Fitzhugh speculates that the Vikings might have become aware of the practice after encountering West Africans with filed teeth during their voyages to Spain and the Mediterranean.
"However, African teeth modification was of a different sort, with teeth filed into points," Fitzhugh said.
Other people have suggested that the Vikings may have learned the practice on their travels to North America.
"Maybe they adopted the idea of mutilating their teeth from people they met on their voyages," Arcini said.
"The only place I know of [where people] have similar horizontal filing marks on their teeth is the area of the Great Lakes in America and the present states of Illinois, Arizona, and Georgia."
People in many cultures have been modifying their teeth for several thousand years.
Some of the oldest cases of tooth modification come from Mexico, dating as far back as 1400 B.C.
But the Viking discovery is the first historical example of ceremonial dental modification among Europeans.
The skeletons Arcini analyzed were discovered at several Viking-era burial sites in Sweden and Denmark.
The 24 skeletons she found with filed teeth all belonged to men.
The marks were cut deep into the enamel and occurred often in pairs or triplets. Arcini adds that the marks appear to be ornamental rather than functional.
"I can conclude that the filed furrows in the front teeth of 24 Viking men are deliberately made and not the result of using the teeth as a tool," Arcini said.
She also noted that the marks are so well made that a person of great skill most likely filed them.
Why the Viking men had their teeth modified remains a mystery, but it's likely that the marks represented some kind of achievement.
"I think the Vikings' filed furrows should be seen as a social identification," Arcini, the Swedish anthropologist, said.
"Maybe they were brave warriors who got a furrow each time they won a battle or tradesmen who traveled together."
Fitzhugh, of the Smithsonian, says the reasons may have been partly aesthetic.
"We do know that the Vikings took pride in their appearance, combed their hair, and ironed their clothes with hot rocks," Fitzhugh said. (See wallpaper photo: tattooed Viking)
"[They] now seem to have taken pain to decorate their teeth."
"When in-filled with pigment, these grooves would have made Viking warriors look even more terrifying to Christian monks and villagers," he added.
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