Biological Sex: body parts & hormones

In nature, many species show a normal diversity within species, across many characteristics.. You can arrange the individuals on a spectrum (nose: Barbra Streisand to Mia Farrow; height: Willy Shoemaker to Wilt Chamberlain, etc.) Why not also gender?  Most humans have chromosome and hormonal mixes that put them pretty close to the “male” or “female” ends of the gender spectrum, but there are more people in between – intersex – than you might think.

bio sex


How common is it to be not completely male or female? The Accord Alliance website notes, “Estimates from specialists working in major medical centers suggest that about one in every 2,000 births at a hospital involves a child whose genitals are atypical enough to make the child’s sex unclear. But… if we count all types of sex anomalies, DSD [Disorders of Sex Development] must be considered much more numerous than 1 in 2,000. [Here they mean not only variations in genitalia but also variations in chromosomes and hormones, which may  not have visible effects.] One review estimates that about one in a hundred persons has some kind of sex anomaly.”(1) A review of medical literature from 1955 to 1998 estimated that as many as 2 in 100 babies had some difference, in body organs, XY chromosomes, and/or hormonal patterns from ‘standard male or female.’  (2)

1-2% is a pretty small minority, but in the context of normal biodiversity it compares to other ‘natural’ differences among humans. For example, we each have 1 of 4 ABO blood types: A, B, O (neither A nor B) and AB (both). and either positive or negative for Rhesus factor, meaning everyone has one of 8 types. People who are B- are only 0.6% of the US population; these folks present a matching challenge to hospitals when they need transfusions, but we don’t consider them freakish.

In fact, given all the different factors involved in the ways our biological sex functions, you might expect even more diversity.  British neurologist and intersex expert Milton Diamond, interviewed in the British newspaper Independent, noted “Nature loves variety. Unfortunately, society hates it.”  The 2010 article gives a good overview of the history of oppression, compounded by some of the common past medical practices.

Intersex and Trans…

“Intersex” is a biological means simply having a variation from the usual binary (male/female) pattern of sex organs, hormones, and chromosomes.

“Transgender” is a psychological term, usually meaning someone who self-identifies differently from the sex s/he was assigned at birth. The biology of transgender people can vary; some have some intersex characteristics, others do not. Most transgender people identify as male or female, but some identify as a combination or separate, third sex. See the Gender Identity post.

What difference do these differences make?

What do these variations mean for the  “real lives” of intersex people? According to the Accord Alliance, many of the people with these variations are not sterile (before any surgery), and most will not be transgender.

The fact that some of these intersex conditions are not readily apparent might work against expanding awareness and inclusion. For those whose looks and/or behaviors push gender boundaries, bullying, harrassment and violence are certainly more prevalent. But most studies do not break out intersex people separately from LGBTQ. There is more about this in the Gender expression post.

“Not monsters, nor marvels, nor battering rams for gender theory, people born intersexed have given the rest of the world an opportunity to think more about the odd significance we give to gender, about the elusive nature of truth, about the understandable, sometimes dangerous human yearning for simplicity – and we might, in return offer them medical care only when they need it, and a little common sense and civilised embrace when they don’t.”  Amy Bloom, in “The third sex: The truth about gender ambiguity,” The Independent 20 March 2010

1. Accordance Alliance,]

2. Blackless, M et al “How Sexually Dimorphic Are We? Review and Synthesis,” American Journal of Human Biology, 12, Page(s): 151-166, 2000,