Some Thoughts on Human Sexual Dimorphism

In biology, the term used to describe the differences between the sexes of a species is sexual dimorphism. Dimorphism is just a fancy word meaning that something has two shapes. Even though the term seems dry and technical, there's something poetic about the notion that the sexes are a single thing with two sides.

The degree of dimorphism between the sexes of a species can vary profoundly. If you were to look at a typical dog, for instance, you'd have to lift the animal up and have a good look at its plumbing. You certainly couldn't make the distinction based on size, of the tone of its bark or even by such behavioral gauges such as its aggressiveness. The differences between male and female angler fish, by contrast, is so profound that it's difficult to accept that they are members of the same species. The males are a fraction of the females size and, disturbingly, attach themselves to the females, like parasites, and actually fuse to the females' bodies, acting as little more than attached sperm repositories.

In the overall scheme of things, humans are more alike than different. The most "obvious" differences are actually superficial. Breasts, to cite the most visually distinctive difference, are essentially the same on both males and females. Male breasts can even be made to engorge and to lactate with the introduction or suppression of certain hormones. Even the genitals of men and women are, essentially, the same organ with male and female versions being little more than complex inversions of one another – a reproductive expert can draw a one to one mapping between every part of them.

One of the common misconceptions about what distinguishes men and women is whether a person has two X chromosomes or an X and Y chromosome. Strictly speaking, the chromosomal set you are born with offers nothing more than a strong genetic predilection towards one sex or the other. What actually determines your sexual development is your uterine environment. If you have a Y chromosome, there's a point in your development when the chromosome "activates" a particular cascade of sex linked hormones (most notably testosterone). It is this chemical environment that drives your sexual development beyond that point. It is entirely possible for this trigger to misfire. There are men who have two X chromosomes and there are women who have X and Y chromosomes. This is a fact that's caused quite a bit of controversy in the Olympics which, misguidedly, uses genetic standards to gauge sex in order to combat cheating.

Given that men and women are so physically close, it should not come as a surprise to find that we are cognitively close. It is, in fact, one of the great crimes of human history that, for millennia, women have been treated as being not only profoundly different from men but intellectually inferior to them. Given this sad history, it ought not be a surprise that once this view was challenged, there was a tendency to go too far in claiming that men and women are entirely identical in mind. Decades of research have shown that there are consistent differences between the way that men and women think but the differences aren't intellectual and they are subtle.

Men and women react to pain differently. Men and women bond with their offspring differently. Men and women deal with spatial and abstract problems differently. There are apparent differences in verbal memory, emotional memory, and how we perform acts of coordination (women do better). In listing the differences it is easy to get swept up in them to the point where we are tempted to declare that men and women are utterly unalike. The truth, however, is that even in the areas where we have differential levels of performance (e.g., performing spatial manipulations) there are broad overlaps.

One of the thorniest questions facing cognitive science (right up there with the genuine minefield of the question of racial differences) is whether or not there are any behavior differences and, if so, what is their source. It is easy to note that women and men exhibit different modes of socialization. In simplistic terms, men have a competitive social environment whereas women tend to focus of building complex interpersonal structures. There is, of course, the endless sort of anecdotal observations such as the that women tend to enjoy shopping more than men all the way down to the banal distinctions between guy flicks and chick flicks. For anyone but a dyed in the wool egalitarian, it's apparent that men and women do behave differently. The big question, however, is why.

Anyone who has spent any time watching the commercials that play during children's cartoon shows knows that there's a heavy amount of sexual segregation in the products that advertisers offer. Excepting only such neutral grounds as breakfast cereals and candies, certain products are pitched exclusively at boys while others are pitched exclusively at girls. Boys are sold miniature cars and trucks, weapon-like toys (nerf guns, spray guns, and the like), and all sorts of monsters and robots. Girl toys tend to focus on motherhood (lifelike baby and child dolls), romantic items (fashion accessories, jewelry, etc), and role playing (doll houses, adult dolls, pets, etc).

It is very tempting to say that boys and girls see themselves as having boy and girl roles because they experience heavy socialization. It may even be largely true, but we must be careful lest we confuse the causative associations. Do boys and girls behave as they do because they get certain cultural messages on how to behave, or do the cultural messages conform themselves to a set reality? Do boys want toy soldiers because that's what they're sold or do we sell boys toy soldiers because girls are, predispositionally, uninterested in them?

It's a damnably difficult question to answer. If it were possible to take children and raise them in a controlled laboratory environment with careful sets of controls, it would be relatively easy to glean some answers. Fortunately, we don't ethically condone that sort of experimentation. For better or worse, researchers are restricted to subjects that have invariably suffered all sorts of potential social contamination. It would be tempting to simply write the whole question off as insoluble. It would be irresponsible for us to do so, however. Even if the answers are not easy to determine, the question is important.

Thirty years of attempts to convince women that they should consider technical careers has done little to improve the presence of women in such fields as physics, mathematics, engineering, computer programming and most of the sciences as a whole. Given that these are precisely the careers that are driving modern technology and, hence, modern culture, this lack of representation is a source of legitimate concern. If there is something that can be done in order to fix this disparity then we, as a society, ought to do so. On the other hand, there are few things worse than misguided attempts at social engineering. It is important for us to know what the reality is and to adjust to it accordingly.

This task is complicated by the presence of all sorts of political agendas. On the one hand, you have proponents of so-called traditional values who think that it's an error to encourage any deviation from the past. On the other hand, you have groups who think that any efforts to so much probe the potential differences between the sexes must, automatically, be construed as acts of sexism and subjugation. Either side is motivated by concerns that it considers legitimate but I firmly believe that reality can not be bent to ideology and that any effort to do so is folly.

We are a dimorphic species. We are also, men and women, far more alike than different. To properly understand ourselves, we must illuminate those differences while, at the same time, resisting the urge to exaggerate them. If we can not manage this task, we can not understand ourselves. If we do not understand ourselves then we are charting our course by false stars.