Roman denarius debased sharply after Antonine plague in 165-180 AD. Imperial Crisis of 235-285 AD brought invasions, civil wars, and economic collapse. Western Roman Empire fully collapsed by 5th century after Theodosius I's death. Post-collapse infrastructure like roads, bridges, and aqueducts decayed. Trade networks broke down, replaced by barter. Agricultural production and population plummeted. Urbanization rates crashed. Meat consumption collapsed from 4th to 5th century per bone remains. Maritime trade dropped massively per shipwreck data. Lead pollution from mining indicates sharp economic decline. Frankish kingdoms marked Europe's partial awakening. Early Middle Ages saw marked intellectual and cultural decline versus Rome. Dark Ages were Europe's nadir in 6th-7th centuries. Written works, scholars, and technology stagnated compared to Rome. Modern historians wrongly deny the wholesale decline.