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Identical twin studies.

There have been very few studies on separated identical twins and homosexuality. There have been a few more non-separated identical twins studies on the subject.

If the tendency for homosexual behavior was purely genetic, then, when one twin exhibits the behavior, the other twin should (in most, if not all cases) also exhibit the behavior. Conversely, when one twin exhibits the tendency for heterosexual behavior, the other twin should also do so.

The studies show, however, that when one identical twin is homosexual, the other twin is usually not! In fact, the tendency for homosexuality in twins is about the same as in the general population. The conclusion seems to indicate that this is a case of "nurture, not nature."

Is this a simplistic overview of the data? Yes. But it is hard to explain away the results without resorting to the environment of upbringing and social interactions of the participants.

Can you please give a reference for that?
I was in a discussion with my very liberal SIL this weekend and could not site a source.

If the tendency for homosexual behavior was purely genetic, then, when one twin exhibits the behavior, the other twin should (in most, if not all cases) also exhibit the behavior. Conversely, when one twin exhibits the tendency for heterosexual behavior, the other twin should also do so.

Even identical twin can recieve different portions of hormones from their mother in the womb. That might explain it.

Capitan,
Do you remember where you read these studies? I'd like to verify the results myself. This article provides some excellent practical guidance to parents of young children. Some of the things I learned: try to get mom to detach a little bit from her boy, have strong male figures in his life who communicate the idea that being a man is terrific, if you homeschool--drive those extra miles to make sure your boy plays with other boys frequently, discourage effeminate behavior in the young boy, etc.
T.W.

Yes, I'd really like a reference on that, too.

The studies show, however, that when one identical twin is homosexual, the other twin is usually not! In fact, the tendency for homosexuality in twins is about the same as in the general population. The conclusion seems to indicate that this is a case of "nurture, not nature."

PLEASE SITE

According to Bailey and Pillard studies -
http://www.worldpolicy.org/globalrights/sexorient/twins.html
you are wrong:
52% of identical (monozygotic) twins of homosexual men were likewise homosexual
22% of fraternal (dizygotic) twins were likewise homosexual
11% of adoptive brothers of homosexual men were likewise homosexual
48% of identical (monozygotic) twins of homosexual women were likewise homosexual (lesbian)
16% of fraternal (dizygotic) twins were likewise homosexual
6% of adoptive sisters of homosexual women were likewise homosexual

At the following site - this study and two others - Kallman (1952) and Heston & Shield (1968) are compared with similar results.

Homosexuality appears to be alot like left-handedness. A right handed person has a right-handed gene, but there is no left-handed gene (yet identified). Those without a right-handed gene can split either way and there are significant brain development difference between those with the gene and those without.

So, homosexuality is not entirely genetic, but it does have a genetic base. The doctors preventive approach above does not appear to be based in anything but wishful science and if worth nothing.