ACD is most commonly associated with the nomadic Huns, who invaded much of eastern and central Europe during the 4th and 5th centuries. Attila the Hun (about 406–453) was one of their most successful and notable leaders.
Veeramah said western Europe was on the fringes of the Hun territory, so he and his colleagues are not sure if the women in the Bavarian graves had any Hun ties. While one of the females had Central Asian genetic ancestry, the researchers think that she migrated from the Black Sea region to Bavaria along with the other 12 women around the year 500.
"While clearly moving around was not as easy as it now — we are probably talking a 50-day journey from southeastern Europe to Bavaria — if you read texts from the preceding Roman period, individuals were already traveling large distances across Europe fairly frequently, particularly the elite classes, simply to get training in Latin," Veeramah said.
The Romans left behind a lot of roads, some of which are even present today. The Roman road of Watling Street, for example, runs through Veeramah's hometown of Dartford in Kent, England.
"These women could have been transported in carts pulled by horses, or moved along rivers like the Rhine and Danube, with guards and servants for protection, particularly if they were elites," he added. "Whether the women moved of their own free will is another question we can’t answer."
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The authors theorize that the women might have married or partnered with men in their new homeland, helping to forge political ties. Royals and other nobles throughout Europe are long known to have wedded foreigners they hardly knew for the sake of political gains.
Senior author Joachim Burger of Johannes Gutenberg University, Mainz said that the ACD women's presence in central-western Europe exemplifies the "long-range female mobility that bridges larger cultural spaces and may have been a way for distant groups to form new strategic alliances during this time of great political upheaval in the absence of a previous Roman hegemony."
He continued, "We must expect that many more unprecedented population-dynamic phenomena have contributed to the genesis of our early cities and villages."
The scientists are also interested in what the DNA reveals about human health, both then and now. It has been known for some time that people of European heritage carry disease-risk alleles that make them susceptible to certain conditions.
The new study found that alleles increasing the risk of contracting common inflammatory diseases — such as Crohn's disease, Type 1 diabetes, multiple sclerosis, and celiac disease — were already well established in northern and central Europe by the year 500.
"One theory for the presence of these variants is that while they contribute to disease today, they may have reached appreciable frequencies in past populations as a result of positive selection by providing protective effects against pathogens," Veeramah said, adding that the theory is called the "hygiene hypothesis.”
"But," he continued, "as people became 'cleaner' and less exposed to such pathogens in modern times, these variants that were originally useful started contributing to the risk of inflammatory diseases."
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The overall long-term goal of the researchers, though, is to obtain a clearer picture of the extent of migration that occurred during what has popularly been known as the Migration Period, or Völkerwanderung in German, which occurred between 300 to 700 AD.
The scientists also hope to learn about barbarian social organization because these tough, scrappy groups left behind no written records.
"Everything we know comes from the Romans or historians writing well after the events in question," Veeramah explained.
He and his colleagues plan to obtain additional genetic data from numerous European sites dating to the Migration Period. The researchers will pay particular attention to cemeteries associated with the various barbarian tribes.
Harbeck added, "There are also still questions remaining with respect to the women with deformed skulls. For instance, right now we are trying to find out at what age they migrated."
It is even possible that people alive today are on the extended family trees of these women. Future DNA analysis of subsequent medieval generations could at least show if they had children with Bavarian men.