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