Autochthonous anisotropy of archaeological materials by the action of water: experimental and archaeological reassessment of the orientation patterns at the Olduvai sites

Anisotropic patterns documented indirectly through M. Leakey's drawings of Olduvai archaeological sites have led to questions about the integrity of these sites. Most experiments on bone transport by water have been carried out using complete elements that do not replicate specimen bone breakage and size as documented in archaeological sites. In the present work, an experimental framework is provided using experimental proxies of archaeological assemblages. Results show that autochthonous assemblages affected by hydraulic processes can adopt anisotropy in their fabric. Archaeological comparisons between drawings and excavated sites at Olduvai stress the bias in Leakey's drawings of FLK Zinj and FLK North in Bed I. A large-scale open excavation recently carried out at TK (Bed II) exposes an area comparable in size to Leakey's excavations. Comparing the orientation patterns of this site to those reported by Leakey, shows how biased the drawing of the site is and how easily this can lead to misinterpretations of isotropy/anisotropy, with fatal consequences for the understanding of site formation processes.