New study rebuts claims about Icelandic genetic heterogeneity

There has been some controversy in the media and within the scientific research community concerning whether Icelanders are genetically homogenous or heterogeneous relative to other European populations.

Following an article published in Annals of Human Genetics in January 2003 by E. Árnason, who concluded that Icelanders were one of the most heterogeneous populations in Europe, researchers from deCODE Genetics and the University of Oxford, have published an article in Annals of Human Genetics (issue 67:4, July 2003) corroborating findings from earlier studies that Iceland is indeed home to one of the most homogenous gene pools in Europe.

This latest research article, ‘A Reassessment of Genetic Diversity in Icelanders: Strong Evidence from Multiple Loci for Relative Homogeneity Caused by Genetic Drift’ by A. Helgason, G. Nicholson, K. Stefánsson and P. Donnelly, both greatly expands sample sizes from individual populations and the number of genetic loci analysed, and uses population genetics simulations to demonstrate that genetic drift, not admixture (as claimed by E. Árnason), has been the overriding factor influencing patterns of genetic variation in Iceland. Moreover, these simulations also reveal that the summary statistics (gene diversity and mean pairwise mutational differences) used by E. Árnason, to argue for the relative genetic heterogeneity of Icelanders in his analysis of mitochondrial DNA (mtDNA) sequences, are poor comparative measures of genetic diversity in closely related populations such as those of Iceland and other European countries.

Agnar Helgason, corresponding author on the new study, says: “A consideration of… 83 unlinked nuclear SNPs, 14 serogenetic loci, Y-chromosome haplotypes constructed from five microsatellites and mtDNA HVS1 and HVS2 control region sequences, provides a clear and consistent picture of Icelanders being amongst the more genetically homogeneous populations in Europe, characterised by small effective population size and relative isolation”.