Laura Martin Francés, researcher from the Dental Anthropology Group at CENIEH, has collaborated with a research team from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP ) in Beijing, in an study published in the journal Quaternary International about dental fossils assigned to Homo erectus 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.The article studied microscopically interproximal surfaces of the teeth of Homo erectus fossils discovered in 1981 and 1982 Yiyuan , a Chinese site in Shandong Province, and shows marks sticks found in five of the seven teeth analyzed, belonging to three individuals.

The accuracy provided by the analysis of the teeth of Yiyuan with binocular microscope and scanning electron microscope allows you to see the wear of the crowns and roots of teeth , ranging from multiple fine grooves to deep interproximal grooves. The location, morphology, and size of these grooves or ridges are similar to artificial tear caused by regular use of toothpicks.