A fragment of a fossilised bone thought to be more than 700,000 years old has yielded the genome of an ancient relative of modern-day horses. This predates all previous ancient DNA sequences by more than 500,000 years.
The study in the journal Nature was made possible because the bone was found preserved in Canadian permafrost following the animal's demise.
The study also suggested that the ancestor of all equines existed around four million years ago.
A remnant of the long bone of an ancient horse was found at Thistle Creek, located in the Yukon Territory of Canada.
Palaeontologists estimated that the horse last roamed the region sometime between 500,000 - 750,000 years ago.
The BBC reports an initial analysis of the bone showed that despite previous periods of thawing during inter-glacial warm periods, it still harboured biological materials - connective tissue and blood-clotting proteins - that are normally absent from this type of ancient material.
We were really excited because it meant that the preservation was really good," Dr Ludovic Orlando from the University of Copenhagen told the BBC.
"So at that stage we thought, let's try a DNA extraction to see how much of the genome we could characterise."