Taphonomic considerations for identifying ochre residues on ostrich eggshell

Abstract

Ochre pigments and ostrich eggshell (OES) products (including beads, engravings, and containers) are proxies for past human economic and social behaviors. Ochre residues are reported from OES fragments and beads across Africa and Asia, starting within the last ∼ 30,000 years. Residues may be the results of different activities—wearing beads against pigmented surfaces, intentional application to beads or the exterior of containers, and transporting, storing, or mixing the ochre in containers or bowls—or acquired post-depositionally. Understanding how taphonomic processes can create, alter, or delete residues offers insight to human behavior and site formation processes. We apply experimental archaeology to test how taphonomic processes, including archaeological recovery practices such as artifact washing, interact with ochre applied to OES surfaces. Ochred OES fragments were buried, washed and buried, or exposed directly or indirectly to a ground fire. We recorded temperature of the fire, residue coverage, and elemental data using portable X-ray florescence analysis at each experimental stage. Our results suggest that washing and burying specimens preferentially removed residues from the cuticle surface, while the effect of burning on residues depended on the proximity to the combustion feature. We compared the experimental data with OES fragments from Terminal Pleistocene and LGM archaeological deposits from the HOR-1 site in northern Malawi, where archaeological ochre residues are observed more frequently and in more substantial amounts on the mammillary surfaces.