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were selected for characteristics according to how well they fit the evolving values, knowledge, social organization, and technologies of the local people. At the same time, each of these components of the social system was also evolving under the selective pressure of how well it fit the evolving ecological system and the other social components. Local knowledge, embedded in myths and traditions, was correct, for it had proven fit and through selective evolutionary pressure, had become consistent with the components of social and ecological systems it explained (Norgaard, 1984).
Within the coevolving mosaic, the boundaries of each area were not distinct or fixed. Myths, values, social organization, technologies, and species spilled over the boundaries of the areas of the mosaic within which they initially coevolved to become exotics in other areas. Some of these exotics were preadapted and thrived; some coevolved; and some died out. But to some extent they all influenced the further coevolution of system characteristics in their new areas. Because of the many combinations of spillovers, the pattern of coevolving species, myths, organization, and technology remained patchy and constantly changing.
Tattered remnants of coevolutionary agricultural development remain today to give us clues to the past. A few agricultural scientists during the past decade have followed the path of anthropologists and discovered a wide array of traditional agroecosystems (Altieri and Letourneau, 1982; Chacon and Gliessman, 1982; Gliessman et al., 1981). In nearly all these systems, farmers deliberately intermix many crop and noncrop species and occasionally animal species. These agroecosystems coevolved with the values, beliefs about nature, technologies, and social organization of indigenous peoples over centuries, sometimes millennia. Farmers selected for adequate and stable rates of food production through as much of the growing season as possible. A dependable food supply was achieved in part by planting many different crops in different places at different times such that average production from year to year varied little because of the law of large numbers (Richards, 1985).
The increased interest in agroecology coincides with an increased recognition of people as biological participants. Whereas natural historians have consistently portrayed the influence of humans as destructive of natural systems, we are now beginning to learn how traditional people at low population densities were less destructive and under some circumstances contributed to the growth of genetic diversity (Alcorn, 1984; Altieri and Merrick, 1987; Brush, 1982). There traditional people created environments within which plants and microorganisms coevolved under selective pressures that were different from those that occur in environments only marginally disturbed by people. Environmental uniformity was not imposed; farmers developed different approaches to agriculture for different microenvironments, adding to variation in selective pressure (Richards, 1985).
Recent development has been distinctly different from the coevolving mosaic of the past. The mechanistic grid of universal truths developed by Western science has boldly overlaid and simplified most of the elaborate coevolutionary mosaic. The global adoption of Western knowledge and technologies has set disparate cultures on convergent paths. And the environment has not been immune to this globally unifying process. Environments are also merging due to the common