During the Migration Age (ca. 300-700 A.D.), "barbarian" groups like the Goths and Vandals roved around Europe, nibbling away at the declining Roman Empire and settling down as they went along. One tribe that got comfortable was the Bavarii, who hunkered down in what is now southern Germany around the sixth century A.D. And inside Bavarii cemeteries, archaeologists find interesting specimens: Women with elongated skulls.

That’s long confused researchers, who associate such skull modification in Europe at the time with places further east such as Hungary. Southeast Europe at the time was home to the feared confederacy of tribes known as the Huns, and their burial grounds contain many more long-skulled ladies than further west in Bavaria. So how did the practice make it to Germany?

One theory is that the Huns or some other group transmitted the skull-modifying technique—the equivalent of a meme that local Bavarian women then took up themselves. But a new study published in the journal PNAS suggests another answer: Maybe the Bavarian women with the unusual skulls weren’t Bavarian to begin with.

An international team of researchers recently analyzed the genomes of 36 sets of bones buried in six Bavarian cemeteries during the fifth and sixth centuries A.D.: twenty-six women, 14 of whom showed signs of artificial cranial deformation (ACD), and ten men. They also analyzed five additional samples, including remains of what is thought to be a Roman soldier and two other women with ACD from Crimea and Serbia.

The women’s skulls didn’t get that way by accident. Their heads were carefully bound starting at birth, and their skulls kept their distinctive looks as they hardened. Archaeologists aren’t sure if the practice had to do with beauty, health, or another reason.

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The researchers sequenced parts of the buried Bavarians’ DNA, and the entire genomes of 11 samples. Then they used the data to learn about the appearance, ancestral origins and health of the long-dead Bavarians.

The men—likely farmers in small communities— looked pretty much alike. But many of the women didn’t look like the men. At all.

It wasn’t just the skull modifications: While the men’s genes showed that they likely had blond hair and blue eyes, the women likely had brown eyes and blond or brown hair.

Looks were just the tip of the iceberg. The researchers compared the ancient genes to those of modern people and found some big differences between male and female.

The men’s genes were similar to those of northern and central Europeans. The women with modified skulls, however, had a much more diverse set of ancestors. The majority matched up with southeastern Europeans like Romanians and Bulgarians, and one even had East Asian ancestors.

“Archaeologically, they are not that different from the rest of the population,” says Joachim Burger, a population geneticist at the University of Mainz and an author of the study. “Genetically, they are totally different.”

From what researchers can tell, the women assimilated and adopted local traditions—and skull modification seems to have stopped with them. So why did they have such different genes?

Burger is quick to admit he doesn’t know for sure. But he and his colleagues have a theory. They think their data shows a previously unconfirmed practice of exchange between the Bavarians and other cultures, even in what Burger calls “relatively boring, blond farm places.”

View Images This engraving based on a 16th-century Raphael fresco depicts Attila, king of the Huns, meeting with Pope Leo 1 in 452 A.D. From the fourth century on, 'barbarian' tribes moved into the power vacuum in Europe created by the decline of the Roman Empire. Photograph by Intrtfoto, Alamy

Though she didn’t work on the current study, Susanne Hakenbeck, a University of Cambridge historical archaeologist, has spent years trying to piece together the stories of the same women and others with ACD throughout Europe.

When Hakenbeck analyzed isotopes from bones in one of the cemeteries in the current study, she found dietary differences between men and women. Her analyses of skull modifications of the era also back up the hypothesis: ACD was common among men, women and children living between Central Asia and Austria at the time, but is only seen in a handful of adult women in places further west, like Germany.

"Nobody thought that marriage and kinship had a really important function in the period,” says Hakenbeck. The new research could prove that wrong; the women seem to have arrived specifically to marry Bavarian men, perhaps as the result of a strategic alliance.

The study has its limitations: It doesn’t deal with a large population, and two of the samples were buried later than the rest of the group. However, those women’s ancestors came from even further away than the others, which might suggest a pattern of marriage migrations.

Think the confrontation between a group of dark-haired, skull-modded strangers and some blond farmers sounds like the premise of a bingeworthy Netflix series? So does Burger. “There are exotic women with exotic skulls coming to these boring foreign places,” he says. “Culture clash.”