Whence the Domestic Horse?

by Sarah C. P. Williams as it appears in Science Magazine.org

“Nobody has applied this method of population modeling to horses before.”

Shards of pottery with traces of mare’s milk, mass grave-sites for horses, and drawings of horses with plows and chariots: These are some of the signs left by ancient people hinting at the importance of horses to their lives. But putting a place and date on the domestication of horses has been a challenge for archaeologists. Now, a team of geneticists studying modern breeds of the animal has assembled an evolutionary picture of its storied past. Horses, the scientists conclude, were first domesticated 6000 years ago in the western part of the Eurasian Steppe, modern-day Ukraine and West Kazakhstan. And as the animals were domesticated, they were regularly interbred with wild horses, the researchers say.

“This is a very good paper,” says biologist Michael Hofreiter of the University of York in the United Kingdom. “Nobody has applied this method of population modeling to horses before.”

Click (HERE) to read report

Throughout their history, horses have been interbred, traded between populations of people, and moved across continents. All of this makes their genetic history hard to follow. Moreover, the wild ancestor of horses, Equus ferus, is extinct, complicating researchers’ efforts to compare the genetics of domestic animals with wild ones. Previous research nailed down a broad area—the Eurasian Steppe, which stretches from Hungary and Romania through Mongolia—as the region where horses originated and were domesticated. But earlier genetic studies relied mostly on mitochondrial DNA, which is inherited only from a mother, to try to understand horses’ evolutionary history.

“The problem was that there was a lot of diversity in the mitochondrial DNA,” says biologist Vera Warmuth of the University of Cambridge in the United Kingdom, the first author of the new study. And the diversity didn’t group the horses into their breed or place of origin. “Every horse breed has almost all the mitochondrial lineages represented,” she says.

Warmuth instead studied sequences of horse DNA inherited from both parents and known to be diverse between horse populations. She and her colleagues collected genetic samples from more than 300 horses at 12 different sites across the steppe. Data were collected for only working animals bred within a local area, not those bred for show or appearance, to minimize any human-guided selection that would make some genes more common. Then, the researchers used computer programs designed to model the spread of a population to simulate how different locations of horse domestication and spread throughout the steppe would influence modern genetic diversity. They compared each model with the real data they had collected to see which fit best.

The best-fit model, the team reports today in the Proceedings of the National Academy of Sciences, showed the wild ancestor of domestic horses originating in eastern Eurasia 160,000 years ago and being domesticated in the western part of the Eurasian Steppe around 6000 years ago. The model also helped explain why there had been so many female lineages when previous studies had tried to rely on mitochondrial DNA. “We think that as domestic horses spread out of the western steppe, local wild females were continuously incorporated into the spreading herds,” says Warmuth. The constant addition of new females made the genetic patterns—in particular, the female lineages—more complex than if the domestic population had been totally isolated.

Hofreiter is impressed. “They have still only narrowed down the domestication region to a fairly big area,” he says, “but they did have enough genetic data to get a signal out of the noise.”

Not all researchers are convinced, however. Archaeologist Marsha Levine of the University of Cambridge thinks using modern genetic samples to retrace horses’ evolution is a dead end. “There’s been mixing of cultures and mixing of horses in this region for many thousands of years,” she says. “And so when you’re looking at any modern horse, you just don’t know where it’s from.”

Bringing together many kinds of evidence is what will ultimately answer the whens and wheres of horse domestication, Levine says. “What we need to be doing is using material from excavations, sequencing ancient genes, and combining that with what we know from archaeological evidence about how animals were used in the past.”

Ultimately, says Hofreiter, getting to the bottom of horse domestication will reveal more than just the history of these animals. “Horse domestication has changed human cultures a lot. It has changed warfare, it has changed transportation,” he says. “Studying the past of horses can tell us a lot about our own past.”

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8 comments on “Whence the Domestic Horse?

    • I agree, the preponderance of evidence gives the origin of the modern horse Equus caballus in North America about 1.7 million years ago with much more recent entries from North America to Asia and Europe and Africa (see Chapter I of my book The Wild Horse Conspiracy, available through me or on amazon.com)

  1. As previously thought. The horse left N. America via the land bridge which leads right to this area where they met with ancient man. A match made in heaven until the BLM showed up!

    • So right, Steve , and the welfare ranchers have backed the BLM for years. They are determined to wipe them out but there are more of us and we must win .

  2. The relationship between horse and man has a complex and long history, and it fascinates me. I love history in general, and if I were young and pursuing a PhD I would probably write about horse and man and the relationship. I know that for 99% of that history it has been mostly a working relationship and a need of man to evolve. The horse did not need us, we needed him. The dog joined us out of a mutual desire, lesser so the cat. Oxen were put into service as well as camel and llama to a lesser extent, perhaps only so to the degree that those were the most appropriate animals available in the area. But horse is different than other working animals (animals not raised as food or clothing/material supplies). This ‘companionship’ of horse and man did not suddenly occur in the 20th century, as the need for horses as beasts of burden diminished. I think it has always been there. The horse, so gentle and peaceful (are you reading Joe Camp’s Soul of a Horse blog about his wild mustang mare?) and yet so wild, that looks at us with such wisdom from a place that is far beyond our comprehension. Many of us are trying to see that place, through their eyes. Surely man has been doing that for 6000 years.

    • I agree with you Kerry. Horses & man have indeed had a very long history together. Throughout history, humans have depended on & highly cherished their horses. In the wild, we are considered a predator to horses, yet they have let us tame them, ride upon their backs, do our work for us, carry us in pleasure & in times of war, be taught so many unnatural behaviors, all for us, to please us. To look into the gentle but wise eyes of a horse is beyond words, it’s a feeling, an unspoken language that both horse & human understand. They are so intelligent, strong, loyal, trusting, at times fearful, sometimes serious, sometimes even humorous & full of playful mischief, much like ourselves. Those of us blessed to know & love horses, as well as other animals, know that special feeling, that special bond. Those who aren’t so fortunate, or who are uneducated, or fearful, are the ones who most likely don’t care. It’s a shame that humans are regressing, rather than evolving to a higher, more intelligent state, that is made apparent by the way we are treating our horses in today’s world, the way we are repaying them for all those centuries of loyality, trust & devotion. Humans are betraying all that brought them together in the first place, so very long ago, so very far away. So, we shall continue the fight to protect them, to the end of time, if that’s what it takes!

  3. i was just brushing her highness, my paint filly, Holly, this morning. talk about companion!~ i told her i’d love to spend the next 30 years just brushing her gorgeous hair and we’ll have a styling session everyday the way girls love to do. maybe rationalizing not doing that ‘first ride’`flying lessons for me!! i understand the companionship of horses now from observing my horses. truly wonderful friends they can be if you’re kind and respectful to them~they allow you into their little ‘world’ i will just be happy with them and believe they came of Noah’s ark with the rest!

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