for National Geographic News
English people are less genetically diverse today than they were in the days of the Vikings, possibly due to two deadly plagues that swept their country centuries ago, a new study says.
The study compared DNA from ancient and modern Englanders and found that the country has a smaller gene pool than it did a thousand years ago.
The findings come in contrast to modern England's reputation as a cultural melting pot, where in many major cities you are as likely to hear Urdu (from India) or Yoruba (from Nigeria) being spoken on the streets as English.
"The findings were unexpected. Modern England is the result of centuries of mixing cultures, and so higher diversity was expected," said Rus Hoelzel, a geneticist from the Britain's University of Durham, who led the study.
Hoelzel and his colleagues obtained DNA samples from the skeletal remains of 48 ancient Britons who lived between A.D. 300 and 1000.
The researchers studied the mitochondrial part of the DNA, which is passed down from mothers to their children (see an overview of human genetics).
By comparing this DNA with that of thousands of people from various ethnic backgrounds living in England today, they found that genetic diversity was greater in the ancient population.
The team also compared the ancient DNA with samples from people living in continental Europe and the Middle East, and found a similar lack of genetic variety.
"Few of the modern populations were as diverse as our ancient sample," Hoelzel said, adding that his team analyzed 6,320 modern samples in all.
The findings are published in the journal Biology Letters.
One possible explanation for this narrowing of diversity might be two major outbreaks of bubonic plague that swept England and much of Europe—the Black Death (1347-1351) and The Great Plague (1665-1666)—Hoelzel said.
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