It's pretty hard to milk a wild mare. So researchers attempting to determine whether ancient Botai in northern Kazakhstan had domesticated horses tested their pottery for evidence that they were as fond as their modern descendants of mare's milk (you can see [left] a modern mare being milked by a Kazakh woman). Their finding, published today in Science: they were—pushing horse domestication to at least 5,500 years ago.

Archaeologist Alan Outram of the University of Exeter in England and his colleagues tested Botai cooking vessels and found clear evidence of mare's milk in nine of them. This constitutes strong proof of domestication, according to geochemist Rosemary Capo of the University of Pittsburgh, who analyzed samples from another Botai site known as Krasnyi Yar, because wild horses don't typically tolerate milking.

The researchers also found that the skeletons of Botai horses closely matched the physical characteristics of domestic horses from the Bronze Age and modern Mongol breeds, thinner than their wild cousins of the same time. This suggests that horses were already being bred for specific physical traits to make them more useful to humans, according to the paper.

Finally, five of 15 horse jaws found in Kazakhstan examined by the team showed evidence of damage from a bit or bridle. In fact, one of the jaws had damage to the teeth that could only have come from wearing a bit, according to the paper. Paired with previous evidence of bone tools that appear to have been carved to straighten and stretch pieces of rawhide—prehistoric bit technology—the wear and tear argues that the Botai may have been the first people to have domesticated the horse.

According to Outram, the reason they used horses instead of sheep, goats or cattle may have been a result of the region's harsh winters: Horses can graze through snow, unlike these other animals. 

The Botai are not the only people in the chase. Other researchers have turned up large quantities of horse remains, like the Botai, with an earlier people in what is now Ukraine. But, to date, the earliest known masters of the horse are the Botai of Kazakhstan.

Credit: Courtesy of Alan K. Outram