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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 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 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 ew of each. Other reasons why Native American societies evolved so few ethal microbes were that villages, which provide ideal breeding grounds for epidemic diseases, arose thousands of years later in the Americas than urasia; and that the three regions of the New World supporting urban
3 5 8 'GUNS,GERMS, AND STEEL
societies (the Andes, Mesoamerica, and the U.S. Southeast) were never connected by fast, high-volume trade on the scale that brought plague influenza, and possibly smallpox to Europe from Asia. As a result, even malaria and yellow fever, the infectious diseases that eventually became major obstacles to European colonization of the American tropics, and that posed the biggest barrier to the construction of the Panama Canal are not American diseases at all but are caused by microbes of Old World tropical origin, introduced to the Americas by Europeans.
Rivaling germs as proximate factors behind Europe's conquest of the Americas were the differences in all aspects of technology. These differences stemmed ultimately from Eurasia's much longer history of densely populated, economically specialized, politically centralized, interacting and competing societies dependent on food production. Five areas of technology may be singled out:
First, metals—initially copper, then bronze, and finally iron—were used for tools in all complex Eurasian societies as of 1492. In contrast, although copper, silver, gold, and alloys were used for ornaments in the Andes and some other parts of the Americas, stone and wood and bone were still the principal materials for tools in all Native American societies, which made only limited local use of copper tools.
Second, military technology was far more potent in Eurasia than in the Americas. European weapons were steel swords, lances, and daggers, supplemented by small firearms and artillery, while body armor and helmets were also made of solid steel or else of chain mail. In place of steel, Native Americans used clubs and axes of stone or wood (occasionally copper in the Andes), slings, bows and arrows, and quilted armor, constituting much less effective protection and weaponry. In addition, Native American armies had no animals to oppose to horses, whose value for assaults and fast transport gave Europeans an overwhelming advantage until some Native American societies themselves adopted them.
Third, Eurasian societies enjoyed a huge advantage in their sources or power to operate machines. The earliest advance over human muscle power was the use of animals—cattle, horses, and donkeys—to pull plows and to turn wheels for grinding grain, raising water, and irrigating or draining fields. Waterwheels appeared in Roman times and then proliferated, along with tidal mills and windmills, in the Middle Ages. Coupled to systems of geared wheels, those engines harnessing water and wind powe were used not only to grind grain and move water but also to serve myna
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manufacturing purposes, including crushing sugar, driving blast furnace Tellows, grinding ores, making paper, polishing stone, pressing oil, producing salt, producing textiles, and sawing wood. It is conventional to define the industrial Revolution arbitrarily as beginning with the harnessing of steam power in 18th-century England, but in fact an industrial revolution based on water and wind power had begun already in medieval times in many parts of Europe. As of 1492, all of those operations to which animal, water, and wind power were being applied in Eurasia were still being carried out by human muscle power in the Americas.
Lone before the wheel began to be used in power conversion in Eurasia, it had become the basis of most Eurasian land transport—not only for animal-drawn vehicles but also for human-powered wheelbarrows, which enabled one or more people, still using just human muscle power, to transport much greater weights than they could have otherwise. Wheels were also adopted in Eurasian pottery making and in clocks. None of those uses of the wheel was adopted in the Americas, where wheels are attested only in Mexican ceramic toys.
The remaining area of technology to be mentioned is sea transport. Many Eurasian societies developed large sailing ships, some of them capable of sailing against the wind and crossing the ocean, equipped with sextants, magnetic compasses, sternpost rudders, and cannons. In capacity, speed, maneuverability, and seaworthiness, those Eurasian ships were far superior to the rafts that carried out trade between the New World's most advanced societies, those of the Andes and Mesoamerica. Those rafts sailed with the wind along the Pacific coast. Pizarro's ship easily ran down and captured such a raft on his first voyage toward Peru.
inaddition to their germs and technology, Eurasian and Native American societies differed in their political organization. By late medieval or Renaissance times, most of Eurasia had come under the rule of organized states. Among these, the Habsburg, Ottoman, and Chinese states, the Mogul state of India, and the Mongol state at its peak in the 13th century started out as large polyglot amalgamations formed by the conquest of other states. For that reason they are generally referred to as empires. Many Eurasian states and empires had official religions that con-»• uted to state cohesion, being invoked to legitimize the political leader-s »P and to sanction wars against other peoples. Tribal and band societies