Wednesday, August 2, 2017

Minoan And Mycenaean Ancient DNA

A new paper with Minoan and Mycenaean ancient DNA is out. 

The (non-Indo-European) Minoan individuals have a significant Caucasian component but lack steppe ancestry, as I've suspected for a long time. The Mycenaeans, unsurprisingly for Indo-European migrant/conquerers of the late Bronze Age, have significant steppe ancestry, but somewhat surprisingly, have about 75%-80% ancestry from pre-Myceneaens of the region who tend to resemble the Minoans.

The following quotes from the paper are via Eurogenes who quotes the abstract:
The origins of the Bronze Age Minoan and Mycenaean cultures have puzzled archaeologists for more than a century. We have assembled genome-wide data from 19 ancient individuals, including Minoans from Crete, Mycenaeans from mainland Greece, and their eastern neighbours from southwestern Anatolia. Here we show that Minoans and Mycenaeans were genetically similar, having at least three-quarters of their ancestry from the first Neolithic farmers of western Anatolia and the Aegean [1, 2], and most of the remainder from ancient populations related to those of the Caucasus [3] and Iran [4, 5]. However, the Mycenaeans differed from Minoans in deriving additional ancestry from an ultimate source related to the hunter–gatherers of eastern Europe and Siberia [6, 7, 8], introduced via a proximal source related to the inhabitants of either the Eurasian steppe [1, 6, 9] or Armenia [4, 9]. Modern Greeks resemble the Mycenaeans, but with some additional dilution of the Early Neolithic ancestry. Our results support the idea of continuity but not isolation in the history of populations of the Aegean, before and after the time of its earliest civilizations.
And, a bit of the body of the paper:
The simulation framework also allows us to compare different models directly. Suppose that there are two models (Simulated1, Simulated2) and we wish to examine whether either of them is a better description of a population of interest (in this case, Mycenaeans). We test f4(Simulated1, Simulated2; Mycenaean, Chimp), which directly determines whether the observed Mycenaeans shares more alleles with one or the other of the two models. When we apply this intuition to the best models for the Mycenaeans (Extended Data Fig. 6), we observe that none of them clearly outperforms the others as there are no statistics with |Z|>3 (Table S2.28). However, we do notice that the model 79%Minoan_Lasithi+21%Europe_LNBA tends to share more drift with Mycenaeans (at the |Z|>2 level). Europe_LNBA is a diverse group of steppe-admixed Late Neolithic/Bronze Age individuals from mainland Europe, and we think that the further study of areas to the north of Greece might identify a surrogate for this admixture event – if, indeed, the Minoan_Lasithi+Europe_LNBA model represents the true history.
Lazaridis, Mittnik et al., Genetic origins of the Minoans and Mycenaeans, Nature (August 2, 2017), doi:10.1038/nature23310 (closed access).

Razib Khan provides some nice historical context.

At least one of the Minoans had Y-DNA J2a1h-M319, a Y-DNA type common in the highlands of Anatolia, the Caucasus and Iran. Per Razib: "the authors note that the Y chromosomes in four out of five individuals in their Mycenaean-Minoan-Anatolians are haplogroup J associated with these eastern groups [i.e. early Caucasian and Iranian farmers], rather than the ubiquitous G2 of the earlier farmer populations." There are two J2a1 Minoans (one is J2a1/mtDNA H, and the other one is J2a1d/mtDNA H13a1), one G2a2b2 Minoan (mtDNA U3b3), one J1a Anatolian (mtDNA H) and one J2a1 Mycenaean (mtDNA X2). Two other Mycenaeans are mtDNA X2 with no Y-DNA.

Like the Minoans "they did not find much steppe ancestry in the Anatolian samples at all." Probably the majority view among linguists is that the Anatolian languages were the first to break off from proto-Indo-European, a linguistic conclusion that the authors struggle to reconcile with this fact (they suggest that the lack of steppe ancestry in Anatolia could be due to thousands of years of dilution with local Anatolian gene pools).

But, I have long maintained, based upon historical accounts and archaeological evidence, that the early Hittites were very new arrivals in Anatolia ca. 2000 BCE. In my view the Anatolian languages seem much different than other contemporaneous Indo-European languages not because they broke off from proto-Indo-European languages earlier, but because the Anatolian-Minoan languages that formed the substrate influencing the Hittite languages as they grew distinct from proto-Indo-European was much different from the substrate encountered by proto-Indo-Europeans elsewhere, resulting in a greater divergence from its contemporaneous sister languages.

More worthwhile observations from Razib:
On the one hand Basques seem to have mostly Indo-European Y chromosomes, but their whole genome ancestry indicates less exogenous input than their neighbors. Speaking of which, we know by the Classical period large regions of western Spain were dominated by Celtic speaking peoples, but the genetic imprint of the Indo-Europeans is still very modest in the Iberian peninsula. 
I think what we’re seeing here is the difference between Indo-European agro-pastoralists arriving to a landscape of relatively simple societies with more primal institutions, and those who migrated into regions where local population densities are higher and social complexity is also greater. This higher social complexity means that external elites can takeover a system, as opposed to an almost animal competition for resources as seems to have occurred in Northern Europe.
This new ancient DNA tends to supports the linguistic hypothesis that the Minoan language and the pre-Hittite non-Indo-European languages of Anatolia are part of the same language family as the Caucasian languages. It also supports the idea that Minoan culture is derived proximately from Anatolia.

Probably, the first wave Neolithic ancestry that makes up 75% of the Minoans was the original substrate. This was probably updated with an Enolithic or early Bronze Age migration of Caucasian derived populations across Anatolia to Crete (and more broadly to all of Greece), resulting in substantial introgression of the Caucasian component into the Aegean populations. This introgression that was probably bigger than it seems, because the Anatolian sourced populations who wound up in Crete and became Minoans were probably already admixed in Anatolia with people genetically very similar to the pre-Minoan Greeks, it could very well have been a 50-50 split of newcomers and pre-existing Neolithic populations. Then, the Mycenaeans arrived and provided most of the steppe ancestry present in Greek today early on, although there was moderately more dilution later of the pre-Mycenaean substrate later on.

It appears that genetically Minoan-like people were present throughout the Aegean Sea region of Greece, and not just on Crete where the Minoan palace culture reached its apogee. 

In the dog that didn't bark department, it is also notable that neither the Minoans nor the Mycenaean populations had any more than trace ancestry that looked Levantine or Egyptian, despite the proximity of those civilizations to Greece and the existence of trade exchanges between the Minoans and Mycenaeans and these civilizations.

This doesn't connect all of the dots when it comes to Minoan mysteries. Most importantly, we don't know yet if it is likely that any populations west of the Aegean Sea received genetic contributions from the Minoans. But, it is definitely progress.

Bell Beaker blogger notes some scholarship in the comments at Eurogenes on this final points:
Two fairly short but dense papers: 
"When the West meets the East: The Eastern periphery of the Bell Beaker Phenomenon and its Relation with the Aegean Early Bronze Age" 
"Seaborne Contacts between the Aegean, the Balkans and the Central Mediterranean in the 3rd Millennium BC - The Unfolding of the Mediterranean World"
Commentator Alogo also notes:
Lots of the underlying data is available in this blog post

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