It Happened. It Is Happening Again

This preprint advances a unified, falsifiable thesis connecting an extreme solar energetic-particle event near 12,350 BCE with terminal-deglacial environmental reorganization, changes in human subsistence and settlement, and the vulnerability of modern industrial civilization to renewed coherence loss. Annual tree-ring radiocarbon measurements establish the strongest known cosmogenic-production event at the predicted horizon. Independent beryllium-10 and chlorine-36 records support an extreme solar-particle origin, while Greenland ice archives preserve a rare ammonium-nitrate disturbance near the corresponding layer. Regional hydrological and archaeological transitions overlap the resulting uncertainty field. The manuscript argues that the solar event supplied an initiating impulse to a threshold-sensitive Earth system and materially participated in the reorganization to which human populations responded. The modern analysis treats food, energy, infrastructure, trade, conflict, public health, labor, and demography as a coupled carrying-capacity system. It concludes that the climatic operating conditions that supported industrial civilization have already been exceeded and that continued contraction can produce mortality measured in billions. The accompanying evidence package identifies the sources, uncertainty fields, alternative explanations, unresolved tests, and observations capable of weakening or falsifying each part of the thesis.