Nature 552, 244–247 (2017); doi:https://doi.org/10.1038/nature25019

In this Letter, errors in Fig. 2c were inadvertently introduced during the production process. The key to the survival graph should state ‘HMb’ for the green line rather than ‘MMb’, ‘HMbMMb−1d’ for the blue line rather than ‘MMbHMb−1d’, and ‘HMbMMb−3d’ for the red line rather than ‘MMbHMb−3d’. The original figure has been corrected online.