Plagues and People

Plagues and Peoples was written by William H. McNeill. The basis of this book all falls on epidemiology, also known as the study of patterns, causes, and effects that disease and health conditions have on certain populations. McNeill’s writing shows how the relationship that mankind, referred to a macroparasites, and parasites, referred to as microparasites, have made an impact on the world through history. The relationship at first during existence was said to be “balanced”, but when mankind in Africa started to leave trees and become hunters, spread into new lands, and eventually become smarter and more advanced, the relationship started to become more and more unbalanced. Thus, creating many of the deadly diseases that have emerged throughout history. In Plagues and Peoples McNeil covers many areas of the world, but the most important happen to be Africa, China, India, Europe, the Mongol empire, and the New World, he claims that, “This book is to bring the history of infectious disease into the realm of historical explanation by showing how varying patterns of disease circulation have affected human affairs in ancient times as well as modern times.” To support his claim he uses migration, immunity, the Columbian Exchange, the Mongols, the Black Death, religion, cleanliness, and the very beginning of mankind and parasites to show its effects on humans throughout time.
Before explaining how his supporting evidence helps his thesis, we must look at how parasites and a plague can affect a population and civilization. When parasites begin to become prominent and flourish, it will infect a host, usually a human or through an animal that humans have much contact with. If the population is small, the parasite will not spread, but over time if and when the population reaches its threshold the parasite will start to attach itself to new hosts. If those hosts are not immune to the new parasite, they will have the disease that the parasite has and thus a plague will form.