99.9% of human genomes are identical. Yet, there continues to be a widespread misconception that males and females are genetically distinct and opposite. Dr. Richardson traces the history of genetic research to show how chromosomes were gendered as part of a cultural imperative to “anchor a conception of sex as biologically fixed and unalterable binary” amidst political challenges to gender roles (2). Against all evidence otherwise, researchers recruited chromosomes into a political agenda to create and reinforce the gender-sex binary. In the 1960s chromosomes came to “represent the essence of maleness and femaleness…the ultimate naturalness of social customs and practices organized around the different roles, interests, and capacities of the two sexes” (9). This had more to do with cultural beliefs than biological facts.
Dr. Richardson concludes that the evidence used to justify chromosomal determination of sex is “limited, uneven, and contradictory” (34) There is “woefully little empirical evidence” (122) for the idea that the presence of the Y chromosome is a mediator of difference between males and females. Studies that seek to establish this connection often “neglect interacting variables such as age, weight, and hormones that are known to affect gene expression” (201). Indeed, chromosomes did not “obey regular laws from species to species, nor were they adequate to explain sex determination in many species” (35). However, the narrative that the X chromosome is the carrier of female-specific traits and that the Y chromosome is the essence of maleness continues to persist. Dr. Richardson argues that it would be more accurate to refer to distinctions in chromosomes as “sex differences in the human genome” rather than “male genome” or “female genome” (200).
Describing X and Y as sex chromosomes was “neither obvious nor inevitable” (201). Initially, scientists were hesitant to posit chromosomes as the genetic determinant of sex. The leading early theories “assumed a model of sex determination that was nondeterminate” (40). Rather than “sex chromosomes,” they used the language of “odd chromosomes,” (35) or “accessory chromosomes” (41). Some researchers recognized that sex was a spectrum trait and that sex involved a host of genetic and developmental factors. Ultimately this fluidity and complexity was compromised, and X and Y were marked as “sex chromosomes.”
Cultural gender stereotypes governed this scientific research: shaping the questions that were asked, the models that were proposed, the research practices employed, and the descriptive language in the field of sex chromosome research (3). For example: femaleness was unquestionably understood as passive, deceitful, absence and maleness as active, simple, presence. This gendering of chromosomes glossed over naturally occurring variations such as Klinefelter’s Syndrome. To this day people may live their entire lives not knowing they have XXY and are frequently described as “XXY Males” (107).
Ultimately, Dr. Richardson argues that it was cultural pressure, not biological evidence, that led to the binary gendering of chromosomes. Amidst the destabilization of gender norms and roles, patriarchal society needed an essence to re-entrench its political division of society into to the binary. Chromosomes became a convenient feature to accomplish this political goal.