What is the motive to evolve? Just to see what you can make?

I think you could add significant value to your game if you had to evolve to
survive! Perhaps your quarry is evolving also and you may become its prey
if you dont evolve quickly enough or in the right directions to counter its/
their evolution? That would be exciting!

Or perhaps you could pit your evolved creatures powers against other creatures
in some kind of combat? Each round the foe would be more evolved, and between
rounds, you could have the opportunity to evolve some also!