Researchers use ancient DNA to map migration during the Roman Empire

The team wondered how much of that diversity was unique to Rome, the capital of the empire, and how diverse more remote areas might have been. In the study, they focused on a narrower window of time — from the conclusion of the Iron Age 3,000 years ago to today — but looked at a geographic area covering the entire Roman Empire. They used existing DNA data from thousands of skeletons that had been collected from the empire as well as central Europe, Eastern Europe and Central Asia, Britain and Northern Europe, and North Africa. They additionally sequenced 204 new genomes from 53 archeological sites in 18 countries. Most were from individuals who died during the time periods known as imperial Rome and late antiquity, from the first to seventh centuries BCE.

“When we started this study, there weren’t a lot of historical genomes from this period in time, so the new samples filled this gap,” said Clemens Weiss, PhD, a former postdoctoral fellow in the Pritchard lab who co-led the work. He is now a research engineer at the Stanford Cancer Institute.

The first thing the team noticed was that, during the period in question, the less diverse areas tended to be those that were geographically isolated, such as the Armenian highlands, which are surrounded by mountains. Overall, however, most areas of the Roman empire had skeletons from a variety of genetic origins. Particularly diverse areas included Sardinia, the Balkans and parts of central and western Europe.

“For the most part, the observations complement what historians and archaeologists hypothesized,” said Margaret Antonio, a graduate student in the Pritchard lab and co-first author of the paper. “For example, North African pottery was found throughout the Roman Empire. Now, we also find genetic evidence of people from North Africa residing in present-day Italy and Austria.”

Mapping connections

To better understand which areas were connected to each other, the team undertook a large analysis of the people unearthed at every location whose genetic ancestry didn’t match where they were found — suggesting that they or their recent ancestors had traveled or migrated.