The Origins of Agriculture. The great ice sheets that covered much of the northern hemisphere for more than one hundred thousand years during the last Ice Age reached their greatest extent about twenty thousand years ago, whereupon they slowly began to recede. Some fourteen thousand years ago, the pace of the melting quickened, causing widespread and rapid changes in local climatic conditions as large-scale climatic zones shifted and reformed. Scattered bands of humans who subsisted by hunting and gathering found it necessary either to adapt themselves to new local environmental conditions or to move in search of an environment with a flora and fauna on which they could more readily subsist. Some thirteen thousand years ago a new culture, termed Natufian, emerged in the Mediterranean Levant—an area stretching from modernday southern Israel northward across western Syria into the foothills of the Taurus Mountains in southern Anatolia...