DIFFUSION AND ADOPTION OF CROPS IN EVOLUTIONARY PERSPECTIVE

Optimization models developed within evolutionary ecology provide a us eful framework for analyzing patterns of acceptance and utilization of new crops by food-producing populations. The deterministic version of the diet choice model predicts that new crops of relatively low profi tability are likely to enter the diet if highly ranked resources are i n short supply, but will be ignored if such items are abundant. A stoc hastic version of the same model (the ''z score'' model) predicts adop tion when the chance of energetic shortfall is very low and addition o f new foods (even if they are of poor quality) may minimize risk by re ducing variance in yields. Similar environments may consequently elici t strikingly different responses to new resources depending on which g oal (e.g., risk minimization or efficiency maximization) guides decisi on-making. A case study, the introduction of the peach to eastern Nort h America, illustrates how these models might be enlisted to develop a nd evaluate adaptation-based explanations of crop adoption. The opport unity cost model is used to predict optimal time allocation to differe nt tasks as a function of the relationship between rising opportunity costs and diminishing returns. Manipulation of the model suggests that high opportunity costs may have limited investment in maize productio n following the initial introduction of this crop to eastern North Ame rica. Both increased productivity of maize and improvement in labor ef ficiency are likely causes of its eventual establishment as an economi c staple. These findings illustrate the heuristic value of evolutionar y ecology models as tools for investigating the origins and developmen t of agricultural systems, including the diffusion of specific crops. (C) 1996 Academic Press, Inc.