How did Sedgwick explain the succession of species?

Question

Adam Sedgwick was a master structural geologist and was one of the primary participants in the early days of stratigraphy - working out how rocks could be distinguished, extrapolated, etc.

Although he did not consider himself a biostratigraphic expert (he would usually send his fossils to the relevant experts for precise identification), he would have definitely been aware of the "succession" of species: That the species in rocks of different ages are different (so much so that they could be used for system identification), and they tend to be fewer and simpler in his own Cambrian, but much more complex and diverse higher up (e.g. in the Secondary and Tertiary rocks).

He was probably also aware of some of the similarities between fossils in rocks of neighboring ages.

Despite retaining a good friendship with one of his former students, Charles Darwin, he never accepted evolution. Presumably this is related to his position in the more conservative side of the Church of England.

So what was Sedgwick's explanation for these patterns seen in the stratigraphic distribution of fossils?

Answer 1

Based on what I've read in Stephen Jay Gould, The Structure of Evolutionary Theory, Cambridge MA: Belknap Press of Harvard University Press, 2002, I would assume that, in fact, the intellectual conflict was the opposite of what you propose.

Darwin's variant of natural selection is founded in Lyell's theory of gradualism. That is, it assumed that infinitesimally small mutations accumulate over geological time until there are so many of them that you have achieved a new species.

Lyell's (and pretty much everyone elses) explanation for the sudden changes in species in the geological record were simply due to missing data. Lyell (and Darwin) held that everything in the geological record could be explained in terms of processes (like erosion) that are observed every day. This was opposed to cataclysmic theories that claimed that some geological strata were actually caused by sudden massive, global events (like meteor strikes). According to the Wikipedia article on Sedgwick, for much of his career he was an opponent of gradualism and uniformatarianism and favored explanations of certain gravel deposits as evidence for the biblical "Great Flood."

The recognition that the sudden species jumps in the geological record represent evidence of very fast (non gradual) evolution, rather than missing data, was popularized in the 1970s and 1980s by Gould.