Just to help eliminate one misunderstanding - Tanzanian Magic is not autoflowering. It is just relatively short for a pure sativa, and hence it flowers more quickly.Rastas went to Ethiopia years ago I think the place is called sashema or something like that , Tanzanian Magic was a strain that was dwarf auto flowering pencil thin leaf pure sativa there is an autobiography of a rasta man who had a commune in Jamaica and the Rastas grew weed there in the 30 s thnk his last name was Howell . The Ethiopian could be from Tanzania or an old Rasta strain from Jamaica .
Even though anything could be true (we'll know when we see the dna), cannabis has been around Africa for a very long time. The oldest descriptions go back to the Nile Valley. Cannabis seems to have diffused very suddenly 2000 BC in Egypt, India, etc.
Within Africa there has long been historic movement of people on an east-west and west-east axis north and south of the Rainforest region.
There was the Borneo people's colonisation of Madagascar about 500 AD. (Some cataclysmic event happened, and the already seafaring people of Borneo ended up in Vietnam/nowadays they're Montagnards and in Madagascar, off the African coast. Over time, the earth is a very small round planet.)
Then, there was the Islamic period of the West African middle ages (Timbouctou, Mali/Mauretania/Morocco), etc. with people going on Haj to Mecca.
Many of the most famous African empires were trading empires. Great Zimbabwe, Malawi, traded as far as Korea and China. (Personally I think there might be a connection between the names Malawi and the Indian Malabar.)
During the colonial era, many Indian laborers and merchants moved to British colonies all over Africa.
What I guess I'm saying is that weed could have been introduced at a very early age, re-introduced over the centuries. Maybe the old strains have survived. Maybe they were replaced by new strains.
Well know when we see the dna.