having predominantly homosexual attractions

有同性戀傾向

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

許多社會學及政治學理論解釋了同性戀的生成原因

what does science say? Is being gay genetic and,

究竟科學如何解讀？同性戀是否與基因有關？

if so, do we all have a gay gene?

若答案為肯定，是否每個人都有同性戀基因？

In the nineties, two studies using the human genome project

90年代，有兩項以人類染色體進行的研究

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

研究發現比起異性戀，同性戀者有更多同性戀親戚

and that gay siblings have similar linkages

另外，同性戀者的兄弟姊妹

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

X染色體上有相似的區間，顯示出高度基因遺傳性

A more recent study of four hundred and nine gay siblings

近期一項針對409名同性戀手足的研究

also found linkages in a specific region

也發現X染色體上有相似的特定區段

of the X chromosome labelled Xq28

該區段標記為 Xq28

and in another region of chromosome 8.

另一在8號染色體上的區段也與此相關

Furthermore a 2014 analysis of fifty years of research

此外，2014年有人分析了一項歷經50年的研究

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

發現同性戀男性比起直男，更可能有同性戀兄弟

and lesbian women are more likely to have

而同性戀女性更可能有

lesbian sisters, further suggesting the traits are

同性戀姊妹，進一步顯示同性戀

genetically linked and passed on.

與基因有相關聯

But, if homosexuality is, in fact, genetic,

但是，若同性戀確實與基因有關

doesn't this create a paradox?

那會不會產生矛盾？

While some gay people, still have children,

雖然有些同性戀者還是有小孩

overall they have 80% less children than heterosexuals, so

但整體來說，他們的小孩數量比異性戀少了 80%

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

這些基因有無可能沒往下遺傳，最後就消失了？

Well, a recent UCLA study used epigenetics

最近一項UCLA（加州大學洛杉磯分校）的研究以表遺傳學的角度

to propose that everyone has a gay gene,

提出每個人都有同性戀基因

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

但這和附加在DNA某特定區域的甲基團

regions of DNA is triggered and turns it on.

是否被觸發、進而啟動同性戀基因有關

Epigenetics is the study of how your environment

表遺傳學研究環境如何

can chemically modify your genes.

以化學的方式改變您的基因

Like, how a queen ant's nutrition and pheromones

就像蟻后體內的營養和信息素（費洛蒙）

can chemically alter an ant embryo to either produce

能以化學方式改變螞蟻胚胎，同時繁殖出

a soldier or worker ant

兵蟻或工蟻

based on what's needed for the colony.

這一切端視整個蟻群所需

The UCLA study used gay and straight male twins

UCLA透過研究同性戀與非同性戀的男性雙胞胎

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

發現某特定的甲基化結構與性別取向息息相關

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

並能預測男性的性取向，準確率達70%

but this data used a small subset of people,

但此數據來自少數子集內的人

and there is some controversy around the research.

整個研究也存在爭議

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

最終並沒有發現特定的同性戀基因，但科學證據

does suggest that human sexual orientation

的確指出人類的性別取向

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

與基因具強烈關聯，並受分子層面緊密控制

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

研究甚至發現，生下男孩後

increases the odds of homosexuality in the next son

下一個兒子是同性戀的機率

by 33% relative to the baseline population.

會增加33%，此數據與人口基數有關

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

假如是同父異母的哥哥，就沒有影響

This has led some researchers to believe that male pregnancy

這項結果讓研究人員相信懷上男寶寶

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

會觸發某種生物機制，影響媽媽的下一胎

A meta-analysis also found that

一項整合分析也發現

statistically, homosexual men

以統計來看，同性戀男性

have more older brothers than heterosexual men.

有哥哥的機率比異性戀男性高

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

另一項研究發現，女性子宮若睪丸激素量多

have higher rates of being not straight.

寶寶有更高機率成為非異性戀

So, why does this happen?

所以，這到底是怎麼一回事？

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

同性戀叔叔假設解釋，家族中同性戀成員就算不生育

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

仍會增加家族後代的同性戀基因

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

因為他們的後代會接觸到更多和同性戀相關的事物

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

畢竟，這不僅只是適者生存

but the fittest family.

還關係到整個家族

Studies also show that there are lower levels of hostility

研究還指出，同性戀男性敵意較低

and higher levels of emotional intelligence,

有較高的情商

compassion and cooperation in gay men,

更富有同理心及合作精神

which may also increase altruism and survival in human groups.

如此也讓他們在人群中更具利他性及生存能力

Another hypothesis suggests that genes from homosexuality

另一項假設提出同性戀者的基因

are ultimately coding for attraction

讓他們更具吸引力

meaning female relatives of gay men who share the same gene

這表示與同性戀男性享有相同基因的女性親戚

will also have stronger attractions to men,

對男性也更有吸引力

providing an evolutionary advantage.

提供了演化上的優勢

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

此外，研究顯示這些女性平均來說有更多小孩

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

同樣的情形也出現在女同性戀和他們的直男親戚

The famous scientist E.O. Wilson once said

著名的科學家 E.O. Wilson曾說

"Homosexuality gives advantages to the group.

「同性戀給整個群體帶來優勢

A society that condemns homosexuality condemns itself."

社會譴責同性戀也就是在譴責自己。」

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

歷史上，科學界對同性戀族群並不友善

In the past, it was generally accepted that the

過去普遍認為

brains and bodies of homosexuals were presumed to be

同性戀者的大腦和身體

of lower status, with a popular belief that homosexual behaviour

較低等，並深信同性戀行為

was a result of defective development.

是發育上的缺陷所造成

Even some LGBTQ2S people fear that scientific research

甚至有些LGBTQ2S人士害怕科學研究

could "other" the community

可能會把他們變成「另類」族群

and be used to exploit or hurt people.

讓他們受到剝削或傷害

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

從現行的研究來看，大多數的

studies only focus on gay men and neglect other groups.

研究僅針對同性戀男性，卻忽略了其他族群

But more research on the genetic and epigenetic factors of homosexuality

不過與同性戀有關的基因及表遺傳學研究越多

will decrease homophobic laws around the world

就能減少世界上因「恐同」而生的法律

by further proving that being gay is not a choice.

並進一步證明同性戀是無法選擇的

But, could we ever genetically get rid of homosexuality?

不過我們能從基因上根除同性戀嗎？

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

請收看第二集影片，我們將討論其可能性及

of continued study into this field.

該領域未來的研究方向

And subscribe for more weekly science videos every Thursday.

歡迎訂閱本頻道收看更多科普影片，每週四見