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.