I have most of a biology degree (and a psych degree as well), and the closest I ever came to integrating evolution into my homebrew was giving the Elder races a "ancestor" sort of animal, from which they 'slowly' evolved through magical intervention. To give true "depth" to evolutionary biology in a gaming world would be maddening, and probably not worth your time, especially if you want to progress along a different path -- if you decide to, oh, base life of silicon instead of carbon, we're talking a whole different kettle of fish.... or if another animal evolved to "human" sentience instead of apes, then we're talking a lot of probability.
In the end, though, I think it boils down to the differences of a red apple versus a green apple -- if a feline ancestor had been the predecessor of humanity, we'd all look different, but the evolutionary pressures of an Earth-like environment tend to produce the same or similar results. You'd have a feline looking creature with extensive cephalization (concentration of sensory organs in the encephalon, large forebrain development), the development of accurate binocular vision, the tendency towards bipedal movement, and the development of tools and other means to alter their environment.