A team of scientists, led by researcher Carles Lalueza-Fox from CSIC (Spanish National Research Council), has recovered - for the first time in history - part of the genome of two individuals living in the Mesolithic Period, 7000 years ago. Remains have been found at La Braña-Arintero site, located at Valdelugueros (León), Spain. The study results, published in the Current Biology magazine, indicate that current Iberian populations don't come from these groups genetically.This appears quite consistent with my model of mostly recent origins of European populations from a West Asian womb of nations. I can't wait to get my hands on this new data.
In the genomic analysis, it is interesting to see that the La Braña individuals do not cluster with modern populations from Southern Europe, including those from the Iberian Peninsula. The first PC separates a north-south distribution, whereas the second follows a general east-west pattern in modern Europeans. The position of La Braña individuals in the 1000 Genomes Project data and the 1KGPomnichip PCAs suggests that the uniform Mesolithic substrate could be related to modern Northern European populations but may represent a gene pool that is no longer present in contemporary Southern European populations. In the latter PCA, where the origin of each Iberian sample is known, it is possible to see that the Mesolithic specimens are not related to modern Basques, contrary to what has been previously suggested in some recent studies .The global PCA of the two individuals shows a clear shift relative to extant Europeans.
pattern in modern West Eurasian populations. As I noted:
With respect to the Asian- and African- shift of West Eurasian populations, I note that northern Europeans (and Basques) are less African-shifted than southern Europeans, and, at the same time they are more Asian-shifted: the 16 least Asian-shifted populations have a coastline in the Mediterranean (excluding the Portuguese), while the 16 least African-shifted populations do not (excluding the French).It now appears clear that the Mesolithic substratum in Europe was:
- Well outside the modern range, contributing a little to extant populations
- Its contribution in northern populations was higher than in southern ones
- It may be responsible for the pattern of Asian-shift observed for non-Mediterranean European populations
UPDATE: Due to the small number of SNPs, I pooled the two Mesolithic individuals into a single composite one; the K7b admixture proportions are: 9.3% African and 90.7% Atlantic_Baltic, which appears consistent with the position of the individuals in the European PCA plot. The sub-1,000 SNPs in common with the K7b do not give me a lot of confidence in the minority element, but, in any case, the high Atlantic_Baltic figure is what I would expect and appears consistent with the similarly high Atlantic_Baltic figure of the Swedish Neolithic hunter-gatherers.
UPDATE II: Using the K12b, the results are: 45% Atlantic_Med, 41.6% North_European, 10.3% East_African, 1% Sub_Saharan.
UPDATE III: In terms of the euro7 calculator, the results are: 89.6% Northwestern, 1.6% Southeastern, and 8.7% Far_Asian.
Current Biology, 28 June 2012 doi: 10.1016/j.cub.2012.06.005
Genomic Affinities of Two 7,000-Year-Old Iberian Hunter-Gatherers
Federico Sánchez-Quinto, Hannes Schroeder, Oscar Ramirez, María C. Ávila-Arcos, Marc Pybus, Iñigo Olalde, Amhed M.V. Velazquez, María Encina Prada Marcos, Julio Manuel Vidal Encinas, Jaume Bertranpetit, Ludovic Orlando, M. Thomas P. Gilbert, Carles Lalueza-Fox
- The first complete Mesolithic mtDNA genome retrieved
- There is a remarkable genetic uniformity in Europe during the Mesolithic period
- Modern Iberians are not direct descendants of the 7,000-year-old hunter-gatherers
- Genetic discontinuity between Mesolithic/Neolithic populations supported by simulations
Summary The genetic background of the European Mesolithic and the extent of population replacement during the Neolithic [1,2,3,4,5,6,7,8,9,10] is poorly understood, both due to the scarcity of human remains from that period [11,12,13,14,15,16,17,18] and the inherent methodological difficulties of ancient DNA research. However, advances in sequencing technologies are both increasing data yields and providing supporting evidence for data authenticity, such as nucleotide misincorporation patterns [19,20,21,22]. We use these methods to characterize both the mitochondrial DNA genome and generate shotgun genomic data from two exceptionally well-preserved 7,000-year-old Mesolithic individuals from La Braña-Arintero site in León (Northwestern Spain) . The mitochondria of both individuals are assigned to U5b2c1, a haplotype common among the small number of other previously studied Mesolithic individuals from Northern and Central Europe. This suggests a remarkable genetic uniformity and little phylogeographic structure over a large geographic area of the pre-Neolithic populations. Using Approximate Bayesian Computation, a model of genetic continuity from Mesolithic to Neolithic populations is poorly supported. Furthermore, analyses of 1.34% and 0.53% of their nuclear genomes, containing about 50,000 and 20,000 ancestry informative SNPs, respectively, show that these two Mesolithic individuals are not related to current populations from either the Iberian Peninsula or Southern Europe.