You posted that Marijuana was not used by humans until recently, I corrected you.
No, You just aren't keeping up with the discussion and took isolated words out of context. As far as the United States was concerned, Marijuana is a recent addition to the available pharmacopeia. I don't care that China knew about it five thousand years ago, that has nothing to do with why it was banned here, and the reason it was banned here was because the Population of the United States had little experience with it. (As a drug anyway.) To them it was recent.
After the bad experiences with cocaine and heroin, the Authorities were not in the mood to put up with a new drug, even one as relatively harmless as Marijuana appears to be. Had it been part of European culture it might have gotten a pass, but as it was relatively NEW to American/European culture, it didn't. So they banned it.