The Finnish population structure A genetic and genealogical study

The distribution of both polymorphic and rare marker genes in the Finnish rural population showed evidence of the effect of genetic drift maintained by national and local isolation. The polymorphic genes belonged to nine loci, all representing blood or serum groups. Their distribution was studied from a weighted population sample and this was compared with the distribution at county, community and village level. Great differences were observed both at community and village level, which indicate that the breeding unit has been small up to the present time, consisting of hundreds rather than thousands of individuals. On the other hand, the distribution at county level showed great uniformity compatible with a uniform origin and lack of substantial later gene flow. The distribution of a variety of rare genes was compared with the dynamic population structure characterized by “isolation of population density”. Several examples of enrichment scattered all over the country covered usually an area of several communities which probably represent the very original large breeding units, “superisolates”. The national enrichment of these genes could hardly be explained without a primary enrichment among the first settlers. The distribution of the very rare genes, with an estimated frequency of .003 or less, was limited to the areas first settled during prehistoric times. This forms a piece of evidence showing that all the early Finns used the same route of immigration, i.e., over the Gulf of Finland, rather than a separate eastern and western route. “Finland is like England six hundred years ago” A rthur M ourant (during a visit to Finland in 1958)