(Mikuriya, Tod H., M.D., Marijuana: Medical Papers, 1839-1972, Medi-Comp Press, Oakland, CA, 1973; Shultes, R.E., Harvard Botanical; Ency. Brittanica; Abel, Ernest, Marijuana: The First 12,000 Years;. Plenum Press, 1980; Vera Rubin, Cannabis and Culture, Institute for the Study of Man, 1968-1974 and second studies 1974-1976; et. al.)
The division of information about this sacred herb and its industrial hemp uses were strictly maintained by the priests for thousands of years, up until the last few centuries. Those outside the priestly class who possessed drug knowledge were considered (by the priests, of course) to be witches/soothsayers/outlaws and the ilk, and were often condemned to death.