Atypical tooth wear found in fossil hominins also present in a Japanese macaque population
Ian Towle cs 2022 AJPA doi org/10.1002/ajpa.24500

Objectives
Atypical tooth wear is often regarded as evidence of non-masticatory, tool use behavior in fossil hominins:
macroscopically visible striations on anterior teeth & within root grooves on posterior teeth.
Both these types of dental tissue loss are often considered unique to Homo: the earliest evidence of human cultural habits.
We describe similar tooth-wear in a wild primate population, and conduct a differential diagnosis of this atypical tissue loss.

Materials & Methods
Wild Japanese macaques (Koshima Island) were provisioned regularly on the beach (one of the longest running primate field sites).
Tooth wear & fractures in this group were compared to 2 other non-provisioned populations.
Information on diet & behavior were obtained from extensive literature & on-going field observations.

Results
All Koshima Island individuals analyzed showed atypical tooth wear.
Large macroscopic striations were visible on many teeth, with sub-vertical striations prominent on the labial surfaces of incisors.
Root grooves on posterior teeth were observed in half of the individuals: clear directional striations, cf. “toothpick” grooves in fossil hominins.
Tool use & the habitual insertion of non-masticatory items in the mouth has not been observed in this population.

Discussion
Accidental ingestion of sand & oral processing of marine mollusks likely creates these atypical wear patterns.
Implications for similar wear that has been ass.x tool-use in fossil hominin samples were discussed.