Shovel-shaped incisors

Shovel-shaped incisors (or, more simply, shovel incisors) are incisors whose lingual surfaces are scooped as a consequence of lingual marginal ridges, crown curvature, or basal tubercles, either alone or in combination.

Shovel-shaped incisors are significantly common in Amerindians from North, Central, and South America. They are also common in East Asians and Central Asians, Inuit, and Aleut peoples of Northeast Asia and North America (including but not limited to Inuit in eastern Alaska, Arctic Canada, and Greenland). In certain European and African groups, shovel-shaped upper incisors are uncommon or not present. There is a spectrum of the degree of shoveled-ness, ranging on a scale from 0 to 7 of spatulate incisors to shoveled incisors. It was theorized that positive selection for shovel-shaped incisors over the spatulate incisors is more commonly found within cultures that used their teeth as tools due to a greater structural strength in increased shovel-shaped incisors.

In some instances, incisors can present a more pronounced version of this called double shovel-shaped. When present, shovel-shaped incisors can indicate correlation among populations and are considered to be one of the non-metrical traits in osteology. Structurally resembling the shovel-shaped incisors, double shovel-shaped incisors are distinguished by a more pronounced mesial ridge compared to the distal ridge. Similarly, the grades for both shovel-shaped incisors and the double shovel-shaped incisors in females are significantly greater than that in males.

Shovel-shaped dental characteristics are also observed in Homo erectus like the Peking Man and in Neanderthals, although the morphology of these shoveled incisors is distinct from the modern human form of shoveling. The morphology of Neanderthal's anterior teeth has been seen as an adaptation to the heavy use of their canines and incisors in processing and chewing food, and the use of their teeth for activities other than feeding.