Sex

I think it is probably politically incorrect to assert that there are biological differences between men and women (males and females). Certain feminists really get upset with me when I bring it up. Still, there are differences (duh, say my two daughters). Are the differences subtle or dramatic? Well, we'll never know if we don't talk about it and study it. I prefer scientific method (descriptive and experimental) for such topics.

I believe there are significant (meaningful) differences between males and females of the human species. Even if the differences are subtle (which is a relative, non-scientific kind of term to use), they can still be significant. It is often said, for example, that the differences between Neandertals and Early Modern Homo Sapiens are "subtle." We survived, however, and they didn't.

The study of sex leads us directly into issues of theory, analysis, philosophy and ethics in ways that I think are unparalleled in the rest of science. Nowhere does science impinge so directly on culture as in the study of sex and gender. The complexities of the science of sex are beyond the scope of the average undergraduate college student (even the ones at the elite schools). Most people in America don't know what a bell-shaped curve is, much less how more complex diagrams work (and what they imply). When we speak of curves, bell-shaped, bimodal or otherwise, we lose the average person. Overlapping, shifting, dynamic curves are worse still. Bell-shaped curves deal with one variable at a time, think what happens when we begin to add in the complexities of the real world. When you get to genes, polymorphisms, structures of X and Y chromosomes, polygenic traits, hormones, hormone precursors, hormone receptors, hormone byproducts (and more) and put it all in your dynamic model...it's probably more than anyone can conceptualize right now.

This is another way of saying that a good, honest scientist will tell you the entire picture of sex is not simple. It is not yet completely understood. To make statements about sex as if all the data were in and it is all well understood is scientifically impossible. Such statements are politically, not scientifically motivated.

Simplistic, incomplete understandings of biology are the ones most prone to political misuse (by feminists/anti-patriarchalists and by pro-patriarchalists). I make some fairly straightforward assumptions in my work that these groups of people don't make:

Both sexes are always going to be around, in fairly equal numbers.

People should be treated fairly and with equal dignity, regardless of their biology.

Treating people as if they are identical is not a form of equality or fairness: it is a form of socialism and represents a political point of view.

As an anthropologist, I am very interested in human variation. I find it truly absurd that some people would hold that everyone should be treated exactly the same. You surely would not want me to sing at your wedding. And I don't want a blind taxi driver. Ethical, humane treatment of people takes into account their variation, it does not try to ignore or suppress it. One of the scariest scenarios I can imagine would be to take the mid-point of some curve and then structure an entire society around it. So long, Mozart. Good-bye, Virginia Woolf.

Having said all this, then, here are the central questions I'm going to try and address:

What are the differences between men and women?

How much variation is there within each sex?

How much variation is there between sexes?

What biological processes determine sex?

How did primate and human evolution shape sex in homo sapiens?

In what way have sex differences been helpful to humans? Not helpful?

How is sex related to gender?

When I speak of biology, it comes naturally to me to say "male" and "female." The words "men" and "women" connote the fully constructed, biocultural entities around us. Interestingly, I was recently criticized on the usenet for using the term "male" instead of "men" by a man who felt dehumanized by the word. I use "male" and "female" to refer to the biological substrates that confer sex upon us, for an analytic reason. I intend no dehumanization.

There are generally thought to be two sexes in the human species: male and female. This is a pretty widespread phenomenon in the animal kingdom. Human beings have a species name: homo sapiens sapiens. We're primates, and we're mammals. We reproduce sexually. I say all this to avoid confusion about who I mean when I say "we." I usually mean "homo sapiens sapiens." If I want to include our nearest cousins, I'll say "hominids." If I want to go a little wider on the family tree, I'll say primates or mammals. Just to keep things clear. All mammals and all primates reproduce sexually, of course. Sexual reproduction is thought to have evolved around 660 million years ago. Many plants reproduce sexually, too (not just animals). So it's a pretty common thing. I am an anthropologist, so I'm interested in everything human (homo sapiens sapiens) and everything primate.

As with anything human, there are immediate controversies and problems with definitions. Males are often said to be chromosomally XY and females are chromosomally XX. If you don't know what chromosomes are, they're made of DNA (dioxyribonucleic acid), a complex protein inside every cell in the body of every living thing. You can go to www.google.com and type in "DNA tutorial" or "basics about chromosomes" and get a bunch of pages to look through.

Many medical scientists classify people with an XY in the 23rd chromosomal position but with androgen insensitivity as women.

Take a look at the slides on this site:

University of Texas Slide Show on Sex

Note that the medical researcher uses the word "women" to refer to these XY chromosome people. That's because there is widespread scientific consensus these days that chromosomes are not enough to create sex. Instead, it is hormones that create and maintain maleness and femaleness. While it is obviously the case that genes underlie hormonal patterns, it is also the case that genes may underlie syndromes such as androgen insensitivity. And if a person with an XY chromosomal pattern begins to experience a loss (or relative lack of) testosterone, and therefore grows breasts or begins to produce breast milk (after having spent his life as male), try telling him that it's okay, he's still got those XY chromosomes. (For a case in which this actually occurred, look up Ken Baker's recent book: Man Made, for this is what he experienced).

A student of mine had a girlfriend. She was XX chromosomally and a female bodybuilder. She began to take anabolic steroids of a type that block production and uptake of estrogen in her body. While, as a woman, she produced very little testosterone, when estrogen was made unavailable, the receptors in her body cells that are looking for sex hormones took up testosterone instead. It didn't matter how much testosterone she had, it only mattered that it was only testosterone that was available. Her muscles increased in size and definition. Her jaw grew larger. Eventually, her voice deepened and she lost body fat all over (including her breasts). She grew body hair and had to shave. Her clitoris enlarged.

At that point, the student was challenged. He had been with this woman for two years. He had been very attracted and committed to her. But he was no longer able to experience sexual arousal in her presence. To his way of thinking, she had become a man. He did a poster project about her for class. The class looked at the pictures and agreed, she seemed to have become a man. The girlfriend's gender identity never changed (she still wore feminine clothing most of the time and thought of herself as a woman; she was still attracted to him). Was she a man or a woman at this point?

So. It's a lot about hormones (and their interaction with various tissues AND other molecules in the body). The next few pages will give you a general background and prepare you to understand some of the more complex research (some of which is published on the web). Note that I have not grouped the hormones by sex, because both sexes can and do have all these hormones. However, some of these hormones are strongly related to chromosomal sex, as you shall see.

The average man and the average woman and their average hormones

The not so average folks

Estrogen and its effects (More dendrites in the brain?)

Testosterone and its effects (Greater sex drive? More aggression?)

Progesterone and its effects (Estrogen's coworker)

Oxytocin and its effects (The chemical of love?)

Prolactin and its effects (Let's feed the baby!)

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