Shape Variation in Aterian Tanged Tools and the Origins of Projectile Technology: A Morphometric Perspective on Stone Tool Function

BACKGROUND: Recent findings suggest that the North African Middle Stone Age technocomplex known as the Aterian is both much older than previously assumed, and certainly associated with fossils exhibiting anatomically modern human morphology and behavior. The Aterian is defined by the presence of 'tanged' or 'stemmed' tools, which have been widely assumed to be among the earliest projectile weapon tips. The present study systematically investigates morphological variation in a large sample of Aterian tools to test the hypothesis that these tools were hafted and/or used as projectile weapons. METHODOLOGY/PRINCIPAL FINDINGS: Both classical morphometrics and Elliptical Fourier Analysis of tool outlines are used to show that the shape variation in the sample exhibits size-dependent patterns consistent with a reduction of the tools from the tip down, with the tang remaining intact. Additionally, the process of reduction led to increasing side-to-side asymmetries as the tools got smaller. Finally, a comparison of shape-change trajectories between Aterian tools and Late Paleolithic arrowheads from the North German site of Stellmoor reveal significant differences in terms of the amount and location of the variation. CONCLUSIONS/SIGNIFICANCE: The patterns of size-dependent shape variation strongly support the functional hypothesis of Aterian tools as hafted knives or scrapers with alternating active edges, rather than as weapon tips. Nevertheless, the same morphological patterns are interpreted as one of the earliest evidences for a hafting modification, and for the successful combination of different raw materials (haft and stone tip) into one implement, in itself an important achievement in the evolution of hominin technologies

Lithic variability and cultures in the East African middle stone age

Lithics are the most abundant archaeological evidence from the remote past, however the way they are used to reconstruct past human groups is often biased. The Middle Stone Age (MSA) is the lithic techno-complex linked to the emergence of Homo sapiens in Africa. However, there is no consensus in the scientific community about the significance of this lithic culture in terms of connections with particular human social groups nor its evolution. This paper focuses on the relation between lithic variability in the East African MSA and its meaning in terms of the structure of human groups, critical for interpreting the behavioral and evolutionary processes that led to Homo sapiens expansion within and out of Africa. Here I examine current knowledge and hypotheses and suggest some methodological advances to overcome the present difficulties