03/18/2010 05:12 am ET Updated Nov 17, 2011

Our Sad Story: The Farce of Sexuality in America

Here's this huge energetic country of 300 million people promoting its way of life as the guiding light of the world -- while under the covers it remains one of the most backward nations on the planet in its understanding of human sexuality. America does move forward, but it's chained to a large boulder of ignorance derived from obsolete religious ideas. We do need an overhaul. Will we break the chain during the 21st century?

Despite the conservative social pundits who continue to look backwards, during the past few decades we've accrued more knowledge about fetal sexual development than during the past five thousand years of human history. We now understand that gender and sexual identity in the fetus are the result of complex interactions between the brain, hormones, and hormonal target tissues, and that input from the environment any time during gestation can twist development in one direction or another.

The idea of hormonal regulation of the sexual differentiation of the reproductive organs of the fetus was introduced in the 1940s as a result of experiments with animals. If testes are removed from fetal male rabbits as soon as they appear, the fetus develops into a female. If testes are removed from a fetal male rabbit and transplanted into a female, the fetus develops into a male. The only reasonable conclusion was that the early fetus has the potential to be either male or female and the outcome depends on hormones secreted by the fetus itself. In the absence of hormonal control, the default development is that of the female reproductive system. A wide variety of early experiments have been repeated many times in many animals, and everything we know about human reproductive biology is consistent with the results of these experiments.

Darwinian evolution has given us the genetic programming for sexual development in the fetus during gestation, but the execution of genetic programming is always dependent on and shaped by environment. Gestation is the period during which each individual's sexuality is first expressed and shaped. Unfortunately, what the general public knows about fetal sexual development is too often based on myth and humbug, on knowledge hardly more advanced than what people knew five thousand years ago. No matter the screeching in the square, the Bible is not a textbook of reproductive biology.

The ancient Greeks believed that the sex of the fetus is determined by the "heat" of the male partner during copulation -- the more heated the passion, the greater the probability of a male fetus. Aristotle advised men to copulate in the summer if they wanted male heirs. The idea became solidified in Western thought and religion and was the common view for the next thousand years into the Middle Ages.

Another myth derived from the ancient Greeks and Aristotle, a myth that lasted through the 15th century and the Renaissance, was the idea that females were simply males whose fetal development had for some reason stopped too early. The female was considered a mutilated male, full development halted because the mother's womb could not overcome the heat of the male semen. This view was accepted by the European Church after declaration by the anatomist Galen in the 2nd century. Since Galen reigned as the supreme authority in anatomy and physiology for a thousand years, this idea of gender lasted until the end of the Middle Ages. In Galen's words:

"Just as mankind is the most perfect of all animals, so within mankind the man is more perfect than the woman, and the reason for this perfection is his excess heat, for heat is Nature's primary instrument... The woman is less perfect than the man in respect to the generative parts. For the parts were formed within her when she was still a fetus, but could not because of the defect in heat emerge and project on the outside."

The general view that environment determines the sex of the fetus persisted until the end of the 19th century, with biologists claiming that constitution, age, nutrition, and environment of the parents were especially important in determining sex at birth. The experts argued that factors favoring the storage of energy and nutrients predisposed the birth of human females, while factors favoring the utilization of energy and nutrients produced human males. Ignorance, in or out of science, easily produces ridiculous ideas.

In one form or another, the general idea of female anatomical inadequacy persists as a social undercurrent today, a relic of the first half of the 20th century when we had a public bemused by media psychologists claiming that the personalities of girls and women are molded by "penis envy" -- by a genital deficiency. The idea derived not only from male ignorance but also from female confusions. Some of us remember an entire generation of female psychoanalysts making the proposition in full force.

Of course the psychologists were only articulating ideas already present in the public psyche. How many mothers, during all these centuries, have hinted to their little daughters while bathing them that little girls are "missing something down there"? To a three- or four-year-old girl, a casual remark about her body can have a non-casual impact on the way she thinks about her body -- a powerful influence on her body-image.

Animals are not always good models for humans, but in this case, what happens in rabbits also happens in our own species. From an embryological standpoint, the penis and clitoris are the same organ in men and women. In the embryo, before the genitals fully form, there's a precursor organ that develops into a penis if it's exposed to certain hormones in the embryonic environment, but otherwise it becomes a clitoris. Does this mean that in principle we can artificially control the genital identity of a developing human fetus? Yes, it's possible in principle. And maybe in a few hundred years or less the control of both biological sex and pychosocial gender will be routine. That's another world--like the past, the future is always another world. We can argue whether such control will be good or bad, but the reality is that if someone can make money providing such control to parents or society, it will likely be done.

Meanwhile, no matter the religionists who hawk ignorance, Americans need to understand that the sexual development of the human fetus is shaped by natural hormonal programming, a consequence of genetics, epigenetics, and a fetal environment often malevolent. As a people, we desperately need more reality in our lives. One reality is that religionists are no more infallible than the rest of us -- with a prime example confused ideas about human sexuality.

Parts of the above text are adapted from More Than Genes: What Science Can Tell Us About Toxic Chemicals, Development, and the Risk to Our Children. Author: Dan Agin. Oxford University Press, 2010.