DISCUSSION
The initial arrival of farmers from Southwest Asia to the present-day Greece occurred ca 9000 years BP. Outside of Southeast Europe, two episodes of early farming are attested archeologically. The first involved a maritime colonization of Crete ca 9000 years BP and Southern Italy ca 8000 years BP and subsequently spread to coastal Mediterranean France and Spain, as exemplified by impressed/cardial pottery. The second involved a migration to Central Europe, from Hungary to France, characterized by LBK (ca 7500 years BP). Within a 3k-year period, the agricultural economy spread across Europe, terminating in Britain and Scandinavia B6000 years BP.
This study has evaluated the spatial and temporal distributions of sub-clades of Y-chromosome haplogroup R1b-M269 in Europe, the Near East, the Circum-Uralic region and the Caucasus, revealing the major M412-defined phylogenetic dichotomy between the Central/Western Europe and more easterly distributed representatives (Figure 1e and f, respectively). In addition, several additional sub-haplogroup varieties, especially those in Central and Western Europe, display patterns with geographic locality (Figure 1g–o) and clinality (Supplementary Figure 1). The enhanced resolution of M412-related lineages permits a finer-grained view of the proposal that R1b-M269 coincides with the arrival and spread of farming into Europe. A recent analysis of 9 Y-STR loci associated with 840 R1b chromosomes resolved just to the level of M269 concluded that all such chromosomes in Europe reflect a recent genetic heritage that was uniformly introduced by exogenous farmers migrating from Western Anatolia. Our highresolution SNP genotype results show that the majority of Central and Western European haplogroups relate to common M412 founders whose sub-clades display phylogeographic and temporal patterns consistent with allele surfing at the periphery of expansions.
