Possible evidence of bone tool shaping by Swartkrans early hominids

Ever since Dart (J. Phys. Anthrop. 7 (1949) 1) interpreted certain bones from Makapansgat as tools, scientific consensus has fluctuated as to whether some bone objects from early hominid sites should be interpreted as artefacts, or the result of non-human taphonomic processes, which are known to produce pseudo-bone tools morphologically similar to human modified or used artefacts. Here we present possible evidence of bone tool shaping from Swartkrans (Members 1–3; ca. 1.8–1.0 Mya). Four horncores and the proximal end of an ulna used as tools in digging activities also have facets covered by parallel spindle-shaped striations characteristic of grinding. Identification of these traces as possibly resulting from deliberate shaping or re-sharpening of the bone tools is based on the characterisation of the use-wear pattern and other taphonomic modifications observed on the Swartkrans bone tools. This interpretation is also supported by the study of the remainder of the horncores from Swartkrans, horncores from other southern African Plio-Pleistocene sites (Sterkfontein, Makapansgat, Gondolin), modern horncores affected by pre- and post-mortem modification, ethnographic, LSA, African Iron Age and experimental bone tools shaped by grinding. These data suggest that early hominids had the cognitive ability to modify the functional area of bone implements to achieve optimal efficiency.