This new way of life initially operated everywhere with a simple technology — the digging stick or hoe. Plows were developed much later. But the several transitions to this hoe-based agriculture, commonly known as horticulture, varied considerably, depending on what plants and animals were available locally. For example, potatoes were found in the Andes region, but not in Africa or Asia; wheat and wild pigs existed in the Fertile Crescent, but not in the Americas. Furthermore, of the world’s 200,000 plant species, only several hundred have been domesticated, and in more recent centuries just five of these — wheat, corn, rice, barley, and sorghum — have supplied more than half of the calories that sustain human life. Only fourteen species of large mammals have been successfully domesticated, of which sheep, pigs, goats, cattle, and horses have been the most important. Because they are stubborn, nervous, solitary, or finicky, many animals simply cannot be readily domesticated. Thus the kind of Agricultural Revolution that unfolded in particular places depended very much on what happened to be available locally; in short, it depended on sheer luck.

Among the most favored areas — and the first to experience a full Agricultural Revolution — was the Fertile Crescent, an area sometimes known as Southwest Asia, consisting of present-day Iraq, Syria, Israel/Palestine, Jordan, and southern Turkey (see Map 1.4). In this region, an extraordinary variety of wild plants and animals capable of domestication provided a rich array of species on which the now largely settled gathering and hunting people could draw. What triggered the transition to agriculture remains a much-debated question. Some have argued that a cold and dry spell between 11,000 and 9500 B.C.E., a very rapid but temporary interruption in the general process of global warming, was the stimulus for the transition to farming. Larger settled populations, now threatened with the loss of the wild plants and animals on which they had come to depend, found a solution in domestication, either during or soon after this cold and dry period passed. Figs were apparently the first cultivated crop, dating to about 9400 B.C.E. In the millennium or so that followed, wheat, barley, rye, peas, lentils, sheep, goats, pigs, and cattle all came under human control, providing the foundation for the world’s first agricultural societies.

Archeological evidence suggests that the transition to a fully agricultural way of life in parts of this region took place quite quickly, within as few as 500 years. Signs of that transformation included large increases in the size of settlements, which now housed as many as several thousand people. In these agricultural settings, archeologists have found major innovations: the use of sun-dried mud bricks; the appearance of monuments or shrine-like buildings; displays of cattle skulls; more elaborate human burials, including the removal of the skull; and more sophisticated tools, such as sickles, polished axes, and awls. From this point on, global climate remained remarkably stable, when compared to sharp variations of earlier times, which proved to be a great advantage for settled life and agricultural development.

At roughly the same time, or perhaps a bit later, another process of domestication was unfolding on the African continent in the eastern part of what is now the Sahara in present-day Sudan. Between 10,000 and 5,000 years ago, scholars tell us that there was no desert in this region, which received more rainfall than currently, had extensive grassland vegetation, and was “relatively hospitable to human life.”12 It seems likely that cattle were domesticated in this region about 1,000 years before they were separately brought under human control in the Middle East and India. At about the same time, the donkey was also domesticated in northeastern Africa near the Red Sea and spread from there into Southwest Asia, even as the practice of raising sheep and goats moved in the other direction. In terms of farming, the African pattern again was somewhat different. Unlike the Fertile Crescent, where a number of plants were domesticated in a small area, sub-Saharan Africa witnessed the emergence of several widely scattered farming practices. Sorghum, which grows well in arid conditions, was the first grain to be “tamed” in the eastern Sahara region. In the highlands of Ethiopia, teff, a tiny, highly nutritious grain, as well as enset, a relative of the banana, came under cultivation. In the forested region of West Africa, yams, oil palm trees, okra, and the kola nut (used as a flavoring for cola drinks) emerged as important crops. The scattered location of these domestications generated a less productive agriculture than in the more favored and compact Fertile Crescent, but a number of African domesticates — sorghum, castor beans, gourds, millet, the donkey — subsequently spread to enrich the agricultural practices of Eurasian peoples.

Yet another pattern of agricultural development took shape in the Americas. Like the Agricultural Revolution in Africa, the domestication of plants in the Americas occurred separately in a number of locations — in the coastal Andean regions of western South America, in Mesoamerica, in the Mississippi River valley, and perhaps in the Amazon basin. Surely the most distinctive common feature of these regions was the relative absence of animals that could be domesticated. Of the fourteen major species of large mammals that have been brought under human control, just two, the llama and alpaca, existed in the Western Hemisphere, and only in the Andes region, where they proved enormously useful for food, fiber, and transportation. Without goats, sheep, pigs, cattle, or horses, the peoples of the Americas lacked sources of protein, manure (for fertilizer), and power (to draw plows or pull carts, for example) that were widely available to societies in the Afro-Eurasian world. Because they could not depend on domesticated animals for meat, many agricultural peoples in the Americas relied more on hunting and fishing than did peoples in the Eastern Hemisphere. Europe too lacked most of the animals that could be readily domesticated, but it was geographically closer to areas that had them and so could borrow from neighboring regions. Farmers in the Americas could not.

While the Americas lacked the cereal grains that were widely available in Afro-Eurasia, they had maize or corn, first domesticated in southern Mexico by 4000 to 3000 B.C.E. Unlike the cereal grains of the Fertile Crescent, which closely resemble their wild predecessors, the ancestor of corn, a mountain grass called teosinte (tee-uh-SIHN-tee), looks nothing like what we now know as corn or maize. Thousands of years of selective adaptation were required to develop a sufficiently large cob and number of kernels to sustain a productive agriculture, an achievement that one geneticist has called “arguably man’s first, and perhaps his greatest, feat of genetic engineering.”13 Thus while Middle Eastern societies quite rapidly replaced their gathering and hunting economy with agriculture, that process took several thousand years in Mesoamerica. Beyond maize, Native American farmers domesticated squash, beans, potatoes, sunflowers, quinoa, pigweed, and goosefoot, which were harvested on a large scale.

Another difference in the unfolding of the Agricultural Revolution lay in the north/south orientation of the Americas, which required agricultural practices to move through, and adapt to, quite distinct climatic and vegetation zones if they were to spread. The east/west axis of North Africa / Eurasia meant that agricultural innovations could spread more rapidly because they were entering roughly similar environments. Thus corn, beans, and squash, which were first domesticated in Mesoamerica, took several thousand years to travel the few hundred miles from their Mexican homeland to the southwestern United States and another thousand years or more to arrive in eastern North America. The llama, guinea pig, quinoa, and potato, which were domesticated in the Andean highlands, never reached Mesoamerica.