An ancient and endangered species of horse known as the Prezwalski has had much research and more domestic type in the domestic horse, but has been proven to be much more distant than previously thought. The famed horse, also known as a Dzungarian, is a rare and endangered species of the wild horse family. It was found primarily dominated by the Mongols due to their wild nature and dire need, but also is a common native of the whole of China, specifically the north.
This fact was discovered as recent scientists began studying the mitochondrial DNA that the mother passes to the offspring and contrasting it to the DNA that a domestic horse or common horse passes to its own offspring. These genes though featuring much similarity have obviously had a radical split many thousands of years ago from the path that is common to the domestic horse. This news has baffled scientists and opens whole new fields of study and research to them. Where the horses tree branch is speculated to be anywhere from 6,000 to 10,000 years ago, with both sharing a very ancient ancestor, with the split being due to clamatorial changes and lifestyle needs adversely affecting both fields of horses. The domestic were thought to have lived in more easy terrain, while the Prezwalski horse is speculated to have moved predominantly in flight of its predators, making its way higher and higher, thus having its home in the Chinese and Mongolian heights. The reason of the harsh conditions affecting it has also made it as rare a species as it is today.
As you can see, this simple step of progress in the research of horses and their past has opened up much room for speculation, even for doubt as to other supposed confirmed theories and will take much more study before it can be said to be officially set right.