Abstract: Large Low Shear Velocity Provinces (LLSVPs) at the base of the mantle remain enigmatic structures whose origin—thermal versus chemical—has long been debated. Focusing on the Perm Anomaly beneath Eurasia, we synthesize seismic observations of D'' layer thickness variations associated with the post-perovskite phase transition to address this question. The data reveal a pronounced north–south temperature gradient along the anomaly’s eastern boundary: cooler conditions with increased D'' thickness in the north, and hotter conditions with reduced thickness in the south. This spatial pattern, correlated with distance from the anomaly, is most consistent with a dominantly thermal origin. The possibility that the Perm Anomaly derived from the African LLSVP further underscores its broader significance for understanding the genesis and evolution of the two major mantle provinces. Taken together, these insights highlight the central role of thermal processes in shaping the structure and persistence of LLSVPs. Future progress will require integrated efforts across mineral physics, seismology, geodynamics, geochemistry, and data science, with particular attention to the combined influence of heat and water on Earth’s deepest domains.