Ancient mtDNA from hunter-gatherers and farmers of Northern Spain (Hervella et al. 2012)

Ancient mtDNA from hunter-gatherers and farmers of Northern Spain (Hervella et al. 2012): Having just finished writing my mega-post on the new exciting ancient DNA results from Sweden, a new paper has caught my attention which presents data from Paleolithic-to-Bronze Age inhabitants of northern Spain. Since this is an open-access paper, I'll let you read it, and post my own comments later as an update to this post.



UPDATE: Just three observations on the study:

1. 50% of the hunter-gatherers belonged to haplogroup U subclades, hence confirming for this region as well that this lineage was over-represented in pre-farming populations; the remainder were assigned by the authors to H subclades on the basis of HVR polymorphisms.
2. Haplogroup V that had been proposed as having originated in the Franco-Cantabrian region is again conspicuously absent in the ancient data
3. It now appears that the N1a dominance in LBK samples (and in a French Megalithic) was not shared by all Neolithic groups, with no N1a turning up in the Spanish samples

From the paper:

The Neolithic sample of France (NEO_FR) is closer to present-day populations in the Near East, because it shows similar frequencies for haplogroups TX, W, J, H and U (the ones with the highest correlation for the first axis in the PCA, data not shown). However, the Neolithic populations from the Iberian Peninsula (NEO_CAT and NEO_NAVARRE) are located between the variability of present-day European populations and those in the Near East. Likewise, the Chalcolithic populations in the Basque Country (Longar, SJaPL and Pico Ramos) occupied a similar position to the Neolithic groups of the Iberian Peninsula (Figure 2).

The results from this paper are hence in agreement with lots of other lines of evidence pointing to an exogenous population element in the formation of the Neolithic in Southwest Europe as in Scandinavia.

The authors attribute this to maritime colonization:

Maritime colonization, transporting small and different Neolithic groups from the Near East pool could contribute to explain the difference.

Hopefully, we will be able to obtain autosomal DNA from some of the Neolithic samples as we did in Scandinavia, and I would be much surprised if these Neolithic inhabitants of Iberia were not Oetzi-like and hence intermediate between most modern populations of Southern Europe and the Near East.



PLoS ONE 7(4): e34417. doi:10.1371/journal.pone.0034417




Ancient DNA from Hunter-Gatherer and Farmer Groups from Northern Spain Supports a Random Dispersion Model for the Neolithic Expansion into Europe




Montserrat Hervella et al.




Abstract




Background/Principal Findings



The phenomenon of Neolithisation refers to the transition of prehistoric populations from a hunter-gatherer to an agro-pastoralist lifestyle. Traditionally, the spread of an agro-pastoralist economy into Europe has been framed within a dichotomy based either on an acculturation phenomenon or on a demic diffusion. However, the nature and speed of this transition is a matter of continuing scientific debate in archaeology, anthropology, and human population genetics. In the present study, we have analyzed the mitochondrial DNA diversity in hunter-gatherers and first farmers from Northern Spain, in relation to the debate surrounding the phenomenon of Neolithisation in Europe.




Methodology/Significance



Analysis of mitochondrial DNA was carried out on 54 individuals from Upper Paleolithic and Early Neolithic, which were recovered from nine archaeological sites from Northern Spain (Basque Country, Navarre and Cantabria). In addition, to take all necessary precautions to avoid contamination, different authentication criteria were applied in this study, including: DNA quantification, cloning, duplication (51% of the samples) and replication of the results (43% of the samples) by two independent laboratories. Statistical and multivariate analyses of the mitochondrial variability suggest that the genetic influence of Neolithisation did not spread uniformly throughout Europe, producing heterogeneous genetic consequences in different geographical regions, rejecting the traditional models that explain the Neolithisation in Europe.




Conclusion



The differences detected in the mitochondrial DNA lineages of Neolithic groups studied so far (including these ones of this study) suggest different genetic impact of Neolithic in Central Europe, Mediterranean Europe and the Cantabrian fringe. The genetic data obtained in this study provide support for a random dispersion model for Neolithic farmers. This random dispersion had a different impact on the various geographic regions, and thus contradicts the more simplistic total acculturation and replacement models proposed so far to explain Neolithisation.





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