Michael Bulmer is well known for his breadth and depth of research in biometry and evolutionary genetics, in which he has solved longstanding and difficult problems. He elucidated genetic and environmental factors affecting the twinning rate in humans. He developed the infinitesimal model for the genetics of quantitative traits and showed how selection would change variance in a predictable way (the ‘Bulmer effect’), a result of great importance in application to breeding. He also undertook definitive analyses of the genetics of sex ratio, particularly of temperature-sensitive sex ratios and driving sex chromosomes. Recently Michael has turned to studies of molecular evolution and shown how biased codon usage can be explained by small differences in translational efficiency.