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Re: paleontolgist, dinosaur and also Re: "Wonderful Life" - repeated.



John Bois wrote of the K/T extinction:

> Since we are talking about terrestrial creatures I beg to differ.
> The non-avian dinosaurs were the ONLY group to be entirely wiped
> out.  This is specific targeting worthy of a smart bomb.

Your use of the word "entirely" makes your statement pretty much true,
but doesn't take away from the fact that it is rather misleading.  The
extinction pattern was not specifically targeted at the dinosaurs.
There was a significant amount of collateral damage by those "smart"
bombs. 

> Even by the end of the Cretaceous the dinosaurs were a robust group
> exploiting many niches.  They were widespread not only with regard
> to niches within a locality, they were also distributed globally.

Look at George's genera count.  Then look at a count of today's known
mammalian genera.  While it's true that there were probably a lot more
genera of dinosaurs than we'll ever know about, there are also a *lot*
more modern animals filling niches that no dinosaurs are known to have
ever filled.  You could (as George is wont to do) postulate thousands
of small dinosaurs that have left no discernible traces, or you could
accept that non-avian dinosaurian diversity may never have been all
that large.  Certainly the known diversity of contemporary dinosaurs
(i.e. birds) is much greater than the known diversity of all extinct
dinosaurs throughout the entire Mesozoic.  Are the other dinosaurs
extinct because of their bad genes, or did they just have a bad run of
luck at the end of the Cretaceous?  Personally I don't think you can
reasonably act like that question is anywhere near settled.  Making a
caricature of the extinction pattern certainly won't help clear the
issue.

>       For argument's sake, assuming for a moment this is what
> happened, the ultimate cause of dino extinction, since only they
> became extinct, is the non-stealthy egg!

John, so far as I know, you're the only person in the entire world who
accepts (apparently without question) that dinosaurs were
"non-stealthy" egg layers.  Why would the smaller dinosaurs be any
less stealthy than the crocodilians which were missed by your "smart"
bomb?

And in another message John complains about my editorial:

> a couple of weeks ago on this list a writer solicited advice on
> (something like) the likelihood of there being a Cretaceous on an
> alternate planet.  Mickey Rowe told him (rather peremptorily I
> thought) that this was unlikely and referred him to S.J. Gould's
> _Wonderful Life_.
 
Actually the request (by Jim Crowell) was for a collaborator on "a
novella about descendants of a colonial ship crashed on a planet where
evolution has reached the early Cretaceous period".  John's
characterization of my response is reasonably accurate in spirit, and
I stand by it as long as Jim meant by "Cretaceous period" that his
hypothetical planet would be populated by the same plants and animals
that lived here during our Cretaceous Period.  I don't think any
biologist worth their salt would accept such a parellel history.
Heck, that was also the point of Tom's recent quotes about the space
aliens...

In any case, although much of Gould's claims about the Burgess fauna
don't withstand close scrutiny, his claims about history not repeating
itself most probably do.  Furthermore, even if we might disagree on
the predictability of certain events, John hasn't really disagreed
with my ultimate objection to Jim's premise.  For instance:

> For me, the point is not how "orderly" the sequence of events was,
> or even how much time they took, but whether the acquisition of a
> nucleus, a mitochonrion, or a chloroplast was in some sense
> inevitable.

and:

>     On page 317  and 318 Gould seems to be saying it was a
> miracle that vertebrates made it onto land.  Wind back the tape,
> he says, and "expunge the rhipidistians by extinction, and our
> lands become the unchallenged domain of insects and flowers."
>      
>      By saying that only the lobe-finned fish were capable of
> developing walking appendages he is truly a slave to his thesis. 

[...]

> Though it might take time in a replaying of the tape, vertebrates
> were destined to come ashore!

Note that even John isn't claiming the inevitability of any one
particular vertebrate lineage taking the anti-plunge.  Had events been
slightly different, a different vertebrate lineage would have
initially colonized the land, and the resulting animals would likely
look quite different from the ones we all know and love.  *That* was
my point.  And if it wasn't true, it would be pretty much impossible
to reconstruct anything at all of evolutionary history.

Jim's use of the verb "reached" in the phrase "a planet where
evolution has reached the early Cretaceous period" suggests that he
thought evolution does proceed in an orderly fashion, and hence John's
defense is off base.  If evolutionary history doesn't progress with
the orderliness that even John won't claim it does, then how can you
possibly recognize a "Cretaceous period" on another planet?  What
would you do, look for a chalky layer in a planet's geology then take
your time machine back to when that chalk was deposited and voila call
it "Cretaceous"?  Do you really think you could find a Velociraptor
anywhere else but in the fossil record or human imagination?  Until
you show me a fossil (or living) Velociraptor from another planet I'll
remain extremely dubious about the possibility that other planets are,
were or will be populated with such creatures.

That's my perspective anyways.

--
Mickey Rowe     (mrowe@indiana.edu)