Cross-System Co-occurrence of Hot-Cold Direction in Medicinal Plants

Abstract Results of 81 multi-system anchors, 68 were concordant and 13 divergent, a multi-system concordance rate of 84.0% (binomial p = 3.81 × 10⁻¹⁰); excluding one species substitution (Gentiana) gives 85.0%, and excluding 19 neutral anchors gives 82.3%, so the conclusion is robust. To assess historical transmission, we recomputed by origin cluster: merging Unani with Galenic yields seven clusters, concordance 85.9% (55/64); restricting to the four relatively independent clusters (TCM, Ayurveda, African, Andean) yields 90.2% (46/51). We state plainly, however, that this conservative estimate rests mainly on TCM and Ayurveda, which did historically exchange; current data cannot exclude transmission and can only establish strong cross-system co-occurrence of direction. Same-species agreement between TCM and Ayurveda: dichotomous κ = 0.841 (n = 50), three-class κ = 0.681 (n = 56), both far above chance. Most mechanistically suggestive is that independent Mexican and Andean ethnographies also encode hot-cold through water and habitat. In the kinship-controlled analysis, all four testable genera showed the expected soil-moisture direction, but with only four independent units (genera) the genus-level sign test gives p = 0.0625, which has no power to adjudicate significance; this is exploratory directional support, not confirmation. Exceptions that a single variable cannot explain also exist, such as Panax ginseng versus P. quinquefolius. A distinction must also be drawn between a plant's water demand and the wetness of its habitat: for cultivated crops the two are not equivalent. Our conclusion is cross-system co-occurrence and external corroboration of direction, not causal proof; disagreements and limitations are reported as they stand.