This required that we 1) obtain parameters for the hazard of developing cancers for BRCA1 mutation carriers; 2) obtain demographic parameters of fertility and survival for the populations considered; 3) determine the mortality hazard of mutation carriers and non-carriers in these populations; and 4) integrate these hazards into a population genetics framework to estimate the magnitude of selection on mutations in BRCA1. We outline these steps below (the code in ‘R’ allowing calculations for steps 1,3 and 4 is provided in the supplementary material entitled Code S1). This evidence concerns the gene BRCA1 and cancer.