from A Separate Creation: The Search for the Biological Origins of Sexual Orientation by Chandler Burr
This page provides the answer to a puzzle called "What is the Trait".
Please first read: The characteristics of that human trait.
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Human handedness, of course. Human handedness is a stable, behavioral bimodal
polymorphism with the majority orientation, right-handedness, expressed in
over 90% of the population and the minority orientation, left-handedness, in
around 8%. There are very few truly ambidextrous people, and the art history
evidence suggests these ratios or right-, left-, and ambi-dexterity have been
constant for five millennia. Handedness is interesting in relation to the
trait we will be looking at in this book, sexual orientation, because of the
striking similarities between the two. Those who know the literature would
know immediately that the trait profile above is not for sexual orientation,
which differs from handedness in several ways: the population ratios for each
trait's two orientations vary somewhat (while left-handed people comprise 8%
of the population, the current figures for homosexuals is between 2 and 6%),
and identical twin (MZ) concordance figures are radically different. Twin
concordance for left-handedness is 12% against a background rate of 8%
whereas for homosexuality, MZ concordance is 50% against a background of only
around 5%, indicating that homosexuality has a much higher purely genetic
component that left-handedness. (Also, and more subtly, the telltale
"maternal effects" which both traits display are expressed somewhat
differently.)
But these are the exceptions highlighting the fact that the trait profiles of the two are extraordinarily alike, and virtually everything we know about the one, we know about the other. Neither left and right-handedness nor hetero and homo-sexual orientation can be identified simply by looking at a person. Since both are internal orientations, the only way to identify them is by the respective behaviors that express them, motor reflex and sexual response. Handedness shows up in children starting at age two or before, and John Money of Johns Hopkins University puts the age of the first signs of sexual orientation at the same age. Neither left-handedness nor homosexuality correlates with any disease or mental illness (although there are studies showing a higher correlation between left-handedness and, for example, schizophrenia.) The grammar school coercion of left-handed children to use their right hands was ended years ago. They also function well as working analogies. If you are right-handed, take a pen in your left-hand and try to write your name. With some effort, you can probably get it down semi-legibly, but the fact that you have engaged in left-handed behavior does not make you left-handed. Behavior is irrelevant; the orientation you have is what counts. And you are just as right-handed sitting still watching a movie as when swinging a tennis racquet with your right-hand. Did you choose to be right-handed? No? Then prove it. (You can't; as one clinical researcher noted tersely, "Science can't 'prove' you don't choose to have appendicitis.") Just as obviously, an interiorly heterosexual person is not homosexual even in the midst of homosexual intercourse, behavior (when it does not reflect the interior orientation) is irrelevant, and a homosexual is equally homosexual during the sex act and driving a car. Incidentally, we actually know less currently about the biological origins of handedness than about those of sexual orientation. No one so far has done any genetic work on handedness, but scientists have started finding genes for sexual orientation.
ADDENDUM: A NOTE ON THE NEWS MEDIAThere is one interesting difference between handedness and sexual orientation: The news media has a ridiculous double standard for the trait "sexual orientation" and every other trait. ABC's science journalist David Marash reported on Nightline that a gay gene "suggests that homosexuality may not be a choice." This is absurd. Marash is suggesting that unless we locate a gene for homosexuality, homosexuality is a choice (or, at a minimum, that we can t know whether it is chosen or not). This is the equivalent of saying that since we haven't found the gene that governs left-handedness-- and we haven't lefthandedness is a choice (or, at a minimum, we can't determine if it is). Scientists know you don t need to look at a gene to determine if a trait is chosen; you need to look at the trait. And we have looked, at both of them.Among scientists today, this issue of choice is as dead an issue for the trait "human sexual orientation" as it is for the trait "human handedness." Unfortunately, ABC (and NBC, Time, The Washington Post, etc. etc.) have not caught up with this yet. |
from A Separate Creation: The Search for the Biological Origins of Sexual Orientation by Chandler Burr