The Romans and Vikings left few genetic traces of their occupations of Britain, research suggests

The Romans controlled much of Britain for nearly 400 years, but they left relatively little genetic evidence of their occupation, new ancient-DNA research reveals.

Instead, the Roman occupation, from A.D. 43 until about 410, seems to have changed the culture of their Britannia province, with most people native to Britain converting to Imperial Roman ways.

A preprint of the study was posted to the bioRxiv server April 29 and has not been published in a peer-reviewed journal yet. Some experts agree with the conclusions, but others are cautious.

However, some of the study's findings agree with the results of earlier genetic studies of the Germanic migration into Britain, Duncan Sayer, an archaeologist at the University of Lancashire in England, told Live Science.

"These results absolutely confirm the data we've had previously," said Sayer, who was not involved in the study.

For their investigations, the researchers looked at the genomes of more than 1,000 individuals who had been buried in Britain between 2550 B.C. and A.D. 1150. They found that Roman DNA — identified as having ancestral origins "outside Britain" — accounted for only about 20% of the genetic profile of individuals buried in Britain during its Roman era. By comparison, in the later Anglo-Saxon era, DNA from "Germanic" sources accounted for about 70% of the genetics of people buried there at that time.

These findings indicate that the native British interbred surprisingly little with people from elsewhere in the Roman Empire but often interbred with people of Anglo-Saxon origin, Sayer said.

"In the Roman period, although people are settling in Britain, it's not in quite the same way as Germanic speakers [Anglo-Saxons] are in the fifth and sixth centuries," James Gerrard, an archaeologist at Newcastle University in England who was not involved in the research, told Live Science.

The team who worked on the latest study said they also found very little genetic evidence of the later Viking Age in the North of England, when most of that region followed Danish traditions and was called the Danelaw: only about 4% of the genetic profiles of people buried in England at this time showed they had Iron Age Scandinavian ancestry, they reported.

Meanwhile, ancestries from Central and Southern Europe rose from the eighth century onward that signified more people migrated into England during the medieval period, the team wrote in the preprint.

Cultural transformation

The authors noted that "previous DNA sampling from Roman Britain has been relatively small-scale and regionally or context specific" and suggested that their "dataset bridges this gap."

But Gerrard, who was not involved in the study, cautioned that the new research might not give an accurate picture of Britain's genetic history.

To begin with, while the new study examined the DNA extracted from 1,039 people buried in Britain between the Bronze Age and medieval times — a span of roughly 3,700 years — only about 200 were from the Roman period.

This is a small sample size compared with archaeological investigations in Britain, where the origins of several thousand people buried during the Roman period have been examined over decades, he said.

In addition, the burials in the new research tended to be from cities, rather than from the countryside, where intermarriage rates may have differed. The results of the study might have also been skewed because the Roman presence would have been greater in the North of England, where many troops were stationed at camps, and in the East of England, where Roman urban settlements were more common, he said.

"We have a problem, I think, of whether ancient DNA is representative of the whole population," Gerrard said.

Celtic women

The Romans invaded and annexed most of Britain at the command of Emperor Claudius in A.D. 43, although his great-great-granduncle (by adoption) Julius Caesar led two short-lived invasions in 55 and 54 B.C. The Roman occupation ended in about A.D. 410, when Roman troops guarding the northern frontier were recalled to the continent to defend Roman territories against Germanic invasions.

Although the study found relatively little genetic evidence of the Roman occupation, the researchers noted that the Romans seemed to have had a marked effect on burial practices. Pre-Roman burials in Britain were often grouped by matrilineal relationships, perhaps reflecting the traditionally Celtic importance of women as the heads of their families, and the researchers found evidence that this practice continued for a time in the West of England — a native stronghold. Under this cultural tradition, women were relatively empowered and stayed in their ancestral homes, and the men they married moved into their communities.

But the DNA extracted from the remains in Roman-era cemeteries in Britain showed no such patterns, the researchers said, which might reflect traditional Roman patriarchal practices.

The authors of the new research declined a request from Live Science to comment, noting that they wanted to wait until the paper is published in a peer-reviewed journal before talking with the media.

What do you know about the Empire's conquest of the British Isles? Find out with our Roman Britain quiz!