Text B. Modern Horses Have Many Origins

Text A. DNA Hints at Origins of Domestic Horses

Exercise 4. Divide into two groups. Each group should read either Text A or Text B on domestication of wild horses. In pairs, share your information with your partner and discuss both texts to combine all the details, so you could answer the questions in Exercise 5.

By Sarah Graham

The last sighting of a wild horse population occurred in 1969 in Mongolia. A far more common sight is a domestic horse, whether on a farm or a racetrack. Now scientists have shed new light on how these magnificent beasts came to be controlled by humans. According to a report published online this week by the Proceedings of the National Academy of Sciences, modern horses were domesticated from several distinct ancestral populations. And because horse domestication may have played a key role in the spread of some European languages, the findings could further the study of language evolution.

To track the trail of domestic horses, Thomas Jansen of Biopsytec Analytik in Rheinbach, Germany, and his colleagues sequenced DNA from 318 horses representing 25 different breeds. Specifically, the team analyzed mitochondrial DNA (mtDNA), which is inherited from the mother, and compared the recent samples to previously published DNA data from 334 other animals. The researchers identified 17 distinct types of mtDNA and calculated that at least 77 different wild mares must have been domesticated in order to account for today's domestic horses. Just how these animals were domesticated remains unclear, however. Because of the necessary diversity of the mares, the team posits that several separate and geographically diverse populations participated in the process. One theory holds that domestication occurred independently at a number of locales. Alternatively, the procedure may have slowly spread from a single starting point. In that case, the authors write, "the knowledge and the initially domesticated horses themselves would have spread, with local mares incorporated en route, forming our regional mtDNA clusters." (From Scientific American Online, July 16, 2002)

By Julia Karow

About 6000 years ago, somewhere in the Eurasian grassland steppe, man started to capture and tame wild horses--at least that's what remains from archaeological sites in Ukraine and Kazakhstan, tell scientists. Initially, people did not only use horses for transport, but also for food; at the time, dogs, cows, sheep and goats had already lived with humans for several thousand years. Now genetic evidence from modern and ancient horses, published in today's Science, completes the picture: the taming of horses did not occur in only one place, but in several, geographically distant locations.

Researchers from Sweden and the U.S. analyzed parts of the mitochondrial DNA of 191 domestic horses from ten different breeds, including the Icelandic Pony, the Arabian horse and the (American) Standardbred. They also included DNA sequences from 12,000 to 28,000-year-old horse bones found in Alaska and from 1,000 to 2,000-year-old horse remains from Northern Europe in the comparison. Mothers alone pass on mitochondria to their offspring, which is why the data represents only the maternal line. But the DNA samples from the modern horses differed so much from each other that they probably originated from several different groups of domesticated horses. And the genetic variation within each breed indicates that probably more female horses and only a few studs were used for breeding--a practice that continues today.

Rather than giving away domesticated horses, people in Eurasia probably taught each other techniques for capturing and keeping wild horses from their own area. That's why today's breeds still carry the genetic hallmarks of many different wild populations. (From Scientific American Online, January 19, 2001)

Exercise 5. Answer the following questions:

1. When was a wild horse population seen for the last time?

2. What methods were used to determine the time of horse domestication?

3. What genetic material was used in each study described in the texts?

4. When and where did domestication of horses start?

5. How was domestication of horses performed?

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