In the News: 700,000-year-old horse genome sequenced

Science nerds and history buffs around the world are freaking out today because an ancient horse genome, 10 times as old as any genome retrieved so far, has been reconstructed.

Top: Przewalski horse skull via Wikimedia Commons

This advancement, made by by researchers at the University of Copenhagen, was announced today in the journal Nature and has since been covered by news outlets including Wired, the New York Times, Washington Post and USA Today.

Clearly it’s a big deal. But what, exactly, does it mean?

Take it away, Wired:

The work rewrites the evolutionary history of the horse and smashes the previous record for the oldest complete genome ever sequenced. In doing so, it redefines how far back in time scientists can travel using DNA sequences as their guide.

The prehistoric horse fossils had been kept frozen for the last 700,000 years in the permafrost of the Yukon, Canada. After being extracted in 2003, scientists used new DNA mapping techniques and technologies to reconstruct the genome sequence. For comparison, they also genetically mapped a DNA sample from a 43,000-year-old horse, five modern horses, a donkey and a modern-day Przewalski’s horse.

Among the conclusions drawn was that the genus that gave rise to modern horses, zebras and donkeys–Equus–arose about four million years ago, twice as far back as had been thought.

According to USA Today,

Horses as a distinct species appear to have split from donkeys 4 million years ago. The results also confirm the Przewalski’s horse, an endangered breed now found in zoos and sanctuaries in Mongolia, as the last wild survivor of all horses, splitting from domestic horses about 50,000 years ago. The genes indicate that horse populations went through a series of booms and busts tied to various Ice Ages that expanded grasslands over the last 2 million years. It also points to a genetic “bottleneck” that horses went through on their way to domestication, finding genes related to blood cells, fertility, color and muscle unique to modern horses and absent in their ancient counterparts.

Przewalski’s horse at Khustain Nuruu National Park. Photo: Wikimedia Commons

Of course, perhaps the most exciting conclusion of all involves the possibility of reconstructing human DNA genomes that are much, much older than any previously mapped.

That the horse DNA had been frozen for the entirety of the time since the horse died was key to the reconstruction. Most human fossils that have been studied have come from warm, tropical climates, but a warming climate and melting permafrost presents new possibilities that an ancient hominid will be found to study.

“Obviously (this) opens great perspective as to the level of details we could reconstruct of our own origins,” wrote study lead author Ludovic Orlando of Denmark’s University of Copenhagen. “And actually the evolutionary history of almost every species living in the world today.”

Go science.