This graph shows the average number of scratches on upper central incisor labial surfaces for a variety of primate species using data from Ungar(1992, 1994) and Ungar and Grine (1991).

Those species with the highest number of scratches, such as Macaca fasciscularis and Cebus olivaceus regularly use their incisors to prepare foods for ingestion. Those with the lowest number of scratches, such as Alouatta seniculus and Hylobates lar less frequently use their front teeth to prepare foods.

Values for human ancestors and other fossil primates can simply be compared to values for living primates with known diets and tooth-use behaviors to infer feeding adaptations for extinct forms.