Ancient genomics support deep divergence between Eastern and Western Mediterranean Indo-European languages

 Ancient genomes provide final word in Indo-European linguistic origins

by Justin Jackson , Phys.org

Distribution of Bell Beaker-derived and Yamnaya-derived ancestry proportions obtained from the IBD admixture model. The proportion of each steppe source is standardized by the total steppe contributions, i.e. the sum of Corded Ware, Bell Beaker and Yamnaya_Samara contributions. Credit: bioRxiv (2024). DOI: 10.1101/2024.12.02.626332

A team of 91 researchers—including famed geneticist Eske Willerslev at the Lundbeck Foundation GeoGenetics Center, University of Copenhagen—has discovered a Bronze Age genetic divergence connected to eastern and western Mediterranean Indo-European language speakers.

• Findings indicate that Spanish, French and Italian populations received steppe ancestry from Bell Beaker groups, while Greek and Armenian groups acquired ancestry directly from Yamnaya populations. 
• Their results are consistent with the Italo-Celtic and Graeco-Armenian linguistic models.

Indo-European languages cover much of Europe and western Asia and are thought to have originated mainly from migrations of Early Bronze Age people across the Pontic Steppe. The Pontic Steppe region stretches north of the Black Sea from the edge of modern-day Bulgaria across southern Ukraine to the shores of the Caspian Sea.

• Relative linguistic models have served as pushpins in mapping European migration, though language speakers' physical origins versus cultural adaptation have remained uncertain.

Prior genetic studies confirmed steppe ancestry across Europe but can not differentiate whether different European populations received steppe input from the same or distinct sources. In order to cement theoretical conclusions, timepoint-specific genetic information from entire regions of the Mediterranean was needed.

In the study, "Ancient genomics support deep divergence between Eastern and Western Mediterranean Indo-European languages," posted on the preprint server bioRxiv, researchers analyzed 314 ancient genomes to clarify the trajectories of steppe-related populations and the possible origins of languages such as Italic, Celtic, Greek and Armenian.

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Ancient genomes from Spain, France, Italy, Hungary, Moldova, Greece, Cyprus, Turkey, Syria and Lebanon, all dated between 2,100 and 5,200 years ago, were sequenced and combined with previously published ancient genomes for a total of 2,403 samples. Steppe ancestry sources were compared using identity-by-descent admixture modeling. To assess mobility within populations, 224 individuals underwent strontium isotope analyses.

Strontium isotope analysis is a technique for tracing human migration. It examines the ratios of strontium isotopes (particularly 87Sr/86Sr) in human remains. Once ingested through drinking water or eating plants, strontium is incorporated into bone and tooth enamel, where it retains the isotopic ratios present during their formation.

Different regions have distinct strontium signatures (87Sr/86Sr ratios) based on their underlying geology. Analyzing these ratios in bones and teeth can reveal the geographic origins of where an individual has lived and obtained their food and water, allowing researchers to infer migration patterns. While not providing a precise location in most cases, it can accurately reveal the difference between local and non-local inhabitants of an area.

Genetic findings revealed a pronounced divide between Eastern and Western Mediterranean populations during the Bronze Age, with two distinct expansions of steppe ancestry into the Mediterranean.

Bell Beaker populations originated from steppe pastoralists who mixed their steppe ancestry with local European farmers. 

• Specifically, Bell Beaker groups carried steppe-related genetic profiles from earlier steppe populations, such as Yamnaya, combined with ancestries related to the pre-existing Globular Amphora Culture in Western Europe.

Local admixture likely facilitated the westward spread of Bell Beaker populations into Italy, France, and Spain, aligning with linguistic models proposing an Italo-Celtic subgroup, as both Italic and Celtic languages share a common origin.

• Steppe ancestry in Greece and Armenia was derived directly from Yamnaya populations of the Pontic steppe without significant admixture of locals.

In Greece, this ancestry was detected in individuals from the Peloponnese as early as 3,800 BP, preceding the emergence of the Greek language and the Mycenaean civilization. Steppe ancestry coincided with the political rise of Mycenaean culture.

• Armenian steppe ancestry appeared during the Middle Bronze Age and was genetically similar to Greek populations, supporting the Graeco-Armenian linguistic hypothesis. 
• Steppe ancestry paralleled the Kura-Araxes culture's decline and the Trialeti culture's emergence.

Genetic data from Northern and Central Italy indicated multiple admixture events, reflecting complex interactions between steppe migrants and local Neolithic farming populations. 

In Greece, steppe ancestry coincided with the political rise of Mycenaean culture.

• Strontium isotope ratios identified 56 non-local individuals in Greece, Cyprus, and Italy, reflecting active mobility patterns during the Bronze Age. An individual from Pian Sultano in Italy showed a non-local signature in the petrous bone but a local signature in the tooth, indicating the individual spent their childhood in a distant land.

Four non-local individuals in Cyprus came from different genetic backgrounds. 

• One showed a high radiogenic strontium isotope signature consistent with a Scandinavian place of origin. 
• This individual's genetic sequences also clustered with Bronze Age Scandinavian ancestry, hinting at Mediterranean trade routes reaching far beyond the local horizons.

When compared with hypothesized linguistic mapping, the combined genetic and strontium data provide compelling evidence for a distinct genetic and linguistic split between ancient Eastern and Western Mediterranean Indo-European populations. Italic and Celtic groups are linked to Bell Beaker populations, while Greek and Armenian groups trace their ancestry to Yamnaya populations.
These findings are consistent with the Italo-Celtic and Graeco-Armenian linguistic migration hypotheses and do not align with alternative models such as Indo-Greek and Italo-Germanic.