Mount Tambora's 1815 eruption erased summer across the Northern Hemisphere. In Baden, the oat harvest collapsed. Horses starved by the tens of thousands. Grain shipments piled up at Mannheim's Rhine harbor with nothing alive to pull them inland.
On June 12, 1817, Baron Karl von Drais straddled a 48-pound wooden frame with two in-line wheels and a steerable front end, then covered 14 kilometers in under an hour. Twice walking speed, no oats required. The famine that killed the horse produced the operating principle behind every bicycle ever built.