Temporal differentiation across a West-European Y-chromosomal cline - genealogy as a tool in human population genetics
Maarten H.D. Larmuseau et al.
The pattern of population genetic variation and allele frequencies within a species are unstable and are changing in time according to different evolutionary factors. For humans, it is possible to combine detailed patrilineal genealogical records with deep Y-chromosome genotyping to disentangle signals of historical population genetic structures due to the exponential increase of genetic genealogical data. To test this approach we studied the temporal pattern of the 'autochthonous' micro-geographical genetic structure in the region of Brabant in Belgium and The Netherlands (Northwest-Europe). Genealogical data of 881 individuals from Northwest-Europe were collected from which 634 family trees showed a residence within Brabant for at least one generation. The Y-chromosome genetic variation of the 634 participants was investigated using 110 Y-SNPs and 38 Y-STRs and linked to particular locations within Brabant on specific time periods based on genealogical records. Significant temporal variation in the Y-chromosome distribution was detected through a north-south gradient in the frequencies distribution of subhaplogroup R1b1b2a1 (R-U106), next to an opposite trend for R1b1b2a2g (R-152). The gradient on R-U106 faded in time and became even totally invisible during the Industrial revolution in the first half of the 19th century. Therefore, genealogical data for at least 200 year are required to study small-scale 'autochthonous' population structure in Western-Europe.The Dutch medieval and post-medieval genetic landscapes
Eveline Altena et al.
Since 2005 many archeological human skeletons have been sampled for DNA research under forensic conditions in The Netherlands. This enables us to perform a large scale genetic survey on reliable genetic data from the prehistory until the present. The majority of the available archaeological DNA samples, though, originate from medieval and post-medieval sites. Here we present preliminary autosomal and Y-chromosomal data from more then 500 archaeological human skeletons, excavated at several medieval and post-medieval sites. We also compare these historical genetic data with data from more then 2000 modern Dutch males.Comparing ancient and modern DNA variability in North Eastern Iberia: the Neolithic impact of first farmers
Cristina Gamba et al.
Archaeological, anthropological and demographic hypotheses can be tested by comparing ancient and modern DNA from human samples in a diachronical context. In this case, it was possible to evaluate genetic continuity or discontinuity between different periods, and/or to infer ancient human migrations in a set of Iberian samples. We evaluated the demographic impact associated to the spread of the Neolithic in North Eastern Iberia. We recovered mitochondrial DNA from 13 Early Neolithic specimens from three archaeological sites: Can Sadurní, Chaves and Sant Pau. A bayesian simulation approach was performed to compare the obtained results with Middle Neolithic and modern samples from the same region. We tested different scenarios to determine which among them better explained the analyzed data. By comparing simulated and observed FST values, we observed genetic differentiation between Early Neolithic and Middle Neolithic populations, which suggests that at the beginning of the Neolithic, genetic drift played an important role.The following abstract is interesting as it suggests we should not view the "Neolithic" as a singular event. X2 was also discovered in Megalithic France, as well as a likely immigrant population from the Near East and the Caucasus in the Tarim Basin, and Bronze Age Eulau. From a paper on the Reidla et al. (2003): Overall, it appears that the populations of the Near East, the Caucasus, and Mediterranean Europe harbor subhaplogroup X2 at higher frequencies than those of northern and northeastern Europe (P less than .05) and that X2 is rare in Eastern European as well as Central Asian, Siberian, and Indian populations and is virtually absent in the Finno-Ugric and Turkic-speaking people of the Volga-Ural region.
Genetic differentiation was also observed between Early Neolithic and modern- day populations. These data are compatible with the arrival of small genetically-distinctive groups at the beginning of the Neolithic, suggesting a pioneer colonization of North Eastern Iberia by first farmers.
Where are all the "WIX"? Rare European maternal lineages W, I, and X2 in the past and present
Esther J. Lee et al.
Studies utilizing ancient DNA to examine past populations in Europe have increased dramatically in recent years. Specifically, mitochondrial DNA (mtDNA) sequences for over 100 individuals in prehistoric Europe have been sequenced and published. Scholars have intensively focused on the so-called Neolithic transition in Europe, the transformation from hunter-gatherer lifestyle to agro-pastoralism, and continue to debate whether the process was a result of population movement or cultural dispersion. Both hypotheses continue to be tested and genetics analyses from past and present populations have suggested a complex movement of people and cultures across Eurasia. This work focuses on the mtDNA haplogroups identified in past European populations that are rare in the present, haplogroups W, I, and X2. New data will be presented from Neolithic Funnel Beaker collective burials sites, a late Neolithic Bell Beaker site, and an Iron Age Halstatt site in Germany, in which the three maternal lineages are identified. Among the published European Neolithic data, haplogroup X2 appears in late Neolithic sites in Germany and France but not in the earlier LBK culture. Haplogroup X2 shows an intriguing phylogenetic landscape with a wide geographical distribution at an overall low frequency, but on the other hand, pockets of high diversity and frequency among certain modern western Eurasian populations have been described. The discussion focuses on whether the presence of the three haplogroups in the past is a result of ascertainment bias or some viable population movement.The following seems to suggest Denisova admixture in the East Asian mainland, and not just the island groups, identified in the recent Reich et al. (2011) paper. The sentence about biased Neandertal similarity with increasing distance to Africa is also interesting; the data that is available so far shows non significant differences in Neandertal similarity among Eurasians, although the published values do seem to show higher (and perplexing) averages in China vs. Europe.
Archaic human ancestry in East Asia
Pontus Skoglund & Mattias Jakobsson
Recent studies of ancient genomes have suggested that gene flow from archaic hominin groups to the ancestors of modern humans occurred on two separate occasions during the modern human expansion out of Africa. At the same time, decreasing levels of human genetic diversity have been found at increasing distance from Africa as a consequence of human expansion out of Africa. We re-analyzed the signal of archaic ancestry in modern human populations and we investigated how serial founder models of human expansion affect the signal of archaic ancestry using simulations. We show that genetic drift coupled with an ascertainment bias for common alleles can cause artificial, but largely predictable, differences in affinity to archaic genomes between descendants of an admixture event. In genotype data from non-African humans, this effect results in a biased genetic similarity to Neandertal with increasing distance from Africa. In addition to the two previously reported connections between non-Africans and Neandertals as well as between Oceanians and a Denisovan archaic human genome from Siberia, we found a significant affinity between East Asians (in particular Southeast Asians) and the Denisovan genome, a pattern that is not expected under a model of solely Neandertal-related admixture in the ancestry of East Asians. This observation could be explained either by substantial migration from Oceania into East Asia, or more common history between anatomically modern- and archaic populations than previously proposed.