McNeill, William H.

A parasite is often to be admired for its ingenuity and persistence, even if it isn’t always attractive. A friend of mine once discovered a worm in his bed. It had come from his own body and had been living there for several months, beginning its tour in the previous March, when it manifested itself by giving him a cough and a bad chest. He found this out later when researching the life of the roundworm, which had apparently completed a convoluted journey round his interior, beginning in the spring. ‘The female roundworm’, he said proudly, ‘lays a quarter of a million eggs a day!’ It is perhaps a good idea to take this sort of positive view of parasitism, because, according to W. H. McNeill, author of Plagues and Peoples, we are all parasites. ‘Most human lives’, he writes, ‘are caught in a precarious equilibrium between the microparasitism of disease organisms and the macroparasitism of large-bodied predators, chief among which have been other human beings,’ the sort involved in ‘war, plunder, enslavement, tax farming’.