A The development of agriculture — the deliberate cultivation of plants and the domestication of animals for food, fibre, and labour — is conventionally described as the most important revolution in human history, a transformation that enabled the growth of large sedentary populations, the accumulation of material surplus, the development of specialised occupations, and the construction of the political, religious, and economic institutions that define civilisation. The transition from foraging to farming, which began independently in at least eight or nine regions of the world between approximately 12,000 and 4,000 years ago, set human societies on a trajectory that eventually produced the globalised, technologically complex world of the present.
B Yet the conventional narrative of the agricultural revolution — in which the discovery of farming was quickly recognised as superior to foraging and enthusiastically adopted by hunter-gatherer populations who immediately benefited from its productivity — is not well supported by the archaeological and skeletal evidence. The transition to agriculture was slow, often spanning centuries or millennia, and frequently reversed when conditions changed. The skeletal remains of early farmers show clear signs of nutritional stress that are less prevalent in their forager predecessors: shorter stature, higher rates of dental caries, evidence of iron deficiency anaemia, and greater frequency of infectious disease consistent with living in closer proximity to other people and to domestic animals. Early farmers appear, by these measures, to have been less healthy and less well-nourished than the foragers who preceded them.
C Why, then, did agriculture spread? Several mechanisms have been proposed. One is demographic: farming, by enabling higher population densities, eventually produced populations large enough to displace or absorb lower-density foraging populations, regardless of whether the individuals involved were better or worse off. A second is the ratchet effect of investment: once communities had invested in the clearing of land, the storage of seed, and the construction of permanent settlements, reverting to foraging became progressively less attractive, since the infrastructure of farming, once built, imposed its own logic. A third mechanism involves social and political change: the accumulation of agricultural surplus enabled the emergence of social hierarchies in which elites controlled food stores, and this political power created incentives to expand production that had nothing to do with the nutritional interests of ordinary farmers.
D The suite of crops and animals that were domesticated in each centre of agricultural origin reflects both the ecological resources available and the specific human uses to which they were put. The founder crops of the Near Eastern agricultural tradition — emmer wheat, einkorn wheat, barley, lentils, peas, chickpeas, bitter vetch, and flax — were all species whose seeds could be stored without special treatment and whose annual reproductive cycle was suited to the agricultural calendar. The domestication of cattle, sheep, goats, and pigs in the Near East and of water buffalo, chickens, and pigs independently in South and East Asia provided draft power, secondary products including milk, wool, and eggs, and dietary protein in addition to meat.
E The Green Revolution of the twentieth century — the introduction of high-yield cereal varieties, synthetic fertilisers, pesticides, and irrigation technology across the developing world from the 1960s onwards — represents the most recent episode in the long history of agricultural transformation. Within two decades of the introduction of high-yield wheat and rice varieties developed by Norman Borlaug and others, grain production in South Asia and Latin America had increased dramatically, averting the widespread famine that demographers had projected as inevitable given population growth. The Green Revolution's success in preventing famine has to be set against its costs: dependence on external inputs, the displacement of traditional crop diversity, soil degradation from intensive tillage and fertiliser use, and the widening of income disparities within farming communities as wealthier farmers were better positioned to invest in the new technologies.
F The history of agriculture is, in one sense, the history of humanity's ongoing negotiation with the ecological systems on which food production depends. Every major agricultural transformation — the shift from foraging to cultivation, the integration of draft animals, the development of irrigation, the mechanisation of the industrial era, the Green Revolution — has resolved some constraints while creating new ones, and has produced unforeseen consequences that only become apparent over timescales that exceed those of any individual farmer, policymaker, or generation of researchers. The challenges of producing food for a growing global population while reducing agriculture's environmental footprint may require yet another transformation whose character and consequences we can only partially anticipate.