Evolution as a concept is intriguing. Implementing it in a game is not unheard of. Basing a game around the concept, now that’s something else entirely.
EVO places you, a prehistoric creature of some sort (you begin as some kind of fish thing) vying for survival. You must kill weaker creatures and feast on their remains to gain ‘evolution points’. You spend these points to upgrade your body parts to be bigger, stronger, or more useful. Your goal? Survive the geologic age, and prove that you’re the ultimate being to Gaia, the spirit of the Earth.
Each age is very different, and a strong body in one age is excessively weak in another. Your sleek fishy physique is pretty useless on land, so you get to change to multi-legged dinosaur form. Your rough and tumble en-fanged dinosaur head with Flesh Rending Razor Teeth(tm) will do nearly zero damage to the new-fangled Warm Blooded Mammals, so you get fur and rodent teeth.
Interestingly, throughout the game you’ll find these mysterious crystals that bestow gifts that range from Big Points ™ to forms of real-world creatures that you get to use for a limited time (they’re super powerful, after all). There is some implication that there is an alien force at work directing evolution for its own unknown motives, motives that I was really never able to divine.
The other interesting thing is that once the appropriate age is reached you can choose to evolve into a human, and eventually into a mer-person. Just like Real Life Humans, the human walks around with a club and is particularly physically weak with a comparatively weak constitution. In other words, don’t evolve into a human. It makes the game much harder, unless you like that kind of challenge. In fact, evolving into a human is a one way street. You can’t go back to the piecemeal animal forms you had been using, and half of the fun is making some crazy patchwork monstrosity and seeing how it will fare. The game even lets you save pictures of your favorites.
I’m not sure that a game has been made since that covers the sheer scope of history that this game does, but it would be fantastic to see this game remade or a sequel to come out. The original was apparently a bit of a low-seller, so it’s tough to find these days and rather expensive if you do.