I endorse this article: 5 Ways That Science Supports Feminism – Not Gender Essentialism. It's making the point that when you actually study the relevant sciences, you discover that they fundamentally support a more complex view of sexuality than the usual boy/girl dichotomy. Here, in brief, are the five points it makes:
1. There Are More Than Two Sexes, Not to Mention a Vast Range of Gender Identities
2. The Environment Impacts Human Development from the Very Beginning at the Cellular Level
3. Socialization Is a Powerful Force
4. When Studies Do Find Gender Differences, They Are Often Too Weak to Serve as the Basis for Generalizations
5. Gender Means Different Things in Different Cultures
One other factor that leads people to adopt gender essentialism is a kind of innumeracy -- I swear, I think the only statistical measure most people understand is the mean. But statistics was developed to describe variation, in addition to taking data sets and crunching them down to a single number.
There is also deficiency of logic. If you take any diverse set, divide it in two, and calculate the mean of any given parameter for both, you'll get…two numbers. This does not validate your initial division as appropriate. It does not mean your artificial dichotomy reveals an absolute truth about the world. It does not mean you have encapsulated the essence of your two groups in a single simple metric. In particular, it's possible to have a mean that does not describe a single individual in your group accurately.
Point 1 weakens the rest of the text:
"In the paper “The Five Sexes” (which actually argues there are more than five), Brown University professor Anne Fausto-Sterling points out that sex exists in a continuum, with intersexuals (people who don’t have all the physical characteristics of males or females) constituting about 4% of births. That’s 1-in-25 people! This number seems shockingly high because surgical intervention often follows birth, so we don’t meet a lot of people who identify as intersexuals into adulthood (and even if we did, we might not know)."
As I could not believe what I read, I checked on Internet and found a website linking to the same author: http://www.isna.org/faq/frequency
indicating a frequency of intersex of 1% not 4%. Even the 1% figure is exaggerated, as late onset adrenal hypeplasia cases are not really intersex.
People having worked with mammals know they can separate them easily in males and females without surgery.
This article is not science, but ideology.
As a transsexual woman (that's MTF, for those that need a translation) who writes extensively on this very science, I agree with Mr. Corcos. There are ONLY two sexes. The rest of the so called "sexes" are those with Disorders of Sexual Development... that is to say, folks for whom something has not developed according to our biological template as a species.
The rest of the points are dead on... though, in the article, the issue of the complexity of transgender, and the fact that there are two completely separate and distinct etiologies, one of which is completely unrelated to any known DSD but IS related to a quirk of their brains leading to an Erotic Target Location Error, which in turn leads to an Erotic Target Identity Inversion.is completly glossed over. Sigh...
For more information regarding this topic, see my blog:
Sadly the general sex-dichotomized cis-panicking public can't be expected to know that biological features such as genitalia do not result from the flick of a two-state switch but are the result of gene expression levels, mediating tissue development by releasing messenger factors such as hormones. Concentration effects in nature simply do not operate in a truly binary fashion; the concentration of e.g. anti-Müllerian-hormone or SRY gene dose does not take only two discrete values in humans but varies in concentration and in time - which should make it clear that resulting "sex" cannot be divided into two absolutely discrete categories but is better discribed as a state existing along a continous axis (or even multi-dimensional if you seperarate the different aspects like geno- and phenotype) with most humans being near the ends of these.
The societal convention of prescribing only two sexes is a construct that works for the majority but ignores the biological diversity in our world.
I would be happy to have some information on the variation of SRY gene dose in humans ;-).