Turning-the-edge, Tranchet, and Social Signalling at Boxgrove

The capacity to relate a signal to an arbitrary, specific and generally understood meaning—symbolism—is an integral feature of human language. Here, we explore two aspects of knapping technology at the Acheulean site of Boxgrove that may suggest symbolic communication. Tranchet tips are a difficult handaxe form to create, but are unusually prevalent at Boxgrove. We use geometric morphometrics to show that despite tranchet flaking increasing planform irregularity, handaxes with tranchet tips have more standardized 3D shapes than those without. This challenging standardization suggests tranchet tips at Boxgrove were part of a normative prescription for a particular handaxe form. Boxgrove presents some of the thinnest handaxes in the Acheulean world. To replicate such thin bifaces involves the technique of turning-the-edge. Since this technique is visually and causally opaque it may not be possible to learn through observation or even pointing, instead requiring arbitrary referents to teach naïve knappers. We use scar ordering on handaxes to show a variety of instances of turning-the-edge in different depositional units at Boxgrove, indicating it was socially transmitted to multiple knappers. The presence of societally understood norms, coupled with a technique that requires specific referents to teach its salient features, suggests symbolism was a feature of hominin communication at Boxgrove 480,000 years ago.