Symbols and selectivity: a statistical analysis of native American medical ethnobotany.

Native Americans use a wide range of plants medicinally. Many of these plants have profound meaning to their users. Does this mean, as some assert, that tribal medicine is "all placebo"? Since the essential character of meaning is the arbitrariness of the sign, then insofar as this medicine is symbolic, the plants used medicinally will be a random representation of plants available in nature. Several regression analyses of plants used by native Americans on plants available to them indicate substantial selectivity in plant use. Native American medical ethnobotany is not only placebo medicine.