Herepton writes:
The claim is though, that God was the author.
The inability to identify any earthly author supports the claim.
Herepton, perhaps you weren't aware of this, but it was common practice in ancient times and up to the Renaissance for authors of certain works to not identify themselves or to sign their works. People back then believed that anything they did was for the glory of god and thus was expected to be humble enough to not claim their own work.