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Fulvio CRUCIANI (Italy)* Human Y-chromosome haplogroup R1b1a (R-V88): A paternal genetic record of early-mid Holocene trans-Saharan connections
Human Y chromosomes belonging to haplogroup R-P25 are quite rare in Africa, being found mainly in Asia and Europe. However, a group of P25 Y chromosomes that are not defined by the presence of a downstream derived marker (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 previously reported R-P25 Eurasian sub-lineages. The incorporation of these new mutations into a phylogeny of the R-P25 haplogroup led to the identification of a new clade (R1b1a or R-V88) encompassing all the African R-P25*, about half of the few European/west Asian R-P25*, and the R-M18 chromosomes. A world-wide phylogeographic analysis of the R-P25 haplogroup provided strong support to the Asia-to-Africa back-migration hypothesis. The analysis of the distribution of the R-V88 haplogroup in more than 1,800 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 9,200-5,600 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.
Posts: 2007 | From: Washington State | Registered: Oct 2006
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Cruciani is known for making observations that don't square with what his actual DNA results show. I've pointed this out with both R1*-M173 chromosomes, E-M78 clusters and E-M34. And so, I now reiterate what's wrong with his so-called "Asia-to-Africa back migration", which he seems bent on promoting, since otherwise would implicate European ancestry directly from Africa...and we know how that gets Eurocentrist and closet-Eurocentrist's pants bunched up.
Previously, when Cruciani thought he had come up with undifferentiated, upstream R1* chromosomes, he considered it a possibility that this could be suggestive of African origin, since the African counterparts were phylogenetically more basal than his non-African sample collection; yet, this didn't phase him to entertain the alternative then, about back-migration to Africa, predicated on a flimsy point about Hg R, in its entirety, not being as diverse in Africa as it appears to be in Asia. At the time, this was essentially Cruciani's sole argument for his preference of a back-migration scenario, which obviously, contradicted the fact then, that his African samples were the ONLY ones which tested positive for the most basal R markers.
So now, he comes up with new markers, and tries to see if he can solidify his earlier flimsy position. But even here, with the further combing of the Hg R chromosomes, he claims that the Hg R chromosomes bearing the new mutations he tested for are still more prevalent in Africa, and rarer in non-African areas. Yet, Cruciani wants to convince us this is some sort of unequivocal proof that Africans must have attained it from back-migration, and he tries to solidify this, by invoking early Holocene dates. However, it is interesting to note that African R1*-M173 chromosomes were tested for the P25 mutation, and came up negative. What does this then mean? It means that while Africans carried rare R1 chromosomes bearing P25, they also carried examples without P25 [see Hassan et al. 2008, for example]. In other words, African R1 chromosomes aren't homogeneous as Cruciani would perhaps like us to believe.
Furthermore, as I have noted here and elsewhere before,...
Interestingly, having re-visited Wood et al. (2005), it should be pointed out that paraphyletic clade of R*-M207 was detected amongst some "Afro-Asiatic" African groups, along with the paraphyletic clade R1*-M173 [both R* and R1* were very likely featured in "Chadic" speaking groups of northern Cameroon, the region where the authors themselves emphasized the also rare Hg R-P25* sub-group's incidence; Egypt could be considered a distant possibility here, based other studies re: Luis et al. (2004), but it is worth noting that Wood et al. implicate the Egyptian sample here as something other than that of Semitic speakers (Arabic), and keeping in mind that even Egyptian incidences of R1* are noticeably lower than that of northern Cameroon], while some Niger-Congo groups — though in small frequencies [pooled] — tested positive for the paraphyletic R1b*, lacking the established downstream R1b markers. Henceforth, R*-M207, lacking downstream mutations have been identified in African groups via this study; and yes, the basic nodes of all Hg R's downstream clades had been accounted for, which means that R*, as predicted above, is NOT relegated to the Indian sub-continent. All in all, this suggests that African Hg R pool is more diverse than many seem to think.
^Once again, African chromosomes lacking the P25 marker have been identified, whereas Cruciani's Hg R chromosomes all appeared to have tested positive for P25; they only differed from subsequent downstream markers - presumably aside from those one or more of the "new mutations" tested for. African chromosomes transcend even the ancestral Hg R1* marker; the paraphyletic R* is also implicated, which is ancestral to R1* marker!
...but I'm sure Cruciani isn't done combing Hg R chromosomes, if he is to unequivocally prove the back-migration scenario he seems to so desire. Posts: 7516 | From: Somewhere on Earth | Registered: Jan 2008
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quote:Originally posted by The Explorer: Cruciani is known for making observations that don't square with what his actual DNA results show. I've pointed this out with both R1*-M173 chromosomes, E-M78 clusters and E-M34. And so, I now reiterate what's wrong with his so-called "Asia-to-Africa back migration", which he seems bent on promoting, since otherwise would implicate European ancestry directly from Africa...and we know how that gets Eurocentrist and closet-Eurocentrist's pants bunched up.
Evergreen Writes:
Your point is a good one. The early Holocene crania of NE Africa and West Africa cluster with modern West African populations. This makes good sense in light of the fact that all of these groups evolve from a common late stone age y-chromosome ancestor as expressed on the E1b1 haplogroup.
Haplogroup E1b1 populations did not migrate into NE Africa until the early last glacial maximum, circa ~ 20,000 kya. However, the pre-last glacial maximum NE African Nazlet Khater specimen cluster with the Khoisan and South African populations and the Late Upper Paleolithic European samples from Harvatia 2009 cluster with the Kenyan and Zulu samples.
As Shomarka Keita notes in "In hot pursuit of language in prehistory":
The issue of how much Paleolithic migration from the Near East there may have been is intriguing, and the mitochondrial DNA variation may need to be reassessed as to what can be considered to be only of "Eurasian origin" because if hunters and gatherers roamed between the Saharan and supra-Saharan regions and Eurasia it might be difficult to determine exactly "where" a mutation arose.Posts: 2007 | From: Washington State | Registered: Oct 2006
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Explorer is right on with the scrutiny! How can Cruciani claim R1* and derivative chromosomes be not as diverse in Africa when his own findings refute this?? I especially find it funny how he tries to associate R-V88 with Chadic or proto-Chadic speakers when Chadic is a branch of Afrasian and the vast majority of Afrasian speakers carry E.
quote:Originally posted by Evergreen: As Shomarka Keita notes in "In hot pursuit of language in prehistory":
The issue of how much Paleolithic migration from the Near East there may have been is intriguing, and the mitochondrial DNA variation may need to be reassessed as to what can be considered to be only of "Eurasian origin" because if hunters and gatherers roamed between the Saharan and supra-Saharan regions and Eurasia it might be difficult to determine exactly "where" a mutation arose.
^ Yes, and I'm sure Keita refers to mitochondrial lineages like U6 and N1a. What Keita says here is merely a rewording of what he said elsewhere about how geneticists should be careful about labeling which paleolithic lineages are 'Eurasian' since all Eurasians are derived from Africans.
Posts: 26238 | From: Atlanta, Georgia, USA | Registered: Feb 2005
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