Saturday, January 23, 2010

New Y-DNA Indactor of "First Neolithic Farmers" coming into Europe?

Reviewing: A Predominantly Neolithic Origin for European Paternal Lineages, by Balaresque et al., 2010.   

The present study does not really challenge, nor does it appear to be the intended goal at any rate, the oft implicated recent African ancestry component in "first Neolithic farmers" of the "Near East" and "Europe", generally represented by Hg E1b1b markers, in tandem with in situ "Near Eastern" genealogical component generally represented by Hg J markers. Rather, the case made here is one of presumably a new revelation, which is that yet another marker appears to have been in the move, presumably alongside Hgs E and J, amongst the "first Neolithic farmers" diffusing into Europe from the "Near East". The idea here, is to explain why there seems to be disconcordance between the extent of the spread of uniparental nuclear (Y-DNA) markers and the relative far reaching and magnitude of the spread of the Neolithic farming subsistence economy across Europe. Here is how the authors at hand framed this observation: low contribution of incoming Y chromosomes to the European Neolithic, despite its antiquity and impact, has appeared anomalous. So, what do the authors' findings reveal to us? Our interpretation of the history of hgR1b1b2 now makes Europe a prime example of how expansion of a Y-chromosomal lineage tends to accompany technological and cultural change. The idea here therefore, is that the seemingly low contribution of "incoming Neolithic farmers" into Europe stems out of not taking into account, until now, the hg R1b1b2 component of these incoming "first farmers". This leaves the impression that the "first Neolithic farmers" coming into Europe had left a fairly modest patrilineal trail, in contrast to the magnitude of their cultural influence. Hg R1b1b2 findings here are supposed to now show that these "first farmers" had in fact left a much stronger Y-DNA mark than that previously imagined. As a matter of observation, the authors are essentially making a mole hill out of hg R1b1b2 distribution, which they base on microsatellite variation and their age estimations. When one looks at their microsatellite network, it is hard not to notice the relative heightened diversity of Iberian clades against that of the Turkish examples. This observation could be off, but let the viewer verify it for themselves below...

Click on the image for greater resolution

Even their geographical plots, while it does show the most intensified concentration in Turkish territory [for microsatellite variance but not frequency; heightened frequency is most concentrated in the Iberian peninsula and parts of far western areas north Europe], one notices a sharp dip in concentration as one proceeds westward south—i.e. past Italy, and then picks up concentration in the Iberian peninsula. A similar trend is observed going south to north, again west of Italy. The concentration drops from that seen in Iberia and then starts to pick up somewhat in the northern-French and Dutch region.

Click on the Image for greater resolution. Image footnote: Geographical distribution of microsatellite STRs variance within hg R1b1b2.

Click on the image for greater resolution. Image footnote: Geographical distribution of frequency of hg R1b1b2.

Guess what, their observations are not that far out from that seen by Cinnioglu et al. 2004. [around the clade R1b3, which now essentially the R1b1b2] Earlier, as pointed out here before,...
"The variance of 49a,f ht35 related chromosomes are lower in the Balkan, Caucasian and Iraqi representatives than those in Turkey(Table 4). Similarly, the variance is higher in Iberia than in Western Europe.

The decreasing diversity radiating from Turkey towards Southeast Europe, Caucasus and Mesopotamia approximates similar results from Iberia tracing the re-colonization of Northwest Europe by hunter-gatherers during the Holocene as suggested by others (Torroni et al. 1998; Semino et al. 2000a; Wilson et al. 2001)...

Haplogroup R1b3-M269 occurs at 40–80% frequency in Europe and the associated STR variance suggests that the last ice age modulated R1b3-M269 distribution to refugia in Iberia and Asia Minor from where it subsequently radiated during the Late Upper Paleolithic and Holocene. The R1b3-M269 related, but opposite TaqI p49a, f ht 15 and ht35 distributions reflect the re-peopling of Europe from Iberia and Asia Minor during that period.

The R1b3-M269 variances and expansion time estimates of Iberian and Turkish lineages are similar to each other (Table 2) but higher than observed elsewhere(Table 4)."
- Cinnioglu et al. 2004
It's worth noting that while Cinnioglu et al. (2004) took into consideration the data for nearby "southwest Asian" region (Georgia/Iraq) outside of Turkey, the present study limits its focus on mainly Europe, with Turkey being the geographical extent or the sole representative of the "Near East". While Cinnioglu et al. (2004) also took into consideration the hg R1b1b2-linked TaqI RFLP haplotype distributions respective to haplotypes 15 and 35, there is no indication in the present study that these haplotypes' distribution patterns were taken into consideration. As for the TMRCA ages cited in the present study,  the estimates all generally fall within the 5,460 and 7,900 year bracket, and interestingly, the Turkish samples ages here are based on published data undertaken by Cinnioglu et al. (2004), which the present study cites as its reference-source for those Turkish samples. Turkish sample age estimations are not the only ones to go over 7,000 years, which should all be taken into consideration along with the cited confidence intervals. The likely wisdom here, in relation to the case being put forward in the present study, is that these "spurts" [of the higher-end age estimations] deep into the western corner of Europe may just be serving as relics of the earliest segments of new "first farmer" settlers in the European population in question. This would suggest that the earliest farmers shortly upon arrival, penetrated deep into Europe, straight to the northwestern corner of the subcontinent through central Europe, and then, possibly made their way down southward in western areas of Europe, thereby reaching the Iberian peninsula (?) or else, a two-pronged situation upon reaching central Europe, wherein some migratory group(s) headed straight to the western corner and the others, southwestern corner [which would have to be the scenario, given the erratic distribution of age estimations given to designated regions, with those in Iberia generally being older than those further north in the western areas, save for the aforementioned spurts in the northwestern corner around northern France area]? However, the conventional estimation is one of a expansion southwestward, following regions along the northern boundaries of the Mediterranean sea, from where in the southeast areas, diffusions into central and then north thereof would have been facilitated, with age estimations of Neolithic sites in Europe reported along the order of earliest to latest, and not in such a short time or fast-paced time span upon arrival from the "Near East" [as suggested by the aforementioned scenarios; there are considerable temporal differences between the earlier sites in southern Europe, esp. southeastern areas and relatively later ones in northwestern and other areas of northern Europe], so that one goes from first southeast Europe, then central Europe, and then northwestern Europe; this is also what's indicated by the traditional "first Neolithic farmer" paternal markers of hgs E and J:

Click on the image for greater resolution. Semino et al. (2004) Hg E distribution.

Click on the image for greater resolution. Semino et al. (2004) Hg J distribution.

Of course, it is not inconceivable that Hg R1b1b2 markers arrived along with Hgs J and E carriers during demic difusion, but it is just as likely, as the above observations suggest, that these supplemented preexisting Hg R1b1b2 carriers who spread earlier from certain refugia at end [as noted above via Cinnioglu et al. (2004)] of the LGM or early Holocene, independent from the expansion ensuing from the Neolithic farming subsistence complexes in the "Near East", and subsequently expanded in their new found refuges. That would explain the distinctive geographical patterns seen Hg R1b1b2-linked TaqI RFLPs.