The History of Human Populations. II. Migration, Urbanization, and Structural Change (review)

This volume is the second in a planned trilogy, constituting a vast enterprise to fit mathematical curves to all types of demographic quantities. The focus is population movements, with a great deal of attention to the slave trade. The author has sifted an enormous deal of quantitative information, but pays only minimal attention to the quality of the data. Time series often reflect no more than the informed guess of contemporary administrators or present-day scholars. His mode of analysis and exposition is the graph. He fits more than 600 series with curves in 152 figures but offers only two tables with actual population numbers, making this volume unsuitable as a sourcebook. The figures are difficult to read and interpret. They are plotted on semilogarithmic scales, without regard for the comparison of the relative magnitudes of different populations. Their conventions and symbols are not explained anywhere in details and appear to vary from graph to graph.

Do the illustrated functional relationships reflect fundamental laws of growth, or are they mere graphical devices? The curves representing trends over time include points that are outside of the particular series they are supposed to fit and are often totally divorced from reality. From that point onward, they incorporate fixed rates of acceleration or deceleration such that eventually they can be fitted to the relevant series. For example, a series purporting to show the number of slave ships from the port of Nantes during the period 1774 to 1791 reaches a maximum point in 1830, when, by all accounts, French slaving had long been abolished (138). A series of "females per 100 Maori" from 1858 to 1976 includes a point for 1800, suggesting that the proportion of females then would have been less than 20 percent (438). In some cases, as many as eight curves are necessary to fit a series; a single straight line would have done a reasonably good job (455).

The main substantive conclusion from this huge project is that human phenomena tend to exhibit regular patterns. To quote the conclusion of the volume, "The most common, the G curve of constantly proportionally decelerating growth at the .03 rate, captures how populations usually expand to exploit some opportunity in their environment" (507). Growth declines as the opportunity progressively loses its unique nature, while the population diversifies in predictable ways—for example, with a larger proportion of women and children. A third volume isplanned, linking demographic trends more closely to social and economic changes.