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  • Two to six percent of people self-identify as

  • 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.

Two to six percent of people self-identify as

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B1 US gay homosexuality gay men homosexual gene chromosome

Does Everybody Have A Gay Gene?

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    韓澐 posted on 2017/07/28
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