Re: The Drunken Sailor's Stumble (was Re: March of "progress")

["Ken Kinman" <kinman@hotmail.com>]

Tim,
    Well, I think there can be some element of "dumb luck" in what survives 
and what doesn't, but Gould just overstates that as well.  There was 
probably some element of dumb luck in what survived the K-T extinction.   
There were probably birds in North America that could have survived if the 
asteroid had smashed into Southern Africa instead.  But most of the bird 
survivors were apparently in the far south, just because the asteroid impact 
was far enough away to spare them (so there was some element of dumb 
luck---how much is debatable), but the bird extinction would have been 
devastating even down there (perhaps fewer than a dozen bird species 
worldwide?).
    There may well have been some kind of extinction event at the beginning 
of the Cambrian as well (I'm not saying that it was a total nonevent), but I 
still believe most of extant Metazoan phyla were present, and the explosion 
would be better termed a radiation of survivors (similar to K-T).  In other 
words, the "explosion" or radiation would be at class, order and families 
levels, but most of the phyla were already in place (and not sure that there 
were that many phyla that went extinct near the beginning of the Cambrian).  
Even the extinct Phylum Petalonamae made it into the Cambrian.
     Lots of vertebrate clades made it through K-T, and it looks like a lot 
of metazoan phyla made it through whatever happened at the beginning of the 
Cambrian.  We are just less certain whether the early Cambrian event was 
caused by a fairly quick physical event (like K-T) or a more drawn-out 
biological event (like an arms race of hard parts), or a bit of both.
                     -------Ken
P.S.  I would guess that even Simon Conway Morris would agree that there was 
some element of dumb luck----but that Gould overstated just *how* different 
things would have turned out if we "reran the tape".  Gould has good ideas, 
but he just tends to exaggerate some factors and therefore somewhat 
neglecting others.   On the other hand, I fear Woese not only exaggerates 
some ideas, but that such exaggerations are having a far more damaging 
impact on science (and Gould's influence does not worry me anywhere near 
that much).  After all, misunderstanding the phylogeny of extinct Cambrian 
animals isn't going to have anywhere near the repercussions that could come 
from misunderstandings of living organisms like bacteria.
*********************************************************
> > The most troublesome is that the so-called Cambrian "explosion" was 
> > supposedly a phyletic explosion of body-plans, when it is more 
> > realistically regarded as an explosion of hard parts scattered here and 
> > there on an already well-diversified Metazoan tree.
>
> I respectfully disagree: I think the Cambrian explosion was real, not an 
> artifact of preservation.  But Gould (in "Wonderful Life") tends to 
> overstate the diversity of Cambrian forms; some "unique" forms are now 
> believed to be members of hitherto known forms (e.g. _Hallucogenia_ is 
> likely to be a spine-backed onychophoran, not a "phylum" unto itself.)  
> Also, Gould's notion that certain Cambrian lineages survived while others 
> didn't was due to chance (Dumb Luck) is a little difficult to swallow, in 
> my very humble opinion.
>
>
> Tim
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