Quaternary Science Advances (Jan 2023)
Sourcing Oldowan and Acheulean stone tools in Eastern Africa: Aims, methods, challenges, and state of knowledge
Abstract
Eastern Africa's Plio-Pleistocene palaeoanthropological record has shaped our understanding of human biological and cultural evolution. Over the years, raw material sourcing has emerged as an important research topic in lithic analysis as it can allow for the identification of resource extraction points and transport distances as a means to infer other aspects of hominin behaviour that are of high evolutionary significance. The goal of this article is to review and synthesise the aims, methods, challenges, and knowledge on raw material sourcing from Plio-Pleistocene contexts in Eastern Africa. Beginning with a review of the Oldowan and Acheulean records, four over-arching patterns are identified based on evidence from 130 localities. First, hominin toolmakers regularly exerted selective criteria when choosing raw materials by way of opportunistic and more specialised procurement strategies. Second, the fragmentation of technological activities across the palaeolandscape emerged as a behavioural characteristic among Oldowan toolmakers before the first appearance datum of the Acheulean. Third, hominins across Eastern Africa preferentially utilised igneous rock types followed by metamorphic and sedimentary lithologies mirroring the regional lithostratigraphy. Finally, Acheulean toolmakers largely mimicked their Oldowan counterparts in terms of raw material provisioning until the late Early Pleistocene, when they began to engage in qualitatively different behaviour best evidenced by stone transport over longer distances.This state of archaeological knowledge serves as the basis to then review the theoretical and methodological underpinnings of raw material sourcing followed by interpretive challenges. On a fundamental level, the identification of raw material sources is contingent on the implementation of a systematic sequence of analysis in which the resulting data abide to the provenance postulate. This serves to preface a devoted section on the array of analytical methods that can be successfully employed by archaeologists to source raw materials. Proven and innovative methods are identified by bringing into dialogue key factors such as accuracy, precision, reproducibility, discriminatory power, sensitivity, destructiveness, throughput, cost, ease, and the question of spatial scale. According to cost-benefit considerations, analytical methods that fall under the umbrella of geochemical fingerprinting are found to generally outperform macroscopic and petrographic techniques. It is also argued that characterising non-obsidian lithologies is best accomplished using more than one analytical method, with the understanding that once positive baseline results are obtained subsequent testing can be narrowed down from a methodological standpoint. Regardless of the characterisation method, it is imperative to implement effective means to analyse the resulting data, which constitutes this article's penultimate section. Ranging from traditional graphical data representations to multivariate statistics and emerging branches of artificial intelligence, there are countless means through which characteristic source signals can be identified regardless of rock type. The final section reviews common interpretive challenges when studying raw material provisioning in deep time. While the concepts of mobility, time-averaging, recycling, source differentiation, and selection criteria each present unique challenges, it is argued that they can be reasonably overcome by way of multidisciplinary lines of evidence. Ultimately, it is found that the future of raw material sourcing from Plio-Pleistocene contexts in Eastern Africa is promising given what is currently known along with the subfield's robust foundations.
