>Art, havn't you heard of local mximum in a fitness field? Local minima can
>be quite deep allowing a certain form to remain unchanged over long time
>periods. Thus a bilaterian can remain basically the same (except for the
>details) for a long time. And this is what we see in the lagerstatten.
Indeed, and this appears to be the predominant manner in which
evolution works itself out among the biosphere.
>Once in a while a population breaks out of a local maximum and finds
>another local maximum. And those that have moved on to other maximum are
>now called by other names.
Is there any experimental evidence to back this up? That is, I'd
be interested in papers where the number of cell types has been
*observed* to increase through evolution.
>Thus evolution has increased the number of
>cellular types by evolving worms into chordates, chordates into fish, fish
>into amphibia, amphibia into reptiles and reptiles into mammals and birds.
Yes, but keep in mind that only one lineage of fish gave rise to amphibians.
The *vast* majority of fish evolution (ASAIK) doesn't entail this increase
in cell types (the same point could be made for each step along your
transitional series).
>So, the answer to your question, like Mike's is that evolution has been
>busy turning worms into men.
Clearly suggesting there is something quite special about this transitional
series given that evolution hasn't been nearly as busy anywhere else in
life's history. In fact, I think I hear an echo of Van Till's "fully gifted"
view here.
Mike