When referring to civilization, historians often think in terms of amalgams of cultural, political and military traits specific to certain geographies, but McNeill refers to civilization in broader terms as infrastructural pools harboring varieties of parasites who live in symbiosis with humankind. These pools are mainly supported by types of food production, with the single distinguishing ecologically significant shift being the turn from hunter-gathering societies to agricultural societies starting at roughly the end of the Ice Age. Thus, civilized humanity is characterized as a collection of “disease pools.”

This view may seem ungenerous. On the other hand, the future may look upon post-20th century civilization as one that simply produced tons and tons of plastic as its major contribution to world history, choking waterways and killing hosts of species in its wake. McNeill’s vision of humanity is a provoking one, but his argument could be that the common vision of a heroic, ever-progressing humankind erases the balance necessary to ecological harmony. Such provocations remind humans of their place.

McNeill states:

…optimal conditions for host and parasite occur, often though not necessarily always, when each can continue to live in the other’s presence for an indefinite period of time with no very significant diminution of normal activity on either side (28).