[jwalsh07]

For this and other reasons, it is unlikely that there will ever be radically new body plans evolving out of established species. New body plans can only emerge from rather simple body plans.

It is my understanding that all the phyla present today were present at the Cambrian. If that is correct, I am wondering if this was a prediction made by early Darwinists.

[js1138]

I don't know the answer to that, but Darwin pushed the metaphor of the tree of life. If you think about a tree or a bush, the largest branches are closest to the origin.

I would expect someday to see a quantitative theory of evolution that explains and predicts such major events as body plan origination.

I may not live to see it.