NEW YORK – Using ancient DNA, a team from the US, Austria, Italy, and other parts of Europe has retraced the genetic ancestry of individuals who have moved and migrated through Rome since the Mesolithic period.
"It was surprising to us how rapidly the population ancestry shifted, over timescales of just a few centuries, reflecting Rome's shifting political alliances over time," co-senior author Jonathan Pritchard, a genetics researcher at Stanford University, said in a statement, noting that "[e]ven in antiquity, Rome was a melting pot of different cultures."
For their study, published online today in Science, the researchers sequenced the genomes of 127 ancient individuals from more than two dozen burial sites in Rome and other parts of central Italy going back some 12,000 years. Their results revealed individuals with ancestry from other parts of Europe, the Near East, North Africa, and elsewhere, with shifts that corresponded to historical events ranging from the arrival of agriculture to Imperial Roman expansions.
"These high levels of ancestry diversity began prior to the founding of Rome and continued through the rise and fall of the empire, demonstrating Rome's position as a genetic crossroads of peoples from Europe and the Mediterranean," Pritchard and his co-authors wrote.
For their analyses, the researchers sequenced DNA isolated from powdered petrous bone samples for 127 individuals dated a few hundred years to more than 10,000 years old. The bones came from 29 archeological sites in Rome and central Italy. The ancient individuals offered a look back at the Mesolithic, Neolithic, Copper Age, Bronze Age, and Iron Age, along with later time points representing the Roman Republic, Imperial Rome, Late Antiquity, and Medieval Period.
The team analyzed the resulting sequence data, covering the genomes at an average depth of just over 1-fold, in combination with sequences for 50 modern individuals from central Italy who were profiled for another study. Along with broad genetic clusters that lined up with Mesolithic hunter-gatherers, early farmers, and post-Bronze Age individuals, more subtle ancestral features in the ancient individuals lined up with the region's history.
"This study shows how dynamic the past really is," co-first author Hannah Moots, a graduate student in anthropology in Pritchard's Stanford lab, said in a statement. "In Rome we're seeing people come from all over, in ways that correspond with historical political events."
With the introduction of farming in the area, for example, the researchers saw an increase in ancestry from populations in Turkey and Iran that have been linked to agriculture's roots, while a population turnover before the Iron Age led to enhanced Steppe, Iranian Neolithic, and North African ancestry.
"The Iron Age individuals exhibit highly variable ancestries, hinting at multiple sources of migration into the region during this period," the authors reported, adding that "Iron Age individuals genetically resemble modern European and Mediterranean individuals, and display diverse ancestries as central Italy becomes increasingly connected to distant communities through new networks of trade, colonization, and conflict."
Still other ancestry changes that the team detected over the last few thousand years included an influx of ancestry from Near Eastern populations, followed by migrations to the area from other parts of Europe as Rome's empire waned and its affiliations changed.
"By the founding of Rome, the genetic composition of the region approximated that of modern Mediterranean populations," the authors concluded. "During the Imperial period, Rome's population received net immigration from the Near East, followed by an increase in genetic contributions from Europe."