But isn’t biology normally dual?

Posted on April 25, 2010


One of the questions students raise at the beginning of this course, confronted with the work of Anne Fausto Sterling and Thomas Laqueur, is about biological sex: yes, they can see that things like musculature, hair length, even height don’t fall neatly into two groups; but isn’t it true that normal sexual biology consists of two reproductive sexes?

I use biological research to directly confront this claim. Historically, biologist Ruth Hubbard was my first introduction to the real scope of intersex, which is the most powerful, simple way to falsify the assumption that there are just two natural biological sexes. I still recommend her book, The Politics of Women’s Biology.

What usually happens is that students raise the objection that intersex individuals are exceptions to the presumed rule of two sexes.

To work through this, I force a discussion of the term normal (as applied to chromosomal/genital-reproductive sex) and its implicit opposite, which is not exceptional: it is abnormal. We explore other words that can describe a third sexual status that is uncommon. We examined how the idea of “normal” is objective when used as a description of a statistical norm; but becomes evaluative when used of human beings. I use different examples of uncommon or rare human characteristics (red hair may work in some places, for example) and ask students to consider whether we would want to call people with that characteristic abnormal, or simply rare, infrequent, or another term of the kind.

This discussion almost always involves interest in how common intersex conditions actually are. Estimates vary depending on what criteria (or which conditions) are included. The Intersex Society of North America provides a thorough overview of the issue. They conclude that as many as 1% of births involve some degree of divergence from normative male/female sex. Anne Fausto Sterling arrives at an estimate of 1.7% of all births involving some degree of intersexuality. More conservative estimates by critics of Fausto Sterling arrived at estimates around 0.018%. While that seems small, it means that in any population of 100,000 people, eighteen will have been born with some kind of intersex biology. Or to put it another way: conservatively, there are more than 55,000 intersex individuals in the United States. Students generally find it hard to assert that 50,000 people should be described as “abnormal”.

More recently, I have begun to integrate the challenging work of biologist Joan Roughgarden in this part of the course. Her book Evolution’s Rainbow explores the real complexity of biological sex formation. For students prepared for the biology, the book is an excellent way to get beyond the claim that sex is “really” or “normally” dual. The discussion of biological sex development is of critical importance to me, and the discussions of non-human animals are rich and at times startling.