Demise of the Megafauna: Approximately 10,000 years ago, the Pleistocene-Holocene deglaciation in North America produced widespread biotic and environmental change, including extinctions of megafauna, reorganization of plant communities, and increased wildfire. The causal links and sequences of these changes remain unclear. Gill et al. (p. 1100 ; see the Perspective by Johnson ) unravel these connections in an analysis of pollen, charcoal, and the dung fungus Sporormiella from the sediments of Appleman Lake, Indiana. The decline in Pleistocene megafaunal population densities (inferred from fungal spore abundances) preceded both the formation of the lateglacial plant communities and a shift to an enhanced fire regime, thus contradicting hypotheses that invoke habitat change or extraterrestrial impact to explain the megafaunal extinction. The data suggest that population collapse and functional extinction of the megafauna preceded their final extinction by several thousand years.