I see this problem all the time with non-Catholics even (not necessarily atheists). They look at Genesis in a vacuum and point out all sorts of errors in it. Meanwhile there has literally been thousands upon thousands of years of study by both Jews and Christians on Genesis. Figuring it out needs to be looked at in light of the commentary of the past, not just in a vacuum.
Honestly, I could never understand that argument. It just seems backwards.
It makes sense, for example, to read Deuteronomy to understand the social background which is implicit in the Gospel. It makes sense to read the Gospel before reading Revelation. In general, it makes sense to use an
earlier text to understand the
later text, because it gives you some context.
However, since Genesis supposedly contains the
earliest history of mankind, then no other text can be used to provide the context for Genesis, because no other text should predate Genesis.
If you say that one should read later commentary to understand Genesis, you are acknowledging that Genesis is not a historical narrative, but rather a symbolical or mythological one, i.e. it is
post hoc attempt by the Jewish culture to describe cosmogony. An attempt naturally limited by then-current understanding of the world.
However, if it is so, then obsessing over what Genesis actually says has as much merit as obsessing over, say, Nordic mythology or Tolkien’s
Valaquenta – i.e., none.