Born perfect, Adam and Eve were given one law: "Don't eat the fruit."
Born imperfect, humanity was given a few laws, then books of them.
Made spiritually perfect by Christ, saved humanity was again given one law.
But it really always was only one law, expanded, explained by situation, revisited in every variation so no misunderstanding could provide an excuse for disobedience.
To Adam and Eve: "Don't be selfish."
To fallen humanity: "Stop being selfish."
To fallen humanity: "Walk in the Spirit and you'll stop being selfish."
