In the account of the Flood, God commanded Noah to bring in seven pairs of "clean" animals and a pair of animals that are "not clean". Here we have a very early distinction of clean and unclean animals, something which was only(?) segregated in the giving of the Law. How come does this distinction appear here? On what basis would Noah know whether an animal was clean or unclean?
Genesis 7:2-3 ESV: Take with you seven pairs of all clean animals, the male and his mate, and a pair of the animals that are not clean, the male and his mate, and seven pairs of the birds of the heavens also, male and female, to keep their offspring alive on the face of all the earth.
Sidenote: how would you also explain the seeming discrepancy of the abovementioned verses to the previous requirement of bringing only(?) two pairs of every animal?
(6:19): And of every living thing of all flesh, you shall bring two of every sort into the ark to keep them alive with you. They shall be male and female.
And this "two and two"?:
(7:9): two and two, male and female, went into the ark with Noah, as God had commanded Noah. (7:15): They went into the ark with Noah, two and two of all flesh in which there was the breath of life.