The settlement of Iceland

Abstract

Phenylketonuria (PKU) is a recessively inherited disease, which occurs with a moderate frequency in people of early Western European (Celtic?) stock. The equally high incidence rates of PKU in Ireland and Iceland are therefore considered indicative of a similar admixture of people of Celtic extraction in the two countries. Norwegian heterozygotes for PKU exhibit a similarity in distribution pattern with the present inhabitants of Ireland, Scotland and Iceland, in the rhesus, Kell and PGM1 genetic marker systems, and differ significantly from the general population of Norway in the same systems. This accords with the hypothesis that Norwegian heterozygotes for PKU may be of ‘Celtic’ stock ‐descendants of Irish, Scottish immigrants to Norway in the Viking Age. The striking resemblance between the present populations of Ireland and Iceland in prevalence at birth of PKU, as well as in gene frequencies in several genetic marker systems including the rhesus, Kell and PGM, systems, is there fore taken as evidence of a similar admixture of people of ‘Celtic’ extraction in the two countries. Consequently, only a small proportion (< 25 %?) of the early settlers in Iceland was therefore of Norwegian breed.