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Proc Natl Acad Sci U S A. 2009 Jun 16;106(24):9590-4. doi: 10.1073/pnas.0900957106. Epub 2009 May 11.

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

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  • 1Institute for Human Evolution and School of Geography, Archaeology, and Environmental Studies, University of the Witwatersrand, Johannesburg PO WITS 2050, South Africa.


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 from acidic to less acidic pH, dehydration of the adhesive near wood fires, and changes to mechanical workability and electrostatic forces. Some of the steps required for making compound adhesive seem impossible without multitasking and abstract thought. This ability suggests overlap between the cognitive abilities of modern people and people in the MSA. Our multidisciplinary analysis provides a new way to recognize complex cognition in the MSA without necessarily invoking the concept of symbolism.

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