Tamed or farmed?: Prehistoric cave paintings, such as this example from France's Lascaux Cave, show a long relationship between humans and horses.
ANCIENT CAVE DRAWINGS show people have long been captivated by wild horses. But at some stage, thousands of years ago, someone realised that these powerful, majestic creatures needn't always be wild.
Perhaps this brainstorm struck only once, or perhaps in several different places. Genetic studies have found that while modern horses appear to originate from a large number of mares, they are descended from a much more limited number of stallions.
It's possible that horses were domesticated by a single clever tribe, and later on others captured additional wild mares to mate with their stallions.
Sandra Olsen, an archaeologist at the Carnegie Museum of Natural History in Pittsburgh, USA, believes this process began somewhere on the Eurasian steppes.
For more than a decade, she's been excavating villages from the Botai culture of northern Kazakhstan, looking for evidence that 5,600 years ago, they were already using horses for meat, tools, and transportation.
In one village, her team has recovered more than 300,000 bone fragments – more than 99 per cent from horses. Marks on the bones indicate the horses were butchered for meat.
But were they domestic animals raised for slaughter, or wild ones, hunted? It's hard to prove either way, because primitive horse tack – a sure-fire sign of domestication – was likely made of leather that rotted away long ago.
But tack and bones aren't the only things archaeologists have discovered. At the Botai village of Krasnyi Yar, Olsen's team has found an array of holes made by ancient posts that looks suspiciously like the remains of a corral.
And in an as yet unpublished find, her team thinks they've discovered traces of horse manure in the soil of the circular enclosure. These traces take the form of high concentrations of phosphates – a nutrient contained in animal manure.
By comparison, levels of nitrate, another nutrient found in manure, were not elevated within the paddock. This makes sense, because nitrates easily leach out of soil in rainstorms, or are decomposed by bacteria.
So the lack of nitrates indicates that the phosphates aren't recent contaminants from a later corral built on the site. "It suggests we've got old stuff," says team member Rosemary Capo, a professor at the University of Pittsburgh.
But Marsha Levine of the University of Cambridge, U.K., thinks the circular structure was a holding pen for wild animals, corralled for subsequent slaughter. "American Indians used to chase [wild] horses into a corral," she says. Chasing wild horses into a corral in the middle of a village, however, might have been risky.
Read the timeline of domestication that goes with this feature here.
So perhaps, Levine suggests, it was used for a few animals kept almost like pets. "It's very easy to capture foals once the mother's been killed." That's a lot different from true domestication, she says, which involves the more difficult task of breeding animals and
raising them from birth.
Still, the manure isn't the only indication that all of those thousands of bones came from domestic animals. Also revealing are the ages of the slaughtered animals, although the conclusions drawn from this information differ wildly, depending on whom you speak to.
"Between 30 and 50 per cent were killed young, which indicates culling," Olsen says. "That's standard in horse domestication."
According to Levine, however: "If you're raising them for meat, you kill them around age three or four." Instead, from her perspective, the Botai excavations reveal an age structure similar to that seen in wild horse herds, suggesting that the Botai engaged in hunting techniques in which entire bands of horses were killed at once.
But Olsen has several strong counters. First of all, she says, some of the horses, particularly stallions, would have been spared from early slaughter and used as steeds. Since they would have lived to much older ages, that skews the age distribution of the bones.
More importantly, Olsen says, the very size of the Botai villages indicates that they were raising horses, rather than hunting them. With at least 160 families living in a small area, subsisting largely on horses, hunting would quickly have depleted the nearby herds. And if the Botai were a hunting culture, she adds, why on Earth didn't they hunt other animals, in addition to horses?
Still more clues come from the manner in which the Botai made their stone tools. Without beasts of burden, it would have been far more convenient to make tools at the flint quarry, rather than lugging hunks of rock back home.
"But they brought in big chunks and made tools," Olsen says. "That indicates pack horses."
Still, none of this, even the presence of phosphates, constitutes proof. "We're talking about lots of different types of indirect evidence," Levine says. "It doesn't prove domestication; it's just interesting and possibly points in that direction."
The ancient animal pen, however, may contain additional secrets. In another unpublished find, Olsen has learned that its soil is 10 times saltier than the surrounding soil. The probable source: urine, presumably from horses. Chemists are also analysing pottery fragments in the hope of finding fat traces from mare's milk. "That will really be the smoking gun," she says. "You don't want to milk a wild mare."
Meanwhile the quest for the earliest site of horse domestication continues. Ancient as their activities were, Olsen doesn't believe the Botai were the first to domesticate horses – they are merely the earliest we can crudely detect with archaeology. "What is the chance that you find the first [example] of anything?" she says.
Read the timeline of domestication that goes with this feature here.
Richard A. Lovett is a contributing editor of Cosmos, based in Portland, Oregon.
