Just like humans, horses can have tooth problems that make them ornery and sap their productivity. So to keep their horses in top shape, Mongolian herders started experimenting with equine dentistry more than 3,000 years ago, according to new archaeological evidence published today in the Proceedings of the National Academy of Sciences.

Through an analysis of skulls excavated from ancient horse burials on the Mongolian steppe, funded in part by a grant from the National Geographic Society, archaeologists determined that nomads initially sawed off their horses’ unruly teeth with stone tools, and, later, pulled teeth that got in the way of metal mouthpieces.

These “incredible innovations” in horse healthcare “came right alongside what looks like the emergence of horse riding,” says archaeologist and grantee William Taylor of the Max Planck Institute for the Science of Human History. His findings suggest that horse dental care may have helped nomadic people travel across larger distances on healthier mounts and, eventually, effectively control horses as weapons of war.

Keeping Your Ride Happy and Healthy

Nomads on the Mongolian steppe tamed horses thousands of years before the infamous horseback conquests of Genghis Khan in the Middle Ages. Though recent genetic studies have complicated scientists’ understanding of horse domestication, this transformative event is generally believed to have occurred in Eurasia, possibly more than 5,000 years ago.

View Images Horses congregate in central Mongolia. Scientists believe the horse was first domesticated in Eurasia some 5,000 years ago. Photograph by William Taylor

The earliest physical evidence for horse domestication, however, appears thousands of years later in the Deer Stone-Khirigsuur Complex, a culture that existed in Bronze Age Mongolia from about 1300-700 B.C., and whose cemeteries were surrounded by dozens—and sometimes hundreds—of sacrificial horse burials.

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Taylor and his colleagues began their work with the Deer Stone burials in 2015. “We wanted to understand what we could learn about horse transport through the teeth,” he says. In 2016, the researchers reported that wear-and-tear patterns on the bones and teeth proved the horses in the Deer Stone burials had indeed been bridled and used for mounted riding. But Taylor and his colleagues also started to notice that some of the skeletal remains had direct signs of human intervention.

According to today's published study, the researchers found two examples of young Bronze Age horses with sideways incisors had been partially hacked off. The earliest example, from 1150 B.C. at the site of Uguumur, marks the world's oldest evidence for veterinary dentistry.

“This animal would have had a ton of trouble with eating correctly and with its behavior,” Taylor says. “It looks like people used a tool to restore the normal flat surface of the mouth by sawing [the wayward incisor] off.”

Traces of silicate on the tooth indicate that a stone tool would have been used for this logistically challenging and dangerous task.

“We interpret this as experimental,” Taylor says. “People had clearly not optimized the easiest way to do this.”

Origins of Equine Dentistry New discoveries suggest that people have ridden horses in the Mongolian steppe since about ca 1200 B.C. The landscape is dotted with evidence that this transportation revolution is tied to innovations in horse health care. Hövsgöl Nuur Mongolia Uguumur Oldest horse dentistry specimen recorded here Ulaanbaatar ChinA Archaeological site Mongolia Map Area Bor Shoroonii Am 100 mi Earliest evidence of horse tooth extraction found here 100 km Leanne Abraham, NG STAFF SOURCE: William Taylor Origins of Equine Dentistry New discoveries suggest that people have ridden horses in the Mongolian steppe since about ca 1200 B.C. The landscape is dotted with evidence that this transportation revolution is tied to innovations in horse health care. Archaeological site Mongolia Uguumur Ulaanbaatar Oldest horse dentistry specimen recorded here Bor Shoroonii Am Earliest evidence of horse tooth extraction found here Mongolia China Map Area 100 mi 100 km LEANNE ABRAHAM, NG STAFF SOURCE: William Taylor

Dentistry For War

Based on skeletal remains from the site of Bor Shoroonii Am, the researchers also discovered that around the middle of the first millennium B.C. Mongolian herders adopted a new practice that is still performed today: extracting the “wolf tooth” in young horses to spare them pain during harnessed riding. This vestigial "wolf tooth" grows in front of the cheek teeth in the spot where a horse is typically controlled with a bit, so it’s not surprising that wolf teeth started to be removed around the same time that hard metal bits replaced softer mouthpieces made from leather or other organic material.

“The innovation of metal bits may have been one of the things that allowed horseback riding to transition from a herding tactic to a military technology,” Taylor says, explaining that metal bits allowed for greater control of horses during stressful situations. “It seems that veterinary dentistry may have played a pretty crucial role in the emergence of horseback riding as a military technology.”

View Images Researchers analyzed evidence for dental wear and modification from the skulls of ritually sacrificed horses, such as this one from central Mongolia. Photograph by William Taylor

Robin Bendrey, a University of Edinburgh archaeologist who was not involved in the study, says the research “makes a major contribution to our understanding of the origins of equine dentistry.”

“Importantly, this work also identifies these dynamic innovations as emerging from pastoral nomadic communities, groups that have often been marginalized in both contemporary and past narratives,” Bendrey says.

The use of horses for transportation was “the fiber optics of its time” because it sped up communication, says Melinda Zeder, an archaeologist at the Smithsonian’s National Museum of Natural History who was not involved in the research, though she reviewed Taylor’s paper and accepted it for publication.

“As a person who deals with bones, it appeals to me that something so prosaic as pulled teeth could speak to a profound change on the course of history,” Zeder says.