Genome shows horses to 4 million years ago

The genome of a horse that lived 700,000 years ago in Canada’s Yukon Territory suggests the common ancestor for modern horses, zebras, and donkeys dates to 4 million years ago.

The DNA discovered from the ancient horse is 10 times as old as any DNA retrieved so far, suggesting it may be possible to get genetic information from animals that lived as long as 1 million years ago, according to a study released Wednesday in the journal Nature.

The finding is remarkable because DNA, the hereditary material in almost all organisms, generally starts to fragment after an organism’s death, the researchers said. The group made its discovery by matching the genetic material of the horse found in Canada against DNA sequenced from a horse that lived 43,000 years ago; a Przewalski horse, thought to be the last wild horse; five modern domesticated breeds; and a donkey. The finding also means that DNA pieces retrieved from old samples may also have information about how the current world evolved, the study authors wrote.

“Our study has pushed the timeframe of paleogenomics back by almost an order of magnitude,” said the authors, led by Ludovic Orlando, Aurelien Ginolhac, and Guojie Zhang, of the universities of Copenhagen and BGI-Shenzhen.

The DNA was partly preserved by the cold environment, the authors wrote.