The combination of chacruna and the ayahuasca vine is cited constantly as proof of deep Amazonian pharmacological knowledge, and it is worth being careful about exactly what it demonstrates.
What it clearly shows is a working understanding of synergy: that two substances together can do what neither does alone. That is not a trivial idea and it was not general knowledge in European medicine until far later. The specific pairing is also not an accident of proximity, since the two plants are prepared differently, look nothing alike and belong to unrelated families.
What it does not show is knowledge of enzymes, receptors or alkaloids, and accounts that imply otherwise are projecting a modern frame backwards. The traditional explanation is not chemical at all. It is that the plants are persons who communicate, and that the knowledge was given rather than deduced. Treating that as a charming way of describing empirical trial and error is a translation the traditions themselves do not accept.
There is a third position worth stating plainly, which is that nobody knows. The Amazon holds an enormous number of species, the practice is old, the record is oral, and the honest answer to how the pairing was discovered is that the evidence to settle it does not exist. The atlas records that as an open question rather than choosing the version that reads best.