There is no single explanation for how Native Americans or others learned the medicinal values of plants. But at least one category of biologically active plants comprises those that have produced substances to protect themselves from browsing. Clearly the effectiveness of such protections would be enhanced if the plants could somehow signal, and browsers could somehow detect, their presence -- perhaps through a distinctive odor or taste -- before too much was eaten.
It seems likely that people have used these same signals as evidence of potentially valuable medicines and, over millenia, human knowledge of the subject accumulated. "Knowledge" is a complex phenomenon with both historical and cultural dimensions: "In their practical projects and social arrangements, informed by the received meanings of persons and things, people submit . . . cultural categories to empirical risks" ( Sahlins 1985:ix). In the process, the explanations for things may change; but a kernel of truth, a sort of natural object (e.g., Sambucus heals sores) may remain, even though it may be accounted for in a multitude of ways. The initial experiments by which this natural object became "known" need not have been repeated many times; things only have to be learned once. The same may be true for Pyrus and Prunus and perhaps even for sweet grass.
The database MPNA was produced with the support of the National Endowment for the Humanities, grant number RT-20408-04. The current paper was written with support from the National Science Foundation, grant number BNS-8704103. Stanwyn Shelter of the Smithsonian Institution Museum of Natural History provided the computer tape with the indispensable Flora North America data. Special thanks to Barry Bogin, Katie Anderson-Levitt, Charlotte Gyllenhaal, and Sally Horvath for providing extremely helpful criticisms of earlier drafts of this chapter. The University of Michigan-Dearborn has supported me in uncounted ways for over a decade.
Bodin F., and C. F. Cheinisse. 1970. Poisons. Trans. H. Oldroyd. New York: McGraw-Hill.