Lower taxon-level punctuations, however, require numerous transitional steps to produce the disparity of the higher taxa. This model also predicts that the increasing diversity of the lower taxa should precede the disparity of the higher taxa. Disparity precedes diversity. The initial appearance of virtually all phyla occurs with very low species diversity. Rather, the dominant pattern is top to bottom, contrary to theory.
Disparity precedes diversity.
We may acknowledge a central and surprising fact of life's history - marked decrease in disparity followed by an outstanding increase in diversity within the few surviving designs. In another article Valentine and Erwin review hypotheses as to the mode of origin of animal body plans for consistency with the fossil evidence. If large populations have gradually evolved there should be unmistakable evidence in the fossil record, yet it is simply not found. Small populations are called for, then, but there are difficulties here also. This is asking a lot.