Re: Quote Mine Project - Part II

catshark wrote:

> On Thu, 11 Sep 2003 01:27:57 +0000 (UTC), John Harshman
> <[EMAIL PROTECTED]> wrote:
> 
> [...]
> 
> 
>>>>>It's now obvious that Gould and Eldredge weren't arguing against
>>>>>_Archaeopteryx_ being a transitional form, but arguing that it wasn't an
>>>>>example of a gradual change between body plans. They state that it's a
>>>>>mosaic, a mixture of both primitive and advanced features. But did Gould
>>>>>believe that _Archaeopteryx_ was a transitional form? He did indeed, as
>>>>>can be seen in his article "The Tell-tale Wishbone" (Gould 1980).
>>>>>
>>>>I think they're making even less of an argument than you say. I think 
>>>>they're saying it's not a smooth intermediate, meaning a creature 
>>>>exactly intermediate in all respects. The creationist caricature 
>>>>requires that each and every character evolve at exactly the same rate, 
>>>>instead of different characters changing at different times and at 
>>>>different rates. Because Archaeopteryx (together with its various more 
>>>>primitive and derived relatives) *is* evidence for a gradual change 
>>>>between body plans, and one that was caught more or less in the middle.
>>>>
>>
>>Actually, this depends on what you mean by "gradual", which Gould has 
>>never properly defined except by caricature. Phyletic gradualism was 
>>taken to mean that if we observe two endpoints, all morphologies in 
>>between, in time, should also be proportionately in between, in 
>>morphospace. And you can indeed find such expectations occasionally in 
>>the old paleo literature. Even in punk eek, speciation (and therefore 
>>evolutionary change according to the theory) takes thousands of years 
>>and proceeds by ordinary selection within populations. And major body 
>>plan alterations don't happen in a single speciation event, but are 
>>spread over millions of years, as with the evolution of birds within 
>>theropods.
>>
>>
>>>While Archaeopteryx is certainly an intermediate, I'm not sure that it's
>>>evidence for a change in body plans. Of course, it depends on which body
>>>plans we're talking about. As you know, at least one specimen of
>>>Archaeopteryx was initially mistaken as an example of Compsognathus,
>>>since they have pretty much identical body plans, which are unlike those
>>>of modern birds.
>>>
>>>But the body plans of "non-avian theropods" are in turn unlike those of
>>>lizards, if only because theropods are bipedal, so Archaeopteryx could
>>>be considered to be in the middle, between "lizard" and bird.
>>>
>>>It did occur to me that Gould and Eldredge were making the argument that
>>>you say they are, but why single out Archaeopteryx? When they used the
>>>term "mosaic" I translated that as "a theropod with feathers and a
>>>reversed big toe". But if they're making the argument that you say they
>>>are, wouldn't every transitional creature be a mosaic?
>>>
>>
>>Yes. Which is their point, I think. Creationist caricatures of 
>>intermediates (or what amounts to the same thing, Gould's caricature of 
>>what "gradualism" implies) are generally lacking in the fossil record, 
>>and in most cases wouldn't make biological sense. I believe they were 
>>using Archaeopteryx just as a well-known example of what real 
>>intermediates look like.
>>
>>("Bauplan" is an overused term. It's unclear just how much of a 
>>difference is required before a lineage gets to a different bauplan. I 
>>believe the term was originally applied to phyla. But I digress.)
>>
> 
> All very interesting.  But can one or the other of you eventually summarize
> this so it can be used in the QMP?


Sorry, I have long since forgotten the original purpose of all this. And 
an annoying file disaster has caused the thread context to disappear 
from my computer. But I would just change the paragraph at the top to 
say this:

"It's now obvious that Gould and Eldredge weren't arguing against 
_Archaeopteryx_ being a transitional form, but arguing that it wasn't an 
example of a perfectly smooth change between body plans. They state that 
it's a mosaic, a mixture of both primitive and advanced features. But 
did Gould believe that _Archaeopteryx_ was a transitional form? He did 
indeed, as can be seen in his article "The Tell-tale Wishbone" (Gould 
1980)." You might add to that, if clarification were needed, "Mosaic 
forms are exactly what we should expect from evolutionary transitions, 
since there's no reason to expect every part of the body to evolve at 
the same rate or at the same time."