Forgetting: How societies lose skills, perception, and knowledge, and then forget that they ever had them

This paper asks whether a society can lose a skill or a trained way of perceiving and then forget it ever had it, and grades each step by its evidence: documented losses from Pacific islands, the Arctic, Roman Britain and a US nuclear weapons program, studies showing that perception is trained and fades with disuse, and measurements of the close-range and faint signals people might read. A seeded simulation of how skills pass between generations, checked against 16 real cases (it reproduces 15 of them) and run on new datasets of early population sizes, epidemics and other shocks, collapse scenarios and memory decay, shows how first a skill, then belief in it, then the idea of it can disappear. This upload holds the paper and a self-contained folder of the simulation code, datasets, research notes and chart data, with a readme for rerunning every simulation and test.