The Yukon horse was a relatively small species (about 1.3 m / 4 ft. high at the shoulders) that was closely related to the modern horse (Equus caballus).
It occupied steppe-like grasslands of Eastern Beringia (unglaciated parts of Alaska, Yukon and adjacent Northwest Territories) in great numbers. It was one of the commonest ice-age species known from that region, along with steppe bison (Bison priscus), woolly mammoths (Mammuthus primigenius) and caribou (Rangifer tarandus).
Our knowledge of the appearance of the Yukon horse is based on a skeleton that was reconstructed from many superbly preserved bones from the Dawson City area, Yukon, and on a partial carcass found in 1993 by placer (gold) miners at Last Chance Creek in that vicinity.
Heavy mining equipment had exposed a foreleg and a large part of the hide from ear to tail. The foreleg had belonged to an adult horse. It still had dried flesh, skin and dark brown hair on the lower part. A sample of the leg bone (which was evidently wolf-gnawed) yielded a radiocarbon date of about 26 000 years old. The hide included long, blondish mane- and tail-hair, as well as some coarse, whitish body hair, which was perhaps part of the winter pelt. Contents of the intestine included grasses, sedges, etc., suggesting that the horse had lived in a parkland environment.
Horses originated in North America during the Eocene Epoch (about 53 to 34 million years ago) when the terrier-sized Hyracotherium arose. Modern horses stemmed in North America from the progressive horse Pliohippus, known from the Pliocene Epoch (5 to 2 million years ago).
Yukon horses probably arose in Beringia 200 000 years ago. Fossils have been found on the Baillie Islands, Northwest Territories, as far northwest as Ikpikpuk River, Alaska, and as far south as Ketza River and Scottie Creek, Yukon. Twelve radiocarbon dates indicate that the species occupied eastern Beringia from about 31 500 to 12 300 years ago—through the cold peak of the last glaciation.
Yukon horses seem to have died out about 12 000 years ago. This was likely due to rapid climatic change near the close of the last glaciation, and was possibly exacerbated by human and wolf predation.