From a presentation at SIGGRAPH Asia 2013, a demonstration of a program that learns how to walk by evolving the orientation of its muscles.
Love these kinds of things. I remember another video like this that went around a few months ago...but instead of bipeds, it was a a shambling collection of cubes that learned how to move around. Anyone have a link?
Update: Ah, here's that other video; I posted it back in April. (thx, @_DavidSmith)