historians are currently divided about the role of "y. pestis" in the black death. some historians said that the black death spread far too fast. therefore, "y. pestis" could not have caused it. dna from "y. pestis" has been found in the teeth of some of the victims of the black death. for this reason, "y. pestis" must have been at least a factor in some (but not necessarily all) european plague epidemics.