It is highly likely that the sharp fall in the population that occurred in Britain and the rest of western Europe about 5,000 years ago was caused by a “Neolithic Black Death.” But this devastating epidemic differed from the fourteenth-century Black Death in one crucial respect. Yersinia pestis did not evolve into a flea-borne bubonic plague until the beginning of the first millennium BCE.[70] Prior to that it would have been transmitted by sneezing and coughing and infected the lungs.
