Guns, Germs & Steel

World was constricted over the whole length of Central America and especially at Panama. Not least, the Americas were more fragmented by areas unsuitable for food production or for dense human populations. These ecological barriers included the rain forests of the Panamanian isthmus separating Mesoamerican societies from Andean and Amazonian societies; the deserts of northern Mexico separating Mesoamerica from U.S. southwestern and southeastern societies; dry areas of Texas separating the U.S. Southwest from the Southeast; and the deserts and high mountains fencing off U.S. Pacific coast areas that would otherwise have been suitable for food production. As a result, there was no diffusion of domestic animals, writing, or political entities, and limited or slow diffusion of crops and technology, between the New World centers of Mesoamerica, the eastern United States, and the Andes and Amazonia.
Some specific consequences of these barriers within the Americas

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deserve mention. Food production never diffused from the U.S. Southwest and Mississippi Valley to the modern American breadbaskets of California and Oregon, where Native American societies remained hunter-gatherers merely because they lacked appropriate domesticates. The llama, guinea pig, and potato of the Andean highlands never reached the Mexican highlands, so Mesoamerica and North America remained without domestic mammals except for dogs. Conversely, the domestic sunflower of the eastern United States never reached Mesoamerica, and the domestic turkey of Mesoamerica never made it to South America or the eastern United States. Mesoamerican corn and beans took 3,000 and 4,000 years, respectively, to cover the 700 miles from Mexico's farmlands to the eastern U.S. farmlands. After corn's arrival in the eastern United States, seven centuries more passed before the development of a corn variety productive in North American climates triggered the Mississippian emergence. Corn, beans, and squash may have taken several thousand years to spread from Mesoamerica to the U.S. Southwest. While Fertile Crescent crops spread west and east sufficiently fast to preempt independent domestication of the same species or else domestication of closely related species elsewhere, the barriers within the Americas gave rise to many such parallel domestications of crops.
As striking as these effects of barriers on crop and livestock diffusion are the effects on other features of human societies. Alphabets of ultimately eastern Mediterranean origin spread throughout all complex societies of Eurasia, from England to Indonesia, except for areas of East Asia where derivatives of the Chinese writing system took hold. In contrast, the New World's sole writing systems, those of Mesoamerica, never spread to the complex Andean and eastern U.S. societies that might have adopted them. The wheels invented in Mesoamerica as parts of toys never met the llamas domesticated in the Andes, to generate wheeled transport for the New World. From east to west in the Old World, the Macedonian Empire and the Roman Empire both spanned 3,000 miles, the Mongol Empire 6,000 miles. But the empires and states of Mesoamerica had no political relations with, and apparently never even heard of, the chiefdoms of the eastern United States 700 miles to the north or the empires and states of the Andes 1,200 miles to the south.
The greater geographic fragmentation of the Americas compared with Eurasia is also reflected in distributions of languages. Linguists agree in grouping all but a few Eurasian languages into about a dozen language

368' GUNS, GERMS, AND STEEL
families, each consisting of up to several hundred related languages. For example, the Indo-European language family, which includes English as well as French, Russian, Greek, and Hindi, comprises about 144 languages. Quite a few of those families occupy large contiguous areas—in the case of Indo-European, the area encompassing most of Europe east through much of western Asia to India. Linguistic, historical, and archaeological evidence combines to make clear that each of these large, contiguous distributions stems from a historical expansion of an ancestral language, followed by subsequent local linguistic differentiation to form a family of related languages (Table 18.2). Most such expansions appear to be attributable to the advantages that speakers of the ancestral language, belonging to food-producing societies, held over hunter- gatherers. We already discussed such historical expansions in Chapters 16 and 17 for the Sino-Tibetan, Austronesian, and other East Asian language families. Among major expansions of the last millennium are those that carried Indo-European languages from Europe to the Americas and Australia, the Russian language from eastern Europe across Siberia, and Turkish (a language of the Altaic family) from Central Asia westward to Turkey.
With the exception of the Eskimo-Aleut language family of the American Arctic and the Na-Dene language family of Alaska, northwestern Canada, and the U.S. Southwest, the Americas lack examples of large-scale language expansions widely accepted by linguists. Most linguists specializing in Native American languages do not discern large, clear-cut groupings other than Eskimo-Aleut and Na-Dene. At most, they consider the evidence sufficient only to group other Native American languages (variously estimated to number from 600 to 2,000) into a hundred or more language groups or isolated languages. A controversial minority view is that of the linguist Joseph Greenberg, who groups all Native American languages other than Eskimo-Aleut and Na-Dene languages into a single large family, termed Amerind, with about a dozen subfamilies.
Some of Greenberg's subfamilies, and some groupings recognized by more-traditional linguists, may turn out to be legacies of New World population expansions driven in part by food production. These legacies may include the Uto-Aztecan languages of Mesoamerica and the western United States, the Oto-Manguean languages of Mesoamerica, the Natchez-Muskogean languages of the U.S. Southeast, and the Arawak languages of the West Indies. But the difficulties that linguists have in agreeing

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table 18.2 Language Expansions in the Old World
Language
Inferred Family Ultimate
Date or Language Expansion Driving Force
6000 or 4000 B.C. Indo-European Ukraine or Ana– food production
tolia –* Europe, or horse-based
C. Asia, India pastoralism
6000 B.C.-2000 b.c. Elamo-Dravid– Iran-*India food production
ian 4000 B.c.-present Sino-Tibetan Tibetan Plateau, food production
N. China-*
S. China,
tropical S.E.
Asia 3000 B.C.-1000 b.c. Austronesian S. China-»Indo– food production
nesia, Pacific
islands
3000 b.c.-a.d. 1000 Bantu Nigeria and food production
Cameroon

-*S. Africa

3000 b.c.-a.d. 1 Austroasiatic S. China-*tropi– food production
cal S.E. Asia,
India