March 14, 2007

Cruciani et al. on Y haplogroups E-M78 and J-M12

This is a very important new paper, and I am sure I will have much to say about it once I digest the information within the advance access manuscript.

UPDATE (March 14)

  • The first important conclusion of this paper is that haplogroup E-M78 originated in northeastern Africa and its presence in eastern Africa and Eurasia is the result of diffusion from that region.
  • Second, the phylogeny of E-M78 has been refined further since the most recent paper by Cruciani.
  • Haplogroup E-M78 arrived in Europe by two routes: through the Middle East and directly from North Africa. According to the authors "Several lines of evidence suggest that E-M78 sub-haplogroups E-V12, E-V22 and E-V65 have been involved in trans-Mediterranean migrations directly from Africa. These haplogroups are common in northern Africa, where they likely originated, and are observed almost exclusively in Mediterranean Europe, as opposed to central and eastern Europe (table 1, fig. 2). Also, among the Mediterranean populations, they are more common in Iberia and south-central Europe than in the Balkans, the natural entry-point for chromosomes coming from the Levant. Such findings are hardly compatible with a south-eastern entry of E-V12, E-V22 and E-V65 haplogroups into Europe."
  • According to the authors: "Considering both these E-M78 sub-haplogroups (present study) and the E-M81 haplogroup (Cruciani et al. 2004), the contribution of northern African lineages to the entire male gene pool of Iberia (barring Pasiegos), continental Italy and Sicily can be estimated as 5.6%, 3.6%, and 6.6%, respectively." The occurrence of E-V12, E-V22 and E-V65 in the Greek samples of the study are 1.36% (Continental Greeks), 0.93% (Greeks from Crete), 1.41% (Greeks from Aegean Islands)
  • By contrast to the above sub-haplogroups, E-V13 came to Europe from Western Asia and diffused from the Balkans into Europe: "As to a western Asia-Europe connection, our data suggest that western Asians carrying E-V13 may have reached the Balkans anytime after 17.0 ky ago, but expanded into Europe not earlier than 5.3 ky ago." This sub-haplogroup makes the majority of European E-M78 (and indeed all E) Y chromosomes.
  • Haplogroup J2 is divided into two main clades J-M410 and J-M12. The latter sub-haplogroup shows the same signal of expansion as E-V13 in Europe: "Thus, the congruence between frequency distributions, shape of the networks, pair-wise haplotypic differences and coalescent estimates point to a single evolutionary event at the basis of the distribution of haplogroups E-V13 and J-M12 within Europe, a finding never appreciated before."
  • The intrusion of E-V13 and J-M12 into northern Europe from the Balkans occurred at the time of the Balkan Bronze Age: "Our estimated coalescence age of about 4.5 ky for haplogroups E-V13 and J-M12 in Europe (and their C.I.s) would also exclude a demographic expansion associated with the introduction of agriculture from Anatolia and would place this event at the beginning of the Balkan Bronze Age, a period that saw strong demographic changes as clearly testified from archeological records (Childe, 1957; Piggott, 1965; Kristiansen, 1998). The arrangement of E-V13 (fig. 2D) and J-M12 (not shown) frequency surfaces appears to fit the expectations for a range expansion in an already populated territory (Klopfstein, Currat and Excoffier 2006). Moreover, similarly to the results reported by Peričić et al. (2005) for E-M78 network α, the dispersion of E-V13 and J-M12 haplogroups seems to have mainly followed the river waterways connecting the southern Balkans to north-central Europe, a route that had already hastened by a factor 4-6 the spread of the Neolithic to the rest of the continent (Tringham, 2000; Davison et al. 2006)." The frequency map of E-V13 shows the traces of this expansion:

  • The discovery of the young age of the E-V13/J-M12 pair in Europe, its diffusion into the greater part of Europe from the southern Balkans after the Neolithic are, in my opinion, an excellent candidate for the dispersal of IE languages into Europe. I don't reject, however, the possibility that the earlier farming dispersals may have also played a part in this process. Certainly, the uncertainties in the time estimates make the E-V13/J-M12 spread in Europe compatible with D'iakonov's earlier Balkan IE homeland argument. This was probably a secondary center of diffusion.
Molecular Biology and Evolution (advance access)

Tracing Past Human Male Movements in Northern/Eastern Africa and Western Eurasia: New Clues from Y-chromosomal Haplogroups E-M78 and J-M12

Fulvio Cruciani et al.

Detailed population data were obtained on the distribution of novel biallelic markers that finely dissect the human Y chromosomal haplogroup E-M78. Among 6501 Y chromosomes sampled in 81 human populations worldwide, we found 517 E-M78 chromosomes and assigned them to ten sub-haplogroups. Eleven microsatellite loci were used to further evaluate sub-haplogroup internal diversification.

The geographic and quantitative analysis of haplogroup and microsatellite diversity is strongly suggestive of a north-eastern African origin of E-M78, with a corridor for bidirectional migrations between north-eastern and eastern Africa (at least two episodes between 23.9-17.3 ky and 18.0-5.9 ky ago), trans-Mediterranean migrations directly from northern Africa to Europe (mainly in the last 13.0 ky) and flow from north-eastern Africa to western Asia between 20.0 and 6.8 ky ago.

A single clade within E-M78 (E-V13) highlights a range expansion in the Bronze Age of south-eastern Europe, which is also detected by haplogroup J-M12. The phylogeography, pattern of molecular radiation and coalescence estimates for both haplogroups are similar and reveal that the genetic landscape of this region is, to a large extent, the consequence of a recent population growth in situ rather than the result of a mere flow of western Asian migrants in the early Neolithic.

Our results not only provide a refinement of previous evolutionary hypotheses, but also well defined time frames for past human movements both in northern/eastern Africa and western Eurasia.


1 comment:

mathilda said...

I suggested that the M78 in North Africa and east Africa should be defined as 'Afro-Asiatic' now, instead of 'sub Saharan' as it seems to be very tightly paired with M1 and various U's, and isn't from sub saharan Africa.It took one hour before an irate Afrocentrist took offence at suggesting the M78 Y chromosome was tainted with Eurasian ancestry.

How would YOU now describe m78 in a Y chromsome study that comments on admixture? If you had too.

I'm guessing it's mixed Asiatic and African, and it follows the movement of Afro-Asiatic languages pretty tightly, and seems to drag M1 around it (I'd also regard the M1 in East Africa as AA too). This really wouldn't make much difference to Ethiopian admixture, but could mean Somalis are over a third Eurasian if the M78 there is linked to a mix of both ancestries.

It might explain why Somalis are closer than Ethiopians to Badarian crania. They've got a much higher percentage of the migration from that area left unaffected by later migrations from the Arabian peninsula and the Bantu expansion.