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Re: Arms into wings



In a message dated 3/6/99 12:43:15 AM Eastern Standard Time, ornstn@home.com
writes:

<< Secondly, it [wing-brooding] is such a basically simple and
 obvious thing to do with wings that it is, to me, not impossible to imagine
 it evolving over and over again.  To use your human analogy, the concept of
 holding something over your head to keep dry in the rain is so basic that
 the use of umbrellas or something like umbrellas has probably arisen many
 times in human history. >>

To me, the most interesting part of this discussion has been the use of living
animals as analogues of extinct forms.  How valid can such non-anatomical
comparisons be?
 
Two of the assumptions that are giving me a difficult time:
The first is in the quote above.
I have to ask, why re-invent the wheel?
Humans may be the most thoroughgoing example, but many animals learn from
example and training, as I'm sure you know better than I.  A behavior can
spread more quickly than a physical trait.
If the behavior spreads first, wouldn't the anatomy be self-selected toward
making the behavior more effective?  
Then the question becomes what advantage is being sought?  Is it leaving the
ground, moving quickly, capturing prey, keeping chicks warm?  Given all the
ways modern birds do these things, do extant animals provide any assistance in
answering this question?

Second, there is an assumption that if all modern species do something a
certain way then it must be basal.
However, to use another human analogy, consider beta vs the vcr tapes we all
use now.  Beta was actually better I've been told, but vhs had better
distribution.  Looking at what we have in our houses now, an investigator
might assume vhs was the only format ever used.  Given extinctions and all the
other illogical (ie, random, etc.)  factors in evolution, can you really
assume that all the large populations eliminated had the same 'basal'
condition?

Just trying to figure out what from current forms can be considered proof.
Thanks.