Early hominid bone tools from Drimolen, South Africa

The earliest use of bone tools is a topic of ongoing debate that concerns the criteria used to identify utilised or minimally modified bone tools, and if verified, the implications for hominid adaptation and cognition. Here we present the first description of 22 possible bone tools from the early hominid site of Drimolen (Gauteng Province, South Africa), dated ∼1.5–2 Mya. We compare the results of a taphonomic, morphometric and microscopic analysis of these pieces with those obtained from the study of faunal assemblages modified by a variety of non-human agents, and experimentally modified bones. None of the naturally modified assemblages contained pieces bearing the wear pattern observed on specimens from Drimolen and on bones experimentally used in digging activities. Fourteen pieces from Drimolen bear a pattern comparable to one previously described on early hominid bone tools from Sterkfontein and Swartkrans. This suggests that Drimolen bone tools were involved in a similar, if not exactly the same, task. Other common features include favoured bone types, fracture patterns, and the length and position of the worn area. Larger bone tools known from Swartkrans are absent at Drimolen, perhaps due to less availability of large mammal bones. The association of a high number of Paranthropus remains with bone tools at Drimolen, and the exceedingly low number of stone tools at the site supports the hypothesis that Paranthropus robustus used these bone tools. Based on implement-assisted termite foraging strategies amongst chimpanzees, we have inferred similar social and cultural behaviours for early hominids. Gorillas were recently proposed as a model for P. robustus social structure due to the high degree of sexual dimorphism observed. According to female aggregation practices present in both models, one can speculate that if P. robustus was the user of the bone tools, the foraging activity in which they were used may have been conducted mainly by females.