Configurational approach to identifying the earliest hominin butchers

Abstract

The announcement of two approximately 3.4-million-y-old purportedly butchered fossil bones from the Dikika paleoanthropological research area (Lower Awash Valley, Ethiopia) could profoundly alter our understanding of human evolution. Butchering damage on the Dikika bones would imply that tool-assisted meat-eating began approximately 800,000 y before previously thought, based on butchered bones from 2.6- to 2.5-million-y-old sites at the Ethiopian Gona and Bouri localities. Further, the only hominin currently known from Dikika at approximately 3.4 Ma is Australopithecus afarensis, a temporally and geographically widespread species unassociated previously with any archaeological evidence of butchering. Our taphonomic configurational approach to assess the claims of A. afarensis butchery at Dikika suggests the claims of unexpectedly early butchering at the site are not warranted. The Dikika research group focused its analysis on the morphology of the marks in question but failed to demonstrate, through recovery of similarly marked in situ fossils, the exact provenience of the published fossils, and failed to note occurrences of random striae on the cortices of the published fossils (incurred through incidental movement of the defleshed specimens across and/or within their abrasive encasing sediments). The occurrence of such random striae (sometimes called collectively "trampling" damage) on the two fossils provide the configurational context for rejection of the claimed butchery marks. The earliest best evidence for hominin butchery thus remains at 2.6 to 2.5 Ma, presumably associated with more derived species than A. afarensis.

Fig. 1.

Experimentally produced trampling mark showing two divergent trajectories; the mark also has heterogeneously spaced microstriations (blue bars) and shallow pseudopits resulting from lamellar flaking (blue arrows) (A). This modern trampling mark compares favorably in morphology to mark D, a purported butchery mark on the DIK-55–3 fossil (details in Results) (B). Experimentally produced trampling groove showing a winding trajectory and internal microstriations (red arrows indicate the groove's inflection points) (C) and a remarkable morphological similarity (in size, shape, and trajectory) to mark G1, a purported butchery mark on the DIK-55–3 fossil (D). Broad, experimentally produced trampling mark showing two sets of ancillary grooves (red arrows) abandoning the mark's main groove and creating a curved trajectory on to the shoulder of the main groove; we infer that each of these ancillary grooves was created by a single sedimentary particle (E). Mark I on the DIK-55–3 fossil shows an identical ancillary effect of a single abrasive particle leaving the mark's main groove (details in Results) (F). The image in A is courtesy of R. Blasco and J. Rosell. The images in B, D, and F are modified from McPherron et al. (1). (Scale bars: 1 mm in A, C, and E.)

Fig. 2.

Examples of striae fields created by experimental trampling (see also ref. 17): pit associated with microstriations (A); isolated striae field with straight trajectory (B); isolate striae field with winding trajectory (C); and microstriations emanating from the green fracture edge of a bone specimen (D). The striae fields illustrated in B and C are morphologically indistinguishable from bone surface marks B and C on the DIK-55–2 fossil and mark D on the DIK-55–3 fossil posited to be stone tool scraping and percussion damage. Compare these incidences of bone surface damage to the pit and associated sets of microstriations (arrows) (E) and isolated striae field (F) created by experimental hammerstone. (Scale bars: 1 mm.)

Fig. 3.

Modern ungulate long limb bone shaft fragment that was experimentally trampled, showing damage typical of that action, including small fracture edge notches and micronotches and conchoidal flaking of its cortical surface (red arrows) and linear trampling marks (white arrow) (A). Marks H1 and H2 on the fossil DIK-55–3, which show, respectively, small notching and conchoidal flaking (H1) and a winding trajectory (H2) (B) that are similar to the modern bone surface trampling damage illustrated in A, C, and D. The winding shallow groove of mark H2 emanates from the fossil's breakage plane, as is common in trampled bones, including that illustrated in C. Note also the shallowness, winding trajectory, and internal microstriations of the experimentally produced trampling mark in D. The image in A is courtesy of R. Blasco and J. Rosell. The image in B is modified from McPherron et al. (1). (Scale bars: 1 mm in C and D.)

Fig. 4.

Examples of modern bone surface marks that are V-shaped in cross-section and were created by trampling in gravel sediment. They range in morphology from broad grooves like marks A1 and A2 on the DIK-55–2 fossil (A, F) to much narrower grooves (D). All of the modern trampling marks have internal microstriations. Modern marks illustrated in A–C are longer than fossil marks A1 and A2. The V-shaped trampling mark illustrated in D preserves sedimentary particles in its main groove, just as does mark A2 on DIK-55–2. The trampling damage illustrated in E shows the overlap of a short mark at the top and longer one with a different trajectory, similar to the damage on the DIK-55–3 fossil. The trampling mark illustrated in F is short and wide, morphologically very similar to marks A1 and A2 on the DIK-55–2 fossil. (Scale bar: 1 mm.)