We study evolutionary population genetics. A founding interest was in the use of molecular markers to reveal population structure and breeding behaviour in natural populations, particularly marine mammals but we also research the ways in which the markers themselves evolve, with a view to increasing the power of the analyses that can be conducted. Our collaborations with mathematicians aim both at modelling the evolutionary behaviour of these markers, and at deriving improved methodologies for gene mapping and genetic distance estimation. Due to the existence of very large data sets from gene mapping studies, we are turning more and more to human studies and the potential for reconstructing historical patterns of migration and population growth. Recently we have been researching the relationship between heterozygosity and fitness in natural populations and humans.