The First 15 Minutes of Seventh Cross (Dreamcast)

Copied from MobyGames:

A life simulation which shows how organisms evolve. Take control of one of life's earliest lifeforms and, depending on what environment and habitat you prefer to use, watch as your organism starts to evolve and adapt to its surroundings.

You control your organism from a third person perspective and you can choose what it feeds on and how it kills its prey and, depending on the method you choose, your organism will evolve to make killing and eating that kind of prey easier.