Nature 541, 102–106 (2017); doi:10.1038/nature20789

After publication, we noticed errors in the Source Data files for Fig. 2, Extended Data Figs 5, 6 and 9 and Supplementary Fig. 1 of this Letter. These result from data mislabelling, and have no effect on any of the figures, statistics or conclusions in the paper. The Supplementary Information to this Corrigendum contains the corrected Source Data files for the original Fig. 2, Extended Data Figs 5, 6 and 9 and Supplementary Figure 1. The original Letter has not been corrected online.