You have to take the long view. First, when Moses came down...

You have to take the long view. First, when Moses came down from Mt. Sinai, man has already progressed to the point where a commandment against cannibalism was no longer necessary. And, second, it's like pissing on a boulder. For the first few thousand years, you don't see any effect. But after that, you start to see a definite impact.