Well, it's not the same. Game must be self consistent, after choosing the level of approximation to historical reality. See, Rhye made it so that horse will not appear in Americas until Europeans. Now one needs to be consistent with this choice. You can't research HR because you never seen horse. Now Gunpowder is a different story.The mining of Chile saltpeter was such a profitable business that three nations, Chile, Peru, and Bolivia fought over the richest deposits in the War of the Pacific. The world's largest natural deposits of caliche ore were in the Atacama desert of Chile. Inca COULD have been researched the gunpowder and Mayans COULD have been strong established nation by the time Aztecs spawn. But there were no Kangaroos in Britain and no horses in Americas. So if Rhye specifically banned horse from the New World American civs should not research it, IMHO.