Climate reversals and the transition to agriculture

Abstract

Abstract. 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 cultivation attractive. Once cultivation began, technological progress, including artificial selection, eventually led to domesticated plants. Farming became a permanent part of the regional economy when productivity growth was combined with climate recovery. The available data on cases of transition and non-transition are consistent with this model but often inconsistent with rival explanations. 1 Acknowledgment.

Humans copy rapidly increasing choices in a multiarmed bandit problem

“…In realms of human social learning such as the adoption of farming technologies and crops, hunting equipment, or symbolic traits, changes in trait frequency over time will be visible and thus a possible cue for adoption (Dow, Reed, & Olewiler, 2009;Mesoudi & O'Brien, 2008;Rogers & Ehrlich, 2008;Rogers, 1995). Like conformist transmission, a copy-increasing strategy will result in accelerating rate of adoption over time.…”

“…Instead, a mix of strategies that can change over time, including individual assessment of trait outcomes, will determine the outcome of such processes. Identifying different learning and assessment strategies and the circumstances under which they are employed, and integrating these findings with other factors such as motivation, ecology, and demography, will be crucial for our understanding of cumulative cultural evolution (Dow et al, 2009;Kirby, Cornish & Smith, 2008;Powell, Shennan & Thomas, 2009). …”

The Climatic Origins of the Neolithic Revolution: Theory and Evidence

“…In taking the position that environmentally triggered population pressure was crucial for the transition to agriculture, this study is related to recent work by Dow et al (2009). According to their analysis, an abrupt climatic reversal (the Younger Dryas) forced migration into a few ecologically favorable locations.…”

“…Thus, huntergatherer economies in relatively stable environments may not experience pristine agricultural transitions. This prediction appears to be the case for cultures in the Amazon, Australia, and Southeast Asia, where, arguably, the tropical environment protected these cultures from major climatic ‡uctuations (Higham, 1995;Dow et al, 2009). Notably, the case of the emergence of agriculture in Highland New Guinea and not in the tropical Lowland, despite common access to similar endowments, is the prime example of a di¤erential transition driven purely by di¤erences in the degree of climatic ‡uctuations.…”

Transition to farming more likely for small, conservative groups with property rights, but increased productivity is not essential

“…In this context, computational models can be helpful in exploring the ecological and social conditions necessary for the transition to agriculture. There are many examples of such models [e.g., 13,[15][16][17][18][19][20][21][22]; also the modeling review by Baker et al (23) and discussion of modeling approaches by Gerbault et al (24)], which, together, have explored most of the major hypotheses for the origins of agriculture (most notably, climate and population pressure).…”