Did you know that on average, men are about five inches taller than women? But has it ever made you wonder what causes this consistent difference? While it’s commonly attributed to hormones, such as testosterone and estrogen, recent research suggests that genetics, particularly the role of sex chromosomes, also plays a significant part.
It is important to note that this height gap isn’t universal across all species. In some animals, females are larger than males, proving that height differences between sexes are not biologically fixed. In humans, however, hormonal and genetic factors contribute to male-taller-than-female trends.
The SHOX gene
One of the key genetic elements influencing height is the SHOX gene (short stature homeobox), which plays a crucial role in bone growth. This gene is located in a region of the sex chromosomes known as PAR1 (pseudoautosomal region 1), found on both the X and Y chromosomes.
In females, two X chromosomes (XX), one of the X chromosomes is largely inactive — a biological process known as X-inactivation. However, some genes in the PAR1 region, including SHOX, escape full inactivation and remain partially active. Despite this, the expression level is not as high as it could be.
In males, who have one X and one Y chromosome (XY), the SHOX gene is present and fully active on both chromosomes. This leads to higher overall expression of the SHOX gene compared to females.
This increased SHOX gene activity in males contributes to greater bone growth and, consequently, taller average height. While hormones still influence physical development, these findings reveal that genetic mechanisms—especially how sex chromosomes express certain genes—play a vital role in determining human height differences between men and women.