FactCheck Q&A: are people born gay?

Kevin Rudd rebukes Pastor Matt Prater on the issue of gay marriage. View the segment here. Source: ABC News.

“I do not believe people, when they are born, choose their sexuality. They are gay if they are born gay.” - Prime Minister Kevin Rudd, ABC TV’s Q&A, 2 September.

Responding to a question from audience member and Christian pastor Matt Prater about the Prime Minister’s support for same-sex marriage, Rudd defended his position by using the starting point that gay people are born that way, rather than deciding at some later stage to be straight or gay.

Many people using social media applauded the PM’s comments, which have since gone viral through YouTube, with well over 300,000 views of the ABC segment in less than 72 hours. However, others have said they felt Rudd was rude to Prater.

Listing several reasons for his recent change of heart on same-sex marriage, Rudd said in part:

“I concluded in my conscience, through an informed conscience and a Christian conscience, it was the right thing to do. And let me tell you why. Number one, I do not believe people, when they are born, choose their sexuality. They are gay if they are born gay. You don’t decide at some later stage in life to be one thing or the other. It is - it is how people are built and, therefore, the idea that this is somehow an abnormal condition is just wrong.” (Read the full Q&A transcript here.)

The debate over whether people are “born gay” has been an active one for several years, but what does the current science indicate?

The best evidence comes from twin studies, which point to a strong genetic influence on sexual orientation.

Twin studies examine many pairs of identical (100% genetically similar) and non-identical (50% genetically similar) twins. These studies invariably show that non-identical twin pairs are more likely than random pairs in the population to have the same sexual orientation, and that identical twin pairs are more likely than non-identical twin pairs to have the same sexual orientation, consistent with a genetic influence on sexual orientation.

Statistical modelling of the concordance patterns suggests that genetic differences account for around 30-50% of the variation in sexual orientation between individuals in the population.

While it is clear that there are substantial genetic influences on sexual orientation, it is just as clear that genes are not the whole story; even identical twins often differ in sexual orientation.

There is some evidence that there are non-genetic influences on sexual orientation that also occur before birth. Evidence from animals and humans suggest that exposure to unusual levels of sex-hormones in the womb can affect later sexual orientation through masculinisation or feminisation of the developing brain.

A strict interpretation of the phrase “born gay” would imply that sexual orientation is fixed at birth and cannot be subsequently influenced. It is not clear whether or not this is true.

There is evidence for an association between adverse childhood experiences and later same-sex attraction. However, the causality of this relationship has not been established. In any case, any influence of childhood experiences on later sexual orientation would not constitute a decision to be gay, which Rudd contrasts with being “born gay”.

In contrast, it appears that choice does not play an important role in the attraction component of sexual orientation (that is, attraction to opposite- or same-sex individuals). Research suggests that same-sex attracted people who try to “choose” to be straight, such as by undertaking “conversion therapy”, cannot do so any more than straight people can “choose” to be gay.

Verdict

The current evidence suggests there are strong genetic factors influencing sexual orientation. But genetics are not the whole story, and it is not clear whether sexual orientation is fixed at birth or not. Kevin Rudd is partly right.

The Conversation is fact checking statements made in the lead-up to this year’s federal election. Normally, these are reviewed. But each week, we will also check significant factual assertions on the ABC’s Q&A program. To allow us to publish these checks as soon as possible, there will be no review process. Request a check at checkit@theconversation.edu.au. Please include the statement you would like us to check, the date it was made, and a link if possible.

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