Extended Data Fig. 5: Anthropogenic modifications observed on ochre piece OP1.

a, squares indicate areas presented in c–g with same letters. b, grey areas represent surfaces that bear striations produced by grinding. Arrows indicate the direction of the grinding motions. c–e, g, striations observed on OP1. f, 3D reconstruction of an area showing striations. The outer surface of the nodule bears five adjacent areas, each covered by parallel striations produced by abrading the nodule on a grindstone with a to-and-from motion (a, b). OP1 contains inclusions of almost pure iron in a more granular matrix. Abrasion has differentially smoothed areas of different hardness with the harder remaining more prominent. The orientation of the striations slightly differs on each facet indicating changes in the direction of the movement and possibly different sessions of use. The latter hypothesis is supported by substantial differences in the size of the striations between modified areas suggesting abrasion on grindstones of different granulometry (c–g).