While Maglio's modified phylo-geography is intriguing, I disagree with his conclusion for roots in a LGM Iberian refuge.
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| V88+ Expansion from Lake Chad (Maglio, 2014) |
But before I get to the points of interest, I have to say I'm surprised to see this Iberian refuge hypothesis continually sit up in the coffin.
It's noteworthy that the red dot in Fig. 7 is at the edge of Valdelugueros (La Brana), the site of two recent, controlled, stratified, Mesolithic hunter-gatherers. They are the totality of their genealogies and their parents, grandparents, brothers, sisters and extended families would have heritable traits and haplotypes similar to them, not like peoples who live in this region now.
(I will comment on these early Iberian archeaogenetic studies in depth on Beaker genetics page 2 which will raise your abundant Late Neolithic eyebrows)
However...
Maglio has re-arranged some of the phylo-geography in a novel way. Most interesting is the shifting center of gravity for V88+ away from the Near East where it has usually been placed to the edge of Earth. V88+ may be young enough that putting a hard and fast origin in the Middle East is a bit forced, especially when its immediate diversity doesn't clearly show this.
So, without getting into the details, I want to use Maglio's "Iberia-Chad" hypothesis and tweak it with an alternate interpretation using the last Saharan pump.
I think what Maglio is looking at is the genetic fray of the African Late Neolithic Subpluvial from which (I think) Beakers and African pastoralists descend.
I'll predict that with more subtropic canvassing we will begin to see a "grass fire pattern" around the Sahara (ie. Iberia, Sub-Sahara, Blue Nile, Levant) with strong founder effects towards super-lineages, but the continued presence of very low frequency, bottle-necked and ancestral lineages in the fray. (479*, 173*, P25*, L-278 (V88-), V88+, L51-, L51*)
As Maglio states in the L-278 paper, we should not be distracted by the super-clades of Europe (and Africa). The reason for their accession is probably statistical and societal (on multiple levels).
This "grass fire effect" is somewhat visible now with the Sub-Sahara "under girded" by R1b in Mali, Mauritania, Niger, Nigeria, Chad, Cameroon and deeper into the Congo. Although these are significantly V88+, it is critical to note that all these lineages are badly under-represented by independents and formal studies.
The problem with understanding the phylogeny of R1b in Africa is that vast regions previously inhabited by pastoralists are now completely uninhabited. This is true in the Western Sahara, where the human population is essentially zero, which is why R1b constitutes 0% of male haplogroups.
Where there is R1b, its usually crowded in inbred oasies where M269 may make 1% with a much larger share to V88.
Only heavy canvassing and deep clade testing will reveal the structure of P297 and L-278 in the continent.
I will have have to study his process better, but reading various forums, it seems the age and spread of these lines is being challenged with deep SNP testing.
Y Chromosome Haplogroup R1b-V88: Biogeographical Evidence for an Iberian Origin Michael R. Maglio, 2014 [Link]
The status on the origins of haplogroup R1b remains split between the Iberian Peninsula prior to the Last Glacial Maximum (LGM) and a West Asian origin coinciding with the Neolithic expansion. The majority of focus on subgroup R1b-V88 has concentrated on African populations and neglected European and West Asian populations. To get a complete understanding of the back to Africa migration, a holistic network approach is necessary. Biogeographical Multilateration (BGM) illustrates directional flow as well as chronological and physical origins at the haplogroup level. The resulting phylogenetic relationships for R1b-V88 support an Iberian origin, a Mediterranean expansion and a Europe to Africa back migration.
Biogeographical Evidence for the Iberian Origins of R1b-L278
via Haplotype Aggregation Michael R. Maglio, 2014 [Link]
The status on the roots of haplogroup R1b remains split between an Iberian origin prior
to the Last Glacial Maximum (LGM) and a West Asian origin coinciding with the Neolithic expansion. Existing methods generalize geographic patterns based on large population genetic frequency and diversity. Haplotype Aggregation delivers a coherent genetic record selection and Biogeographical Multilateration (BGM) illustrates directional flow as well as chronological and physical origins at the haplogroup level. The resulting phylogenetic relationships across multiple high level branches of R1b support an Iberian origin and a rapid Western Atlantic migration.
While the "Out of Chad" theory is novel and in principle possible, given the date sequences, a common ancestral population from which both very basal R1b-V88 in linguistically Chadic people in Africa, and later R1b populations in Europe, seems far more plausible.
ReplyDeleteAlso, archaeological dates that a very likely to be associated with the Chadic people and the arrival of V88 in Africa point to a date more like 5500 BCE, which is about two sigma older than the suggestion of this author.
A deep origin of R1b in West Asian is admitted, but no attention is given to the when and how of a migration of R1b from West Asia to a putative secondary point of dispersal in Iberia, presumably during the LGM era.
ReplyDeleteOn second review, the 5700 BCE date for the origin of V88 given is pretty much in line with the archaeology. The later date ca. 1200 BCE is the supposed back to Europe date. The notion to a back migration of Chadic pastoralists up the Nile and across the Mediterranean to Central Europe and outward from there ca. 2200-200 BCE, who spread R1b there in the Bronze Age, however, has no archaeological support despite occurring in a time period where we have fairly complete and comprehensive Egyptian, Hittite and classical Greco-Roman written history. There were no linguistically Afro-Asiatic people to the North of the Levant in the Bronze Age, and there is no evidence that there have ever been linguistically Chadic people even as far north as North Africa at any time. This theory is a dog that won't hunt.
The notion of Crete potentially being pivotal of R1b's spread has merit, although the notion that the spread was from Mesolithic Iberia (as claimed in one of the two papers) is not well supported.
For someone so concerned about the distribution of the most basal branches of Y-DNA R, the total absence of Iranian data, when that region is home to the greatest diversity of basal Y-DNA R branches of R1a, R1b and R paragroups, per Grugni (2012) (http://dienekes.blogspot.com/2012/07/huge-study-on-y-chromosome-variation-in.html) is a serious oversight that likely greatly undermines the thesis. The failure of the author to recognize that small residual percentages of a population that predominantly has a more recent mutational variant of a Y-DNA haplogroup will have the ancestral variant for any decent effective population size of the ancestral population is also short sighted. Y-R1b-L278 and V-88 in the population that subsequently expanded along the European Atlantic Coast out of Iberia is very likely of this character.
Good points all around. As you've said, it is difficult to find a scenario where V88 could blanket Europe at a low frequency within an archaeological scenario. Attributing its European presence to Jewish migration or another ethnic enclave also seems unlikely in that there is no ethnic group with the frequency or diversity of these V88 clades to properly explain its European manifestations.
DeleteI would cautiously guess that it was present alongside expansion of either of the major R1 clades. I lean slightly toward the possibility that it was present at low frequency with the spread of Beaker lineages from Iberia (of course I view Beakers to have come the Sahel which I sounds crazy at first),
but looking at V88s respectable distribution in Eastern Europe, it's plausible that it could have entered via a more easterly route.
Also, thanks for the link.
DeleteMichael Hammer has a more mainstream analysis of entry of R1b generally into Europe via an easterly route based upon phylogeny. http://eurogenes.blogspot.com.au/2013/11/the-story-of-r1b-its-complicated.html
ReplyDeleteWhile I don't contest the overall cline proposed by Hammer, I think that it is often misinterpreted as suggesting a population migration of individuals rowing up the Lower Danube while having deep clade mutations. Perceivable deep clines would only be truly valid within the Neolithic demic model where people settled as they encroached 1.5 miles a year (or whoever's method is used), but this doesn't fit what is known of Neolithic Danubian or Lower Balkan genetic profiles.
DeleteThe speed to which R1b prevailed in places where it has been previously undetected in Europe, may not invalidate a cline model, but I put less stock in it because the people in question were crawling over Europe with eight generations of the first tanged dagger thrown in the ground. (Assuming Beakers were generally R1b)
Personally, I think there is multidisciplinary evidence to link "pots and people" with North Africa and virtually nothing to link Beakers with Eastern Europe. Admittedly, making this case is difficult for the paternal lineages of Western Europe, but I think this will become easier as the full picture of R1b in Africa is understood (or I could get pie in the face)