Past : The jaguar comes from the first carnivore on earth called the Miacids so does every other carnivore on the earth now, back when the Bering straight still existed the Asian ancestry of the jaguar crossed it into america, and went down to mexico then to the whole of south america. The jaguar has lots of cousins which are all the carnivores alive today. Jaguars are ancestors of old world cats.
Present : The jaguar is short & stocky and is able to climb trees swim and crawl, its a stalker hunter so it waits for its prey to get close and then jumps out kills it and eats it. it has a orange-yellow base coat for its fur then has rosettes that are large and black to make it really easy to camouflage in the rain forest since it is so dense in trees and has low light. The jaguar has an extremely powerful mandible enabling it to bite through turtle shells to eat its prey. Jaguars has color morphism so sometimes jaguars wont always be yellow with black spots but will be black morph or be albino, the black morph ones are normally called black panthers but the extremely rare albino ones are sometimes called white panthers.
Future : The future jaguar most likely will get a color morphisim gene to make it dark brown to camouflage into the tree stubs and ruins of the old amazon forest and the black morph gene will become more popular since it will most closely resemble the ruins, the jaguar will become longer in size lighter and will get longer legs, it will get longer paws and wont need to climb trees anymore, it will develop a special respiratory system to cope will the the carbon dioxide emissions the human race created, it will run faster since it cant stalk prey anymore in a open rainforest ruin. It will not swim anymore since all the rivers are too toxic and will kill the jaguar.
Sources : http://en.wikipedia.org/wiki/Jaguar