NEW YORK – An international team led by investigators in Switzerland and Greece relied on ancient genome sequencing to retrace population ancestry in Bronze Age cultures scattered along the Aegean Sea, documenting a shift from genetically similar populations with European Neolithic farming ancestry in the Early Bronze Age to more recent populations with additional Pontic-Caspian Steppe- and Caucasus hunter-gatherer-related ancestry.
"The Early [Bronze Age] genomes are homogeneous and derive most of their ancestry from Neolithic Aegeans, contrary to earlier hypotheses that the Neolithic [Early Bronze Age] cultural transition was due to massive population turnover," Democritus University of Thrace researcher Christina Papageorgopoulou and University of Lausanne and Swiss Institute of Bioinformatics researcher Anna-Sapfo Malaspinas, co-senior and -corresponding authors on the study, and their colleagues wrote in a study appearing in Cell on Thursday.
Using targeted-enrichment whole-genome sequencing, machine learning, and other methods, the researchers assessed four Middle Bronze Age individuals from Helladic, Cycladic, and Minoan cultures on the Aegean Sea during the Early Bronze Age. Those sequences were complemented by new mitochondrial genome sequences from 11 more Aegean individuals, as well as two newly sequenced individuals dated to the Middle Bronze Age from a Helladic culture in northern Greece.
From the mtDNA sequences and insights from millions of nuclear SNPs, the team concluded that Bronze Age Cycladic individuals on the Cycladic islands, a Minoan culture in Crete, and the Helladic civilization on mainland Greece were genetically similar to one another around 5,000 years ago, despite documented differences in their art, architecture, burial traditions, and other cultural clues. All three cultures shared ancestry with Neolithic farming populations, with much smaller Caucasus-related ancestry components.
"These culturally different populations were genetically homogeneous across the Aegean and western Anatolia at the beginning of the [Bronze Age]," they wrote, noting that the Early Bronze Age individuals carried ancestry from local Neolithic farming populations with a smaller proportion of Caucasus-related hunter-gatherer ancestry.
On the other hand, Middle Bronze Age representatives from northern Greece around 4,000 years ago were more genetically distinct and varied, the researchers reported, carrying not only Neolithic Caucasus-related ancestry, but also significant ancestry related to Bronze Age populations from the Pontic-Caspian Steppe.
When the team considered the ancient genetic profiles in the context of present-day populations, meanwhile, it saw genetic continuity between the Aegean individuals living in northern Greece in the Middle Bronze Age and individuals found in Greece today.
Even so, "future work will be required to determine how representative the analyzed genomes of the Aegeans are of the [Bronze Age] Cycladic, Minoan, and Helladic cultures as a whole," the authors cautioned, noting that additional genomes from Armenia and the Caucasus across the Mesolithic and Bronze Age "could help to further pinpoint the origins and the mode of gene flow into the Aegean and to better integrate the genomic data with the existing archaeological and linguistic evidence."