How/where do I get a protein to evolve? How do I become an evolver?
You have to be in a group (e.g. the Void Crushers) :) to be able to download shared solutions of your teammates and evolve them. You can also share your solutions with your teammates and use the group chat.
Another way is to play in an all-hands puzzle, which essentially puts everyone into one group for "evolution" purposes. While All Hands scores are in a different category, you do unlock the "Evolver" achievement for improving a public solution in an All Hands puzzle.