All tigers are related to an ancestral species of “carnivorous” mammals who appeared during the Paleocene and Eocene periods. The Paleocene period took place from 66 to 56 million years ago, and the Eocene period took place from 56 to 36.9 million years ago. This means that the tiger’s ancestors were around during the same period as the dinosaurs — i.e. 252-66 million years ago. One of these ancestral species was the Dormaalocyon, a carnivorous mammal which inhabited the Earth over 56 million years ago. Dormaalocyon is one of the very oldest carnivorous mammals, who’s lineage can be traced to “present day Carnivora”.
Although our evidence of the existence of modern-day tigers only goes back a couple of million years, the taxonomical Order that the Sumatran tiger belongs to, Carnivora, evolved in North America out of the Miacidae family, about 42 million years ago. The Miacidae family is a mammalian family, which scholars think evolved from “insectivore stock”. These animals were typically small, and looked similar to a modern-day weasel. They contained fairly large brains — larger than “their creodont contemporaries”. The Miacidae quickly split into cat-like and dog-like groups (Feliformia and Caniformia). Feliformia are those who happen to be “cat light”, such as hyenas and cats. Their most significant attribute is the “auditory bullae” — these are bony capsules which close in the middle and inner ear. The Caniformia suborder animals have a “long snout” and “non-retractile claws”,(as opposed to the Feliformia, who do not).
The oldest of cat records in the form of fossils go back to the Proailurus cats. These are “carnivoran felids” who derive from Mongolia, Germany and Spain, dating back approximantly 25 million years. These cats had long tails, large eyes, sharp claws and teeth. They typically weighed between 25 and 30 pounds. They inhabited trees, and had 8 more teeth than modern-day cats, indicating a stark change in tigers’ evolutionary history.
Cats in fossil records originating around 20 million to 8 million years ago, are known as Psudaelurines. They are known as the most “direct” descendants of the 37 present-day cat species. They are ancestors of present-day felines and pantherines, and came after the extinct carnivorans: Proailurus. They have short “viverrid-like legs” which indicate their expertise in climbing trees, they have “aerodynamically” shaped heads, and long tails.
The very earliest tigers began to evolve around 3.9 million years ago, and the tiger then evolved into a distinct species during the Pilocene epoch, approximately 3.2 million years ago. Interestingly, tigers might be more old and unique than you might think. Tigers are not as closely related to other “big cats,” like lions, leopards and jaguars, as these other cats are related to each other. Genetic analysis shows that the tiger’s closest living relative is the snow leopard. The ancestor of tigers and snow leopards “became different” or “branched out” 3.9 million years ago. The tiger and snow leopard are “sister species”, researchers report in the journal of Molecular Phylogenetics and Evolution.
In order to survive, tigers had to adapt to their environment. One example of an adaptation is the tiger’s keen sense of hearing. Another is their distinctive and beautiful camouflage — tigers developed a striped coat which makes them very difficult to see in the forests and jungles where they normally live. Sunlight gets to a very small amount of the forest, so there are many shadows. The stripes look like shadows, camouflaging the tiger.
Here’s a cool video on tiger evolution!
Alex's Sumatran Tiger Website 
Really interesting! I really like all the information you have and it’s extremely thorough. I also didn’t realize how long tigers have been around for.
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