PCA of Acheulean bifaces from 18 sites, based on 11 variables measured from individual bifaces (length, breadth, thickness, five other planform variables and three further thickness variables: see the electronic supplementary material). KAR, Kariandusi; COR, Cornelia; KF, Kalambo Falls; V, Vaal; STIC, STIC, Casablanca; KIL, Kilombe.