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World's Oldest Horse Genome Decoded, Reveals Evolution of Horses Much Slower Than Imagined

Update Date: Jun 26, 2013 11:07 PM EDT

The evolution of horses actually took much longer than previously imagined. New genetic research shows that wild horses existed some 700,000 years ago, making it the world's oldest ever creature to reveal its DNA to modern science.

Before this recent discovery, the oldest genome belonged to a polar bear that lived more than 110,000 years ago. The horse sequence highlights how far back scientists can look into the biochemical history of advanced life, the journal Nature noted on Wednesday.

"The sequence was extracted from a foot bone of a horse that lived between 780,000 and 560,000 years ago. By sequencing the animal's genome, along with those of a 43,000-year-old horse, five modern domestic horse breeds, a wild Przewalski's horse and a donkey, researchers were able to trace the evolutionary history of the horse family in unprecedented detail," according to the journal.

"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 old2, 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 also found no genomic evidence to suggest that the Prezwalksi's horse has mixed with domestic horses, thereby confirming that it is the last truly wild horse. "There is no domestic genetics present in these horses," said Willerslev. Furthermore, the Prezwalksi's horse has retained significant genetic diversity, good news for the future of the species.

For most researchers, however, the real significance of the study lies in the fact that it pushes the timeframe for paleogenomics back by almost 10 times. "Until this study, many experts would have thought that it was impossible to recover a genome from a sample of this age because of the rapid degradation of DNA into ever shorter fragments that occurs following the death of an organism," wrote Lambert and Miller in their commentary.

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