In 2007 it was the old gray Thoroughbred mare Twilight from New York. Then in 2012 it was 18-year-old Sugar, a Quarter Horse mare from Texas.
Now in 2013 it’s Thistle Creek, a Middle Pleistocene stallion from the Yukon permafrost near the eastern Alaskan border. He’s roughly 700,000 years old. That makes Thistle Creek—posthumously named for the excavation site where his leg bone fragment was discovered—the oldest equine to have its DNA fully sequenced.