It's clear that something like what we call The Big Bang happened. But we can only trace back time and space to the origin. What happened "before" the origin is probably unknowable to us on this side of the origin. The best we can do is speculate, in scientific or literary terms.

So think of this as speculative fiction, expressed in terms of the author's time.

Personally I thought the progression of man through the ages was the most interesting part of the story.