Horse domestication traced to ancient central Asian culture

Central Asia’s vast grasslands hosted a prehistoric revolution in transportation, communication and warfare, thanks to the humble horse. Remains from Kazakhstan’s more than 5,000-year-old Botai culture have yielded the earliest direct evidence for domestication of these versatile beasts, scientists report.

The Botai people were hunter-gatherers who lived in large settlements for months or years. Their culture lasted from 5,600 to 5,100 years ago. Researchers have long suspected that the Botai rode domesticated horses while hunting for wild horses to eat but did not domesticate other animals or cultivate crops.

Butchered horse remains found at four Botai sites include two tell-tale signs of domestication: slender lower-leg bones like those of later domesticated horses and cheek teeth worn down by bits that attached to bridles or similar restraints, says a team led by archaeologist Alan Outram of the University of Exeter, England.

Chemical analyses of animal fat residue on the inside surfaces of Botai pottery fragments suggest that the vessels had once held mare’s milk, probably gathered in summer months, the researchers report in the March 6 Science. Modern Kazakh horse herders milk mares in the summer to produce a fermented, alcoholic drink called koumiss.

Milking of horses and other animals arose in areas, such as northern Kazakhstan, that lacked agricultural practices often regarded as precursors of milking, Outram and his colleagues propose.

“This is certainly the earliest culture by some margin with such compelling evidence for domesticated horses,” Outram says.

The new report presents the first evidence for horse milk in Botai pots and for Botai horses having domesticated-looking leg bones, remark David Anthony and Dorcas Brown, archaeologists who teach at Hartwick College in Oneonta, N.Y., who study the origins of horse domestication. “If you’re milking horses, they are not wild,” Anthony says.

Outram’s group compared 18 lower-leg bones from Botai horses, excavated in 2005 and 2006, to corresponding bones already excavated by others at sites of the nearby, roughly 5,000-year-old Tersek culture. Comparisons were also made to leg bones from modern and 3,000-year-old domesticated horses and from wild Siberian horses that lived more than 20,000 years ago. Botai horses displayed the relatively slender legs of domesticated animals. Tersek horses’ legs looked more like those of wild horses.

Additionally, one Botai horse molar displayed deep, parallel grooves typically observed on the molars of domesticated horses that hold bits in their mouths, Outram says. Bits may also have produced less-pronounced tooth wear on two other Botai horses. Evidence of bone damage and regrowth appeared on four Botai horses’ jaws where bits or bridles would have rubbed through gums.

The evidence of bit use described by Outram’s team is interesting but preliminary, according to Anthony and Brown. Researchers are still debating whether other proposed signs of bit damage on Botai horses’ teeth, reported by Anthony and Brown in 1989, might instead have resulted from natural causes.

The Botai people didn’t invent horse domestication and milking, Anthony and Brown propose. These practices were borrowed from inhabitants of the nearby Russian steppes, who included possibly domesticated horses in sacrificial rituals with domesticated sheep and cattle by 6,500 years ago, they say. Those Botai neighbors probably domesticated horses after learning about cattle and sheep domestication from farming groups, in Anthony and Brown’s view.