The full genome of a horse that lived between 780,000 and 560,000 years ago has been sequenced by Danish scientists. The finding, published in Nature today, pushes back the known origins of the equine lineage by about 2 million years, and yields a variety of evolutionary insights.
http://www.nature.com/news/first-horses-arose-4-million-years-ago-1.13261
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| Ludovic Orlando |
“We have beaten the time barrier,” says evolutionary biologist Ludovic Orlando of the University of Copenhagen, who led the work with colleague Eske Willerslev. Noting that the oldest DNA sequenced before this came from a polar bear between 110,000 and 130,000 years old, Orlando says: “All of a sudden, you have access to many more extinct species than you could have ever dreamed of sequencing before.”
The team was able to sequence such old DNA partly because of the freezing ground temperatures in the area where the bone was found, which would have slowed the rate of DNA decay.
But the researchers were also successful because they had perfected techniques for extracting and preparing the DNA to preserve its quality for sequencing. They targeted tissue within the fossil which has high DNA content, such as collagen. They also combined DNA sequencing techniques to get maximum DNA coverage — using routine next-generation sequencing with single-molecule sequencing in which a machine directly reads the DNA without the need to amplify it up which can lose some DNA sequences.
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| Eske Willerslev |
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