Sex and the human genome

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Sex and the human genome

Are scientists repeating their mistakes from the past?

by Susan Fisk on Tuesday, June 12, 2012 - 12:08pm

View of a skull (c. 1489) is a drawing by Leonardo da Vinci (source: Wikimedia)What really determines sex? A look back in history reveals that scientific advances keep changing the answer. In the 16th century, scientists believed that differences in blood were the cause. The pelvis was the culprit in the 18th century. By the 19th century, scientists shifted focus to the skull, then to the brain and, in the 20th century, to hormones. Now, scientists believe that sex differences lie in the human genome.

These advances suggest that we are closer to understanding how biology makes women and men seem different, and farther from the mistakes of the past. Harvard University Professor of History of Science and of Studies of Women, Gender, and Sexuality, Sarah S. Richardson, argues that we should be cautious before jumping to either of these conclusions. She makes this case in her forthcoming book, “Sex Itself: Male and Female in the Human Genome.”

Overstating sex differences

In a talk Richardson gave at Stanford University about her research, she argued that a more critical examination of sex differences is needed and that the, “finding of differences should not be an end of itself.” Richardson argued that there is a bias in biomedical literature towards finding and publishing claims of difference because they support our existing belief that women and men are different. However, in terms of the human genome, Richardson contended that, “the provocative finding is the overwhelming similarity between men and women.”

Karyotype of a human male (Courtesy: National Human Genome Research Institute)Even when sex differences are discovered in the human genome, the differences are generally extremely small and insignificant in terms of biological impact. Furthermore, findings of difference are rarely replicated more than once in  scientific research: only a handful of “sex difference” claims have met this bar.

For this reason, Richardson argued that we must critically examine genetic claims of difference between women and men to avoid reproducing errors and biases of sexual science of the past. Although the, “visually compelling binary of the X and Y chromosome,” may suggest that women and men are genetically and unalterably programmed to be different, Richardson explained the history of sex research is littered with findings of difference that were later found to be unimportant or untrue.

Heeding the historical record of bad science outcomes

Historically, discoveries of difference have been used as scientific evidence to prove the popular stereotypes of the day. For instance, in the late 19th century, it was widely assumed that women were less intelligent than men. Thus, when scientists discovered that female brains were, on average, smaller than male brains, they attributed the supposed lower intelligence of women to their smaller brains. Since it was scientifically proven and congruent with existing stereotypes, there was little critical examination of the core claim: that larger brains lead to greater intelligence. Further research has shown that there is not a link between brain size and intelligence, and that women are not less intelligent than men.

While many previous scientific claims to explain sex differences were proven false, this does not imply that women and men have no meaningful genetic differences. But to produce good science, Richardson argued that scientists must critically examine their results while keeping in mind the failures of earlier work on sexual differences. In particular, she contends that by assuming an X- and Y- chromosome sex binary, we neglect the variation that occurs within each sex as well the overlap between the sexes.

According to Richardson, this could create, “bad science that could harm women’s and men’s health.” In an age of increasingly personalized medicine, doctors might prescribe treatment based on an individual’s sex as opposed to their individual traits. For instance, while men generally weigh more than women, there is immense variation: there are women who weigh more than most men, and men who weigh less than most women. For this reason, making dosing decisions based on sex category, as opposed to an individual’s weight, would be disastrous: some individuals would get too much of a drug, while others would get too little. Either way, the results could be life threatening.

The crossover between science and society

On an ethical level, Richardson argued that focusing on difference is also harmful. It leads us to overstate the difference between women and men, the end result being a reinforcement of stereotypes (e.g. men are aggressive, women are emotional) and ignorance of the great variation and overlap between men and women. “I do think that these claims cause harm in terms of our conception of males and females as species beings who have biologically conscribed sex and gender roles,” she said.

Although sex-difference research is marred with biases and inaccuracies, Richardson contended that, “we have a choice.” “We have an opportunity for critical intervention, and we urgently need to have an open methodological, conceptual, and also at once ethical debate about conceptualizing sex differences in the human genome,” she said. “There are good methodological, empirical, and ethical reasons to look at sex differences in the genome in new ways, and this is the interdisciplinary conversation I hope to open.”


Professor Sarah Richardson's talk at Stanford University “Sex Itself: Conceptualizing Sex Differences in the Human Genome” was part of winter quarter-long symposium, Ms. at 40 and the Future of Feminism. The event was organized by the Program in Modern Thought and Literature as part of their 40th Anniversary Speaker Series.

Professor Sarah RichardsonSarah Richardson is Assistant Professor of the History of Science & of Studies of Women, Gender, and Sexuality at Harvard University.  A historian and philosopher of science, her research focuses on race and gender in the biosciences and on the social dimensions of scientific knowledge.  Richardson was Clayman Institute 2007-08 Graduate Dissertation Fellow.

Susan Fisk is a graduate student in Stanford's Department of Sociology.  She is a member of the Clayman Institute's student writing team.

Responses to Sex and the human genome

Lori Mackenzie's picture
14 June, 2012 Lori Mackenzie

Making a similar point to Sarah.... "Proposed Olympic policies for testing the testosterone levels of select female athletes could discriminate against women who may not meet traditional notions of femininity and distort the scientific evidence on the relationship between testosterone, sex and athletic performance, says a Stanford University School of Medicine bioethicist and her colleagues."