Shovel-shaped incisors

Variation in modern human incisor shoveling has been associated with the presence/absence of the V370A allele of the Ectodysplasin A Receptor (EDAR) gene. The EDAR V370A isoform arises from a single nucleotide polymorphism/missense mutation which changes the 370 Valine residue to an Alanine on the EDAR gene. 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. ==History==

The first description of shovel-shaped incisors was in 1870. During the 20th century, it was accepted that incisor shoveling yielded a direct advantage to the possessor. The proposed explanation for this at the time was that shovel-shaped incisors were stronger than non-shovel shaped incisors, resulting in the evolution of shovel-shaped incisors in regions where having stronger teeth would provide an evolutionary advantage. The greater size and mass of shoveled incisors was said to have provided increased strength and durability as a means to prevent breakage. However, current research shows that part of the genotype, the EDAR gene, which may have been 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. ==Applications==

In the mid 20th century, shovel-shaped incisors were considered to be a trait useful for racial categorization, since the occurrence of shovel-shape incisors varies between many populations. The presence of shovel-shaped incisors, among many dental characteristics, is used in forensic dentistry to identify an individual's ancestry, since this trait occurs predominantly in Asian and Native American populations. ==See also==