DUAL ORIGINS OF FINNS REVEALED BY Y-CHROMOSOME HAPLOTYPE VARIATION

The Finnish population has often been viewed as an isolate founded 2,0 00 years ago via a route across the Gulf of Finland. The founding even t has been characterized as involving a limited number of homogeneous founders, isolation, and subsequent rapid population growth. Despite t he purported isolation of the population, levels of gene diversity for the Finns at autosomal and mitochondrial DNA loci are indistinguishab le from those of other Europeans. Thus, mixed or dual origins for the Finns have been proposed. Here we present genetic evidence for the dua l origins of Finns by evaluating the pattern of Y chromosome variation in 280 unrelated males from nine Finnish provinces. Phylogenetic anal ysis of 77 haplotype configurations revealed two major starshaped clus ters of Y haplotypes, indicative of a population expansion from two co mmon Y haplotypes. Dramatic and quite significant differences in Y hap lotype variation were observed between eastern and western regions of Finland, revealing contributions from different paternal types. The ge ographic distribution and time of expansion for the two common Y haplo types correlate well with archeological evidence for two culturally an d geographically distinct groups of settlers. Also, a northeastern to southwestern gradient of Y haplotype frequencies provides convincing e vidence for recent male migration from rural areas into urban Finland.