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09th Oct 2015

Twins study suggests homosexuality ‘may be triggered by environment’

Katie Mythen-Lynch

Controversial new research suggests that environmental influences after birth could have a bigger part to play in affecting sexual orientation in boys than previously thought.

Scientists now believe they can predict if someone is gay or straight simply by examining their DNA – with up to 70 per cent accuracy.

Diet and exercise, stress, exposure to certain chemicals and childhood abuse were all taken into account in a small study of 37 sets of male identical twins, where only one brother was gay.

Previous studies suggest that only 20 per cent of identical twins are both gay, leading scientists to investigate whether tiny changes in DNA function, triggered by environmental and life events, could determine how a person develops.

The University of California research, which remains unpublished, is currently being discussed at the annual meeting of the American Society of Human Genetics in Baltimore.

According to Dr Tuck Ngun, from the University of California, LA: ‘To our knowledge, this is the first example of a predictive model for sexual orientation based on molecular markers.’

Dr Ngun added: ‘Sexual attraction is such a fundamental part of life, but it’s not something we know a lot about at the genetic and molecular level.

‘I hope that this research helps us understand ourselves better and why we are the way we are.’

While the study is certainly intriguing, the method is still more than 30 per cent inaccurate, leading many experts in the field to take the findings with a pinch of salt.

Prof Darren Griffin, Professor of Genetics at the University of Kent said he waits “with baited breath” for a full peer-reviewed article:

“While there is strong evidence in general for a biological basis for homosexuality my personal impression has always been one of a multiple contributory factors, including life experiences.” he said.

“My gut feeling it that, as the complete story unfolds, the association may not be quite as simple as suggested.

“To claim a 70 per cent predictive value of something as complex as homosexuality is bold indeed.”

Speaking to New Scientist, Dr. Ngun himself revealed he has concerns that the test has the potential to be abused. “I’m gay,” he says, “and I’ve always wondered why I am the way I am. But once you have this information, you can’t control how it’s used or disseminated.”

Do you believe environmental factors can affect a person’s sexuality? Join the conversation on Twitter @HerFamilydotie.