Complex Spread of Indo-European Languages

June 22, 2017

In this recent post, I talked about how ancestry clines in Italy could be due to the way Indo-European languages spread, and a new study suggests the same thing. Italy and the Balkans, especially the southern parts, differ from the rest of Europe by having a lot of the Caucasus Hunter-Gatherer (CHG) component of Yamnaya, but not much of the Eastern Hunter-Gatherer (EHG) component. The authors conclude that Italic, Greek and Balkan branches of Indo-European may have spread directly from the Caucasus through Anatolia and not via the Russian Steppe.

The most recent literature demonstrated significant impact of Caucasus-related ancestry in the Central European Late-Neolithic and Bronze-Age through the migrations of Yamnaya/Pontic-Steppe herders. Accordingly, our results confirm that Caucasus-related admixture via Yamnaya is present in Eastern and Central-Western European clusters (i.e. Continental Europe; Supplementary Table S8, Supplementary Information). However, among our Mediterranean groups, evidence of Yamnaya (and EHG) introgression seems to be present at a lesser extent and was detected mainly in Balkan-related groups (Supplementary Table S8, Supplementary Information), which in turn display traces of admixture with Eastern Europe (Fig. 4, Supplementary Fig. S2). In addition, outgroup-f3 values for Late Neolithic/Bronze Age samples (especially Yamnaya) appear lower in all our newly analysed Mediterranean populations (Supplementary Fig. S9). These results suggest that the genetic history of Southern Italian and Balkan populations may have been, at least in part, independent from that of Eastern and Central Europe, involving specific migratory events that carried Caucasian and Levantine genetic contributes along the Mediterranean shores (see Supplementary Information). This picture may bring important implications for our understanding of the cultural history of Europe, and in particular for the diffusion of Indo-European languages. The Steppe in the Early Bronze Age has been supported as a source of at least some Indo-European languages entering North-Central Europe at that time. In southern Mediterranean Europe, however, our results suggest lower impacts. Any significant Steppe/northern component may have arrived in the south Balkan mainland and southern Italy only later, by which time Indo-European languages of the Italic, Greek and various Balkan branches had already established themselves there. This would suggest that a Bronze Age Steppe source may be not highly consistent with all branches of the Indo-European family (see also Broushaki et al.).


Summing it up, our analyses show that a Caucasus-related ancestry is observed in both Southern Italian and Southern Balkan populations. Nevertheless, these populations do not seem to reveal such significant evidence of Bronze-Age Yamanya-like introgressions, which have been interpreted as the most probable vectors of CHG-like ancestry in Central-Eastern and Northern Europe and were also linked with the demographic diffusion of some Indo-European languages. These results may suggest that Caucasus-related ancestry reached our Mediterranean populations through migratory events at least partly independent from those postulated for Central Europe, most likely through Anatolia. If so, the spread of Indo-European languages in Europe may be envisaged as a more complex multi-way phenomenon, rather than the one-way result of a single diffusion process.

Sarno et al. "Ancient and recent admixture layers in Sicily and Southern Italy trace multiple migration routes along the Mediterranean". Scientific Reports, 2017.

Genetically Southern European

May 31, 2017

Genetic studies on Italians often say that Northerners are "closer" to Central and Northern Europeans while Southerners are "closer" to Middle Easterners and North Africans. Technically that's true because of simple geography, but it's misleading because it makes it seem like they cluster with those distant populations, which is false. All Italians cluster with other populations from Southern Europe.

This new study is mainly about Peloponnesean Greeks and how they haven't changed much since ancient times, but they also happen to be the group of Greeks who are genetically closest to Southern Italians. In addition to 5 Italian samples from all over the country, the study also has a large sample of Spaniards (including Andalusians from the south), who are genetically closest to Northern Italians.

Confirming many other studies, this PCA plot shows that the Italian samples — Lombards (labeled "Italians"), Venetians, Tuscans (including "TSI"), and Sicilians — cluster in a North-to-South cline between the Spanish and Greek samples, i.e. Southwestern and Southeastern Europe on the map. (Sardinians, as always, are outliers because of their almost purely Neolithic farmer ancestry.)

In these plots, with the Peloponnesean Greeks (in red) acting as a proxy for the southernmost Italians (and therefore all Italians and Southern Europeans in general), we can see that they're genetically distinct from all non-European populations of Western Eurasia, North Africa and beyond.

Supplementary Figure 2: Comparisons of Peloponneseans with non-European populations. PCA analysis of Peloponneseans and A. Near East. B. Caucasus. C. North Africa. D. East Africa. E. Arabia. F. West Siberia populations.

Stamatoyannopoulos et al. "Genetics of the peloponnesean populations and the theory of extinction of the medieval peloponnesean Greeks". Eur J Hum Genet, 2017.

Italian Beauty: Adua Del Vesco

May 1, 2017

Stage name of Rosalinda Cannavò, an actress from Messina, Sicily.

Much Better Population Structure

April 16, 2017

This new study confirms the results of previous studies by Di Gaetano et al. (2012) and Fiorito et al. (2016) but has much better geographical coverage of samples, with 737 individuals from 20 locations in 15 different regions being tested, making the earlier genetic "gap" between North-Central and Southern Italians disappear, filled in by an intermediate Central Italian cluster, creating a continuous cline of variation down the peninsula (with Sardinians as outliers) that mirrors geography.

The four new Italian samples from this study (N_ITA, C_ITA, S_ITA and SARD) cluster right on top of older Italian samples from Bergamo, Tuscany, Abruzzo, Sicily and Sardinia used in earlier studies, which are barely visible underneath, showing that the results are consistent. Northern Italians once again cluster with Spaniards, and there's a small Greek sample this time, but it's not from the areas closest to Southern Italians, clustering more with the Central Italians instead.

The study also for the first time includes a formal admixture test that models the ancestry of Italians by inferring admixture events using all of the Western Eurasian samples. The results are very interesting in light of the ancient DNA evidence that has come out in the last couple years.

When top 1% of most significant f3 values were retained according to computed Z-scores, 85% of tested population trios actually involved Italian clusters (Supplementary Table S2). In addition to the pattern described in the main text, the SARD sample seemed to have played a major role as source of admixture for most of the examined populations, especially Italian ones, rather than as recipient of migratory processes. In fact, the most significant f3 scores for trios including SARD indicated peninsular Italians as plausible results of admixture between SARD and populations from Iran, Caucasus and Russia. This scenario could be interpreted as further evidence that Sardinians retain high proportions of a putative ancestral genomic background that was considerably widespread across Europe at least until the Neolithic and that has been subsequently erased or masked in most of present-day European populations.

It's known that Sardinians are almost identical to Early European Farmers from the Neolithic, and that the Indo-Europeans who spread their languages all across Europe in the Bronze Age were a mix of Eastern Hunter-Gatherers from the Russian Steppe and either Caucasus Hunter-Gatherers or Chalcolithic Iranians (who are very similar).

So it looks like Italians resemble other Europeans in being a mix of early European farmers and later Indo-European invaders. The farmer ancestry (which is ultimately from Anatolia) has an expected southeast to northwest cline in Europe, but surprisingly not within Italy. According to the study's estimates, it's about the same amount in the North as it is in the South. The two regions actually differ in their Indo-European related ancestries, caused by inverse clines of the "Caucasus/Iran" and "Russian Steppe" components.

The purple component was predominant in Southern European groups and equally distributed along the peninsula (average frequency of 46%), almost reaching fixation in Sardinians (85%) plausibly due to their long-term isolation especially to Post-Neolithic processes. [...] The green component was considerably represented in samples from Caucasus and Middle East, being also evident in some Southern European populations (e.g. Greeks) and, especially, in Southern Italy (28%), progressively decreasing towards the northern part of the peninsula (12%). [...] The red component characterized most of Central and Eastern European populations, being reduced in Sardinia (7.4%) and showing a decreasing north-south gradient in peninsular Italy (from 39% in N_ITA to 20% in S_ITA).

This difference could be explained by the fact that Ancient Italy was home to a variety of Indo-European speakers: Italic languages spread everywhere, Celtic languages were spoken in the North, and Greek and Illyrian languages in the South. It's likely that some of these arrived via southern route through the Balkans while others took a northern route over the Alps, and the people who brought them thus had different levels of "Caucasus" and "Russian" ancestry.

Sazzini et al. "Complex interplay between neutral and adaptive evolution shaped differential genomic background and disease susceptibility along the Italian peninsula". Scientific Reports, 2016.