How did Noah know what was clean and unclean? Did he guess?
Christendom believes only two of unclean showed up and seven pair of the clean, however that doesn’t answer the specificity of God telling Noah to ‘take.’
When combined with the dozens of other Torah specific commands obeyed throughout Genesis the glaring conclusion is that Noah knew exactly what the Almighty told him because he had the Torah, handed down from his father’s.
Clearly, the Torah was in, even before, Gan Eden, and it is God’s instructions for righteous living to all mankind.