Painting of a smilodon walking on grass.

What is a Cat?

The ancestors of modern cats were much more diverse than today’s felines. Big cats were the first to form a distinct group. Smaller cat groups branched out later and at surprising speed. The domestic cat group is the latest addition to the family tree.

The ancestor of the carnivores, or meat-eating mammals, which include the cat family, ate insects and is thought to have resembled a modern tree shrew. It lived more than 65 million years ago during the late Cretaceous period.

Called Cimolestes, it already showed rudimentary signs of having teeth with a scissor like cutting action—essential for slicing through flesh and bone—which made it possible to change from feeding on insects to eating meat. From this tiny animal two groups of carnivorous mammals evolved, both now extinct: the creodonts and the miacids.

Creodonts, which appeared first, were the earliest meat-eaters and occupied many of the same ecological niches as would the carnivores yet to come.  Later, the miacids took over, and it is from this group that the “true” carnivores, and eventually cats, arose.