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Re: Feathers for S excretion (very long)



> This is interesting.  However, have you considered Vitamin B12, a
necessary
> part of everyone's diet, which contains cyanide compounds?  Although
> hydrogen and potassium cyanide are deadly to many vertebrates in small
> amounts, we consume and depend on Vitamin B12 for our health and survival,
> and so far as I know, our kidneys and liver are adept at breaking B12
down.

Vitamin B12 normally (not in medicaments) contains CH3 instead of CN, it is
a methyl carrier. And, above all, we need it in TINY amounts, not comparable
to amino acids.

> What might be interesting to see would be the amount of sulfur-containing
> amino acids produced versus the H2S or Sulfur content of hair or feathers
in
> various animals, and perhaps a comparison of these things with reptile
> scales as well.

Sure... AFAIK nothing has been done.

> David reports further:
>
> "This led me to an unusual idea: Are feathers maybe not a product of
> direct adaptation, but arose out of a protein excess? [and then continues
> with an evolutionary scenario wherein the ancestors of birds chased
insects
> through the trees for food]"

Reichholf doesn't mention trees here. Of course he presents no evidence
against feather evolution happening in trees, but he writes about "higher
running speeds".

> My question would be, couldn't the protein and sulfur "excretion" also
have
> evolved post hoc.  In other words, the feathers may have become an H2S and
> sulfur-containing amino acid dump AFTER they evolved, and the body just
> "took advantage" of this resource once it appeared.

Erm... yeah... just in this case you need an extra hypothesis to explain the
origin of feathers. Let's find fossils to test this, OK? :-) :-]

> To test your hypothesis
> that sulfur excretion is tied to feather development, it might be
> interesting, again, to look closely at the sulfur and sulfur-containing
> amino acid content of various reptilian scales, including crocodilians.  I
> am aware that in certain embryological experiments, the genes for feather
> development in chicks can be "toggled" such that scales, not feathers,
> develop.  Could such experimental animals have less, the same, or more
> sulfur, etc., in their integument than control groups?
[...]
> Is the sulfur content in the
> hair of insectivorous mammals greater than that of other mammals?  How
many
> species of flying or gliding mammals are purely insectivorous?  These
sorts
> of questions would have to be addressed to improve the explanatory power
of
> your hypothesis, but it could be very interesting.  You have offered a
> hypothesis that can be investigated and empirically tested and repeated by
> others -- we need more of this in dinosaur research.

Very good questions -- I can't give an answer, and AFAIK nobody can at this
moment...

> Another area to look at would be insectivorous mammals.  Your hypothesis

Reichholf's.

> predicts two things: 1) feathers or hair evolved as sulfur (meaning the
> elements you site, sulfur-containing amino acids, etc.) dumps;

This isn't a prediction but the hypothesis itself.

> and 2) an
> insectivorous lifestyle could lead to flight.

Nope. The topic is the origin of feathers, not that of flight. A feathered
animal may more easily evolve flight under certain selective pressures where
others would evolve something else, or it may not. IMHO the evolution of
feathers, wings and flight are three totally separate issues, and I use
Reichholf's hypothesis to explain the first, HP Hopp and Orsen's to explain
the second, and Ebel's for the third.

> My personal suspiscions (and note that I am not even proposing a testable
> hypothesis, so take this with a very large grain of salt) are that feather
> evolution was intiated by the more prosaic vagaries of evolution -- the
> lengthening and/or differentiation of reptilian scales with subsequent
> display advantages or perhaps just neutral survival significance were
> selected for or maybe just not selected against.  Perhaps all the
advantages
> of feathers evolved subsequent to something like this, without a "purpose"
> for flight, sulfur dumping, etc.  But I realize this is all speculation
with
> no testable hypothesis being proposed.

I personally think feathers would be confined to certain exposed places if
they would have evolved for display. Of course I have no evidence here.

> Interesting information and hypothesis, David.

Thanks! Pity that I can't forward that to Reichholf...