The Non-Random Selection of Medicinal Plants Theory: a Case Study of a Kichwa Community in the Ecuadorian Amazon

The non-random selection of medicinal plants theory, which states that
phylogeny affects the selection of medicinal plants, was proposed by Daniel Moerman
to indirectly prove that traditional medicinal systems are rational and based in part by
the therapeutic efficacy of plants. The logic of this theory is that because members of
a taxonomical group share similar characteristics, some groups will be more
medicinal and will be over-used in pharmacopoeias, while other groups bereft of
secondary metabolites and therapeutic potential will be under-used medicinally. To
test this theory, Moerman linearly regressed the total number of medicinal plants per
family against the total number of plants per family present in an area and examined
residual values to find over-used and under-used medicinal plant families. The
method has been praised for its simplicity. Nonetheless, shortcomings have been
noted and criticized, inspiring researchers to propose new procedures to test for
phylogenetic biases in pharmacopoeias. Negative Binomial regression and
examination of studentized residuals, the method used in this investigation,
ameliorates the original one with a few corrections, conserving the simplicity and solving for all the criticized flaws. Also, this study incorporated different
sociodemographic factors to determine if the intracultural homogeneity of traditional
knowledge affects the results of the non-random selection of medicinal plants theory
analysis. By testing Moerman’s theory, which is one of Ethnobotany’s major theories,
this investigation is in agreement with the call to have more hypothesis-driven
research within a theoretical framework to continue to advance the Ethnobotany field.