# What determines sexual orientation/sexuality?

**URL:** <https://boards.straightdope.com/t/what-determines-sexual-orientation-sexuality/770576>\
**Category:** Factual Questions\
**Created:** [November 4, 2016, 1:14am UTC](https://boards.straightdope.com/t/what-determines-sexual-orientation-sexuality/770576 "2016-11-04T01:14:53Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Machinaforce](https://avatars.discourse-cdn.com/v4/letter/m/aeb1de/32.png) [@Machinaforce](https://boards.straightdope.com/u/Machinaforce)\
**Post date:** [November 4, 2016, 1:14am UTC](https://boards.straightdope.com/t/what-determines-sexual-orientation-sexuality/770576/1 "2016-11-04T01:14:53Z")

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> **[No One is Born Gay (or Straight): Here Are 5 Reasons Why](https://socialinqueery.com/2013/03/18/no-one-is-born-gay-or-straight-here-are-5-reasons-why/)**
>
> This post has been elaborated here. 1.  Just because an argument is politically strategic, does not make it true:  A couple of years ago, the Human Rights Campaign, arguably the country’s most powe…

> **[Some Clarifications on “No One is Born Gay”](https://socialinqueery.com/2013/10/31/some-clarifications-on-no-one-is-born-gay/)**
>
> I wrote this post a while back and had I known how many people would read it and how many excellent questions and comments I’d continue to receive, I would have addressed the subject more exhaustiv…

So the above links got me thinking, what exactly forms ones sexuality/orientation?

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**Author:** ![running\_coach](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/running_coach/32/15836_2.png) [@running\_coach](https://boards.straightdope.com/u/running_coach)\
**Post date:** [November 4, 2016, 1:21am UTC](https://boards.straightdope.com/t/what-determines-sexual-orientation-sexuality/770576/2 "2016-11-04T01:21:28Z")

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Reported for forum change.

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**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\
**Post date:** [November 4, 2016, 2:18am UTC](https://boards.straightdope.com/t/what-determines-sexual-orientation-sexuality/770576/3 "2016-11-04T02:18:17Z")

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As I understand it: Identical twins have a higher correlation of sexuality than fraternal twins, and biological siblings have a greater correlation than adopted siblings, which implies that there’s a nonzero component from genetics.  
Fraternal twins have a higher correlation than non-twin siblings, which implies that there’s a nonzero component from the uterine environment (presumably prenatal hormone exposure of some sort).  
Biological siblings raised together have a higher correlation than siblings adopted into different families, and adopted siblings have a higher correlation than random general-population individuals, which implies that there’s a nonzero component from post-birth environmental factors.

Last I heard, the jury was still out on the relative strengths of these three factors, beyond the fact that they’re all nonzero. But research should be getting easier with time, as the social stigma fades away and people become more willing to answer surveys honestly.