At one time, tamed horses were tales of mythology—in classical Greece, they were depicted as the half-man, half-horse centaurs. With a few exceptions, wild horses are now a myth, a throwback to a time when they roamed the grasslands of Eurasia.

In the wild, early horses were hunted for their meat. Once domesticated, however, horses went on to take their place in history—transporting goods and people, harnessed to Roman chariots, and as partners to soldiers, crusaders, and explorers.

A new study, published in this week’s Science magazine, seeks to demystify the transition of the horse from wild animal to a human tool and companion. The study’s authors present DNA evidence that suggests that horse domestication spread through the knowledge of how to tame the animal, which was used to domesticate distinct local horse populations.

By showing domestic horse DNA to be genetically diverse, the study contradicts theories that suggest horses were domesticated in one location and then distributed throughout Eurasia.

The Evolution of Equus

Fossils found in Eurasia show that between 75,000 and 10,000 years ago, small wild horses roamed the grassland and steppe. But 10,000 years ago, the fossil record of the wild horse disappears.

About 6,000 years ago, the horse returned. But unlike earlier horses, their fossils have been found in Eurasian human-inhabited sites, suggesting the beginning of a human-horse relationship.

The horses, said Hartwick College archaeologist David Anthony, were likely first domesticated where humans already interacted with wild horses. Like marriage, he explained, “You don’t put that kind of investment into something you’re not familiar with.”

Horses began as a food source for humans, one that was hardier in a cold climate than cows and goats, which had been domesticated about 2,000 years earlier. They went on to become an important form of transportation, one that has been credited with revolutionizing hunting and warfare, as well as spreading Indo-European languages.

The horse was later transported from its Eurasian home to areas like the Americas where earlier wild horse species had become extinct.

Bringing the Modern Horse Home

Although much of the domesticated horse’s role in history is agreed upon, the specifics of its earliest dispersal are still unclear.

One hypothesis maintains that horses were tamed in a single Eurasian location and then distributed—in domesticated form throughout the region.

A second hypothesis agrees that wild horses were tamed first in the Eurasian steppe. “I donÕt think the idea can spread without an example, ” said Anthony.

But Anthony believes that although this first population of horses reached other areas, they were not the only source of the domesticated horse. “Once horses became valuable … their value was so high that people brought a variety of local stock into the bloodline,” he explained.

This process of domestication throughout the wild horse’s range differs from that of cattle and sheep, maintains Anthony. Other domestic populations “were treated differently, ” he said, and were therefore more genetically homogenous than horses.

The DNA study published in Science confirms this. “We … found a high diversity of matrilines,” the authors, headed by Carlos Vilaà of Sweden’s Uppsala University, report.

This diversity, they conclude, suggests that “transfer of technology rather than selective breeding may have been the critical innovation leading to [horses’] widespread utilization.”

The idea of taming horses came out one Eurasian location, they maintain, not necessarily the domestic horse itself.