A multistep process for the dispersal of a Y chromosomal lineage in the Mediterranean area

Tn this work we focus on a microsatellite-defined Y-chromosomal lineage (ne twork 1.2) identified by us and reported in previous studies, whose geograp hic distribution and antiquity appear to be compatible with the Neolithic s pread of farmers. Here, we set network 1.2 in the Y-chromosomal phylogeneti c tree, date it with respect to other lineages associated with the same mov ements by other authors, examine its diversity by means of tri- and tetranu cleotide loci and discuss the implications hi reconstructing the spread of this group of chromosomes in the Mediterranean area. Our results define a t ripartite phylogeny wit-bin HG 9 (Rosser et al. 2000) with the deepest bran ching defined by alleles T (Haplogroup Eu 10) or G (Haplogroup Eu9) at M172 (Semino et al. 2000), and a subsequent branching within Eu9 defined by net work 1.2. Population distributions of HG 9 and network 1.2 show that their occurrence in the surveyed area is not due to the spread of people from a s ingle parental population but, rather, to a process punctuated by at least two phases. Our data identify the wide area of the Balkans, Aegean and Anat olia as the possible homeland harbouring the largest variation within netwo rk 1.2. The use of recently proposed tests based on the stepwise mutation m odel suggests that its spread was associated to a population expansion, xvi th a high rate of male gene flow in the Turkish Greek area.