For most of the twentieth century, writing about ritual plant use in South America concentrated on the visionary substances: ayahuasca, yopo, San Pedro, the Amanita speculations. Tobacco was treated as background, a familiar thing that everyone had and that therefore explained nothing.
Johannes Wilbert's 1987 survey put the case that this was backwards. Working across the continent, he found tobacco in use among an extraordinary range of peoples, by more methods and in more contexts than any of the more celebrated plants, and argued that it is the single most widespread shamanic plant in South America. The argument reframed the field, and it did so without any new discovery, simply by counting what was already in the literature.
The practical consequence for an atlas is that tobacco has to be treated as a religious material in its own right rather than as a habit that happens to appear near religious materials. In the western Amazon today mapacho is bound up with ayahuasca practice, used to open and close a session and to work on a person during it, and it travels internationally with that practice. It is now sold worldwide, which puts it in the same position as several other objects in this region: a thing with a long and specific local history that is also, now, a commodity.