Shovel-shaped incisors

[13] The 1540C allele of EDAR is also strongly correlated with the presence of shovel-shaped incisors and hair thickness, as found in a study conducted on the DNA from Japanese populations.

This may likely have conferred a survival advantage to those with the allele during the Last Glacial Maximum in certain environments with high altitudes and low Vitamin D.[14] The first description of shovel-shaped incisors was in 1870.

[16][17] The greater size and mass of shoveled incisors was said to have provided increased strength and durability as a means to prevent breakage.

[18] However, current research shows that part of the genotype, the EDAR gene, which was selected for because of its role in nutrient transfer in breast milk during the era of the Beringian refugium, also determines the degree to which teeth shovel.

[14] In an interview, Dr. Hlusko suggests that human populations who had the trait migrated from Asia to the Americas, thus leaving their genetic trace around the world.

[20] The presence of shovel-shaped incisors, among many dental characteristics, is used in forensic dentistry to identify an individual's ancestry,[21] since this trait occurs predominantly in Asian and Native American populations.