Two words that are often used as synonyms, “feral” and “wild.” I
learned recently that they
are not quite the same. A “wild” animal is an animal that has not
itself been domesticated (or is not descended from formerly domestic
animals). A “feral” animal is one that was (or had ancestors were)
domesticated and have since returned to the wild. I have no idea what
the standard is for ancestors, or how to deal with animals that are
crosses between feral and wild animals.

Thus the Rolling Stones were likely
correct, as the only true wild horses in the world are tahki.