The yardstick of time in Table B-1 in Appendix B showing the rate at which agriculture has progressed encourages the belief that progress will continue. The connection between several of the events on the yardstick and more food per plot is clear. For example, the reader can see clearly that both Mendel's learning how peas inherit smooth and wrinkled skin and Jones' inventing double-cross hybrid maize raised yields. On the other hand, connecting such events as the birth of villages. cities, and railroads to agricultural progress may seem hard.
I connect villages and cities to yield by connecting them first to technology, a method for getting more output from the same input. That learning and technology raise yields is a commonplace. Remarking how they come about is less common. Boserup (1981[Bos81], 76-77) asserted that the very density of population that we fear may overwhelm food supply and thus spare no land for Nature induces the technology that raises yields.
Urbanization meant that a number of new problems had to be solved by the intellectual elite. The elite met their many new demands by pooling their knowledge. ...Cross-fertilization of ideas and systematic specialized training were possible because the elite now could live together ... An elite unburdened by daily toil existed before urbanization; the new feature was that such an elite could live together. Urbanization was accompanied by rapid progress in the technology of large-scale construction, transport, and agriculture. ...Increasing population density and urbanization went together with improvement of rural infrastructure, either by construction of transport facilities and irrigation facilities as in Mesopotamia, or by improvements of organization (``administrative technology") as in Mesoamerica. Literacy is an urban skill, developed in response to demands that existed only in urbanized societies. ...
So I placed urbanization in Mesopotamia and Mesoamerica on the agricultural yardstick.
Another quotation from Boserup (1981,[Bos81] 129) suggests why I placed railroads on the yardstick:
The worst handicap to technological development for sparsely populated areas ...was the low technological levels in the transport sector, especially land transport. ...The inhabitants of large, sparsely populated continents were doomed to be illiterate subsistence producers. Their rich natural resources were of little use to them.She goes on to write that the new means of transport made it feasible for areas of relatively low population density to export their rich natural resources to larger markets. After the Industrial Revolution, some areas with low population densities underwent rapid technological change thanks to improved transport. Trucks, of course, hauled produce from the spaces between the rails, and I remember newly graveled roads justified in the 1940s as ``farm-to-market." Transport appears on the yardstick, not because it fattened the billfolds and brightened the lives of farmers. Transport appears because it carried the technology and the incentive to use it to raise yields and thus support more people per plot.
Plant introductions like sugar cane or tobacco easily are connected to pleasure or to diversity. Introductions also can be connected to supporting more people per plot. In 1990 in Spain, the maize introduced from the New World centuries before yielded 6.6 t or 27 million cal/ha. In the same European nation and year, Old World coarse grains yielded 4 million cal/ha rye and 9 million cal/ha barley. Soybeans provide a reverse example. In 1990 in the United States, soybeans yielded an average 2.2 t or 7 million cal/ha, while the native sunflower yielded only 1.4 t or 6 million cal (See caloric contents in Table A-1 in Appendix A.). The famous introduction of the potato to Ireland will come up later when I examine the changes in diet that enable new plants to feed more people per plot.