>Both show the hallmarks of novelty radiations (phenotypic
>diversity increases much more rapidly than species
>diversity across an ecologically undersaturated and thus
>low-competition landscape) [...]
I'm preparing a paper on the origin of animal body plans for a
conference in China this summer, sponsored by the Chinese Academy
of Sciences, and am wondering how "open ecological space," or
an "ecologically undersaturated" landscape, is assessed empirically.
Here's the problem. A paleontologist might say (and many do) that
the Cambrian explosion took place in part because ecological space
was open to be occupied; competition was low (sorta like the Oklahoma
land grab, if you will). But how is this known? Mainly by the
relative absence of fossils, it seems -- which apparently gives the
whole of the historical signal for ecological openness.
If that is the case, then one seems to have gone in a circle.
(1) Complex metazoans evolved because they could; metazoan
ecological space was open. (2) We know ecological space was
open because we have no, or relatively few, fossils of complex
metazoans. (3) Thus, complex metazoans evolved because they were
no complex metazoans yet; and we know this because the complex
metazoans, which had not yet evolved, left no fossils.
Help from the paleontologists, please. How is ecological
space assessed -- independently of fossils which are to occupy,
and, as far as I can tell, will actually define, that space?
Paul Nelson
Senior Fellow
Center for the Renewal of Science and Culture
The Discovery Institute, Seattle