They are descendants of outcasts employed to perform the originally taboo and still disdained trades of butchery, leatherwork, garbage collection, and the handling of corpses.
They descend from outcasts and as a result are expected to handle the disdained trades.
It might not be the oldest, but Castleton is regarded by many as the  father  of tropical gardens in Jamaica because of its work in the propagation and distribution of new plant genera.