Interproximal grooves on the Middle Pleistocene hominin teeth from Yiyuan, Shandong Province: New evidence for tooth-picking behavior from eastern China

An assortment of hominin cranial and seven dental fossils assigned to Homo erectus were discovered in 1981 and 1982 at Yiyuan, a Middle Pleistocene fissure site in Shandong Province, eastern China. The present study analyzes microscopically the seven teeth interproximal surfaces from Yiyuan using a binocular microscope and Scanning Electron Microscopy. The crowns and roots of the teeth exhibit different degrees of wear, which range from multiple fine striae to deep interproximal grooves. The location, morphology, and dimension of these grooves or striae are similar to artificial wear caused by habitual tooth-picking. The Yiyuan teeth provide one of the earliest evidence of tooth-picking among Pleistocene hominins in eastern Asia.