"Arab" Found in Danish Iron-Age Grave
for National Geographic News
|June 24, 2008|
An ancient Dane with Arabian genes is part of a DNA study that suggests Scandinavians of 2,000 years ago were more genetically diverse than today.
Researchers say the Iron Age man may have been a soldier serving on the Roman Empire's northern frontier or a descendant of female slaves transported from the Middle East.
The Roman Empire at the time stretched as far as the Middle East, while Roman legions were based as far north as the River Elbe in northern Germany.
The study analyzed 18 well-preserved bodies from two burial sites dating from 0 to A.D. 400 in eastern Denmark. The sites were originally excavated some 20 years ago.
Mitochondrial DNA, which provides a genetic record of an individual's maternal ancestry, was taken from teeth by a team led by Linea Melchior of the Institute of Forensic Medicine at the University of Copenhagen.
One skeleton had a type of DNA signature—known as a haplogroup—closely associated with the Arabian Peninsula, according to Melchior.
"It's especially found among some Bedouin tribes, but it has also been found in the southern part of Europe," the researcher said.
Iron Age Grave
The skeleton came from Bøgebjerggård, an Iron Age site on the southern part of the island of Sjælland (Zealand).
(See a map of Denmark.)
The bodies likely belonged to poor farmers, the team said.
Other unusual haplogroups were identified, including one representing a prehistoric European lineage which today is found in only about 2 percent of Danes, Melchior said.
"It may have been one of the ancient Nordic types which has been diluted by later immigrations from Scandinavia and Germany," she said.
In contrast, the other burial site, at nearby Skovgaarde, contained bodies with a genetic signature common to modern Scandinavians, the study found.
"They were typically of a Nordic type and the diversity is lower," Melchior said.
This group consisted mainly of women and was distinguished by rich grave goods, including finely made rings, necklaces, and ornate hairpins.
"You can see they were dressed up very nicely with beautiful jewelry before being buried," Melchior said.
The Skovgaarde burials are thought to represent the elite of society—people the researchers think arrived from elsewhere in Scandinavia.
The findings, published in November in the American Journal of Physical Anthropology, are part of a wider study that suggests Denmark's ancient populations were much more diverse genetically than they are today.
Reliable DNA results have been obtained for 56 individuals from the late Stone Age through medieval times, Melchior said.
(Read a DNA primer.)
"At all the sites we have investigated in Demark we have found rare [genetic] types and types that are not common or present in Europe today," she said.
"When we go back in time we find much higher diversity," the Melchior added. "It was quite surprising that the lowest diversity was found among Danes of the present day."
One possible explanation put forward by the team is that certain groups were more vulnerable than others to medieval outbreaks of bubonic plague, most notably the Black Death, which alone wiped out around a third of the European population between 1347 and 1351.
Such a theory has been proposed by another recent study, which recorded a similar loss of genetic diversity in English people.
Researchers, including Rus Hoelzel of the School of Biological and Biomedical Sciences at Durham University, U.K, found that during the medieval period one particular haplogroup in England became much more widespread.
This may reflect the fact that families who shared certain genes survived the plague much better than others, said Hoelzel , who was not involved in the Danish study.
"Plague, given the timing, seems a strong candidate, though it isn't the only one," he said.
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