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Re: As a voracious reader-yet-amateur, how does this upset the applecart?
"If birds descended from dinosaurs, we would expect
the same 1, 2 and 3 pattern,"
No we wouldn't. The fine points of the 123 vs 234
issue aside (such as "234" really being "123"[*]), it
would be the only such case of a developmental
frameshift in one limb pair only (IIRC), but it is at
least technically possible, and the history of life on
Earth is full of "the only such case"s.
What may well argue against is a break of the
consecutive sequence, not a shift of the whole
unbroken sequence. If Feduccia were up to date on the
state of research in homeobox and segmentation
genetics, he would be able to imagine a mechanism for
such a shift.
*If* we had digits 124, 125, 235, ... in birds, *that*
would indeed be a problem. Shift/expansion/contraction
of evo-devo-genetics patterns is a no-brainer.
Interruption of what essentially is (at digit-bud
initiation) a homogenous wave function is hard to
accomplish by comparison even in theory.
[*] That would deserve a note: the "234" concept is a
theoretical consideration, while there is some amount
of evidence arguing for it really being 123 in birds
too. Of course, that point is moot in a BAND phylogeny...
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