You know, the binding receptors that the chemicals act upon.
Oh, like the CB1 and CB1 2 cannabinoid receptors present on the surface of cells in different parts of the central nervous system?
You're right, they're still around so we haven't "evolved" them out of ourselves after several millennia, much less a mere century.
What was your point again?
Do try to keep up. The point was that we are not immuned to what happened to China because we still have the same physiology.