The belief that Homo sapiens is absolutely dimorphic with the respect to sex chromosome composition, gonadal structure, hormone levels, and the structure of the internal genital duct systems and external genitalia, derives from the platonic ideal that for each sex there is a single, universally correct developmental pathway and outcome. We surveyed the medical literature from 1955 to the present for studies of the frequency of deviation from the ideal male or female. We conclude that this frequency may be as high as 2% of live births. The frequency of individuals receiving "corrective" genital surgery, however, probably runs between 1 and 2 per 1,000 live births (0.1-0.2%).
This figure - quoted by Anne Fausto-Stirling in her definitive work Sexing the Body as 1.7% - has been criticised on the basis that the definition of Intersex should be more restrictive.
From How common is intersex? A response to Anne Fausto-Sterling. Sax L. J Sex Res Aug 1 2002 :
Subtracting these five categories--LOCAH, vaginal agenesis, Turner's syndrome, Klinefelter's syndrome, and other non-XX and non-XY aneuploldies--the incidence of intersex drops to 0.018%, almost 100 times lower than the estimate provided by Fausto-Sterling.Of course most people would consider that a girl born without a vagina (vaginal agenesis) is Intersexed. And so is someone born with neither the 46XX chromosomes usually found in women, nor the 46XY ones usually found in men, but 47XXY ones. But it's necessary for political reasons - Sax is over-sensitive to the fashionable RadFem denial of sexually dimorphic characteristics - to reduce the figure. But his critique hasn't been used the way he intended. Instead, the Unscrupulous have battened onto it like leeches, as is their habit. Hence this little gem from the Hate Group, the Traditional Values Coalition: Homosexual Urban Legend Exposed.
Leonard Sax has stated the obvious about Fausto-Sterling’s views. They are bogus and based upon flawed research, bad definitions, and inflated statistics.You can see why they richly earn the sobriquet of "Hate Group".
Yet, these are the statistics quoted by Time magazine and promoted by the Intersex Society of North America in its campaign to normalize what are, in fact, birth defects.
Intersex Activism Is Part Of The Homosexual Revolution
Oddly enough, I can see where Leonard Sax is coming from. Because he believes, as I do, that there are innate differences between the way men and women think. His website - although flogging his books with the verve of a Saudi member of the Ministry for the Suppression of Vice and Protection of Virtue - is quite informative.
I just see that while there are two distinct sexes, there's an area between, neurologically and anatomically, where things are not so straightforward. Someone can be neurologically usual, but otherwise anatomically unusual, or the reverse. It's by studying these people - like myself - that we can learn more about the extremes, and what causes them. And it's by realising that Male and Female are really, really good approximations, but there are few (if any) people who are total stereotypes of either that we can learn to treat people as individuals. By all means have separate-sex classrooms, for many that will be appropriate. But consider that for some it's not, and for some it is appropriate for some areas of study, in others not. Biology drives all of this, but Biology is messy and fuzzy and multi-variant.
Hence back from science, through politics, back to science again.