He's choosing a logical point in life where we can say that life begins with some justification. Unless, as I said or implied here before, we continue back to the Big Bang which was a Singularity, which means a happenning we can't explain, caused/uncaused by we don't know what,, why, and where or in what Nowhere, once or more times or, say, -1 times, or -n times, even if that seems impossible to us, humans at the present time in our developement.
None of this proves that there was never, or n times, or -n times never, that there was/wasn't a beginning. It does indicate the utter futility of a Metaphysics that cannot admit the above facts and its own limitations.