Homosexuality is not written in the genes, major study discovers

GENES play just a small role in whether a person is gay, scientists have found, after discovering that environment has a far bigger impact on homosexuality.

In the biggest ever study into the genetic basis of sexuality, researchers from more than 30 institutions including Cambridge University and Harvard, looked at the DNA of nearly 500,000 people in Britain and the US.

They found that genes were responsible for between eight to 25 per cent of the probability of a person being gay, meaning at least three quarters is down to environment.

Scientists said it worked in a similar way to height, in which genes are partly responsible, but other factors – such as nutrition – also play a major role, adding or knocking off inches.

In this case, environment could mean anything from being exposed to certain conditions in the womb to differences in upbringing or education.

Although the research may seem controversial, suggesting that homosexuality is not primarily “written in the genes”, the scientists say it does not mean that sexuality is a choice or can be altered. “Some people will misunderstand or even deliberately twist our findings,” said Dr Ben Neale, the senior author and a statistical geneticist at Harvard Medical School.

“There is a long history of people using genetics in harmful ways to advance their own misguided agendas.

“As a gay man, I’ve experienced homophobia and I’ve felt both hurt and isolated by it. This study disproves the notion there is a so-called ‘gay gene’ and disproves sexual behaviour is a choice. Genetics absolutely plays an important role, many genes are involved, and altogether they capture perhaps a quarter of same-sex sexual behaviour, which means genetics isn’t even half the story. The rest is likely [to be] environmental.

“It’s both biology and environment working together in incredibly complicated ways.”

Previously, research has suggested there could be multiple genetic variations in the X chromosome of men, driving homosexuality, but the new study ruled that out.

Instead it found a large number of genes were having a tiny effect. Even

‘It’s both biology and environment working together in incredibly complicated ways’

the five gene areas which had the most impact only had a cumulative impact of just 1 per cent.

The new study, which involved 100 times more people than previous research, used DNA data from the genetic testing service “23andme” and the UK Biobank.

They found one important area of DNA was linked to genes related to sense of smell, which is known to be important for sexual attraction.

However, the genetic picture is so complex, the researchers concluded, that it will never be possible to determine whether someone is gay simply by looking at their DNA.

Researchers said the findings should be reassuring to people who were worried that genetic testing may one day reveal their sexuality.

“The research was published in the journal Science.