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Re: DWARFED TETRAPODS



In a message dated 97-01-25 17:05:04 EST, martz@holly.ColoState.EDU (Jeffrey
Martz) writes:

<< > Plus a lot of this so-called "dwarfing"
 > is an artifact of the differential survival of smaller forms versus the
 > simple extinction, without descendant species, of larger forms.
 
      Are you saying that "true" dwarfing is driven by some other
 evolutionary mechanism other than natural selection?  What you just
 described in natural selection favoring smaller individuals.  Unless you
 are proposing dwarfing is NOT an evolutionary process, your statement is
 meaningless.   >>

Here is "true" dwarfing:

B = descendant species, of small animals
|
|
|
|
|
A = ancestral species, of large animals

Here is "fake" dwarfing:

B = descendant species, same size as A
|
|
|     C = descendant species, larger than A
|    /
|   /
|  /
| /
A = ancestor species, unrecognized in fossil record

(Time runs upward in these diagrams.) The extinction of C together with the
survival of B makes it seem as if C has dwarfed into B, because the common
ancestor A is not recognized, even though no "true" dwarfing has occurred
along either lineage and indeed, C is not even directly ancestral to B.
Assume for purpose of this discussion that a few random changes other than
size have occurred (perhaps anagenetically) along each lineage to make A, B,
and C clearly distinct.