Data for fossil insect origination are quite spiky, but they show five peaks above the ambient, background level (Fig. 4a, arrows 1–5). This background level of origination averages ≈20 families per geologic stage, but has a large variation from zero to a persistent plateau of ≈45 families. The background origination values remain constant throughout the late Paleozoic to late Paleogene, but essentially are zero during the Devonian to Mississippian and for the past 20 m.y. The five bouts of exceptional origination, significantly exceeding the background level, are