Evolution is easier than we think, and one great way to see why is to look at what we know about protein evolution.
Proteins have been evolving on our planet for about 4 billion years. Their appearance almost certainly precedes the beginning of life itself. We still don't know how the whole thing got off the ground, but once the stage was set (in living cells), evolution began exploring Protein Space. As it did so, it slowly created the Protein Universe. Since these two concepts — Protein Space and the Protein Universe — are so central to understanding and picturing protein evolution, we should carefully define what they mean.
