25-05-2025
What exactly makes men taller than women? New study reveals genetic truth that might surprise you
Men are generally taller than women, with an average height gap of about five inches. While hormonal differences have often been credited for this, new research points to genetic factors—particularly the role of the sex chromosomes—as a significant contributor to this long-standing biological difference.
A comprehensive study recently published in the Proceedings of the National Academy of Sciences (PNAS) analyzed genetic data from nearly one million adults. The research drew from three major biobanks: the UK Biobank and two from the United States—MyCode and All of Us. Among the 928,605 participants, 1,225 individuals were identified with atypical numbers of sex chromosomes, providing a rare insight into the biological mechanisms influencing height.
The Role of the SHOX Gene
At the core of the study is the SHOX gene—short stature homeobox—which plays a key role in regulating height. The SHOX gene resides in a specific region shared by both the X and Y chromosomes, known as pseudoautosomal region 1 (PAR1). This allows it to function similarly in both chromosomes.
In typical human females (XX), one of the X chromosomes is largely inactive, except for genes in PAR1, including SHOX. However, these genes still experience partial silencing. In contrast, males (XY) have both an active X and Y chromosome, each expressing SHOX without inactivation, leading to higher gene expression.
By comparing individuals with various chromosomal configurations—such as those with extra X or Y chromosomes—the researchers found that an additional Y chromosome contributed more significantly to increased height than an additional X chromosome. This pattern held true across different ancestry groups, highlighting a consistent genetic influence on stature.
Beyond Hormones: Statistical Evidence
To measure the impact of these chromosomal differences, researchers used multivariate linear regression to account for the influence of hormones, inactive chromosomes, and conditions like Klinefelter syndrome and Turner syndrome. Their analysis concluded that genetic contributions from the Y chromosome explained a substantial portion—up to 22.6%—of the average height gap between men and women.
Matthew Oetjens, senior author of the study and a
genetics
researcher at Geisinger College of Health Sciences, emphasized the biochemical significance of SHOX. He pointed out that its position near the tip of the sex chromosomes allows it to escape silencing in females, though only partially. In males, both chromosomes actively contribute, enhancing the gene's expression and its effect on height.
Impact and Implications
While the SHOX gene accounts for roughly a quarter of the average
height difference
, researchers believe other factors—such as sex hormones and yet-undiscovered genetic elements—also play important roles. According to Eric Schadt, professor at Mount Sinai School of Medicine, the use of large-scale biobank data was instrumental in shedding light on a mystery that has puzzled scientists for decades. He acknowledged that while the gene's effect is modest, it represents a key step forward in understanding human growth.
Earlier research has also noted trends in height change over the past century, indicating that men have gained height at a faster rate than women, further widening the gap. Social studies have shown that women tend to prefer taller male partners, though scientists caution that taller individuals may also face higher risks for certain cancers due to increased cell division.
The findings not only enhance our understanding of
human height
differences but also provide a foundation for exploring genetic explanations behind other sex-based disparities. Researchers hope that further study into genes like SHOX and their interactions with hormones and other biological systems will continue to reveal more about the complexities of human growth and health outcomes.
