Here's something for you. Carthage introduces elephants to Spain. These are selectivly breed to obey humans, and to do everyday farm labor. The Romans see how useful they are and how powerful they arm in combat, and Adopt them breeding new varieties to create a northern breed which they introduce to all the countries that would later become colonising powers. Aztecs fear Spainards who come with Steel armor, Swords, Guns, and fully armored horses and elephants. Dito for the Incas. Some survive the sinking of a ship, and being great swimmers swim to the shores along side horses. Wild breeds of mustang elephant and horses begin to evolve in the Americas. The horse and elephant, two species which where driven to extinction in the Plestocene Americas are reintroduced.