In those parts of the Americas that did support Native cheap louis vuitton handbags American
     agriculture, it was constrained by five major disadvantages vis-a-vis
     Eurasian agriculture: widespread dependence on protein-poor corn,
     instead or
     HEMI S P H E R E S COL L IDI NG ? 3 5 7
     Eurasia's diverse and protein-rich cereals; hand planting of individual seeds, instead of broadcast sowing; tilling by hand instead jordan heels of plowing by animals, which enables one person to cultivate a much larger area, and hich also permits cultivation of some fertile but tough soils and sods that difficult to till by hand (such as those of the North American Great Plains); lack of animal manuring to increase ugg boots clearance 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 uggs clearance DI F FERENCES 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 ugg boots clearance 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 nike jordan heels 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 nike jordan heels 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