Hair thickness / shovel-shaped incisors

EDAR shapes hair, teeth and sweat glands during development. A variant common in East Asians produces thicker, straighter hair and shovel-shaped front teeth.

What the EDAR variant does

EDAR is a receptor in the ectodysplasin pathway, which sets up hair follicles, sweat glands, teeth and mammary glands during development. This variant, V370A, increases receptor signalling, and because one pathway builds all of those structures, a single change alters several traits at once.

A mouse engineered to carry the human variant grew thicker hair, more sweat glands and more densely branched mammary tissue, which confirmed experimentally what human association studies had suggested.

What it changes in people

The documented effects are thicker, straighter hair shafts, shovel-shaped incisors, meaning upper front teeth with a scooped back surface, and higher sweat gland density. Associations with breast density have also been reported.

The site's evidence file records the hair morphology association from a Han Chinese study of 2,899 people, and ClinVar lists the variant under hair thickness. None of these are health effects; they are a set of ordinary structural differences that happen to share one developmental pathway.

One of the strongest selection signals in the human genome

The frequency pattern is extreme. In 1000 Genomes reference data, about 72% of East Asian-ancestry individuals carry two copies and 25% carry one, along with roughly 23% of admixed American-ancestry individuals, while it is essentially absent in European and African-ancestry samples.

Computational analysis places the variant's origin in central China around 30,000 years ago, and the surrounding region carries one of the clearest signatures of recent positive selection anywhere in the genome. What was being selected for is unresolved: sweat gland density in a humid climate and mammary gland branching have both been proposed, and neither is settled.

What this variant does not tell you

It says nothing about hair loss, hair colour, or scalp health, and nothing about sweating problems in either direction. Hair thickness is also affected by other genes and by age, hormones and treatment.

What each rs3827760 genotype means

rs3827760 has three possible genotypes: TT, CT and CC.

Finer hair type (rs3827760 TT). You have the ancestral version of EDAR, so you have the more common, finer hair texture and typical tooth shape. The thick-hair EDAR variant is rare outside East Asia and the Americas.

Intermediate hair type (rs3827760 CT). You carry one copy of the EDAR variant that's common in East Asia. It can give slightly thicker, straighter hair and subtle tooth-shape differences, though one copy has a milder effect than two.

Thick hair, shovel teeth (rs3827760 CC). You have two copies of the EDAR variant common in East Asia, which typically gives thick, straight hair and shovel-shaped front teeth (a slight scoop on the back of the upper incisors). The same gene also tweaks sweat-gland density.

Evidence & sources

Across global populations, about 3% of people carry two copies of this variant, and about 93% carry none.

This variant appears in 3 published genetic studies: PubMed 26926045 · PubMed 27487801 · PubMed 29895819.

Common questions

Does this variant affect how much I sweat? It is associated with a higher density of sweat glands, shown both in human studies and in a mouse carrying the same change. That is not the same as sweating problems, which have other causes entirely.

What are shovel-shaped incisors? Upper front teeth with raised edges and a scooped back surface, giving a shovel-like profile. They are common in East Asian and Native American populations and are one of the visible effects of this variant, which also thickens hair.

Related

Earwax type / body odor · Endurance / aerobic capacity (PPARGC1A) · Eye color (blue, green/hazel, brown) · Height · Male-pattern baldness tendency · Muscle fiber type (power vs endurance) · Skin pigmentation (light vs dark)