What this means

EDAR is a receptor in the ectodysplasin signalling pathway, which during development shapes hair follicles, sweat glands, and teeth. The V370A variant (rs3827760) reached near-fixation in East Asian and Native American populations through positive selection somewhere around 30,000 years ago. People with two G copies tend to have thicker individual hair fibres, denser eccrine sweat glands, and shovel-shaped upper incisors — a striking case of one variant pulling several seemingly unrelated traits in the same direction.

EDAR is a gene that, during development, helps build hair follicles, sweat glands, and teeth. One version of it became extremely common in East Asia and the Americas roughly 30,000 years ago. If you carry it, your individual hair strands tend to be thicker, you have more sweat glands, and the backs of your top front teeth tend to be slightly scooped — a single DNA change quietly pulling several unrelated-looking features in the same direction.

Caveats

• Effect sizes are modest for any one trait; the pattern is clearest in aggregate.
• The variant is near-fixed in East Asian populations, so within-population predictive value is low.
• Hair shape (curly vs straight) is controlled by different genes.
• The "shovel-shaped incisor" trait is subtle and not always obvious without a dental mirror.

References

• Fujimoto et al. — A scan for genetic determinants of human hair morphology: EDAR is associated with Asian hair thickness (Human Molecular Genetics, 2008)
• Kamberov et al. — Modeling recent human evolution in mice by expression of a selected EDAR variant (Cell, 2013)