Contributions to population history and genetic anthropology include pioneering work on the mutation rate and mechanisms in mitochondria and the Y chromosome;  comparing ancient to contemporary DNA; characterization of the respective Norse and Celtic roots of mitochondria and Y chromosomes in the Icelandic population; observations of the phenomenon of genetic drift, as an isolated population diverges from it source populations over time; the relationship between kinship and fertility; the impact of population structure on disease associated variants and vice versa, and a population-wide catalogue of human knockouts, people missing certain genes.  