Three thousand years ago, a horse in Mongolia had a toothache that was probably making it—and its owner—miserable. So the owner tried to help, by attempting to saw the painful top off the offending incisor. The procedure is among the earliest evidence of veterinary dentistry in the world, according to a new study, and the practices that flowed from it may have helped horses transform human civilization.

“It’s a great study,” says Robin Bendrey, an archaeologist and ancient horse expert at the University of Edinburgh who was not involved in the work. As horses became more important, he says, nomadic herders “are investing greater effort in understanding how to care for them.”

William Taylor, an archaeologist at the Max Planck Institute for the Science of Human History in Jena, Germany, first came across the strange sawn tooth in the collections of the National Museum of Mongolia in Ulaanbaatar. “I could not for the life of me muster an explanation,” he says.

He turned to his Mongolian colleagues, archaeologists Jamsranjav Bayarsaikhan and Tumurbaatar Tuvshinjargal, who grew up in the Mongolian countryside and have firsthand knowledge of traditional horse husbandry. The group concluded that the sawn tooth was an early, if inefficient, form of dentistry. The tooth had grown in crooked and was likely painful, but rather than pulling the incisor out completely, the notch shows that the ancient herder tried to cut its top off to restore a flat chewing surface , the team reports today in the Proceedings of the National Academy of Sciences . (The procedure may not have worked, as the herder only made it halfway through the tooth. Shortly after, the horse was sacrificed and ritually buried.)

Together with another cut tooth from around the same time, the discovery shows that about 2000 years after horses were first domesticated , people were still figuring out the best way to take care of their teeth using basic stone tools.

Over time, horse dental care in Mongolia became much more systematic, Taylor and colleagues found. In the 3000-year-old horse skulls the team studied, many horses still had their “wolf teeth”—small, pointy teeth that grow in the space between the teeth in the front of a horse’s mouth and those in their cheeks. Wolf teeth are an evolutionary relic, and horses no longer use them for chewing; many horses don’t even develop them.

In today’s horses, when wolf teeth do grow in, they occupy some of the space where the bit sits. The contact between the tooth and the metal riding equipment can cause pain and tooth damage, so both Western veterinarians and Mongolian herders routinely remove these teeth.

But back when ancient herders were making their first forays into horse dentistry, bits were still made of leather. With softer equipment, early domesticated horses could keep their wolf teeth.

Beginning around 750 B.C.E., however, nearly all of the horses Taylor’s group examined were missing their wolf teeth. In many of the skulls, they could see a healed hole where a wolf tooth had been pulled out. That shift coincides with the adoption of bronze and iron bits in Mongolia, which gave riders much greater control over their horses—but meant that wolf teeth had to go.

“They’re adapting to new ways of riding and new ways of using the horse,” says Alan Outram, an archaeologist at the University of Exeter in the United Kingdom who studies horse domestication and wasn’t involved in the new research. “People innovated fairly quickly.”

Without such innovations, world history might look a lot different. Metal bits enabled herders to use horses in war and for long distance travel, shaping Mongolia and its nomadic cultures in ways that ultimately led to the rise of Genghis Khan’s mounted army and the Mongol Empire that controlled most of Eurasia in the 13th century. “Horses absolutely transformed Mongolia into a cultural and economic center of the world,” Taylor says.