Horse Genome Sequencing Pushes Back Origins 2 Million Years

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Horse genome sequencing has pushed back the origins of the species 2 million years.  That’s due to the discovery of a specimen more than half a million years old of a horse’s foot bone that was found frozen in the permafrost of the Canadian Arctic. The findings were published today in Nature. The discovery pushes back the origins of horses by about 2 million years, according to the article.

The particular horse’s foot bone that was discovered is between 780,000 and 560,000 years old. When its genome was sequenced, researchers used the knowledge they’d gained to place the animal in the evolutionary lineage that leads up to modern-day horses.

The ancient horse was probably about the size of current Arabian horses, according to the researchers. It didn’t have the same genes for large muscles that make today’s breeds good for racing, and it was larger than researchers once thought.

Scientists estimate that the ancient ancestor of the modern Equus genus, which includes horses, donkeys and zebras, branched off from other animal lineages about 4 million years ago. This finding pushes back the origins of horses to a time that’s twice as long ago as scientists had previously thought.

Evolutionary biologist Ludovic Orlando of the University of Copenhagen, who led the work with colleague Eske Willerslev, dramatically said:

“We have beaten the time barrier. All of a sudden, you have access to many more extinct species than you could have ever dreamed of sequencing before.”

One of the reasons the team was successful is that the freezing ground temperatures in the area slowed down the rate of DNA decay.

Another reason is that the researchers had developed an improved method for extracting and preparing the DNA to preserve its quality for sequencing.

Knowing that the collagen has high DNA content, the researchers targeted it in the horse’s foot bone. What’s more, they combined DNA sequencing techniques to get maximum DNA coverage.

They used 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.

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

What species will these techniques be applied to next?

Can these same techniques also be applied to other species, like ancient human ones? That might prove difficult, as it’s unlikely that any such specimens will be found buried in the DNA-preserving permafrost.

According to Willerslev and Orlando, it would theoretically be possible to resurrect the ancient horse by implanting a modern horse egg with the ancient DNA. However, they have no plans to do so.

They say that it has been a formidable task just to assemble the genome from many small fragments of DNA. They prefer, for now, to focus on further improving their techniques, before they test them on other samples.

Willerslev predicts that when they have mastered the technique, it will have a huge impact on evolutionary biology. “Ancient genomics will change a lot of the ways we look at evolution to date,” he states.

 

Written by: Douglas Cobb

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