Competing Interests
The authors declare no competing interests.
Manuscript format: Nature
Authorship statement: The study was conceived by ELCS and AR. EL undertook the data analysis with input from all authors. The manuscript was first drafted by EL and ELCS with further contributions from all authors.
Data statement: All data generated or analysed during this study are included in the submission of this article (and its supplementary information files) and will be available with publication.