NEW YORK – Every horse in the world can be traced to a single mare that trotted the earth about 130,000 to 160,000 years ago, scientists discovered for the first time.

The research identified 18 different genetic clusters that arose from the ancestral mare, suggesting that domestication occurred in many places across Europe and Asia, according to work published Monday in the Proceedings of the National Academy of Sciences.

The study helps pinpoint the time when humans began domesticating horses, though it was known to be after dogs, sheep, pigs and cattle.

The research may also help scientists classify horse fossils, figure out the pedigree of modern breeds and perhaps evaluate how genetics affect racehorse performance, said Samantha Brooks, an assistant professor of equine genetics at Cornell University.

”When you think about animals that shaped human history, the horse is No. 1,” said Brooks, who wasn’t involved in the study. ”Domesticated animals define what it is to be a human. Without that, it’s unlikely we’d have the culture and technology we have today.”

Horses and chariots were used as weapons until the 20th century, when machine guns, tanks and airplanes were developed. They were used to clear forests, plow land and herd cattle. Until the 1800s, the fastest way to travel over land was on horseback.

The study, led by Alessandro Achilli, a researcher in the department of cellular and environmental biology at the Universita di Perugia in Italy, analyzed mitochondrial DNA, which contains genes that are essential for the cell’s energy functions. These genes are inherited solely from the mother.

Horses lived throughout Europe and Asia during the Paleolithic period, although many lineages probably didn’t survive the peak of the last glacial period, from 26,500 to 20,000 years ago and another later period that covered Europe in ice.

There were probably horse refuges in the Ukraine, Turkestan and the Iberian Peninsula, because those places were less cold.

The 18 genetic clusters suggest that horses were domesticated multiple times, in different places. At least one horse domestication happened in Western Europe, possibly in the Iberian Peninsula, the authors wrote.

The study was conducted using 83 genomes from horses across Asia, Europe, the Mideast and the Americas.