Aquinas tells us that there is no contradiction in affirming that something was created and that it was never non-existent. The reason that this might appear to be counter-intuitive to the modern reader is that many misunderstand what it means to say that something is created in the strict sense. All things which are composites of act and potency, essence and existence, etc. by definition require God to perpetually maintain their existence. This is not to say that all things necessarily have a beginning in time, they need not have one, but it is to say that there is a hierarchy of existential dependence that is separate from the temporal order. That there was or wasn't a Big Bang is irrelevant to the question of whether man, the world, and the entire universe are created things. Here's a good rule of thumb to tell whether or not something is a created thing: If it is God, no. If it is anything else: yes.