Today's horses come in a variety of colors and sizes, but don't credit humans. According to a new study, most of these traits existed long before we
domesticated them. As researchers report online this month in BMC Evolutionary Biology, they analyzed the complete mitochondrial genome—the DNA found within cell's energy powerhouses—of 45 diverse horse breeds, looking for clues to the timing of horse domestication. They found that modern horses arose nearly 7000 years ago, a result that agrees with previous studies. The data also show that the ancestor of all domestic horses—which some scientists believed lived as long as 1 million years ago—roamed much more recently, between 38,000 and 93,000 years ago. In addition, more than 70% of today's horse lineages already existed before domestication, suggesting that a large number of wild founder mothers were used to build up the modern horse population.
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