The genetic data is pointing toward something dramatic: a severe population bottleneck at the end of the last ice age. Between roughly 14,500 and 11,000 years ago, approximately six million cubic miles of glacial ice disappeared from the continents in just three millennia. That ice had accumulated rapidly starting around 26,000 to 30,000 years ago, and its swift buildup remains poorly explained. What followed was equally extreme. The ice didn't just melt gradually. It converted into water and transferred into the oceans through floods of unimaginable scale. The thermal energy required to drive that kind of melting in such a short span is staggering, and the source of that energy is still not well understood. If the ice melted that fast, what forced it? And if floods of that magnitude reshaped entire landscapes, what did they do to the human populations living through it?