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Ancient Manure May Be Earliest Proof of Horse Domestication

Richard A. Lovett
for National Geographic News
October 26, 2006
 
Traces of ancient horse manure have been found in a remote 5,600-year-old Kazakh village—a discovery that could be the earliest known
evidence of horse domestication.

A team of archaeologists and geologists discovered the traces inside a circular array of postholes in the village.

While no actual smelly remains were present, the researchers did find that the level of nutrients called phosphates was ten times higher in the soil within the array than in soil adjacent to it.

Animal manure is high in nutrients, including phosphates, so the find is a strong indication that the enclosure used to be a corral.

The village, called Krasnyi Yar, was inhabited at the time by the Botai culture of the Eurasian steppes (map of Kazakhstan).

These people are believed to have relied heavily on horses for meat, tools, and transport.

Andrew Stiff, a graduate student at the University of Pittsburgh in Pennsylvania, presented the findings this week at the annual meeting of the Geological Society of America in Philadelphia, Pennsylvania.

Gathering Clues

In addition to phosphates, animal manure is high in nitrates. But elevated levels of nitrates were not found within the enclosure.

Team member Rosemary Capo, a professor at the University of Pittsburgh, says the lack of nitrates supports the theory that the manure evidence dates back more than 5,000 years.

Nitrates easily leach out of soil during rainstorms or are decomposed by bacteria, she notes, while phosphates can remain for millennia.

So the lack of nitrates indicates that the researchers didn't simply find evidence of a later animal enclosure built on the same site.

"It suggests we've got old stuff," Capo said in a statement.

While the existence of manure alone does not prove that the animals housed in the corral were horses, there is strong evidence that they were, says team member Sandra Olsen of the Carnegie Museum of Natural History in Pittsburgh.

Her team recovered more than 300,000 animal bone fragments in just one of the five Kazakh villages being studied.

"Of those, over 99 percent are from horses," she said.

Nor are there any signs that the villagers hunted horses rather than raising them.

The researchers found horse skulls and backbones in the villages, indicating that horses were butchered on site.

(Related news: "Ice Age Horses May Have Been Killed Off by Humans, Study Finds" [May 1, 2006].)

If the horses had been hunted, Olsen said, the hunters wouldn't have bothered to bring back such heavy, useless bones.

"We call it the 'schlep effect,'" she said.

She also notes that thong smoothers are among the most common tools found in the five villages.

Thong smoothers were likely used to make rawhide thongs, or strips, that could have been part of equestrian accessories such as bridles.

The most common tools were hide scrapers, "which you also use for leather thongs," she said.

Indirect Evidence

The Kazakh village is one of two sites competing for the honor of being the first place where humans are thought to have domesticated horses.

The other is in the Ukraine, where large numbers of horse bones have been found along with worked pieces of antler that might have been cheek pieces for bridles.

In general, definitive evidence for the earliest dates of horse domestication has been difficult to pin down.

Many bridle parts have been discovered dating back to 2000 B.C.—1,600 years after the settlement of the Kazakh village—as well as chariotlike carts buried with horses.

"But [such carts are] an advanced thing," Olsen said. Even the saddle is a relatively new invention.

"If you look at classical Greek statues of people on horseback, they don't have saddles, horseshoes, or stirrups," Olsen said. "And that's in Greek times, in 400 B.C."

Also, the earliest horse domesticators probably made what little stable gear they used out of leather, which rapidly decomposes.

Therefore all the earliest evidence of horse domestication is indirect and should be taken with a grain of salt, says Marsha Levine of the McDonald Institute for Archaeological Research at the University of Cambridge in England.

In a recent 54-page article, Levine says that indirect evidence can be useful. But, she cautions, nothing must be assumed and everything must be tested.

She says that she looks forward to seeing the new results once they are published.

"I am not a chemist," she wrote in an email to National Geographic News, "so I can't judge the results … although it appears to me that there could be a variety of explanations" for the elevated nutrient levels.

But soil in the ancient animal pen may contain additional secrets.

Only a week ago, the Carnegie Museum's Olsen says, she learned that the supposed corral's soil is ten times saltier than the surrounding earth. The probable source: horse urine.

Geochemists are also analyzing the soil for traces of fatty chemicals unique to horse manure.

"If we find those," Olsen said, "that really nails it."

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