How sexually dimorphic are we? Review and synthesis

The belief that Homo sapiens is absolutely dimorphic with the respect to se x chromosome composition, gonadal structure, hormone levels, and the struct ure of the internal genital duct systems and external genitalia, derives fr om the platonic ideal that for each sex there is a single, universally corr ect developmental pathway and outcome. We surveyed the medical literature f rom 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%). (C) 2000 Wiley-Liss, Inc.