Update 24/04/2013: The Neolithic mtDNA H paper has just been published at Nature Communications, and I've reviewed it here.
...
The two abstracts below come from the American Association of Physical Anthropologists (AAPA) 2013 annual meeting PDF, and they are fascinating.
Neolithic human mitochondrial haplogroup H genomes and the genetic origins of Europeans
Haplogroup (hg) H dominates present-day Western European mitochondrial (mt) DNA variability (>40%), yet was less prevalent amongst early Neolithic farmers (~19%) and virtually absent in Mesolithic hunter-gatherers. To investigate this haplogroup’s significance in the maternal population history of Europeans we employed novel techniques such as DNA immortalization and hybridization-enrichment to sequence 39 hg H mt genomes from ancient human remains across a transect through time in Neolithic Central Europe.
The results of our population genetic analyses reveal that the current patterns of diversity and distribution of hg H were largely established during the Mid-Neolithic, but with substantial genetic contributions from subsequent pan-European cultures such as the Bell Beakers, which expanded out of Iberia in the Late Neolithic (~2800 BC). Using a strict diachronic approach allowed us to reconcile ‘real-time’ genetic data from the most common European mtDNA hg with cultural changes that took place between the Early Neolithic (~5450 BC) and Bronze Age (~2200 BC) in Central Europe. This revealed the Late Neolithic (2800-2200 BC) as a dynamic period that profoundly shaped the genetic landscape of modern-day Europeans.
Furthermore, linking ancient hg H genome sequences to specific points in time by using radiocarbon dates as tip calibrations allowed us to reconstruct a precise lineage history of hg H and to calculate a mutation rate 45% higher than traditional estimates based on the human/chimp split.
...
Investigating lactase persistence in a Medieval German cemetery: A step towards understanding the rise of the European lactase persistence polymorphism (-3910C/T)
Milk and milk products are important foods in European, African, and Middle Eastern societies, but in other parts of the world lactose intolerance predominates. In mammals, lactase, the enzyme that hydrolyzes the milk sugar lactose, is normally down-regulated after weaning, but in Europe a single nucleotide polymorphism at -13910C/T in the gene MCM6 causes adult lactase persistence (LP). When and where this polymorphism evolved and the process by which it became the majority allele in Europe has been the subject of strong debate. A history of dairying is presumed to be a prerequisite, but current archaeological evidence is ambiguous.
In this study, DNA was extracted from the dentine of 36 individuals excavated at the Medieval (c. AD 1000-1200) cemetery of Dalheim in Germany. After PCR amplification and cloning, successful sequences were obtained for 25 individuals, of which 13 exhibited a European LP genotype (CT or TT).
Previous ancient DNA-based studies on the Neolithic found that the incidence of LP falls below detection levels in most regions. Our research shows that between the Neolithic and Medieval periods, the frequency of LP rose from near 0% to over 50%. Also, given that the frequency of LP genotypes in modern-day Germany is estimated at 78.5%, our results indicate that rather than being stable by the Medieval period, the lactase persistent genotype has continued to increase in frequency over the last 1000 years. This new evidence sheds light on the dynamic evolutionary history of the European lactase persistent trait and its global cultural implications.
I can't wait for the papers to come out, but these abstracts, along with other recent information, are perhaps enough to draw some very important conclusions about how modern Europeans came to be.
- The main components of the modern European gene pool were most likely already present in Europe during the Neolithic, so it's not necessary to speculate about significant post-Neolithic population movements into Europe from the Pontic-Caspian Steppe and/or West Asia.The modern European "R1 + H" gene pool shows very clearly on the PCA below, courtesy of Der Sarkissian et al. The PCA is based on mtDNA haplogroup data only, but that's a good thing for a number of reasons, including the fact that Y-DNA haplogroups are more easily affected by founder effect and genetic drift. European populations represented by yellow dots create a tight cluster which basically sits between modern West Asians and ancient European hunter-gatherers, but is also relatively distinct from both. I think this fits very well with the points I made above that modern Europeans are largely of Neolithic West Asian stock with significant native Mesolithic European ancestry, and also the result of late and post-Neolithic in-situ expansions and massive intra-European population movements.
- In-situ expansions and large-scale migrations of pan-European cultures during the late Neolithic were key processes in the formation of the modern European gene pool.
- The high incidence of lactase persistence in Europeans is not due to a massive expansion of pastoralists from the Pontic-Caspian Steppe or Anatolia into Europe, but the result of strong positive selection which has continued to the present day.
- Europeans carry high frequencies of Y-DNA R1 and mtDNA H, and it's likely these markers became dominant across the continent thanks to the same in-situ expansions and subsequent migrations of two late Neolithic/Chalcolithic pan-European cultures known as Corded Ware and Bell Beaker.
- Large-scale migrations from Western and Central Europe to the east from the late Neolithic to historic times caused population replacements and extinctions across much of Eastern Europe.
References...
Program of the 82ndAnnual Meeting of the American Association of Physical Anthropologists
Der Sarkissian C, Balanovsky O, Brandt G, Khartanovich V, Buzhilova A, et al. (2013) Ancient DNA Reveals Prehistoric Gene-Flow from Siberia in the Complex Human Population History of North East Europe. PLoS Genet 9(2): e1003296. doi:10.1371/journal.pgen.1003296
See also...
First R1b from Neolithic Europe...and it ain't from the steppe
Post-Mesolithic population replacement/extinctions in Northeastern Europe
They had blond hair and light eyes, and came from the north…but they were racially impure
These are very interesting and important studies indeed. It makes me wonder again about the origin of the Lactase Persistence gene (3910C/T) in Europeans again. Did this mutation arise in only one individual initially I wonder? We may never know I suppose.
ReplyDeleteWhich pre-historic cultures most likely spread the ''North European'' component from your different ADMIXTURE runs such as K13 around Europe?
ReplyDeleteAll the cultures that carried North European Mesolithic ancestry with them. So it's a long list, starting with the Mesolithic hunter-gatherer cultures like PWC.
DeleteSo basically all of the Mesolithic cultures from Ireland and Britain in the far west to Lithuania and Russia in the east spread the ``North European`` autosomal component that can be seen in your ADMIXTURE analysis at GEDmatch such as the K9 and K13 around Europe correct?
ReplyDeleteThis my my last question.
Yes, it seems the so called North European component is in large part the result of a small, homogenous, but widely dispersed population of Mesolithic hunter-gatherers all the way from Iberia to Central Siberia, which was incorporated in varying degrees into more southerly populations that moved north during the Neolithic.
DeleteVery interesting. Thank you.
ReplyDeleteWhy is there such strong continuity between paleolithic, neolithic and modern Europeans, but there is such a genetic upheval on both the maternal and paternal haplogroups between ancient and modern Europeans?
ReplyDeleteMilk?
Delete