Both Steppe And Iranian Ancestry Arrived in Sicily During The Bronze Age

Earlier this year, a new ancient DNA paper on steppe and Iranian farmer migrations into the Western Mediterranean escaped my notice. 

Steppe ancestry arrived in the Western Mediterranean region not long after it arrived in continental Europe often via Iberia. 

Iranian ancestry entered the Mediterranean (in the Aegean and Sicily) not long after the 4.2 kiloyear climate event and long before Bronze Age collapse, ca. 1200 BCE.

Sicily didn't undergo significant outside admixture from its population derived from Europe's first farmers until the Iron Age.

Steppe-pastoralist-related ancestry reached Central Europe by at least 2500 BC, whereas Iranian farmer-related ancestry was present in Aegean Europe by at least 1900 BC. However, the spread of these ancestries into the western Mediterranean, where they have contributed to many populations that live today, remains poorly understood. 

Here, we generated genome-wide ancient-DNA data from the Balearic Islands, Sicily and Sardinia, increasing the number of individuals with reported data from 5 to 66. 

The oldest individual from the Balearic Islands (~2400 BC) carried ancestry from steppe pastoralists that probably derived from west-to-east migration from Iberia, although two later Balearic individuals had less ancestry from steppe pastoralists. 

In Sicily, steppe pastoralist ancestry arrived by ~2200 BC, in part from Iberia; Iranian-related ancestry arrived by the mid-second millennium BC, contemporary to its previously documented spread to the Aegean; and there was large-scale population replacement after the Bronze Age. 

In Sardinia, nearly all ancestry derived from the island’s early farmers until the first millennium BC, with the exception of an outlier from the third millennium BC, who had primarily North African ancestry and who—along with an approximately contemporary Iberian—documents widespread Africa-to-Europe gene flow in the Chalcolithic. Major immigration into Sardinia began in the first millennium BC and, at present, no more than 56–62% of Sardinian ancestry is from its first farmers. This value is lower than previous estimates, highlighting that Sardinia, similar to every other region in Europe, has been a stage for major movement and mixtures of people.

Daniel M. Fernandes, Alissa Mittnik,  […] David Reich, "The spread of steppe and Iranian-related ancestry in the islands of the western Mediterranean" 4 Nature Ecology & Evolution 334–345 (February 24, 2020,  an author correction to this article was published on April 15, 2020).