Modern uniformitarians assume long geological ages, but in recent years advocates of the Flood theory of geology have found many problems that make it more reasonable to interpret the fossil evidence in terms of catastrophism rather than long ages of evolution. The complexity of the Cambrian and other lower Paleozoic strata creates a very difficult problem for the evolutionist, but indicates that these rocks represent a natural habitat buried suddenly. The sudden extermination of the trilobites, and the irregular distribution of the ammonities all point to catastrophism. The coal beds have many problems that evolutionists fail to explain, but which can be solved if such beds are assumed to represent an ancient type of habitat or life zone. The extinction of the dinosaurs fits well into the same explanation, as also does the peculiar distribution of the mammals in the Tertiary rocks. All in all, the Flood theory offers the most satisfactory explanation of ancient paleoecology, in what has been designated the "ecological zonation theory.