These horses escaped or were intentionally released and over time, they established themselves as wild herds.
The genetic makeup of a mustang is therefore a mix of various breeds brought over from Europe, including:
* Spanish horses: These were the dominant breed in the early days of colonization, and they heavily influenced the mustang's physical characteristics.
* English Thoroughbreds: Brought later, they contributed to the mustang's speed and agility.
* Other European breeds: Including Arabian, Barb, and Hackney horses, all contributing to the diversity of the modern mustang.
So, while a mustang is a wild horse, it's not a specific breed, but rather a mixed breed of horses descended from various domestic breeds.