Human Y chromosome haplogroup R-V88: a paternal genetic record of early mid Holocene trans-Saharan connections and the spread of Chadic languages

• DOI: 10.1038/ejhg.2009.231
• Publication Date: 2010-01-06T11:27:40Z
• Authors: Fulvio Cruciani; Beniamino Trombetta; Daniele Sellitto; Andrea Massaia; Giovanni Destro-B...; Elizabeth Watson; Eliane Beraud Colomb; Jean-Michel Dugoujon; Pedro Moral; Rosaria Scozzari
• Keywords: Male; 0303 health sciences; Asia; Chromosomes, Human, Y; Time Factors; Chad; Geography; Emigration and Immigration; Fathers; 03 medical and health sciences; Africa, Northern; Haplotypes; human migrations; chadic-speaking populations; y chromosome haplogroups; holocene; africa; Humans; Phylogeny; Language; Microsatellite Repeats

Although human Y chromosomes belonging to haplogroup R1b are quite rare in Africa, being found mainly in Asia and Europe, a group of chromosomes within the paragroup R-P25(*) are found concentrated in the central-western part of the African continent, where they can be detected at frequencies as high as 95%. Phylogenetic evidence and coalescence time estimates suggest that R-P25(*) chromosomes (or their phylogenetic ancestor) may have been carried to Africa by an Asia-to-Africa back migration in prehistoric times. Here, we describe six new mutations that define the relationships among the African R-P25(*) Y chromosomes and between these African chromosomes and earlier reported R-P25 Eurasian sub-lineages. The incorporation of these new mutations into a phylogeny of the R1b haplogroup led to the identification of a new clade (R1b1a or R-V88) encompassing all the African R-P25(*) and about half of the few European/west Asian R-P25(*) chromosomes. A worldwide phylogeographic analysis of the R1b haplogroup provided strong support to the Asia-to-Africa back-migration hypothesis. The analysis of the distribution of the R-V88 haplogroup in >1800 males from 69 African populations revealed a striking genetic contiguity between the Chadic-speaking peoples from the central Sahel and several other Afroasiatic-speaking groups from North Africa. The R-V88 coalescence time was estimated at 9.2-5.6 [corrected] kya, in the early mid Holocene. We suggest that R-V88 is a paternal genetic record of the proposed mid-Holocene migration of proto-Chadic Afroasiatic speakers through the Central Sahara into the Lake Chad Basin, and geomorphological evidence is consistent with this view.