While the written sources emphasise settlement from Norway, genetic evidence shows that the founder population of Iceland came from Ireland, Scotland, and Scandinavia: studies of mitochondrial DNA and Y-chromosomes indicate that 62% of Icelanders' matrilineal ancestry derives from Scotland and Ireland (with most of the rest being from Scandinavia), while 75% of their patrilineal ancestry derives from Scandinavia (with most of the rest being from the Irish and British Isles). Archaeogenetic evidence suggests that the actual founding population included a higher proportion again of settlers from the Irish and British Isles: one study found that the mean Norse ancestry among Iceland's settlers was 56%, whereas in the current population the figure was 70%. It is thought likely that most of the settlers from Ireland and Scotland came as slaves, and therefore reproduced less successfully than higher-status settlers from Scandinavia, making them ancestors of a smaller proportion of the modern population.