Earliest evidence of proto-dental treatment in the late Upper Paleolithic.

Prehistoric dental treatments have been known from the Neolithic 9,000-7,500 years before present (BP) [1], when the adoption of early farming culture caused an increase of carious lesions [2]. Only a few early cases have been documented [3], some were characterized by in vivo perforation of the crown surface made by a drilling tool [1]. Here we document the earliest evidence of proto-dental therapeutic intervention on a Late Upper Paleolithic modern human lower right third molar (RM3) from a burial in Northern Italy [4]. The RM3 belongs to a young male individual (ca. 25 years old) unearthed in 1988 from the Epigravettian deposit of Riparo Villabruna (Sovramonte – Belluno, Italy), and dated around 14,160-13,820 BP. This tooth presents a large occlusal cavity, with a polished internal surface and extensive enamel chipping traces on the steep mesial wall. Within the cavity four caries are present. The cavity is sub-squared on the lingual and mesial sides but rounded on the buccal and distal sides. Using Scanning Electron Microscopy (SEM) we show the presence of striations within the cavity, which fade out towards the occlusal surface probably as a consequence of tooth wear. The striations have a ”V” shaped transverse section and microstriations at the bottom, sharply defined, with a high apex, steep sides, narrow cross-sections and well-defined parallel ancillary ridging, as typically displayed by cutmarks on teeth [5]. Based on in vitro experimental replication and a complete functional reconstruction of the Villabruna dental arches, we confirm that the identified striations and the associated extensive enamel chipping on the mesial wall of the cavity were produced ante-mortem by pointed flint tools during scratching and chiseling activities. The Villabruna specimen is therefore the oldest known evidence of dental caries intervention, suggesting rudimentary knowledge of disease treatment well before the Neolithic. This study also suggests that primitive forms of carious treatment in human evolution entail an adaptation of the well-known toothpickings for levering and scratching rather than drilling practices.