The Myth of Two Sexes

The New Scientist reviews Gerald N. Callahan's new book, Between XX and XY: Intersexuality and the myth of two sexes. The reviewer, Deborah Blum, can't go wrong quoting the American pragmatist William James.

"I AM satisfied with a wild free Nature," the psychologist-philosopher William James once wrote to a quarrelsome colleague. "You seem to me to cherish and pursue an Italian Garden, where all things are kept in separate compartments, and one must follow straight-ruled walks."

I've always admired the way James challenged what he perceived as scientific dogma. In this case, he raised a conundrum we still wrestle with today. Science, with its love of classification, seeks to impose a strict order on the world around us. Yet life on Earth is (forgive the pun) by nature tangled, messy and, in James's words, "everywhere gothic". Review: Sex in shades of grey

While the Victorian thinkers were classifying things, spirits like James and Thoreau and Peirce were un-classifying, exploding taxonomies, paring away cognitively-imposed schemes in order to see the world as it is. They are easily seen as the ones who set the stage for the modern science of dynamic systems, including chaos theory, complexity theory, studies of self-organization. The world is fundamentally messy and in itself is resistant to fitting neatly into boxes.

This Jamesian perspective pervades Gerald Callahan's smart and compassionate book. Callahan's argument arises from the fact that human sexuality spans a slippery biological spectrum. The stereotypical view of two sexes - me Tarzan, you Jane - is not only cartoonish, it limits our understanding and appreciation of our own biology.

I want to linger over that word "cartoonish," which is only the set-up. I like the sound of it. Cartoonish.

"We still see a gap where none exists," Callahan writes, "a mirage that shimmers over the hot land of sex." He argues instead that there is a range of sexual characteristics that stretches from the testosterone-inflated Tarzan to the womanly "perfection" of a stereotypical Jane and all the variations that lie in between. "In truth, we are all intersex," he concludes.

The standard model of human development is built on 46 chromosomes, including two that determine sex: XX for female, XY for male. But, as Callahan points out, not everyone ends up 46XX or 46XY.

Variations in sperm or egg, in the mixing of cells from mother and father and in the cell division that follows can all stir the genetic soup into alternative outcomes. The possibilities, Callahan writes, "are as grand and as varietal as the fragrances of flowers: 45X; 47XXX; 48XXXX; 49XXXXX; 47XYY; 47XXY; 48XXXY; 49XXXXY; and 49XXXYY." These variations are familiar to geneticists - the first on the list, for instance, is known as Turner's syndrome - but the general public is still stuck in a black and white, XX/XY world.

And it is time for the general public to awaken to the idea of variation.

Much of Callahan's book is spent exploring our understanding of intersexuality, from the physicians of ancient Greece to today's neuroendocrinologists. He also weaves in the stories of people who live in the stretch between the classic male and female endpoints. "Truthfully, I think the most important thing I would like people to understand about me is that I am a person," Kailana, who is hermaphrodite, tells him in a diatribe of anger, grief and courage.

It is shameful that there is any question of that, that any person is treated as less than equal, less than deserving, because they do not match a stereotype.

It will be interesting to follow the science of sex and gender over the next few decades, as nature breaks out of its overly-facile taxonomies and human understanding expands to absorb the immensity of the variation among human beings.