GUNS, GERMS AND STEEL - Cloverport Independent Schools

HEMISPHERES COLLIDING • 357
Eurasia's diverse and protein-rich cereals; hand planting of individual
seeds, instead of broadcast sowing; tilling by hand instead of plowing by
animals, which enables one person to cultivate a much larger area, and
which also permits cultivation of some fertile but tough soils and sods that
are difficult to till by hand (such as those of the North American Great
Plains); lack of animal manuring to increase soil fertility; and just human
muscle power, instead of animal power, for agricultural tasks such as
threshing, grinding, and irrigation. These differences suggest that Eurasian
agriculture as of 1492 may have yielded on the average more calories and
protein per person-hour of labor than Native American agriculture did.
SUCH DIFFERENCES IN food production constituted a major ultimate
cause of the disparities between Eurasian and Native American societies.
Among the resulting proximate factors behind the conquest, the most
important included differences in germs, technology, political organization,
and writing. Of these, the one linked most directly to the differences
in food production was germs. The infectious diseases that regularly visited
crowded Eurasian societies, and to which many Eurasians consequently
developed immune or genetic resistance, included all of history's
most lethal killers: smallpox, measles, influenza, plague, tuberculosis,
typhus, cholera, malaria, and others. Against that grim list, the sole crowd
infectious diseases that can be attributed with certainty to pre-Columbian
Native American societies were nonsyphilitic treponemas. (As I explained
in Chapter 11, it remains uncertain whether syphilis arose in Eurasia or in
the Americas, and the claim that human tuberculosis was present in the
Americas before Columbus is in my opinion unproven.)
This continental difference in harmful germs resulted paradoxically
from the difference in useful livestock. Most of the microbes responsible
for the infectious diseases of crowded human societies evolved from very
similar ancestral microbes causing infectious diseases of the domestic animals
with which food producers began coming into daily close contact
around 10,000 years ago. Eurasia harbored many domestic animal species
and hence developed many such microbes, while the Americas had very
few of each. Other reasons why Native American societies evolved so few
lethal microbes were that villages, which provide ideal breeding grounds
for epidemic diseases, arose thousands of years later in the Americas than
in Eurasia; and that the three regions of the New World supporting urban