The validity of evolutionary theory is not contingent on being able to demonstrate how life began. The phylogenetic relationship of all living organisms is a demonstrable fact capable of stand on it's own evidence, and is irrelevant to the question of how life stared. Maybe life began as a creation of God, as many evolutionists claim, or perhaps it started through a process of abiogenesis; both are theories which reject spontaneous generation ought-right. So even if you could prove that a naturalistic origin of life is impossible, and even go so far as to infer the existence of a creator, that wouldn't have any baring on the fact that evolution is a proven theory. You'd simply have proven that evolution began with a divine creation.