There is no "I" in "You"

[quip]

No it doesn't. I'm not attempting to ascertain or refute the existence of the self.

 I could not have been born in another time because my brain only exists in the temporal 'now' and not at any other point in existence.

This does not necessarily follow.  

Prior to the established "I" what (mundane factors) determines the particular "I" to which you refer?  Is it contingent upon specific factors or simply chance?  If the latter, under what conditions (milieu) make possible the calculation of said "chances"?

Or alternatively, Can the atheist rationally avoid the inquiry by simply asserting that there was nothing "prior to the established "I""?