Implications for complex cognition from the hafting of tools with compound adhesives in the Middle Stone Age, South Africa

• DOI: 10.1073/pnas.0900957106
• Publication Date: 2009-05-12T01:43:15Z
• Authors: Lyn Wadley; Tamaryn Hodgskiss; Michael Grant
• Keywords: Middle Stone Age

Compound adhesives made from red ochre mixed with plant gum were used in the Middle Stone Age (MSA), South Africa. Replications reported here suggest that early artisans did not merely color their glues red; they deliberately effected physical transformations involving chemical changes acidic to less pH, dehydration of adhesive near wood fires, and mechanical workability electrostatic forces. Some steps required for making compound seem impossible without multitasking abstract thought. This ability suggests overlap between cognitive abilities modern people MSA. Our multidisciplinary analysis provides a new way recognize complex cognition MSA necessarily invoking concept symbolism.