having predominantly homosexual attractions

and, while there are many social and political theories on why,

what does science say? Is being gay genetic and,

if so, do we all have a gay gene?

In the nineties, two studies using the human genome project

found that gay men have a higher number of homosexual relatives compared to heterosexual men

and that gay siblings have similar linkages

on their X chromosome, showing a high level of genetic heritability.

A more recent study of four hundred and nine gay siblings

also found linkages in a specific region

of the X chromosome labelled Xq28

and in another region of chromosome 8.

Furthermore a 2014 analysis of fifty years of research

found gay men are more likely to have gay brothers compared to straight men

and lesbian women are more likely to have

lesbian sisters, further suggesting the traits are

genetically linked and passed on.

But, if homosexuality is, in fact, genetic,

doesn't this create a paradox?

While some gay people, still have children,

overall they have 80% less children than heterosexuals, so

wouldn't the genes not be passed down and eventually die out?

Well, a recent UCLA study used epigenetics

to propose that everyone has a gay gene,

but it's whether or not the attachment of a methyl group to specific

regions of DNA is triggered and turns it on.

Epigenetics is the study of how your environment

can chemically modify your genes.

Like, how a queen ant's nutrition and pheromones

can chemically alter an ant embryo to either produce

a soldier or worker ant

based on what's needed for the colony.

The UCLA study used gay and straight male twins

and found that a specific methylation pattern was closely linked to sexual orientation.

The model was able to predict the sexuality of men with 70% accuracy,

but this data used a small subset of people,

and there is some controversy around the research.

Ultimately, a specific gay gene has not been found, but scientific evidence

does suggest that human sexual orientation

is strongly linked to genetics and tightly regulated at the molecular level.

It's even been found that giving birth to a son

increases the odds of homosexuality in the next son

by 33% relative to the baseline population.

If an older brother is from a different mother, there is no effect seen.

This has led some researchers to believe that male pregnancy

triggers a biological mechanism that affects the mother's successive births.

A meta-analysis also found that

statistically, homosexual men

have more older brothers than heterosexual men.

Another study found that women exposed to high levels of testosterone in utero

have higher rates of being not straight.

So, why does this happen?

The gay uncle hypothesis suggests that gay members of a family that don't reproduce

still increase the prevalence of their family's genes in future generations

by helping to provide resources for offspring that they're related to.

After all, it's not just survival of the fittest individual,

but the fittest family.

Studies also show that there are lower levels of hostility

and higher levels of emotional intelligence,

compassion and cooperation in gay men,

which may also increase altruism and survival in human groups.

Another hypothesis suggests that genes from homosexuality

are ultimately coding for attraction

meaning female relatives of gay men who share the same gene

will also have stronger attractions to men,

providing an evolutionary advantage.

And, studies have shown that these females have more babies on average.

The same would be true of lesbians and their straight male relatives.

The famous scientist E.O. Wilson once said

"Homosexuality gives advantages to the group.

A society that condemns homosexuality condemns itself."

Historically, science has not been kind to the queer community.

In the past, it was generally accepted that the

brains and bodies of homosexuals were presumed to be

of lower status, with a popular belief that homosexual behaviour

was a result of defective development.

Even some LGBTQ2S people fear that scientific research

could "other" the community

and be used to exploit or hurt people.

Even from the available research, it's clear that most

studies only focus on gay men and neglect other groups.

But more research on the genetic and epigenetic factors of homosexuality

will decrease homophobic laws around the world

by further proving that being gay is not a choice.

But, could we ever genetically get rid of homosexuality?

Watch our second video where we discuss if it's possible and the implications

of continued study into this field.

And subscribe for more weekly science videos every Thursday.