Nelson asks:

>>CN asks:
>>
>>>In view of the above, can anybody here in sbe or elsewhere show how genes
>>>might
>>>determine bird morphology? Even a speculation on a defensible mechanism
>>would
>>>be a great revelation. 
>>
>>One word, Benjamin: Proteins.
>>
>>Wirt Atmar
>>
>I appreciate your one-word answer. With all due respect, I don't know whether
>anyone in sbe makes anything of  ":Proteins" as an answer to
my question (How
>genes determine bird morphology). To me it makes no more sense than other
>one-word answers ( "God", Lipids", "Atoms",
"Environment", etc.) do. No word
>has ever been used as a substitute for a mechanism, and a mechanism is
>exactly
>what my question asks.  
>
>However, you have a chance to prove that your answer makes sense: elaborate
>how
> a protein or a group of proteins would provide information for the complex
>and
>highly specific arrangement of billions of cells of tens of different types
>of
>cells in the process of the development of any organ.
>Please, illustrate with a SINGLE example (don't forget, we are fed up with
>general unsubstantiated statements).

Given the level of assertiveness implicit in your insistence that such a thing
is not possible, I'm not sure how much I'm wasting my time by replying.
Nevertheless, let me try.

I suspect that you, like a great many other people, are under the impression
that there is a great underlying "genetical program" ensconced
somewhere in the
genome of a species, not unlike the kind of program that an engineer would
write. But that's not true. Genes actually don't code for much. They certainly
don't code for grand designs.

Rather, genes only encode the information on how to construct the little things
of life, the pawls, cogs, screws and fasteners, each of which is a protein.
Genes certainly don't encode wings or eyes or fingers, at least not in any
direct sense.

The machinery of life is -- perhaps astonishingly -- self-assembling. It's been
that way from the very beginning, from the first bi-lipid membranous walls that
formed the first cellular vessicles to the modern embryological self-assembly
of an eye or a wing. While this answer may sound on first hearing to verge on
the mystical, there's nothing magical all about the process.

Proteins autonomously fold into their conformational shapes based on their
distributions of electric fields, and they lock onto one another for the very
same reasons. But proteins are most normally not the product of just one gene,
but often the result of the actions of hundreds of genes. If one of the
encoding genes is modified just a very little bit, a different amino acid may
wind up being substituted in the ultimately realized protein, and that protein
may fold in a completely different manner, making it structurally or
catalytically more or less acceptable to the selective demands of the current
environment.

Selection chooses only among and between the available protein variants, and
wholly then only on the relative appropriatenesses ("fitnesses")
of the various
alternatives to current environmental demands. Selection does not however
choose among and between the various underlying genes, other than in the most
indirect manner. 

As time passes, the machinery of cell inherently becomes more complex for no
reason more complicated than the evolving phenotype is becoming increasingly
more appropriate to the environmental demands it encounters and simultaneously
more efficiently exploitive of those same environments. The most salient
attribute of evolution is that it is a learning algorithm. But evolution is not
a process that operates only through time. As phyletic lineages increasingly
better learn their environments, they simultaneously become bound to the those
environments as well. Species diversification, the evolution of complexity --
both behaviorally and morphologically -- and the evolution of intelligence are
all similar questions interwoven onto a biogeographic tapestry.

But the one word remains: "Proteins."

If this explanation is insufficient -- and of course it's very short -- let me
recommend the following sequence of classes at your nearest university:

     one semester of organic chemistry
     two semester of biochemistry 
     one semester of enzyme kinetics
     one semester of comparative anatomy
     one semester of animal physiology

By the end of this sequence, you will be able to very clearly answer the
question of how genes (even they don't encode much, certainly not a grand
design) "encode" the construction of a particular species of bird.

Wirt Atmar
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