for Nogales, Arizona.
The other part of the geography hypothesis is that the
tropics are poor because tropical agriculture is intrinsically
unproductive. Tropical soils are thin and unable to maintain
nutrients, the argument goes, and emphasizes how quickly
these soils are eroded by torrential rains. There certainly is
some merit in this argument, but as we’ll show, the prime
determinant of why agricultural productivity—agricultural
output per acre—is so low in many poor countries,
particularly in sub-Saharan Africa, has little to do with soil
quality. Rather, it is a consequence of the ownership
structure of the land and the incentives that are created for
farmers by the governments and institutions under which
they live. We will also show that world inequality cannot be
explained by differences in agricultural productivity. The
great inequality of the modern world that emerged in the
nineteenth century was caused by the uneven
dissemination of industrial technologies and manufacturing
production. It was not caused by divergence in agricultural
performance.
Another influential version of the geography hypothesis is
advanced by the ecologist and evolutionary biologist Jared
Diamond. He argues that the origins of intercontinental
inequality at the start of the modern period, five hundred
years ago, rested in different historical endowments of
plant and animal species, which subsequently influenced
agricultural productivity. In some places, such as the Fertile
Crescent in the modern Middle East, there were a large
number of species that could be domesticated by humans.
Elsewhere, such as the Americas, there were not. Having
many species capable of being domesticated made it very
attractive for societies to make the transition from a hunter-
gatherer to a farming lifestyle. As a consequence, farming
developed earlier in the Fertile Crescent than in the
Americas. Population density grew, allowing specialization
of labor, trade, urbanization, and political development.
Crucially, in places where farming dominated, technological
innovation took place much more rapidly than in other parts
of the world. Thus, according to Diamond, the differential
availability of animal and plant species created differential
intensities of farming, which led to different paths of
technological change and prosperity across different