title: Human Y chromosome haplogroup R-V88: a paternal genetic record of early mid Holocene trans-Saharan connections and the spread of Chadic languages.
abstract: 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.
authors.affiliation: Dipartimento di Genetica e Biologia Molecolare, Sapienza Università di Roma, Rome, Italy.
authors.forename: Fulvio
authors.initials: F
authors.lastname: Cruciani
authors.forename: Beniamino
authors.initials: B
authors.lastname: Trombetta
authors.forename: Daniele
authors.initials: D
authors.lastname: Sellitto
authors.forename: Andrea
authors.initials: A
authors.lastname: Massaia
authors.forename: Giovanni
authors.initials: G
authors.lastname: Destro-Bisol
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Watson
authors.forename: Eliane
authors.initials: E
authors.lastname: Beraud Colomb
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Dugoujon
authors.forename: Pedro
authors.initials: P
authors.lastname: Moral
authors.forename: Rosaria
authors.initials: R
authors.lastname: Scozzari
mesh_terms: D000352:Africa, Northern; D001208:Asia; D002596:Chad; D041322:Chromosomes, Human, Y / Q000235:genetics*; D004641:Emigration and Immigration; D005220:Fathers; D005843:Geography; D006239:Haplotypes / Q000235:genetics*; D006801:Humans; D007802:Language; D008297:Male; D018895:Microsatellite Repeats / Q000235:genetics; D010802:Phylogeny; D013997:Time Factors