Going over the 322 pages of thesis may take a while, but feel free to comment on it if you discover any interesting nuggets in the text. The following view of West/East Eurasian mtDNA surrounding the beginning of the Iron Age may be useful, and seems to parallel the results of a recent paper on Pazyryk mtDNA:
Of course, since the thesis was published we have new data from West Siberia/Ukraine that suggest that the penetration of east Eurasian lineages covered a great area to the west of the indicated region even prior to the Iron Age.
We can be fairly sure that "non-East Eurasian admixed" populations existed during the Bronze Age in three portions of the Eurasian landmass, separated by the Black and Caspian Seas: west of the Black Sea (Balkans/Central Europe); between Black and Caspian Seas (Caucasus) and east of the Caspian Sea (Kazakhstan and Turkmenistan). But how did these three regions contribute to the West Eurasian elements found on a west-east axis across Eurasia today? And, to what extent did the early east Eurasian elements that penetrated well into eastern Europe in the Neolithic-to-Bronze Age contribute to latter populations of the area vs. more recent expansions from the Altai and Central Asia during the Iron Age?
Here is a PCA of the pre-Iron Age individuals, compared with modern populations:
Both "Tarim" (TAR) and "Neolithic Lake Baikal" (LOK) appear well within east Eurasian variation. But, of the West Eurasian groups, Pitted Ware Complex (PWC), i.e., Neolithic hunter-gatherers from NE Europe and Bronze Age Altai (ALT-BA) appear clearly "northern Europeoid" across the 2nd PC, as do, to a lesser extent, C/N European Hunter-Gatherers (HG) and Kurgan burials from south Siberia (KUR-BA), but Bronze Age Kazakhstan (KAZ-BA) appear to be southern Europeoid, and, also, noticeably more "West Eurasian" than the others. Clearly, the West Eurasian elements were not homogeneous, with some of them (such as KAZ-BA) apparently derived from the southern Caucasoid zone -which largely did not experience east Eurasian admixture- and others from the northern Caucasoid zone that did.
The Rostov Scythian sample (in red) appears to belong to the southern Caucasoid zone (across PC2), but East Eurasian-shifted relative to modern Europeans and Bronze Age Kazakhstan.
Now, let's look at the Iron and post-Iron Age samples:
Egyin Gol (EG) from Mongolia and Sargat Siberians appear clearly as East Eurasians; Pazyryk Altai (ALT-IA), Iron Age Kazakhstan (KAZ-IA) and South Siberia Kurgan (KUR-IA) show decreasing East Eurasian influence; also notice the decidedly "southern" shift of the West Eurasian element among them.
This seems broadly consistent with the ideas of Molodin et al. about the gradual appearance (in their Siberian sample) of Caucasoid mtDNA types from the Neolithic to the Iron Age, with the early Neolithic U-dominated population finally receiving a full set of diverse West Eurasian lineages only during the Iron Age from the south.
It will certainly be very exciting when samples such as these can be tested for autosomal or Y-chromosome DNA, and I'm looking forward to the day when this can be done on a large scale.
Title: Mitochondrial DNA in ancient human populations of Europe.
Author: Dersarkissian, Clio Simone Irmgard
Issue Date: 2011
School/Discipline: School of Earth and Environmental Sciences
Abstract: The distribution of human genetic variability is the result of thousand years of human evolutionary and population history. Geographical variation in the nonrecombining maternally inherited mitochondrial DNA has been studied in a wide array of modern populations in order to reconstruct the migrations that have participated in the spread of our ancestors on the planet. However, population genetic processes (e.g., replacement, genetic drift) can significantly bias the reconstruction and timing of past migratory and demographic events inferred from the analysis of modern-day marker distributions. This can lead to erroneous interpretations of ancient human population history, a problem that potentially could be circumvented by the direct assessment of genetic diversity in ancient humans. Despite important methodological problems associated with contamination and post-mortem degradation of ancient DNA, mitochondrial data have been previously obtained for a few spatially and temporally diverse European populations. Mitochondrial data revealed additional levels of complexity in the population history of Europeans that had remained unknown from the study of modern populations. This justifies the relevance of broadening the sampling of ancient mitochondrial DNA in both time and space. This study aims at filling gaps in the knowledge of the genetic history of eastern Europeans and of European genetic outliers, the Saami and the Sardinians. This study presents a significant extension to the knowledge of past human mitochondrial diversity. Ancient remains temporally-sampled from three groups of European populations have been examined: north east Europeans (200 – 8,000 years before present; N = 76), Iron Age Scythians of the Rostov area, Russia (2,300 – 2,600 years before present; N = 16), Bronze Age individuals of central Sardinia, Italy (3,200 – 3,400 years before present; N = 16). The genetic characterisation of these populations principally relied on sequencing of the mitochondrial control region and typing of single nucleotide polymorphisms in the coding region. Changes in mitochondrial DNA structure were tracked through time by comparing ancient and modern populations of Eurasia. Analysis of haplogroup data included principal component analysis, multidimensional scaling, fixation index computation and genetic distance mapping. Haplotypic data were compared by haplotype sharing analysis, phylogenetic networks, Analysis of the Molecular Variance and coalescent simulations. The sequencing of a whole mitochondrial genome in a north east European Mesolithic individual lead to defining a new branch within the human mitochondrial tree. This work presents direct evidence that Mesolithic eastern Europeans belonged to the same Palaeolithic/Mesolithic genetic background as central and northern Europeans. It was also shown that prehistoric eastern Europeans were the recipients of multiple migrations from the East in prehistory that had not been previously detected and/or timed on the basis of modern mtDNA data. Ancient DNA also provided insights in the genetic history of European genetic outliers; the Saami, whose ancestral population still remain unidentified, and the Sardinians, whose genetic differentiation is proposed to be the result of mating isolation since at least the Bronze Age. This study demonstrates the power of aDNA to reveal previously unknown population processes in the genetic history of modern Eurasians.