The dancing plagues were ergot poisoning

Tested 25 October 2026 (scripts/ergot_climate.py). If the dances were ergot years they should look like the 117 recorded ergot epidemics: cold and somewhat wet. They do not. Over the 9 outbreaks the same summer was warmer than normal (+0.40; if they were ergot-type years a mean this warm would happen about 1 time in 70) and the summer before was drier than normal (-0.54; about 1 time in 100). Only 2 of 9 dances have an ergot epidemic within a year (1237 and 1374), close to what chance gives. The 1950s ergot argument for 1518 (Backman) assumed floods; the records show the opposite, a severe drought. Caveat: 9 outbreaks is few, and 1374 on its own looks more ergot-like (a wet summer before, ergotism in France in 1373).