Wednesday, May 15, 2013
High mtDNA affinity between Bronze Age Minoans and Western Europeans
The first ever study on the ancient DNA of Minoans suggests that these enigmatic Bronze Age inhabitants of Crete were very similar in terms of mtDNA to present-day Cretans. Overall the Minoan sample shows the greatest affinity to the modern population of the Lasithi Plateau, in eastern Crete, where it originated. But here's the other really interesting part: as per the spatial maps below, the Minoan mtDNA sequences also show unexpectedly high affinity to those of modern English (a) and Bronze Age Sardinians and Iberians (b). See also Table 1 from the paper, where the top ten "nearest neighbors" to the Minoan sample are ancient and extant Western European populations.
So the results imply genetic links between Bronze Age Crete and Western Europe. Now, Martinez et al. 2007 found that 36.6% of Cretans from the Lasithi Plateau belonged to Y-chromosome haplogroup R1b. They only tested 41 individuals, but that's still an interesting result for Southeastern Europe, where R1b is generally uncommon. Indeed, perhaps the Minoans carried a much higher frequency of R1b, and they (or a related seafaring culture) spread this marker to Western Europe via maritime routes, where it has since become the most important Y-chromosome haplogroup? It's a valid question considering the ancient mtDNA data. The pics of Minoan bull leaping and Spanish bullfighting below are courtesy of Wikipedia (see here).
Update 16/05/2013: To add to my comments above about the Minoans, or a related group, being potentially responsible for the introduction of Y-DNA R1b to Western Europe, it's interesting to note that one of the Minoan mtDNA sequences belonged to the rare H13a1a haplogroup. Both H13a1a and R1b were recently found in late Neolithic Bell Beaker remains from Germany (see here). Moreover, today H13a1a shows a peak in frequency and diversity in the Caucasus, particularly in Dagestan, but also occurs at low frequencies in Italy, Sardinia and Iberia. Interestingly, R1b is found at fairly high frequencies among some ethnic groups in and around Dagestan, like the Lezgins, and it's obviously also common in Italy and Iberia. So what am I getting at? Well, it looks like a group with loads of R1b from what is now Dagestan or surrounds - perhaps the deep ancestors of Bell Beakers and Minoans - learned to sail, crossed the Mediterranean Sea from east to west, settled a few islands along the way, and eventually their descendants conquered much of Western and Central Europe. This is certainly not the most parsimonious theory of how R1b might have appeared on the scene in Western Europe during the late Neolithic, but it does make sense considering all the data. But what might have caused this purported population movement from the Caucasus, and is it a coincidence that both R1a and R1b only appear among European ancient DNA from the late Neolithic onwards? It's unlikely that the Minoans and Bell Beakers were part of the Indo-European expansion, but perhaps their ancestors in the Caucasus felt the pressure of this expansion from the steppe to the north, which was at that time most likely dominated by Kurgan groups high in R1a? Update 18/05/2013: Maju isn't convinced that the gradient maps and "nearest neighbor" analysis show explicit links between the Minoan and post-Neolithic Western European mtDNA gene pools. He calls it a "pseudo-affinity" which should be taken with a pinch of salt (see here). Moreover, he suggests the Minoan mtDNA shows closest links to early European Neolithic mtDNA because of four HVS-1 sequence matches. But the high affinity between the Minoan and post-Neolithic Western European mtDNA can be seen clearly in two different analyses, so it's real, even if mostly indirect. Therefore, there's no need to take the results with a pinch of salt, they should just be viewed in their proper context. In other words, this affinity is certainly not due to a massive invasion of Western Europe by Minoan women, but the result of the same processes acting on the post-Neolithic Western European and Minoan mtDNA gene pools, which probably included some direct gene flow from the Eastern Mediterranean to Europe during the Bronze Age. References... Hughey et al., A European population in Minoan Bronze Age Crete, Nature Communications 4, Article number: 1861, doi:10.1038/ncomms2871, Published 14 May 2013 Martinez et al., Paleolithic Y-haplogroup heritage predominates in a Cretan highland plateau, European Journal of Human Genetics (2007) 15, 485–493. doi:10.1038/sj.ejhg.5201769; published online 31 January 2007