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Scientists shatter record for oldest genome sequencing with 700,000-year-old horse DNA

Using new methods and computations, an international team of researchers has now 'broken a time barrier', by pushing back the date of the oldest 'map' of a DNA sequence ever done of an animal by hundreds of thousands of years, and pushing back what we know about horses by nearly 2 million years.

The team, lead by Natural History Museum of Denmark scientists Dr. Ludovic Orlando and Professor Eske Willerslev, and including scientists from Canada, China, Denmark, France, Norway, Saudi Arabia, Sweden, the United Kingdom and the United States, spent the last 10 years working on this project, sequencing the DNA found in a fossil bone dug up out of the Yukon permafrost from a horse species that lived between 780,000 and 560,000 years ago, along with the DNA from several modern horse species and from donkeys, and came up with new insights about this animal that has had a long history in human civilization.

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The results of their study not only push back the limits of how far back scientists can look (the last 'hominid' DNA sequence is from around 70,000 years ago, and the oldest polar bear DNA sequence is from 110,000 to 130,000 years ago), and expand the limits of where scientists can gather samples from (it's not just the cold Arctic anymore), but they also revealed that horses diverged from similar species like zebras and donkeys around 4 million to 4.5 million years ago (twice as long as previously thought).

As a result of this research, scientists don't have to limit their fossil searches to the frozen tundra just to have a chance to find DNA that they can use. The problem before was that warmer climates caused DNA to deteriorate much more quickly than in cold climates. This deterioration causes the DNA strands to break down into tiny pieces, making it hard to see the entire sequence of a species. With many more species living in warmer climates than colder climates, this put a big limitation on what species scientists could study.

The new methods developed during this research now allow scientists to reassemble the bits into a full sequence again, like putting together a puzzle, effectively lifting that limitation.

"We have beaten the time barrier," said Dr. Orlando, according to Nature. "All of a sudden, you have access to many more extinct species than you could have ever dreamed of sequencing before."

An added bonus of the research was that it finally brought vindication for efforts to conserve the Przewalski’s Horse of Mongolia, which is now identified as the world's last remaining species of wild horse. The species was apparently considered extinct in the wild as of the late 1960s, but conservation efforts since then have brought it back, allowing it to graduate from the 'extinct in the wild' list to the 'endangered' list.

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Horses occupy a special place in human history, as they have helped drive the development of our civilizations since they were domesticated over 5,000 years ago. Our current civilization may be more driven more by the machine now, but it's fitting that, after all the assistance they've given us in the past, they've stepped up again to help us push the boundaries of science so that we can know more about the entire history of life on this planet.

(Photo courtesy: Wikimedia Commons)

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