The Transition to Agriculture: Climate Reversals, Population Density, and Technical Change

Until about 13,000 years ago all humans obtained their food through hunting and gathering, but thereafter people in some parts of the world began a transition to agriculture. Recent data strongly implicate climate change as the driving force behind the transition in southwest Asia. We propose a model of this process in which population and technology respond endogenously to climate. After a period of favorable environmental conditions during which regional population grew, an abrupt climate reversal forced people to take refuge at a few favored sites. The resulting spike in local population density reduced the marginal product of labor in foraging and made agriculture attractive. Once agriculture was initiated, rapid technological progress through artificial selection led to domesticated plants. Farming became a permanent part of the regional economy when this productivity growth was combined with climate recovery. The available data on cases of transition and non-transition are consistent with this model but are often inconsistent with rival explanations.