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> At least in molecular cladistics an equal weighting scheme is
> reasonable, since the four bases of DNA have a practically even chance
> of being at any particular locus.
Oh dear me, nothing coud be further from the truth. There's a LOT going on
at the molecular level, and one cannot never *assume* stationarity.
Synonymous codon usage in genes and secondary structure of ribosomal RNA are
just two examples of why the four bases DO NOT have a practically even
chance of being at any particular locus. I could go on, but this is way
> E.g., if morphological cladistic analysis contends that avian flight
> developed from the ground up, this disagrees with physics and
> functional anatomy, and perhaps we should rethink the cladistics, not
> necessarily the physics or the functional anatomy.
An interesting exam question: "In 1000 words or less, please list and
describe all the errors present in the above statement."
I'll mention a few...
1) Current theropod phylogenies are amenable to either a "ground-up" or a
"trees-down" origin of avian flight.
2) For the thousandth time (and counting), the traditional "ground-up" vs
"tree-down" dichotomy is an outdated mindset. As Padian and others have
stated _ad nauseum_, there is no compulsion for a hypothetical pro-avian to
adhere exclusively to a terrestrial or arboreal ecology.
3) Physics and functional anatomy have yet to disprove a gravity-opposing
("ground-up") origin of flight. Sure, it's more challenging that a
gravity-assisted origin of flight; but as long as its physically feasible,
it's on the table. Evolution does not have to take the "easiest" course; it
can only act on the raw material available.
4) Heck, insects did it. The available evidence (fossil, functional
anatomical, experimental) indicate that insect flight arose without the
assistance of gravity.