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Study of identical twins shows homosexuality is not genetic


Being gay is not in our genes.

Being gay is not in our genes.

For the past several years, some have claimed same-sex leanings are genetic. This means people have no control over their desires and can’t change.

However there has been one major problem with this theory namely identical twins. Identical twins have the same genetic make up, so if one twin was gay the other should automatically be gay as well, if it is based on genes.

However, this is not the case and it was confirmed again in a recent study conducted by the University of California (UCLA). In this study, researchers looked at the the genetic make up of 27 identical twins where at least one twin was gay and ten sets where both were gay.

The researchers concluded that environment, not genetics, determined if a person was gay or not.

While we have our basic genes that determine our make up, there is another molecular layer of information called “epigenetics” that influences how we live.

This layer has the ability to affect our genes. It is described as “molecular switches” that they believe turn genes off or on.

The Telegraph describes the layer this way:

“epigenetics act as another layer of information which parts of the [genetic] text are important and which can be ignored.”

However, this switch layer is formed by our environment that can include a variety of things such as “parental nurture”, abuse, chemicals, stress, diet and even exercise, etc.

It is outside factors such as these that affect our sexual leanings not genetics.

In an interview with the The Telegraph, Tim Spector professor of Genetic Epidemiology at London’s King College, said:

“It has always been a mystery why identical twins who share all their genes can vary in homosexuality.”

He added that “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.”

The UCLA researchers claimed by studying the epigenetics they had a 70% accuracy in determining a person’s sexual orientation. Others questioned this accuracy because of the small sample size.

This is not the first study of identical twins to show that homosexuality is not genetic.

There have been huge databases compiled in both the US, Europe and Australia of identical twins. Containing information on tens of thousand of identical twins, these repositories provide researchers with an incredible amount of data for genetic research.

According to Dr. Neil Whitehead, who holds a PhD in statistics and biochemistry, these studies have shown repeatedly that being gay is not based on genetics but rather a person’s environment.

Whitehead says “no one is born gay.” Instead there was something in one twin’s environment that led to the person being gay that was not in the other twin’s. He calls them “non-shared factors.”

He also added it’s possible the two shared similar experiences, but the two responded differently. In other words it was a choice.

A 2002 study of tens of thousands of US identical twin showed that if one twin was gay there was only a 5.5% chance the other was gay for women and 7.7% chance for men.

A 2000 study of 25,000 Australian twins came to a similar conclusion. If one twin was gay there was only 11% chance the other was gay for men and 14% for women.

Other studies done in Australia, Scandinavia and US involving smaller sample sizes had less of a correlation. These studies showed that if one of the twins was homosexual the chances the other was homosexual ranged from 5% to 7%.

Though these are higher than the 3% homosexuality rate for the wider population, it may reflect that twins often share similar environments to some extent.

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