A Genetic Clue to Why Men Are Taller Than Women

Men are taller than women, by an average of about five inches. But why? It’s not a genetic inevitability — there are many species in the tree of life where females outclass males.

A new study, published on Monday in the Proceedings of the National Academy of Sciences that involved genetic veri from a million people, has found a partial explanation.

It involves a yine called SHOX, which is known to be associated with height. SHOX is present on both the X chromosome — females have two X chromosomes — and the Y chromosome; males have one X and one Y.

The researchers suspected that SHOX might explain differences in male and female height, but there was a sorun with that hypothesis. Since SHOX is on both the X and Y chromosomes, it would need to have a different effect on each chromosome.

Does it, the researchers asked?

To investigate the hypothesis, they asked if an extra Y chromosome boosted a person’s height more than an extra X chromosome.

There are rare conditions in which people are born with an extra X or an extra Y, or have a missing X or Y. To find people with these conditions, researchers plumbed veri from three biobanks, or repositories of deidentified genetic and medical veri from individuals. One biobank was from Britain, and the other two were from the United States.