Beasts of the Earth: Animals, Humans, and Disease

Chapter Four: Humans as Farmers: Microbes Move into the Home

= 3 3 4= C H A P T E R Humans as Farmers Microbes Move into the Home Directly or indirectly, every creature survives at some expense to others. It stays alive only if it creates proteins; to do so, it must take in proteins or the amino acids from which proteins are built. The ways one creature makes another’s protein its own range from predation to parasitism, but all are paths to the same end. Arno Karlen, Man and Microbes Nobody fully understands why humans domesticated crops and farm animals when they did. Changes in climate are only part of the explanation. Perhaps the continuing evolution of the human brain also played a role, allowing people to plan ahead and work together in ways that had not previously been possible. Whatever the reasons, the Neolithic revolution, as it is commonly called, changed the relationship between humans and other animals more profoundly than any other event in history. By the beginning of the Neolithic period, hominids had spread broadly across the earth. They migrated from Africa into the Middle East and Asia approximately 1.7 million years ago and into Europe by 1 million years ago.1 Homo sapiens, the only species of Homo that survived and that from which modern humans descend, spread widely around the earth beginning approximately one hundred thousand years ago and by the Neolithic period had reached Australia and South America. Whereas the total hominid population of eastern Africa had probably been no more than fifty thousand individuals before they began dispersing, by the Neolithic period the widely scattered humans numbered approximately five million.2 The climate in many areas of the earth became more hospitable to agriR3186 .indb 33 R3186.indb 33 11/3/04 6:44:19 AM 11/3/04 6:44:19 AM 3 4 = B e a s t s o f t h e E a r t h culture as the glaciers started to recede approximately fifteen thousand years ago. As the earth slowly warmed, grasslands and forests increasingly replaced the tundra across much of Europe, the Middle East, and Asia. One area especially rich in agricultural potential was the Fertile Crescent, which stretches for almost one thousand miles from what are now Israel and Palestine through Lebanon, Jordan, Syria, and southeastern Turkey into Iraq and Iran. Growing wild in the Neolithic grasslands of the Fertile Crescent were ancestor grasses of wheat, barley, rye, lentils, and chick-peas.3 According to Steve Olson in Mapping Human History: “Of the fifty-six grasses with the largest seeds, thirty-two grow in the Middle East, including wheat and barley. No other part of the world has more than a few such plants.”4 The upper reaches of the Tigris and Euphrates rivers, which cover part of northern Iraq and southeastern Turkey, were especially rich in the Neolithic founder crops and have been called “the cradle of agriculture.”5 There is evidence that agriculture developed independently in other areas of the world as well, including Southeast Asia, northern China, Africa, Papua New Guinea, Mexico, and Peru. The Fertile Crescent, however, was unique in having a wide variety of cultivatable plants, as well as wild olives, figs, grapes, dates, and apples.6 Agriculture, of course, did not develop at a single site or at a single time. Over hundreds, perhaps thousands, of years, humans picked the wild plants, harvested the edible parts, and discarded the seeds nearby. Inevitably some of the seeds grew into new plants. The cereal grains were ground, baked, and mixed with water to make an edible gruel. When gruel is allowed to stand, it uses bacteria to ferment and change into a type of beer. This development almost certainly added both impetus and enthusiasm to the agricultural revolution. Neolithic people valued most the foods that they could store and that were good sources of calories—cereals such as wheat, barley, millet, rye, corn, and rice, as well as tubers such as potatoes, yams, and manioc (cassava).7 Once a plant became well established as a source of food among one group of Neolithic farmers, its use spread to other parts of the world. The use of increasingly sophisticated tools also encouraged the development and spread of agriculture during the Neolithic period. Recent experiments using a flint-bladed sickle demonstrate that one person could gather enough wild wheat in one hour to produce a kilo of grain. Experiments with a polished stone axe head report that “three men...