The topic of interest for me became the ancestor of the domestic horse. It seems that the predominate thinking is that modern horses are descended from a species of Asiatic wild horse. Things get kind of fuzzy from there.
There is one living species that has resisted domestication,and hangs on by a slim hoofhold. It's called the Przewalski's Horse.They once existed only in captivity, but they have been re-introduced into a few select areas. One interesting place where they seem to be thriving is the Chernobyl, (sp) Exclusion Zone that was created to keep people away from dangerous levels of radiation. The place is now Eastern Europe's greatest wildlife refuge. Besides the horses, European Bison, Moose, Brown Bears, and Wolves are all thriving, along with a slough of other creatures.
This painting is not meant to be Przewalski's Horses per se, but the ancestral horses that were painted on the cave walls in France. I spent a lot of time on this one, because of a paucity of reference materials. I had to guess at various details.