sotto voce

We don't. We know that these story myths are part of ancient cultures, not their own history. As has been recently pointed out, the modern age is concerned about mundane historical accuracy. One might with justification call it an obsession. It is a great obstacle to understanding the mindset of the ancients if one stubbornly persists in imposing modern thought habits on the ancients. Or, it could be a form of obscurantism, of course. The ancients were simply not concerned with what happened. They had no records of the distant past, and quite often they wished not to know what had happened during the memorable past. They were at the mercy of the elements, and each other, they were concerned with an afterlife. But, more than anything, they were concerned with concepts of truth as applied in societies that were invariably unstable because they were invariably despotic to some degree. Until one understands that, one will never be able to make sense of the ancient past and its story myths. The last thing that one should mistake them for is history.

At some point in Genesis chapter 11 there is a transfer from story myth to chronicle (or chronicle, as intended, depending on your pov). So it would be nonsensical to behave as fundamentalists do and try to extrapolate firm history from anything much before verse 26 of that chapter. Only two names have any modern resonance from before that verse; Shem, who gives the modern word 'Semitic', and Eber, whose name may have given rise to the name of the Hebrews. But anything more than merely noting this is very liable to be idle conjecture.