9,000-Year-Old Drilled Teeth Are Work of Stone Age Dentists

Amitabh Avasthi
for National Geographic News
April 5, 2006
Human teeth excavated from an archaeological site in Pakistan show that dentistry was thriving as recently as 9,000 years ago.

Researchers excavating a Stone Age graveyard found a total of 11 teeth that had been drilled, including one that had apparently undergone a complex procedure to hollow out a cavity deep inside the tooth.

The discovery suggests a high level of technological sophistication, though the procedure, which involved drills tipped with shards of flint, could hardly have been a painless affair.

"The finding provides clear and compelling evidence that earlier people had knowledge of manipulation of dental hard tissues in living people," said Clark Spencer Larsen, an anthropologist at Ohio State University in Columbus, who was not part of the excavation.

Scientists from the Université de Poitiers in Poitiers, France, and the Musée Guimet of Paris made the discovery.

The team's findings appear in this week's issue of the journal Nature.

Therapeutic Reason?

"We think the drilling had medical reasons," said Roberto Macchiarelli, a paleoanthropologist at the Université de Poitiers and lead author of the study.

"While some teeth had been drilled more than once, four showed signs of decay … suggesting a possible therapeutic intervention."

The procedure could not have had an aesthetic purpose, since its results were not easily visible, he added.

But the real motive is still uncertain.

"The reason is difficult to ascertain," said Jeffrey Schwartz, an anthropologist at the University of Pittsburgh in Pennsylvania.

"As the authors [of the study] admit, encroaching on the [tooth's] pulp cavity would cause pain, and leaving these holes so close to the pulp cavity, where they would accumulate food and lead to infection and continue to cause pain, would hardly seem to be therapeutic."

Macchiarelli's team made the discovery while excavating a 9,000-year-old graveyard in Baluchistan, a region of Pakistan that borders Afghanistan and Iran (map).

The people of Mehrgarh, the site of the dig, were once nomadic hunter-gatherers who settled into a more sedate lifestyle, growing crops and raising cattle.

During the dig, the researchers identified nine individuals with a total of 11 drilled teeth.

"One individual had three drilled teeth, while another had a tooth that had been drilled twice," Macchiarelli said.

A closer look with a microscope revealed that at least in one case, not only had the tooth been drilled, but the resulting cavity had also been delicately reshaped.

And in all cases, the researchers noticed smoothening of the teeth. That meant the drilling had been conducted on living people who then continued to use the teeth for chewing food.

Flint Drill

To make a hole on the relatively small surface of a tooth, Mehrgarh's dentists probably used a contraption quite similar to the one used in making a fire.

Rope from a bowlike device was looped around a slender piece of wood that was tipped with a sharp shard of flint. When the bow was moved sideways, it created a drill-like circular motion and pushed the flint into the tooth.

"It was very fast and also generated heat, enabling the dentist to drill holes smaller that 1 millimeter [0.04 inch] in diameter," said Macchiarelli, who created a replica of the drill by studying related artifacts.

He thinks that know-how for the early dentistry was probably transferred from artisans skilled at drilling holes in bead ornaments.

The researchers have yet to find evidence of dental fillings. Macchiarelli thinks that some sort of tarlike material or soft vegetable matter was stuffed into the tooth cavity. However, there is no evidence to prove the theory.

"[The fillings] could have degraded over time," he reasoned.

Out of Fashion

Though the dental manipulation lasted near Mehrgarh for about 1,500 years, the practice completely disappeared with the onset of the metal age about 7,000 years ago, Macchiarelli said.

"There is no evidence of this procedure in graveyards from much later periods, despite the continuation of poor dental health. We have no idea why it stopped," he said.

Schwartz, the Pittsburgh anthropologist, agreed the purpose of the drilling remains mysterious.

"In Pre-Columbian Mesoamerica, the lip-side surfaces of front teeth were drilled to receive semiprecious stones and gold, but that was clearly ornamental," he said.

"So I'm stumped as to why these holes were drilled."

Perhaps the pain caused the practice to lose popularity, he added.

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