"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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