New research, published in the journal eLife, calls our conventional understanding of biological sex into question. It’s a call to action to recognize that we should not just label it as male or female. Titled “Fast evolutionary turnover and overlapping variances of sex-biased gene expression patterns defy a simple binary sex classification of somatic tissues,” this research conducted by Chen Xie and colleagues reveals the complexity of sex-biased gene expression patterns in human tissues.
The paper, recently made available to the public with URL DOI 10.7554/elife.99602.4, provides important perspectives. It helps to uncover how these sex-biased genes act in different biological systems. It reminds us how often we reduce biological sex down to an overly simplistic binary. This remarkable oversimplification ignores an awful lot of deeply interesting variation in gene expression.
Findings on Sex-Biased Gene Expression
Digging deeper, the researchers explored how these sex-biased genes function in various human tissues. They pointed out a binary classification of biological sex is inadequate. This work reveals that a surprisingly high number of genes show sex-specific roles that can differ depending on time scales of evolutionary divergence. In particular, they noted that among mouse species that have diverged within the last two million years, most genes have either lost or altered their sex-specific roles.
The authors argue that this evolutionary turnover suggests a more intricate relationship between genes and biological sex than previously understood. This complexity further underscores the need to take a more granular approach when it comes to biological sex classification. We need to get past the binary male and female sexes.
“Sex-biased genes and sex-biased gene expression indices for data from human tissues.” – eLife (2025). DOI: 10.7554/elife.99602.4
Implications for Understanding Biological Sex
We believe that this research has monumental implications, far beyond the academic discussion alone. It has the power to impact medical practice and policy around gender and health care. By acknowledging that organs and tissues cannot be strictly classified as male or female, healthcare providers may better address the unique health needs of individuals with differing biological characteristics.
As noted by phys.org, this study emphasizes the importance of recognizing individual differences and the evolutionary forces that shape them. The authors suggest that instead of rigid classifications based solely on molecular features, biological sex should be viewed as a complex mosaic influenced by various factors.
“Sex is therefore not rigid and clear-cut, but shaped by evolution, overlaps and individual differences.” – [source]
Moving Towards a Nuanced Understanding
Chen Xie and the team have done important pathbreaking research. Their results represent a critical shift in how researchers—and by extension, doctors—should think about biological sex. It questions decades-old orthodoxy and it forces us to reconsider our historical frameworks that have been applied throughout research and in the clinic.
This research lays the foundation for future studies. It will explore how various manifestations of biological sex affect health outcomes, treatment responses and quality of life. By moving towards a more inclusive understanding, the scientific community can enhance its efforts to tailor medical care to the individual characteristics of patients.