Much is unknown and contriversial on the history and evolution of the cats. For what Paleontologists could tell, the modern day felines evolved rapidle within the past 12 million years.
The earilist known cat- Proailurus lived about 30 million years ago, the size of a small bobcat. In the last 12 million years the felines we know today, evolved. This is concedered a very rapid event but still much is unknown since few bones are found, and what is found are usually just jaw bones making the puzzle even harder to put together.
Big Cats, such as the Sabor-tooth (Smilodon) and the American lion (Panthera Atrox) used to roam from the top of Alaska down into Mexico, becoming extinct around 10,000 years ago. Why? we don't know. Possibly from few prey, remember this was the ice age and many were whiped out through this Oligocene period.
or perhaps from lack of a good gene pool. Today in-breeding is affecting the Cheetah and the Florida Panther.
only time and much study will tell, or maybe not. The question may go unanswered.
Proailurus From the Oligocene 30 million years ago (ma). Was about 21 inches shoulder height. Concidered the first true cat. Proailurus Lemanensis was found in french deposits with dates around 30 ma. It was a small sized animal with a 6 inches skull length. The skull containing more teeth then the modern day cats.
Pseudaelurus came along some 20 ma in the maiocene.
P. Lorteti was about the size of a large lynx. (19 inches) and had much in common with the modern day cat.
P. Schizailurus was almost undistenguishable from the modern cat.