It just might be that BM was having a lot more sex than the average guy.
Probability alone would account for 12 (or 22) children.
Quality could also have been affected.
There is some debate there apparently. I once heard a wailer say that it was actually 22, but checking wikipedia it says 11.
He only had 12 kids.
The rate he went through groupies I would expect 100+
Weed was a lot less potent back then.
Probably not the stuff Bob Marley was smoking.
I was reading somewhere Bob Marley had 12 acknowledged children so for him it wasn’t a problem. I wonder how his smoking affected his his offspring though