Dental morphology is highly differentiated among human populations and research indicates that it may be influenced by genetic factors.
Teeth vary among individuals in size and shape. In addition, there are certain dental characteristics that are more common in certain populations. For example, in Asian and derived populations, synodontia is common and includes a combination of dental characteristics with first and second incisors that are spade-shaped and not aligned with the rest of the teeth, upper first premolars with a single root and lower first molars with three roots. In particular, shovel-shaped incisors show clear regional differences, being very frequent in Asia and Native Americans and rare or absent in Africa and Europe.
Spade-shaped incisors are characterized by lingual surfaces with marked marginal ridges, with significant curvature at the crown. It is a trait that has been investigated for a long time, especially by anthropologists who have used it to study relationships between populations. It seems clear that it is a genetic trait, with an estimated heritability of 75% and associated with genes involved in the developmental pathways of organs and tissues of ectodermal origin, although the polymorphisms influencing this trait are not fully established.
Kimura R, Yamaguchi T, Takeda M, Kondo O, Toma T, Haneji K, et al. A Common Variation in EDAR Is a Genetic Determinant of Shovel-Shaped Incisors. Am. J. Hum. Genet. 2009 Oct;85(4):528–35.
Park JH, Yamaguchi T, Watanabe C, Kawaguchi A, Haneji K, Takeda M, Kim YI, Tomoyasu Y, Watanabe M, Oota H, Hanihara T, Ishida H, Maki K, Park SB, Kimura R. Effects of an Asian-specific nonsynonymous EDAR variant on multiple dental traits. J Hum Genet. 2012 Aug;57(8):508-14.