Last month two Nature studies on the Y chromosome were in the news, trumpeted as revealing “differences in men’s and women’s bodies, differences found as deep down as the cellular level.” The coverage of the studies offers an allegory for our age about the way scientific hype and a fascination with the sex binary continue to influence scientific research on sex today.
The New York Times reported that scientists had discovered 12 genes on the Y chromosome that play “high-level roles in controlling the state of the genome and the activation of other genes.” They “may represent a fundamental difference in how the cells in men’s and women’s bodies read off the information in their genomes.” The Huffington Post quoted one of the studies’ authors as saying that these “special” genes “may play a large role in differences between males and females.”
Yet what the Nature articles actually show is the exact opposite. The 12 genes residing on the Y chromosome exist to ensure sexual similarity. The genes are “dosage-sensitive,” meaning that two copies are needed for them to function properly. We’ve long known that those 12 genes exist on X chromosomes. Females have the 12 genes active on both of their X chromosomes. If males, who have just one X, didn’t have them on the Y, they would not have a sufficient dosage of those genes. Now we know they do. Just like women.
Furthermore, the 12 genes do not specialize in sex differences. The studies demonstrate that they are part of a family of genes that play an all-purpose regulatory role in the human genome. Scientists don’t yet know precisely what the genes do, but the studies show that they are important, because fetal viability is impaired without two doses of them.
How did a study of gene dosage equalization between males and females get framed as a major new finding of sex difference?
A little literary forensics reveals the story. In the very last lines of one of the Nature papers—the part of a paper where researchers typically engage in a bit of speculation—the scientists wonder if the X-derived and Y-derived versions of the proteins encoded by the 12 genes might “exhibit subtle functional differences.” They venture that if this is the case, the possibility of a role in sex differences in disease might be explored in the future.
And with that, the study’s most speculative moment became the headline.
Genetic sex difference claims will proliferate in the coming years, as more studies based on the genome come out. Yet reports of newly found sex differences in the genome need to be viewed with healthy skepticism and an awareness of how gender beliefs can distort our interpretation of scientific results.
This rush to see sex differences where they may not exist is nothing new. A 2005 Nature paper declared that the sexes differ at up to 350 genes on the X chromosome, a finding that garnered major media coverage and led one commentator to gush that “women and men differ genetically almost as much as humans differ from chimpanzees.” Follow-up studies confirmed only nine such genes—but no headlines touted the corrective.
A 2007 paper in the Journal of the American Medical Association reanalyzed 188 claims of genetic sex differences in recent peer-reviewed scientific articles and found that 55.9 percent were not statistically significant. Additionally, almost none of the findings of sex differences had been replicated by other studies—a critical measure of the validity of genomic findings. The authors concluded that in genetic sex difference research, “investigators very often seem to fall into classic traps.”
Last month’s Y chromosome studies show the continuing, stubborn influence of what I call the “sex difference paradigm.” The studies presented the unsexy claim that certain genes on the Y chromosome work to ensure sexual similarity. Filtered through our gender scripts and scientific hype generator, it became a revolutionary finding said to have groundbreaking implications for our understanding of the genetic basis of sex differences.
How can we break the difference paradigm? Top scientists such as Randy Schekman have recently drawn attention to the pernicious role of leading journals such as Nature in encouraging scientists to make big media-ready claims that later don’t hold up scientifically. But hype is only part of the problem. When it comes to sex, scientific reviewers, journals, funders, and reporters simply find similarities less interesting than differences.
What can be done to change that? A project at Stanford University is leading the way, working to “identify gender bias and understand how it operates in science and technology.” The Gendered Innovations initiative, funded in part by the National Science Foundation, is all about showing how critical analysis of gender assumptions can contribute to scientific knowledge. Now the challenge is filtering that understanding to the media and to the public so that we all bring some skepticism to too-tidy findings, and recognize that the real discoveries happen when we free ourselves from old mindsets.