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The Science of Sexual Preference

By Duke Heath

Many people believe that sexual orientation is just a choice. For me, it is far more than a choice, it is who I am. I am attracted only to females. I am heterosexual to the core. Others are not so adamant that their sexual activity should exclude same sex individuals. There are still others who are homosexual to the core and have absolutely no interest in the opposite sex. Which ever group one may fall into, the final decision is simply a matter of choice...or is it? What factors lead one group to make a different choice than another group? This essay is a look at one of the main factors which influence sexual preference. For most of us, the actual act of sexual choice was made long ago by the molecules with which we came in contact while still within the womb.

Evolution has invested billions of years in fine tuning the reproductive urges of all creatures big and small. Without the urge to have sex, species would become extinct. From the evolutionary aspect, there is no urge more important to a species: not eating, not sleeping and not self preservation.

Other than man, no creature associates the sex act with reproduction, with keeping the species going. Even early man, at first, could not have associated sex with giving birth. Nature, therefore, has had to create, not only, an overwhelming need for sex, but also rewards for having sex to encourage creatures to procreate. How does nature accomplish this feat? With the help of a magic substance called hormones. It is because of hormones that a male black widow spider will risk being eaten alive by his mate just to ensure that his DNA will mix with her DNA and produce a new generation of arachnids. We are but the end result of chemical reactions within our bodies and the master chemical which controls our sexual nature is the hormone testosterone.

The power of testosterone is so great that a genetically male embryo deprived of testosterone will be born with what appear to be female genitals. Without testosterone, mammals develop phenotypically as females. Likewise, a genetically female embryo, if exposed to slightly higher than normal concentrations of testosterone, will develop normal looking male genitals. The clitoris enlarges to become a normal looking penis and the labia join to form a scrotum with no testicles.

Androgenital Syndrome is a genetic metabolic disorder characterized by overproduction of male sex hormones. In females, this syndrome is manifested by ambiguous genitalia, deep voice and partial masculinization of female behavior. One in every two thousand babies are born with genitalia which make it difficult to determine its genetic sex. This is caused by either a little too much or too little testosterone exposure in the first few weeks of pregnancy.

Concerning these facts, Carl Sagan states in Shadows of Forgotten Ancestors, "If so great a physical change can be caused by a little more or a little less exposure to testosterone in the first weeks of embryonic life, it seems reasonable to assume that even more subtle changes in embryonic testosterone exposure levels could affect the sexual appetite and preference of the individual as an adult."

Studies show that where there are multiple births, such as twins or triplets, where there are both male and female sharing the womb at the same time, the female is exposed to higher than normal levels of testosterone from the male. Females who were exposed to higher than normal levels of testosterone in the womb tend to prefer guns and cars to dolls, boy to girl playmates, and enjoy rough housing and the outdoors more so than the "average" female. They may also find women more sexually attracting than men.

Prenatal and early infant hormone exposure also has profound effects on rats. Male rats which were castrated at birth displayed lordosis, the typical female act of submitting for mounting, as adults. Other studies similar to this one seem to prove that testosterone levels before as well as shortly after birth, dictate sexual preference in adult rats. With these studies on both humans and rats, it seems reasonable to conclude that one of the main, if not the chief determining factor in an adult's sexual preference is the amount of testosterone exposure experienced in the womb. A recent study of cochlear sensitivity of humans seems to confirm this theory. It was found that heterosexual women have a cochlear sensitivity three times greater than a male. Lesbian females, however, displayed the same level of sensitivity as males. Cochlear development occurs before birth. Cochlear development and sensitivity are attributed to prenatal exposure to testosterone related hormones called androgens.

The conclusion the scientists drew from this study is that because the physical trait of sensitivity is linked to androgen exposure and lesbian cochlear sensitivity is more similar to men than to heterosexual women, "the auditory systems of homosexual females and the brain structures responsible for sexual orientation have been masculinized by exposure to high levels of androgens prenatally."

We all know individuals who seemed to be gay since kindergarten or earlier. It is as if they had been born gay. They were, just as most of us were born heterosexual.

The real question on this issue, however, is not what factors shaped these individuals to make the choices they do. The real question is whose business is it what choice someone else may make in their private life.