Identical twins, one gay, one straight

[zgnak]

Given that sexual orientation is defined at birth, how is it that one identical twin can be straight, the other gay?

Thanks.

[John Mace]

No one has demonstrated that sexual orientation is defined at birth. Twin studies have shown, I believe, that if you have an identical twin who is gay you only have a 50% chance of being gay yourself. All the evidence points to a complex suit of factors (genes, hormones in the uterus, and others that I can't recall off hand).

I don't think anyone has yet found a gene (or set of genes) that will predict with 100% certainty ANY specific behavior the individual will exhibit if he/she has that gene (or set of genes).

[Urban Ranger]

Originally posted by zgnak
Given that sexual orientation is defined at birth, how is it that one identical twin can be straight, the other gay?

Thanks.

That will be interesting. Do you have any actual cases?

[Walloon]

ABC News: Where Did the Gay Gene Go? (http://abcnews.go.com/sections/living/DailyNews/gaygene990422.html)

World Policy Institute: Twin Studies and Homosexuality (http://www.worldpolicy.org/globalrights/sexorient/twins.html)

ASU Research: Supporting the Biological Link (http://researchmag.asu.edu/stories/supporting.html)

[Dunderman]

Originally posted by zgnak
Given that sexual orientation is defined at birth
At best unproved, at worst unprovable.

[zgnak]

Dear Urban Ranger,

Yes, I know of two gentlemen, identical twins, one is gay, the other straight. There is no ambiguity about their stated orientation.

Thanks for asking.

[Mangetout]

That's hardly an impressive statistic.

[zgnak]

Dear Walloon,

Thank you so much for posting the articles or sexual orientation and identical twins. It helped clear up my confusion even though studies and expert opinions are not definitive.

zgnak