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Why Was Silcrete Heat-Treated in the Middle Stone Age? An Early Transformative Technology in the Context of Raw Material Use at Mertenhof Rock Shelter, South Africa

Fig 3

Correlation plots showing the relation of the percentage of chert artefacts in relation to the percentage of heat-treated silcrete.

(a) By contexts (CT) and (b) by (sub)groupings. Chert percentages refer to the total number of artefacts in the contexts, heat-treated silcrete percentages refer to the number of silcrete artefacts in the contexts. The coefficient of determination of the correlation is r2 = 0.973, p<0.001 for (a) and r2 = 0.999, p<0.001 for (b).

Fig 3