Genetics
The European distribution of Y-chromosome haplogroup R1a has been suggested to have occurred as a result of receding glacial activity allowing males bearing the lineage from the present day territory of Ukraine to migrate and gradually populate central, northern, and western Europe. Alternatively, it has been proposed that males from Haplogroup Hg P*(xR1a1) or R1b (Y-DNA) repopulated most of Europe shortly after the Last Glacial Maximum, related to population expansions out of the Franco-Cantabrian region. The European distribution of Y-chromosome Haplogroup I and various associated subclades has also been explained as resulting from male post-glacial re-colonization of Europe from refuge in the Balkans, Iberia, and Eastern Europe.
Males possessing Haplogroup Q are postulated as representing a significant portion of the population that crossed Beringia and populated North America for the first time.
The distribution of mtDNA haplogroup H has been postulated as representing the major female repopulating of Europe after the Last Glacial Maximum from the Franco-Cantabrian region. mtDNA haplogroups A, B, C, D, and X are interpreted according to some as supporting a single pre-Clovis populating of the Americas via a coastal route.
Read more about this topic: Late Glacial Maximum