This is what i think.. God made primitive man.. that man evolved with marijuana.. marijuana evolved too.. then they joined hands and waltz down history together.. sooner or later we where being born with receptors just for marijuana.... then after the years we began mass growing and smoking.. then one day all man will rely on is MJ.. and other sorces too.. but mostly MJ...

Primitave man " Me find good smell plant "
Primitave marijuana plant " Smooookkee meeeee "
Primitave man " Me want smoke plant "
after about an hour of smoking..
Primitave man " Me so stoned... me swell long time "