Dental scratches and handedness in East Asian Early Pleistocene hominins

Abstract

The current study aims to characterize dental scratches found on an East Asian hominin upper left central incisor (I¹) and lower left lateral incisor (I₂) from the Early Pleistocene (Meipu site, Yunxian County), and infer the preference for handedness of this two individuals by quantifying the orientation of dental scratches. The labial surfaces of these two teeth were observed and imaged using light microscopes and/or scanning electron microscope (SEM) under different magnifications (5x-70x). The angle, width, and length of each dental scratch was measured and analyzed. The dental scratches described and quantified on the labial enamel surface of Meipu I¹ and I₂ fit the description of cutmarks caused by "stuff and cut" behavior. Most scratches are oriented in the right oblique direction, averaging 47.11 degrees in I¹ and 44.60 degrees in I₂. This result indicates preference for the right hand as the dominant one in holding a tool during "stuff and cut" behaviors. This is the earliest reported "stuff and cut" behavior and inferred right-handedness in East Asia. It fills a temporal gap between the earliest known example in the African Early Pleistocene (~1.8 Ma) and the next known instance in the European Middle Pleistocene. This is also the first time the "stuff and cut" behavior and right-handedness has been reported in a hominin assigned to Homo erectus sensu lato.

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