Nature 474, 502–505 (2011); doi:10.1038/nature09992

Dr Michael Lynch has indicated that he no longer has confidence in the original data presented in this Letter, and would like to have his name removed as a co-author. Dr Ariel Fernández has conducted his own statistical analysis, firmly stands by the data and has claimed that differences in interpretation are at the basis of this disagreement. Nature’s editors have concluded that it is necessary to alert the readership to this controversy until further clarification is obtained.