Ancient horse genome oldest ever sequenced

How did the zebra get its stripes? To answer part of that question and better understand the evolution of all members of the Equus genus, a team of researchers have produced the draft genome of a 700,000 year old fossilized horse bone excavated from frozen ground in the Yukon territory, Canada. It is almost ten times older than the oldest genome sequenced till now.

The team of researchers was led by Ludovic Orlando at the Natural History Museum of Denmark and included Khaled Al-Rashied at the King Saud University, Riyadh. They used statistical software to compare the genomic data of the ancient horse to that from contemporary Przewalski's – a type of wild horses – and domesticated horses and donkeys, publishing their results in Nature¹.

They date the most recent common equine ancestor to 4.0–4.5 million years ago, twice as old as previously thought. By analyzing mutation frequencies observed in the genomic data, they also found that over the past 2 million years, the population size and demographics of various members of the Equus genus changed considerably, especially during periods of major climatic change.

The linage of wild Przewalski's horse and domesticated horses split some 38,000–72,000 years ago with no further interbreeding. This supports the argument that Przewalski's horses are the last surviving wild horse population.

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