Sarah Richardson, “Sexing the X” (Guest Lecture by Ella LaRose)

Posted: Wed, Mar 26, 2025

In-Class Activity

  • Bring me up to speed… give me a crash course of where y’all are at.
  • What (if anything!) does it mean for a biological marker (like chromosomes, hormones, genetic makeup, etc.) to determine something about you?

Previous Assumptions Made by the Scientific Community

  • The Y chromosome carries a critical genetic switch for sex determination
  • ‘Sexing genes’ are carried on the chromosome itself—X genes and traits are found on the X and same for the Y and maleness
  • Gendering of the egg and sperm
  • Gendering of sex steroids—estrogen and testosterone
  • The standard picture: the X and the Y are a heterosexual couple (p. 911), if not rivals in a battle of the sexes (p. 912).

How the X Became the Female Chromosome

  • Originally, folks believed that the X was the sex-determining chromosome in humans—resulting in a hyperbinary.
  • We have failed to distinguish between the sex of the gamete and the sex of the organism.
  • There was a historical focus on sperm in research, since it was easier to study and more plentiful—and centering the Y in this research led to the result that X=female Y=male.
  • But… if X is the female chromosome, what does the extra X do for XX females? What does the X do for XY males?

X-Chromosomal Theories of Human Sex Differences

  • The “greater male variation theory”: “While females enjoy the security of a second X, it dulls their potential for extraordinariness. Males are superior where it counts: intelligence.”
  • X mosaicism: a condition where an individual has cells with different chromosome complements, including variations in the sex chromosomes (X and Y), arising from errors in cell division during early development. (p 920-1)
  • The Barr body: in cells with two X’s, one becomes inactive early on in embryonic development. (p 914)
    1. In those with XX chromosomes, about half of their cells express the material X and the other half the paternal X.
    2. This genetic mosaicism reinforces social “conceptions of women as more mysterious, contradictory, complicated, emotional, or changeable.”

We see these hypotheses at work in speculative scientific conceptions of femaleness and gender difference.

So…

  1. The gendering of objects of biological study shapes our perceived scientific knowledge
  2. Feminist analyses of science have revealed synecdochic (part for whole) errors.
    1. The world of human bodies is divided into two kinds by sex
    2. Additional properties are culturally attributed to these bodies, and
    3. The same properties that have been ascribed to the whole are then attributes to the subcategories of, or processes associated with, these bodies. (p 910).
  3. The X carries important genes involved in spermatogenesis, but plays no special role in “female” sexual development (these genes are located elsewhere).
  4. Most men also carry an X, and because most men carry only one copy of X, they are much more susceptible to X-linked recessive diseases.
  5. The X is not female-determining; the Y is responsible primarily for initiating male sexual development.

Class Discussion

  • Can we identify and unpack the synecdochic errors?
  • How can scientists avoid making these errors?