About the Authors
Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, Scotland, United Kingdom
Medical Research Council Clinical Trials Unit, London, United Kingdom
The authors have declared that no competing interests exist.
Conceived and designed the experiments: AJLB. Performed the experiments: GH. Analyzed the data: GH SJL. Contributed reagents/materials/analysis tools: EF DD AR. Wrote the paper: GH AJLB.