Humans began drilling teeth to remove decay at least 9,000 years ago, more than 4,000 years earlier than previously believed, according to new evidence from an ancient graveyard at Mehrgarh in western Pakistan.
Studying more than 300 bodies exhumed from the ancient burial ground, a team from the University of Poitiers in France found nine with a total of 11 drilled teeth. All of the precisely drilled holes were on molars that would not have been readily visible to the patients' contemporaries, indicating that the work was done not for decoration but to alleviate the pain of decay.
One hole, for example, was on the inside back surface of a tooth.
The holes were shallow -- no deeper than a seventh of an inch. But that is deep enough to reach sensitive nerves, so the drilling process could have been quite painful, the researchers said. Many of the teeth show post-drilling wear, indicating that the dental work was not done after the patients' death.
The research team, led by anthropologist Roberto Macchiarelli, found flint drill bits at the site that were used for drilling holes in beads for jewelry and other ornaments. They speculate that the same techniques could have been used to drill the teeth.
In experiments using similar bits powered by a bow, Macchiarelli was able to drill similar holes in isolated teeth in about a minute.
No fillings were found in the teeth, but the team said the early dentists could have used asphalt fillings that disintegrated after death.
The Mehrgarh complex sits beside the Bolan River in the Indus River Valley, home of one of the earliest known agricultural civilizations.
Previously, the earliest evidence of dentistry was in teeth from a Neolithic graveyard in Denmark dating from about 3000 BC.