Although sexual orientation and love may be seen by some as being very different topics, they are so interconnected that both must be addressed in order to come to a full understanding of homosexual relationships. When attempting to determine the causes of homosexuality, one theme that comes up often is the question of whether our sexual orientation is caused by our genes or our environment. In other words, is it due to Nature or Nurture? Researchers began looking into this by examining the differences between males and females and their scores on the Kinsey Scale. The Kinsey Scale, developed by early sex researcher Alfred Kinsey in the late 1940s and early 1950s, is a scale that rates sexual orientation from 0 to 6, where 0 indicates exclusive heterosexuality and 6 indicates exclusive homosexuality. Kinsey believed that sexual orientation was not black and white, and that most people would score somewhere in between 0 and 6.
Here is what the Kinsey Scale looks like:
| 0 | Exclusively heterosexual with no homosexual |
| 1 | Predominately heterosexual, only incidentally homosexual |
| 2 | Predominately heterosexual, but more than incidentally homosexual |
| 3 | Equally heterosexual and homosexual |
| 4 | Predominately homosexual, but more than incidentally heterosexual |
| 5 | Predominately homosexual, only incidentally heterosexual |
| 6 | Exclusively homosexual |
When examining the Kinsey scores of males and females, researchers found that males appeared to be more rigid in their sexuality. Most often males were either exclusively heterosexual or exclusively homosexual. Females, on the other hand, were more spread out along the scale, showing varying degrees of bisexuality. Also, it was found that males almost always retained the same sexual orientation for their entire lives, while females sometimes changed orientations one or more times.
To see a page that has more information and statistics about the Kinsey Scale, click here.
As a result of the Kinsey Scale findings and other observations, researchers noticed that male sexual orientation seemed like a genetically influenced trait. Because the males were either straight or gay, and their orientation lasted their entire lives, it made sense that this trait might be hard-wired into their genes . Female sexual orientation, however, did not display as many genetic characteristics. Because it was less permanent and more continuous, it seemed more like a trait that came from the environment.
To further explore this possible dichotomy between males and females, researchers examined the family trees of both male and female homosexuals to see if there was any evidence that their sexual orientation ran in their families. In both the males and females, it was found that homosexuality did cluster in families. This did not necessarily prove that it was a genetic trait, however, since families also share a common environment. Upon further investigation it was found that, for the males, most of the homosexuals were related through their mothers. Since males receive their X chromosomes from their mothers, this was seen as evidence that homosexuality in men was at least partially a genetically linked trait. For women, however, the findings were different. It was found that daughters of lesbians were 33% more likely to become lesbians themselves, while sisters only had a 6% chance. Genetically, the findings were impossible, so researchers came to the conclusion that female homosexuality, unlike that of their male counterparts, must be somehow transmitted socially. In other words, male homosexuality was found to be primarily genetic, while female homosexuality was found to be primarily environmental.
The next step for researchers was to look for a gene that made males gay. Hamer and Copeland (1998) studied gay brothers hoping to find some kind of linkage on the X chromosome, and they found a region that was shared by 86% of the gay males. In straight males, the same region was found to be shared only 22% of the time, confirming that it played some role in sexual orientation. Although the particular gene has not yet been located, these findings are encouraging to geneticists. It is likely that researchers are well on their way to proving that there is a definite genetic basis for male homosexuality. However, twin studies have showed that homosexuality is only 50% inherited, so there are many other factors at play. Although genes account for half of a male's sexual orientation, the role of the environment cannot be ignored.
References:
Hamer, D. & Copeland, P. (1998). Living with our genes. New York: Anchor Books.
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