In this book, historical geographer Thomas M. Whitmore revives the controversy over the “magnitude and causes of the immediate postconquest population decline in … the Basin of Mexico” specifically, and by extension in the rest of the Americas as well (p. 3). Using a system dynamics computer simulation called MEXIPOP that takes into account the dynamic relations between population, disease, environment, and culture, Whitmore tests the demographic data of various scholars in order to determine which historical reconstructions most likely approximate what occurred.
The author organizes sets of numbers into three cases of demographic decline: mild, utilizing those figures that posit smaller populations in 1519 and larger populations at the end of the sixteenth century; severe, relying on estimates of large numbers of natives on the eve of the Spanish conquest and small numbers by 1620; and moderate, using figures ranging between the other two extremes. After running these cases through the simulation, Whitmore concludes that while none of the figures can be eliminated as statistically impossible, the scenario posed by the moderate case, a preconquest population for a narrowly defined “Basin of Mexico” of 1.59 million and a nadir population of 183,000 in 1607, is the most likely to be valid. Testing of estimates for the hemispheric Amerindian population in 1492 results in similar conclusions: moderate figures, ranging from 43 million to 73 million, probably represent historical reality more accurately than higher or lower numbers.
Whitmore goes to great lengths to explain the mechanics of his methodology. Chapters 2, 3, and 4 detail the construction of simulation models, the “runs” of the three cases, and their respective interpretations. All this is presented in as clear and jargon-free a manner as possible, but as a historian, this reader would have appreciated a bit more summary information about the work of geographers mentioned in the text.
After testing various possible causes of population collapse, Whitmore concludes that epidemics of Old World diseases accounted for the scale of the disaster. Using mortality and morbidity statistics gathered from later periods and other areas where “virgin soil” epidemics occurred, he is able to offer some of the most detailed findings to date regarding the likely effects of various diseases such as smallpox, measles, plague, and typhus on specific segments of the native population. He defends this extrapolation of data by arguing that Amerindians “were not genetically less able to resist successfully the diseases they encountered,” but that high morbidity rates and the ensuing breakdown of social services—to be found in any population without previous exposure to a particular disease organism—accounted for exceptionally high mortality rates.
All those who have followed the debate over the demographic collapse of New World Indian populations will want to read this book. By devising MEXIPOP and introducing historians and others to this valuable tool, Whitmore has performed a valuable service, and his book has made an important contribution to the literature concerning this controversy.
