In the version of this Article originally published, the authors mistakenly included duplicate entries in the flake datasets for the new Pech de l���Az�� IV and Warwasi collections, resulting in minor errors in the statistical analysis. The authors have now repeated this analysis with the correct flake datasets. As a result, in the following two sentences, the number of flakes has been changed from 19,000 to 18,000: ���Using more than 18,000 flakes from 81 assemblages spanning two million years..��� and ���We applied a comparative approach..on more that 18,000 complete and unmodified flakes.��� In addition, in Figs. 1���3 and Supplementary Fig. 1, some of the data points for the Pech de l���Az�� IV and Warwasi collections have moved; the original and corrected figures are below. Supplementary Tables 1 and 2 have been updated to reflect the corrected statistics, and datasets ���Flake_data��� and ���Summary_data��� have been replaced with the corrected data files. Furthermore, the data availability statement has been updated with the text ���Open access to these data and the R code generated for this study is provided at https://zenodo.org/record/1408081#.W6iyn84zaHs���. The authors would like to thank L. Premo at Washington State University for finding the duplicate entries in the published flake dataset.