Re: Crucible of Creation (was "some articles from American Scientist")

[Daniel Bensen <dbensen@gotnet.net>]

>>     The transition from PreCambrian to Cambrian faunas is not as abrupt as
the word "explosion" would imply.  It's probably more an explosion of "hard
parts" popping up in a variety of groups.  Gould's phyletic explosion is
misleading at best.<<

I actually liked some of Gould's analogies, especially the one with critters on
different peaks (representing different body-plans) that I couldn't explain if I
tried.
I was _very_ intrigued by the "Great Token-Stringer" theory (p. 215-218 of
Wonderful Life), in which Cambrian diversity was achieved by gluing together
traits from various phyla into various forms.  "Suppose that such
shared-but-primitive features as the bivalve carapace...do not indicate
continuous lineages.  Suppose that in this early age of unparalleled
experimentation and genetic lability, such traits could arise again and again,
in any new arthropod lineage---not by slow and separate evolution for common
function (for the traits would then represent classic analogies), but as latent
potentials in the genetic system of all early arthropods, separately recruitable
for overt expression in each lineage."  This idea is very weird, like something
out of a Greg Bear novel.  Gould may have been totally mistaken, or simply have
been speaking metaphorically, but I, for one, would love to be able to switch on
the right genetic sequence and grow some segmented tentacles.

Dan