Foraging remained the basic way of life for most of human history, and for groups living in extreme environments, such as tundras or deserts, it was the only possible way to survive. In a few especially fertile areas, however, the natural environment provided enough food that people could become more settled. About 15,000 years ago, the earth’s climate entered a warming phase, and more parts of the world were able to support sedentary or semi-sedentary groups of foragers. In several of these places, foragers began planting seeds in the ground along with gathering wild grains, roots, and other foodstuffs. By observation, they learned the optimum times and places for planting. They removed unwanted plants through weeding and selected the seeds they planted in order to get crops that had favorable characteristics, such as larger edible parts. Through this human intervention, certain crops became domesticated, that is, modified by selective breeding so as to serve human needs.

Intentional crop planting first developed around 9000 B.C.E., in the area archaeologists call the Fertile Crescent, which runs from present-day Lebanon, Israel, and Jordan north to Turkey and then south and east to the Iran-Iraq border. In this area of mild climate, wild barley and wheat were abundant, along with fruit and nut trees, migrating ducks, and herds of gazelles and other animals. Over the next two millennia, intentional crop planting emerged for the most part independently in the Nile River Valley, western Africa, China, India, Papua New Guinea, Mesoamerica, and perhaps other places where the archaeological evidence has not survived.

Why, after living successfully as foragers for tens of thousands of years, did humans in so many parts of the world begin raising crops at about the same time? The answer to this question is not clear, but crop raising may have resulted from population pressures in those parts of the world where the warming climate provided more food through foraging. More food meant lower child mortality and longer life spans, which allowed populations to grow. People then had a choice: they could move to a new area — the solution that people had always relied on when faced with the problem of food scarcity — or they could develop ways to increase the food supply. They chose the latter and began to plant more intensively, beginning cycles of expanding population and intensification of land use that have continued to today.

A very recent archaeological find at Göbekli Tepe in present-day Turkey, at the northern edge of the Fertile Crescent, suggests that cultural factors may have played a role in the development of agriculture. Here, around 9000 B.C.E., hundreds of people came together to build rings of massive, multiton elaborately carved limestone pillars, and then covered them with dirt and built more. The people who created this site lived some distance away, where archaeological remains indicate that at the time they first carved the pillars, they ate wild game and plants, not crops. We can only speculate about why so many people expended the effort they did to carve these pillars and raise them into place, but the project may have unintentionally spurred the development of new methods of food production that would allow the many workers to be fed efficiently. Indeed, it is very near here that evidence of the world’s oldest domesticated wheat has been discovered. Archaeologists speculate that, at least in this case, the symbolic, cultural, or perhaps religious importance of the structure can help explain why the people building it changed from foraging to agriculture.