lot of genes so that if one were homosexual then there would be a high chance of the other twin being homosexual. However, fraternal twins shares as many genes as regular brothers and sisters so they don't have as high a chance as being homosexual if the other twin is, in theory. Kellman found out that if one identical twin was homosexual then there was a 100% chance that the other identical twin was homosexual too.  This lead him to believe that homosexuality was indeed caused by genetics.

Although it may seem like this study proves that homosexuality is caused by genetics there were some flaws in his study. First of all, Kellman used a lot of participants that were in correctional and psychiatric facilities so it could be said that his participants are not like the average person. Another flaw was that he never explained how he determined whether the pair of twins were identical or fraternal so there is a chance that he could have skewed the results in order to falsely show that homosexuality is caused by genetics. And lastly even if the study was done correctly, it would be hard to determine whether or not homosexuality is caused by genes in identical twins because a majority of the time, identical twins grow up sharing the same experiences and they are raised almost the same. I can say that from my own experience my twin brother and me share many of our experiences because we do a lot together, and I would even say that we do a lot more things together than normal siblings. After the study was done, researchers that looked over Kellman's study came to the conclusion that the chance of both identical twins being homosexual was closer to around 50%.

I think the best way to test this theory would be to do a correlation study between identical twins that have been raised by different families in different settings. This would be very difficult though because it would be hard to find a large sample size of identical homosexual twins that grew up apart.

After looking at this study I have come to my own conclusion that although homosexuality may be linked to genetics, it is without a doubt affected by social and environmental factors. The reason why I think that is because even though someone may be homosexual they might not admit to it because of societal factors that keep them from admitting it.


Source: Cooper, Edith Fairman. Homosexuality: Selected Studies and Review of Possible OriginsScience Policy Research Division (CRS), April 15, 1993.

1 Comment

I really like that you're a twin and you did this topic. I believe that the best way to prove if homosexuality is a genetic thing is through twins. I personally like to think of homosexuality as being a gene but it hasn't been proven one way or the other. I think you bring up a good point of how its hard to prove this because some people don't "come out." well done!

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