What Your DNA Says About Medieval History

Earlier this year, researchers from Oxford University published a study showing how the slave trade and colonization shaped the genetics of North and South America.

Analyzing more than 4,000 DNA samples from across both continents, as well as Europe and Africa, they were able to detect patterns in line with what historians knew about migrations across the Atlantic.

Many people in Colombia and Puerto Rico had Sicilian ancestry, for example, on account of the wave of Italian immigrants to those areas in the 1800s and early 1900s. Most African Americans shared a genetic ancestor with the Yoruba of West Africa, which supplied around one-third of the slaves sent to the Americas in the 1600s.

“We can see the huge genetic impact that the slave trade had on American populations, and our data match historical records,” Cristian Capelli, the lead study author and a professor of zoology at Oxford, said in a statement at the time.

In a paper published today in the journal Current Biology, the same  team moved its analysis to the other side of the ocean and tweaked the order. This time, they used genetic data to create a historical record as well as confirm it, discovering evidence for previously unknown patterns of movement across Asia and Europe over the past 1,500 years.

Using around 2,000 DNA samples—slightly more than half from 63 locations in Europe and the Middle East, and the rest taken from another 87 locations elsewhere in the world—the researchers looked at where certain shared genetic markers fell on the chromosome to determine the date of admixing, the term for when two previously separate groups begin to merge.

As with the earlier study, much of what Capelli and his colleagues discovered meshed with what historians already knew. For example, among northern Europeans, highest rate of admixing took place “around the late first millennium C.E., a time known to have involved significant upheaval in Europe,” while admixture between north African and southern European populations was dated to a time span “consistent with migrations associated with the Arabic Conquest of the Iberian peninsula.”

But there were surprises, too. Most notably, Capelli and his colleagues discovered evidence for an influx of Mongolians into Europe that predated the reign of Ghengis Khan.

The research of Capelli and his colleagues is different than paleogenetics, which relies on ancient DNA rather than samples taken from people alive today. But ancient DNA intact enough for analysis can be hard to come by, and the researchers see their work as a complement: “Placing this work within the context of ancient DNA samples will further aid our understanding of European prehistory and disease,” they wrote, with contemporary bodies filling gaps in historical understanding that older bodies haven’t been able to supply.

If the research holds up, it will mean that each of us contains an archive of journeys taken by people who existed millennia before we were born.