The EDAR V370A variant, almost fixed in northeast Asia, is known to cause coarser hair, smaller breasts with increased branch density, shovel-shaped incisors, more eccrine sweat glands, and changes in the shape of the earlobe. The changes in eccrine sweat glands and the hangey-down part of the ear have only been noticed recently.
It’s a gain-of-function mutation: you’re getting more of the effect that EDAR normally has.
Some people have loss-of-function mutations in EDAR: hypohydrotic extodermal dysplasia, HED. This was first identified by Charles Darwin. In The Variation of Animals and Plants under Domestication, he noted a family in India that produced ten men in four generations, all suffering from missing teeth, very little hair, inability to sweat, etc.
HED patients also have messed-up fingernails and have problems with the lacrimal glands (tear glands), the sebaceous glands, the Meibomian glands, and salivary glands. Presumably you would see the opposite effects in people with a gain-of-function mutation like EDAR V370A.
So – somebody should look for characteristic racial differences in tears, sebaceous glands, Meobomian glands, and salivary glands. And possibly fingernails. They may well exist, be driven by this EDAR mutation, and some might play a role in its selective advantage.