If death did not exist before the sin of Adam, how could evolution have happened?

The doctrine that death did not exist before Adam comes from Calvinism. This assumes a false doctrine of the "fall" of man. This is the same doctrine that gives us the false doctrine of original sin–the very unfortunate doctrine that we inherit the sins committed by another person (which is proved wrong by Ezekiel 18:19-20 and hundreds of other passages).