"There are indications that cannabis was used as early as 4000 B.C. in Central Asia and north-western China, with written evidence going back to 2700 B.C. in the pharmacopeia of emperor Chen-Nong. It then gradually spread across the globe, to India (some 1500 B.C., also mentioned in Altharva Veda, one of four holy books about 1400 B.C.1), the Near and Middle East (some 900 B.C.), Europe (some 800 B.C.), various parts of South-East Asia (2nd century A.D.), Africa (as of the 11th century A.D.) to the Americas (19th century) and the rest of the world.2"
"A Century of International Drug Control," United Nations Office on Drugs and Crime: Vienna, Austria, 2009.