The genetic history of Europe includes information around the formation, ethnogenesis, and other DNA-specific information about populations indigenous, or living in Europe.
European early modern human (EEMH) lineages between 40 and 26 ka (Aurignacian) were still part of a large Western Eurasian "meta-population", related to Central and Western Asian populations. Divergence into genetically distinct sub-populations within Western Eurasia is a result of increased selection pressure and founder effects during the Last Glacial Maximum (LGM, Gravettian).
By the end of the LGM, after 20 ka, A Western European lineage, dubbed west European hunter-gatherer (WHG) emerged from the Solutrean refugium during the European Mesolithic. These Mesolithic hunter-gatherer cultures are subsequently replaced in the Neolithic Revolution as a result of the arrival of Early European Farmer (EEF) lineages derived from mesolithic populations of surrounding West Asia (Anatolia).Population replacement in the Neolithic, and again in the Bronze Age, was nearly complete in Prehistoric Britain, the Mesolithic WHG population accounting for just about 10% of the ancestry of the modern indigenous British population. In the European Bronze Age, there were again substantial population replacements in parts of Europe by the intrusion of Western Steppe Herder (WSH) lineages from the Pontic–Caspian steppes, arising from admixture between Eastern Hunter Gatherers (EHG) and peoples related to Near Easterners. These Bronze Age population replacements are associated with the Bell Beaker and Corded Ware cultures archaeologically and with a second wave of Indo-European expansion linguistically.
As a result of the population movements during the Mesolithic to Bronze Age, modern European populations are distinguished by differences in WHG, EEF and Ancient North Eurasian (ANE) ancestry.Since Lazaridis et al. (2014), further studies have refined the picture of interbreeding between EEF and WHG. In a 2017 analysis of 180 ancient DNA datasets of the Chalcolithic and Neolithic periods from Hungary, Germany and Spain evidence was found of a prolonged period of EEF-WHG interbreeding. Admixture took place regionally, from local hunter-gatherer populations, so that populations from the three regions (Germany, Iberia and Hungary) were genetically distinguishable at all stages of the Neolithic period, with a gradually increasing ratio of WHG ancestry of farming populations over time. This suggests that after the initial expansion of early farmers, there were no further long-range migrations substantial enough to homogenize the farming population, and that farming and hunter-gatherer populations existed side by side for many centuries, with ongoing gradual admixture throughout the 5th to 4th millennia BCE (rather than a single admixture event on initial contact). Admixture rates varied geographically; in the late Neolithic, WHG ancestry in farmers in Hungary was at around 10%, in Germany around 25% and in Iberia as high as 50%.Lipson et al. (2017), Fig 2. The contribution of EEF is more significant in Mediterranean Europe, and declines towards northern and northeastern Europe, where WHG ancestry is stronger; the Sardinians are considered to be the closest European group to the population of the EEF.
Ethnogenesis of the modern ethnic groups of Europe in the historical period is associated with numerous admixture events, primarily those associated with the Migration period and the decline of the Roman Empire, associated with the Germanic, Norse, and Slavic expansions
Research into the genetic history of Europe became possible in the second half of the 20th century, but did not yield results with high resolution before the 1990s. In the 1990s, preliminary results became possible, but they remained mostly limited to studies of mitochondrial and Y-chromosomal lineages. Autosomal DNA became more easily accessible in the 2000s, and since the mid-2010s, results of previously unattainable resolution, many of them based on full-genome analysis of ancient DNA, have been published at an accelerated pace.
Prehistory
Due to natural selection, the percentage of Neanderthal DNA in ancient Europeans gradually decreased over time. From 45,000 BP to 7,000 BP, the percentage dropped from around 3–6% to 2%. The removal of Neanderthal-derived alleles occurred more frequently around genes than other parts of the genome.
Paleolithic
Neanderthals inhabited much of Europe and western Asia from as far back as 130,000 years ago. They existed in Europe as late as 30,000 years ago. They were eventually replaced by anatomically modern humans (AMH; sometimes known as Cro-Magnons), who began to appear in Europe circa 40,000 years ago. Given that the two hominid species likely coexisted in Europe, anthropologists have long wondered whether the two interacted.Even before the advent of genetic studies, some anthropologists believed they had discovered skeletons representing Neanderthal-modern human 'hybrids'. These results were deemed 'ambiguous'. Archaeological evidence points to an abrupt change from Neanderthal artefacts to those related to AMH during the Upper Palaeolithic. The question was resolved only in 2010, when it was established that Eurasian populations exhibit Neanderthal admixture, estimated at 1.5–2.1% on average. The question now became whether this admixture had taken place in Europe, or rather in the Levant, prior to AMH migration into Europe.
There has also been speculation about the inheritance of specific genes from Neanderthals. For example, one MAPT locus 17q21.3 which is split into deep genetic lineages H1 and H2. Since the H2 lineage seems restricted to European populations, several authors had argued for inheritance from Neanderthals beginning in 2005.Introgression and microcephalin FAQ John Hawks However the preliminary results from the sequencing of the full Neanderthal Genome at that time (2009), failed to uncover evidence of interbreeding between Neanderthals and modern humans. By 2010, findings by Svante Pääbo (Max Planck Institute for Evolutionary Anthropology at Leipzig, Germany), Richard E. Green (University of California, Santa Cruz), and David Reich (Harvard Medical School), comparing the genetic material from the bones of three Neanderthals with that from five modern humans, did show a relationship between Neanderthals and modern people outside Africa.
Upper Paleolithic
It is thought that modern humans began to inhabit Europe during the Upper Paleolithic about 40,000 years ago. Some evidence shows the spread of the Aurignacian culture.
From a purely patrilineal, Y-chromosome perspective, it appears that Haplogroup C1a2, F and K2a may be those with the oldest presence in Europe. They have been found in some of the oldest human remains sequenced from the Paleolithic era. However, other haplogroups are far more common among modern European males, because of later demographic changes.
Currently the oldest sample of Haplogroup I (M170), which is now relatively common and widespread within Europe, has been found to be Krems WA3 from Lower Austria dating back to about 30–31,000 ybp. At about this time, an Upper Palaeolithic culture also appeared, known as the Gravettian.
Earlier research into Y-DNA had instead focused on haplogroup R1 (M173): the most populous lineage among living European males; R1 was also believed to have emerged ~ 40,000 BP in Central Asia. However, it is now estimated that R1 emerged substantially more recently: a 2008 study dated the most recent common ancestor of haplogroup IJ to 38,500 and haplogroup R1 to 18,000 BP. This suggested that haplogroup IJ colonists formed the first wave and haplogroup R1 arrived much later.
Thus the genetic data suggests that, at least from the perspective of patrilineal ancestry, separate groups of modern humans took two routes into Europe: from the Middle East via the Balkans and another from Central Asia via the Eurasian Steppe, to the north of the Black Sea.
Martin Richards et al. found that 15–40% of extant mtDNA lineages trace back to the Palaeolithic migrations (depending on whether one allows for multiple founder events). MtDNA haplogroup U5, dated to be ~ 40–50 kYa, arrived during the first early upper Palaeolithic colonisation. Individually, it accounts for 5–15% of total mtDNA lineages. Middle U.P. movements are marked by the haplogroups HV, I and U4. HV split into Pre-V (around 26,000 years old) and the larger branch H, both of which spread over Europe, possibly via Gravettian contacts.
Haplogroup H accounts for about half the gene lines in Europe, with many subgroups. The above mtDNA lineages or their precursors, are most likely to have arrived into Europe via the Middle East. This contrasts with Y DNA evidence, whereby some 50%-plus of male lineages are characterised by the R1 superfamily, which is of possible central Asian origin. Ornella Semino postulates that these differences "may be due in part to the apparent more recent molecular age of Y chromosomes relative to other loci, suggesting more rapid replacement of previous Y chromosomes. Gender-based differential migratory demographic behaviors will also influence the observed patterns of mtDNA and Y variation".
Last Glacial Maximum
The Last Glacial Maximum ("LGM") started c. 30 ka BCE, at the end of MIS 3, leading to a depopulation of Northern Europe. According to the classical model, people took refuge in climatic sanctuaries (or refugia) as follows: Northern Iberia and Southwest France, together making up the "Franco-Cantabrian" refugium The Balkans Ukraine and more generally the northern coast of the Black Sea Italy.
This event decreased the overall genetic diversity in Europe, a "result of drift, consistent with an inferred population bottleneck during the Last Glacial Maximum". As the glaciers receded from about 16,000–13,000 years ago, Europe began to be slowly repopulated by people from refugia, leaving genetic signatures.
Some Y haplogroup I clades appear to have diverged from their parental haplogroups sometime during or shortly after the LGM.
Cinnioglu sees evidence for the existence of an Anatolian refuge, which also harboured Hg R1b1b2.Cinnioglu et al. Excavating Y-chromosome haplotype strata in Anatolia. 2003 Today, R1b dominates the y chromosome landscape of western Europe, including the British Isles, suggesting that there could have been large population composition changes based on migrations after the LGM.
Semino, Passarino and Pericic place the origins of haplogroup R1a within the Ukrainian ice-age refuge. Its current distribution in eastern Europe and parts of Scandinavia are in part reflective of a re-peopling of Europe from the southern Russian/Ukrainian steppes after the Late Glacial Maximum.
From an mtDNA perspective, Richards et al. found that the majority of mtDNA diversity in Europe is accounted for by post-glacial re-expansions during the late upper Palaeolithic/ Mesolithic. "The regional analyses lend some support to the suggestion that much of western and central Europe was repopulated largely from the southwest when the climate improved. The lineages involved include much of the most common haplogroup, H, as well as much of K, T, W, and X." The study could not determine whether there were new migrations of mtDNA lineages from the near east during this period; a significant input was deemed unlikely.
The alternative model of more refugees was discussed by Bilton et al.