Chromosomes, hormones and culture
Published on -10/1/2012, 10:06 AM
Our last column offered left-handedness as an analogy for non-traditional sexual identity/orientation (SISO). This isn't so far-fetched.
The Latin word for "left" is "sinister." Lefties were regarded with suspicion or hostility, thought to be in league with the devil. That Latin word has come to mean "ominous, threatening," though today left-handedness is correctly considered a normal variation.
SISO has been with us since our species dawned. When our ancestors were hunter-gatherers, SISO behavior was regarded as diverse, not deviant. Surviving hunter-gatherer cultures tend to demonstrate this tolerance. For example, many Amerindians saw transitional sexes in nature. Lakota transsexuals were termed "winkte," considered special and powerful beings, sometimes playing important ceremonial roles. Zunis and Hopis recognized the berdache, or man-woman, a structural male who feels and acts like a woman, and marries a man.
However, when humans settled into agricultural communities, land ownership became an issue for the first time. A family's land couldn't be subdivided equally among their children very many times before each parcel would be inadequate.
But it was still important to keep land in the family. A patrilinear system evolved -- typically, a man's oldest son inherited all the land. His male siblings could stay on to help work the farm, or strike out on their own.
SISO offspring could not contribute to a continuing lineage. As guarantors of the land's ongoing family ownership, they were worthless.
And they were obviously different. So as patriarchal systems consolidated, SISO's became persona non grata, eventually subjected to demonization and even execution.
What started as a practical, if unfair, distinction led to outright prejudice and ostracism. Such is the history of the patriarchal Religions of the Book -- Judaism, Christianity and Islam. Even Buddhism and Hinduism developed antagonism to SISO.
Humans were copulating long before we understood concepts such as fertility and paternity. Randy cavemen didn't say "let's do that thing that feels good, so we can have a baby to raise."
The pleasure associated with the sex act itself evolved as a "piggyback" phenomenon, naturally selected because it enhances the likelihood of sexual exchange and species survival. Pleasure, or just alleviating an intense physiologic drive (such as impels a male mantis to seek potentially fatal sexual encounters), underlies much of the allure of sex and came to overshadow its reproductive function. (Plants have sex too, but it's passive.)
The sex drive is powerful, but like most human attributes, it's subject to extensive variation.
There is clear evidence that a variable genetic predisposition to SISO exists among humans. Developmental influences, such as intrauterine exposure to outside hormones or disrupted maternal hormone production, can also radically alter a person's sexual makeup.
It's unlikely that a single gene "controls" sexual development; more likely, it's a cluster of genes, or interacting gene complexes. People who carry the gene might nonetheless be straight heterosexuals, since the gene might not "turn on" in the absence of specific environmental triggers.
It's common for genes and environment to collaborate in producing observable traits. Baby ducks are genetically disposed to "imprint" on the first figure they see after hatching, leading to long-term bonding with the being upon which they imprint.
Even if that being is a dog, or a human, the duckling will go right ahead and imprint on it. Both genes and environment interact to produce those cutesy pictures of ducklings lined up to follow a dog across the street.
Sexuality is an extremely complex phenomenon, and the combination of genetics, epigenetics, pre-birth hormonal and other chemical exposures, and environment is difficult to unravel. All components play their roles.
When the process gets diverted in any of many ways, the result might strike us as bizarre. A person can develop "fetishes," which focus sexuality on normally non-sexual objects -- feet, hats, even seeing a balloon popped! He or she does not, and probably cannot, "choose" to find balloons arousing. Nor can he/she explain it, in terms of upbringing or culture; it's just the way it is.
In humans, the intrauterine hormonal environment has a lot to do with sexual development. The end product can be typical heterosexuality, though many "normal" people's heterosexuality is anything but "typical." Homosexuality can occur -- for example, a man who regards himself as a man is attracted to other men. A bisexual woman might be attracted to both men and women, but experiences herself as a woman. A transsexual who possesses male genitalia might consider herself to be a woman; her attraction to males is not homosexual.
Sexuality is much, much more than a particular set of genitalia, or of genes, for that matter.
For those who think that a particular bodily construction absolutely defines a person's sexuality -- a Y chromosome and a phallus makes you "male," and that's all there is to it -- I submit this question: is your deity male or female? If the answer is "male," does this deity possess a Y chromosome or male genitalia? If your god is a "spirit," and has no body at all (except for the occasional incarnation as Homo sapiens), either it can't be male, or any specific physical gender package is optional. Sex is also a state of mind.
It's not uncommon for babies to be born with "ambiguous genitalia," which don't fall clearly into any gender category. "Male" babies raised as females don't generally develop into homosexual males, and certainly not into females, despite parents' best efforts.
* Next time: Sexes, brains and judgments.
Jon Hauxwell, MD, is a retired family physician who grew up in Stockton and now lives outside Hays. firstname.lastname@example.org