Yukon Horses and the Evolution Toward Modern Day Horses

Ancient Horse DrawingHorses first evolved in North America around 55 million years ago. At the time, they were one of the most common animals in the Ice Age Yukon, hence these first horses, Equus lambei, being named the Yukon horse. Like most horses at the time, they were remarkably short, standing only about 4 feet tall once fully grown. Most of our knowledge comes from scattered fossil remains across the Yukon area, as well as a well-preserved, mummified horse found in 1993. This find included parts of skin and hair, and even some mummified tissue. Scientists were able to determine that the hair was white, likely part of a winter coat, and from the stomach, it was concluded that the grasses pointed to a parkland grazing environment. Part of this horse’s leg bears evidence of wolf bites, indicating that they could have been the cause of death, or hungry Ice Age wolves came across the horse after it had died. What’s really interesting is that all of this information was preserved so well since 26,000 years ago.

Adult Full-Grown HorseWhile horses have been extinct in North America during most of the time of humans and were re-introduced by Europeans, North America is actually where they first originated in the Eocene Epoch, 55 million years ago. At first, horses were small, close to the size of modern-day dogs. Since then, they have gotten bigger, developed the type of hoofed feet they have today, and eventually gave rise to the Yukon horse and contemporaries, which in turn went extinct 12,000 years ago and brought us to the modern horse, Equus caballus. Why did they go extinct? It is not likely that they were victims of the globe warming as we came out of the Ice Age. This would have been a gradual warming that receded the glaciers and caused the oceans to rise nearly immeasurably during a single life time. This all happened over thousands of years. Also, as with many other species that we’ve talked about here, human predation may have been a key factor in their extinction. Also, scientists think that predation from wolves could have contributed in a large way to this extinction event.

Equus lambei was not the only Ice Age horse in the region, though. Also known is the American “Stilt-legged” horse, which was much taller and thinner than the Yukon horse and probably would have had a harder time surviving in the frigid climate. The stilt-legged horse went extinct 35,000 years ago. Fossil remains have also been found of a much larger horse than the Yukon horse in the same area, as big as a modern day draft horse. There hasn’t been much in the fossil record and scientists still do not know how these species are related to one another. Further, as many as 50 other Ice Age horse species may have been discovered, although we know significantly less about these.


Do you know anything about any of these horses that we didn’t mention? Please leave that in the comments below to contribute to our discussion! We publish a new blog every Tuesday and Friday and we hope to see you again next week. Until then, thank you for reading and goodbye!

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