Finnic peoples are also significant minority groups in neighbouring countries of Sweden, Norway and Russia.
According to the Migration Theory that was based primarily on comparative linguistics, the proto-Finns migrated from an ancient homeland somewhere in northwestern Siberia or western Russia to the shores of the Baltic Sea around 1000 BC, at which time Finns and Estonians separated. The Migration Theory has been called into question since 1980, based on genealogy, craniometry and archaeology. Recently, a modified form of the Migration Theory has gained new support among the younger generation of linguists, who consider that archaeology, genes or craniometric data cannot supply evidence of prehistoric languages.
During the last 30 years, scientific research in physical anthropology, craniometric analyses, and the mitochondrial and Y-chromosomal DNA frequencies have reduced the likelihood of the Migration Theory - a major westward migration as recently as 3,000 years ago. The Settlement Continuity Theory asserts that at least the genetic ancestors of the Finno-Ugric peoples were among the earliest indigenous peoples of Europe.
The origin of the people who lived in the Baltic Sea area during the Mesolithic Era continues to be debated by scientists. From the middle of the Neolithic onwards, there is agreement to a certain extent among scholars: it has been suggested that Finno-Ugric tribes arrived in the Baltic region from the east or southeast approximately 4000–3000 BC by merging with the original inhabitants, who then adopted the proto-Finno-Ugric language and the Pit–Comb Ware culture of the newcomers. The members of this new Finno-Ugric-speaking ethnic group are regarded as the ancestors of modern Estonians. The Y-chromosomal data has also revealed a common Finno-Ugric ancestry for the males of the neighboring Balts, speakers of the Indo-European Baltic languages. According to the studies, Baltic males are most closely related to the Finno-Ugric-speaking Volga Finns such as the Mari, rather than to Baltic Finns. The results suggest that the territories of Estonia, Latvia and Lithuania have been settled by Finno-Ugric-speaking tribes since the early Mesolithic period.