There is a biological cause to homosexuality

Thanks to Pro for providng an opportunity to review some very interesting science. 1. Epigenetics is the biological mechanism explaining variation in sexual preferenceFirst some background. Translating scientific jargon into plain English is a problem, and there is a mistake in equating “genetic” with “biological.” Epigenetics refers to "heritable traits (over rounds of cell division and sometimes transgenerationally) that do not involve changes to the underlying DNA sequence. The Greek prefix epi- in epigenetics implies features that are "on top of" or "in addition to" genetics; thus epigenetic traits exist on top of or in addition to the traditional molecular basis for inheritance." [1. http://en.wikipedia.org...] The basic mechanism of epigenetic tags and its use to explain the characteristics of identical twins is explained in the a video. [2] http://georgefebish.wordpress.com...; (go to the link to see it.) The second video (embedded here) explains the epigenetic basis for the transmission of homosexuality and explain why twins may be different. [3]. http://www.youtube.com... I have repeated the arguments in the text, so the videos are not essential, but I think they are useful as background. Consider a related question: is there a gene that determines whether a person will be tall or short? No, there is no "tallness gene." Yet, as far as I know, no one claims that whether a person is tall or not depends upon whether there was a tall person in the family that served as a role model, or that any other non-biological cause dominates the trait of height. In the case of tallness, many biological factors are involved, including multiple genes determined before birth and some post-natal biological factors like the amount of calcium in the diet. Tallness is generally not a subject that bears upon preconceived beliefs, so no one attempts a non-biological explanation of why some people are tall and others short. It is accepted to be the product of many biological factors. There are hundreds of personal attributes that depend upon multiple biological factors, and sexual preference is one of them. There are at least four categories of influences upon a person's characteristics:1. Genetics are the genes that determine the basic human species. Humans begin with exactly one fertile cell that includes all the genes needed to build the human. 2. Pre-natal epigenetics comprise the set of biological genetic tags that switch genes on and off as the human grows before birth.3. Post-natal epigenetics comprise the biological genetic tags that switch genes on and off after being born.4. Psychological influences are the factors affecting the faculty of reasoning.Epigenetics is a relatively new area of genetic science. For one thing, epigenetics explains the mechanism by which the original fertilized cell differentiates into cells for blood, bones, and the organs of the body. In the case of identical twins, the original cell divides into two individuals before developing. Epigenetics explains why identical twins are not completely identical. The pre-natal biological environments of the two twins are not identical, so the epigenetic tags may not be set identically. One twin may be left-handed and the other right-handed. The twins may or may not have the same fingerprints. One twin may have the same sexual preference as the other twin, but sometimes the sexual preferences are different. Because the womb environment is similar for both of the twins, there is a high correlation between the sexual preferences of twins. Whatever sets the epigenetic tags for one often sets the tags the same way for the other.Epigenetic tags can be triggered after birth. Identical twins become less like each other over a lifetime. Their personality traits diverge, and physical traits such as a tendency to fatness or thinness may occur. This is due to variations in the physical environments of the individual producing changes in the epigenetic tagging. 2. The scientific consensus is that the mechanism in humans is biological"Environment" in the context of the literature on sexual preference usually means the biological environment, not the psychological environment. For example, Pro cites Bearman's attribution of a fraction of concordance to twins having a shared placenta rather than to common genes. A shared placenta leads to common epigenetic tags, which are biological, not psychological. A summary of a major research paper in Science Daily says: Homosexual behavior is largely shaped by genetics and random environmental factors, according to findings from the world's largest study of twins. ... environmental factors (which are specific to an individual, and may include biological processes such as different hormone exposure in the womb), ... "Overall, genetics accounted for around 35 per cent of the differences between men in homosexual behaviour and other individual-specific environmental factors (that is, not societal attitudes, family or parenting which are shared by twins) accounted for around 64 per cent. In other words, men become gay or straight because of different developmental pathways, not just one pathway." For women, genetics explained roughly 18 per cent of the variation in same-sex behaviour, non-shared environment roughly 64 per cent and shared factors, or the family environment, explained 16 per cent." [4. http://www.sciencedaily.com...] So, social attitudes and family or parenting account for only 1% of homosexual differences in males and 16% in women. The difference between men and women is attributable to women having XX and men XY chromosomes. 99% and 84%, respectively, are biological causes. 3. Homosexuality occurs in 1500 species due to biological causesWikipedia provides a list of animal species in which homosexual behavior has been observed together with references. [5. http://en.wikipedia.org...]It notes, "Bagemihl's research shows that homosexual behavior, not necessarily sex, has been observed in close to 1500 species, ranging from primates to gut worms, and is well documented for 500 of them." This does not of itself prove conclusively that the mechanism producing the behavior in humans is biological, but it proves that biological mechanisms are commonplace. It's not plausible that gut worms et al are subject to psychological causes. There is no logical reason why humans would be an exception. 4. Sexual preference is immutable Alan Chambers, CEO of an organization that attempts to cure homosexuality admitted that 99.9% of homosexuals never change their sexual orientation. [6. http://wthrockmorton.com... ] Virtually any learned behavior can be changed with conventional positive and negative reinforcement techniques. [7.http://www.mentalhelp.net...] That sexual preference cannot be changed proves that it is biological. Pro's Case a. Pro is correct that there is no consensus on exactly what causes homosexuality. We also have no consensus on what causs tallness. Nonetheless, the causes ae known to be biological. It is not known what genes are relevant, what epigenetic tags are operative, and what environmental factors set the epigenetic tags. However, all the andidates are biological. b. The shared placenta effect is prdicted by epigenetics. It's biological. c. As Pro quotes Whitehead, the "10%genetic" counts only the non-epignetic part of DNA. the numbers are superceded by [4] d. Bailey et al determined that there is no "gay gene." That's consistent with the epigenetic origins of sexual preference now favored by scientists. e. I fully dcussed twin studies. They convincingy support the epigenetic origins.