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Genetic causes of homosexuality, yup, it's being looked at!
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Genetic causes of homosexuality, yup, it's being looked at! Today I wanted to discuss the emerging science behind the genetic causes of homosexuality. Yes, this is being studied in earnest. Well, instead of saying genetic, the appropriate term would be epigenetic. Epigenetics is still emerging field of science. It has been known of for a long time but until recent times, it was exceedingly difficult to study. Now it is just exceeding expensive  And what is epigenetics? It is chemical modification of your DNA, so that additional code information can be added on top of DNA, usually to influence genetic expression. The crazy catch is that now it is known that this chemical modification can also be sometimes inherited. But the details of this type inheritance are still quite shady at the moment. As I said, this is a fascinating field of science that is only just beginning in earnest. And it appears that homosexuality is at least in part driven by epigenetics.  The theory of epigenetic influence on homosexual tendencies was only recently first proposed, in a paper published right at the end of 2012 bye Rice et al. Authors noted that while it is known that homosexuality has a substantial heritability component, no genetic markers among such related individuals were ever found. Believe me, in our day and age, it is not difficult to find correlation between genes and specific trait. You just need to have large enough study population, and I don’t think we’d have a problem finding big enough gay community these days! In addition, there is no sexual preference concordance between identical twins. Identical twins share same DNA, and if specific genes or segments of genome were responsible for sexual preference, identical twins should be exhibiting it to similar effect. But that is not seen. Furthermore, you would think that homosexuality would be selected against in evolution as a fitness-reducing trait (since it can reduce birth rate) but persistently remains common in society.  These authors proposed that androgen-dependent sexual development is influenced by additional factors (epigenetics) so that in XY fetus the male development is boosted (by enhancing sensitivity to androgens levels such as testosterone) while in XX fetus female development is enhanced (by blunting sensitivity to androgens levels). It is this gender characteristics enhancing mechanism that can be carried over across generations as epigenetic markers but influencing different genders, leading to development of homosexuality. So if epigenetic marker that was supposed to be enhancing masculine attributes is actually inherited by a woman, you got yourself a lesbian! Vice versa, if epigenetic marker that was supposed to be enhancing female development, you end up gay. Ok, I am also simplifying it, but you get the idea. Furthermore, this type of epigenetic marker must be of restricted effect, influencing only sexual preference without impacting sexual identity or genitalia development.  The primary reason why authors suggested this because there substantial overlap in circulating androgen levels during the development of either gender, and yet rarely are there observed mistakes in both genitalia and gonad development occurring, which would be expected to be observed more often if the development were to be influenced by variable circulating androgen levels alone.  At the time it was a brilliant and bold theory, but not substantiated by empirical evidence, only a well working model that could explain the previous confusing data on development. Now there is emerging evidence that they were correct. This was demonstrated late last year in a study of once again discordant monozygotic twins, and just as the theory predicted, there was a strong correlation between epigenetic modification of DNA and twin sexual preference! However, I wasn’t able to get the paper, so I am only basing this on the abstract I read. However, this study had quite small sample size of only 37 pairs of twins, and would need to be reproduced on a much larger scale to get to the bottom of this (pun intended of course). As I said, this work is not cheap!  Interestingly enough, at the same time recently there was another paper published looking into societal acceptance of homosexuality. It turns out that as the genetic concepts of our population grows, so is the tolerance towards homosexuality based on the idea of its genetic causality. So inaccurate concepts of genetics (determinism) associated with a trait that appears not to even be caused by traditional genetic inheritance is bringing wider acceptance of gays. That is because these beliefs tend to produce thinking that if being gay is genetic, it is not subject to one’s choice, and therefore should be accepted. Well, let’s substitute genetic with epigenetic, and I am always for greater tolerance amongst humanity Heck, that is why I started this blog here! Oh, and by the way, the homosexuality concordance between monozygotic twins is about 20%. In case you wanted know
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A well written post with beautiful pictures to go with ti (Virtual Symposium Group) use Virtual Symposium Group
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