"Every paleontologist knows that most new species, genera, and families, and that nearly all categories above the level of family appear in the record suddenly and are not led up to by known, gradual, completely continuous transitional sequences"

This quote by George G. Simpson is referring to the fossil record and the fact that the majority of brand-new types, genera, and households appear all of a sudden in the fossil record, instead of being led up to by gradual, constant transitional series. This recommends that species evolve rapidly, instead of slowly over time. This idea is referred to as punctuated stability, which suggests that types stay fairly the same for extended periods of time, and after that experience rapid bursts of advancement. This concept is supported by the fossil record, which shows that types appear all of a sudden and are not preceded by steady shifts. This quote is an essential suggestion that evolution is not a direct process, however rather a complex one that is often stressed by quick bursts of change.