Showing posts with label R1b. Show all posts
Showing posts with label R1b. Show all posts

Thursday, 7 March 2013

Y chromosomes of Bulgarians (Karachanak et al. 2013)

Bulgaria had been something of a blank area in studies of uniparental markers, so it's nice to finally see a comprehensive Y-chromosome study of the country.
The dates in the paper are based on the "evolutionary mutation rate". I suspect that ancient DNA will be the final arbiter in this issue, because, for example, a Mesolithic TMRCA of E-V13 in Bulgaria implies that we'll find a lot of it in Neolithic contexts, whereas a Bronze Age one implies that we'll find a little if any of it, and a discontinuity across time.
Of interest is the occurrence of some E*(xM35, M2) in this sample in Burgas, Varna, and Plovdiv. It would be interesting to trace the ancestry of the bearers of these Y-chromosomes. I know that there still exists a minority-within-a-minority of Black Muslims in Greek Thrace, and it's not inconceivable that these Y-chromosomes may represent the legacy of a similar population; in any case, their haplotypes can be found in Table S5 for anyone wanting to investigate.
SNP Diversity within R seems substantial, and as always, it is difficult to say much, since this may be a consequence of either (i) a plausible role of the Balkans as a staging point of the likely invasion of Europe in late prehistory, or (ii) back-migration of derived R-bearers into the Balkans, be them Slavs or Goths or "eastern" folks of various stripes during history. Once again, I suspect that ancient DNA might solve this riddle, or, alternatively, routine high-coverage sequencing of the Y chromosome that might inform us, e.g., about the TMRCA of a Bulgarian and a German R-U152 or a Bulgarian and Polish R-M458.
PLoS ONE 8(3): e56779. doi:10.1371/journal.pone.0056779
Y-Chromosome Diversity in Modern Bulgarians: New Clues about Their Ancestry
Sena Karachanak et al

To better define the structure and origin of the Bulgarian paternal gene pool, we have examined the Y-chromosome variation in 808 Bulgarian males. The analysis was performed by high-resolution genotyping of biallelic markers and by analyzing the STR variation within the most informative haplogroups. We found that the Y-chromosome gene pool in modern Bulgarians is primarily represented by Western Eurasian haplogroups with ~ 40% belonging to haplogroups E-V13 and I-M423, and 20% to R-M17. Haplogroups common in the Middle East (J and G) and in South Western Asia (R-L23*) occur at frequencies of 19% and 5%, respectively. Haplogroups C, N and Q, distinctive for Altaic and Central Asian Turkic-speaking populations, occur at the negligible frequency of only 1.5%. Principal Component analyses group Bulgarians with European populations, apart from Central Asian Turkic-speaking groups and South Western Asia populations. Within the country, the genetic variation is structured in Western, Central and Eastern Bulgaria indicating that the Balkan Mountains have been permeable to human movements. The lineage analysis provided the following interesting results: (i) R-L23* is present in Eastern Bulgaria since the post glacial period; (ii) haplogroup E-V13 has a Mesolithic age in Bulgaria from where it expanded after the arrival of farming; (iii) haplogroup J-M241 probably reflects the Neolithic westward expansion of farmers from the earliest sites along the Black Sea. On the whole, in light of the most recent historical studies, which indicate a substantial proto-Bulgarian input to the contemporary Bulgarian people, our data suggest that a common paternal ancestry between the proto-Bulgarians and the Altaic and Central Asian Turkic-speaking populations either did not exist or was negligible.
Link

Thursday, 21 February 2013

Algerian Y chromosomes and mtDNA

From the paper:
For the R-M343 subdivision, the Iberian Peninsula reflects a genuine European profile [45] except for the presence of one Sahel R-V88 type. In contrast, all R-M343 detected in W. Saharan-Mauritanian belong to sub-group R-V88, reaching a frequency of 7%, similar to those observed in other Sahel samples [40]. In the Maghreb countries, the frequency of R-V88 drops to around 1%. On the other hand, the presence in this area of representatives of the European sub-groups R-M412, R-S116, R-U152 and R-M529 points to North-South maritime contacts across the Mediterranean
It would be interesting to estimate the depth of common ancestry of the North African "European" Y chromosomes to determine the epoch during which they arrived there, i.e., whether the common ancestry stems from recent historical contacts (Roman Empire, Vandals, etc.) or from the early settlement of both Mediterranean coasts during the arrival of R-M269 into Europe.


A few observations on Y-haplogroup frequencies:

  • The ubuquity of haplogroup Q at trace frequencies in most regions except North Africa (only a little in ALG) is interesting and it's high time that someone looked at the relationship between West Eurasian Q-bearers and their much more numerous East Eurasian cousins.
  • I find the paucity of Y-haplogroup I in North Africa noteworthy; given its high levels in most of Western Europe, its relative absence might indicate that the people who brought "European" R-M269 into N Africa were not occasional recent migrants, but rather earlier settlers. 
  • The relative absence of J2 is expected, given that neither of the two main strata of population ("Berber" and "Arab") may have possessed it initially; it has also not been found in a historical sample from the Canary Islands, whereas its J1 counterpart has.
  • The paucity of haplogroup G, which is the European Neolithic lineage par excellence probably argues against the involvement of the people who colonized Europe during the Early Neolithic in similar events on the south shore of the Mediterranean.
  • The further study of F chromosomes could also be further attempted, given their possible involvement in the Upper Paleolithic of Eurasia

The authors highlight that 80% of mtDNA is Eurasian vs. 90% of Y chromosomes. This might point to asymmetric gene flow from Sub-Saharan Africa. Alternatively, it might point to some mtDNA that is characterized as non-Eurasian (because it does not belong to the M, N macro-haplogroups) being in fact so. It is a persistent question whether lineages that have a wide frequency differential in two regions do so because of gene flow (from the high- to low-frequency area), or because of other processes.

PLoS ONE 8(2): e56775. doi:10.1371/journal.pone.0056775

Introducing the Algerian Mitochondrial DNA and Y-Chromosome Profiles into the North African Landscape

Asmahan Bekada et al.

North Africa is considered a distinct geographic and ethnic entity within Africa. Although modern humans originated in this Continent, studies of mitochondrial DNA (mtDNA) and Y-chromosome genealogical markers provide evidence that the North African gene pool has been shaped by the back-migration of several Eurasian lineages in Paleolithic and Neolithic times. More recent influences from sub-Saharan Africa and Mediterranean Europe are also evident. The presence of East-West and North-South haplogroup frequency gradients strongly reinforces the genetic complexity of this region. However, this genetic scenario is beset with a notable gap, which is the lack of consistent information for Algeria, the largest country in the Maghreb. To fill this gap, we analyzed a sample of 240 unrelated subjects from a northwest Algeria cosmopolitan population using mtDNA sequences and Y-chromosome biallelic polymorphisms, focusing on the fine dissection of haplogroups E and R, which are the most prevalent in North Africa and Europe respectively. The Eurasian component in Algeria reached 80% for mtDNA and 90% for Y-chromosome. However, within them, the North African genetic component for mtDNA (U6 and M1; 20%) is significantly smaller than the paternal (E-M81 and E-V65; 70%). The unexpected presence of the European-derived Y-chromosome lineages R-M412, R-S116, R-U152 and R-M529 in Algeria and the rest of the Maghreb could be the counterparts of the mtDNA H1, H3 and V subgroups, pointing to direct maritime contacts between the European and North African sides of the western Mediterranean. Female influx of sub-Saharan Africans into Algeria (20%) is also significantly greater than the male (10%). In spite of these sexual asymmetries, the Algerian uniparental profiles faithfully correlate between each other and with the geography.

Link