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Re: flights of fancy (or "I'm brave, but I'm chicken****")
Before I proceed to respond to a bunch more of the traffic, I'd like
to second Chip's sentiments about people trying to use fewer, longer
messages. I actually have the listprocessor shut down right now (my
"now", that is) because ancillary problems caused by the number of
messages this machine was asked to process this weekend seriously
tasked my poor fishy computer. I've rebooted lepomis (which likely
had the effect of "unsticking" some old messages that you didn't know
you hadn't gotten, but that were taxing this machine anyway), and have
left the listprocessor off in order to put the brakes on everyone in
an incredibly effective fashion ;-) In terms of the way that e-mail
operates, it really does make a difference whether you send one long
or a bunch of short messages. This machine has to contact all of your
machines (or at least machines that have agreed to talk to your
machines) for every individual message it receives for the list.
On to substance. Rob Meyerson attempted to dispute my argument
against group selection by referring to animals that leave a lot of
"disposable" young (r-selection). That situation is not the same as
the one that I was arguing against. Simplistically put, there are two
ways of ensuring that you leave copies of your genes: make a lot of
copies, or take very good care of the few copies you make
(k-selection). In either case, you have to look at the strategy from
the perspective of the parents -- either strategy can result in you
outcompeting your conspecifics, and hence can be selected for. (Sorry
about the preposition, George ;-) This is in marked contrast to a
strategy in which you flail your wings about in the hopes that your
actions will save your friends; your friends don't carry your genes.
On to George:
>> I'll try to be brief,
I never said I'd succeed!
> Given one sentence and half a minute to compose a reply in, sure it
> is. I'm not going to write a treatise on the merits of fluff as an
> airfoil and then send it out on e-mail.
Hmmmm... it seems to me that the purpose of our having discussions
like this is to try to teach, learn and convince. In the instance in
question you appeared to be trying to convince. Don't you think you
might want to do the task well enough that you have at least a modest
chance of succeeding?
>> Has anybody ever considered testing such an idea by doing a
>> comparative survey of the density and mechanical properties of hair
>> and feathers across a large number of cursorial vs. arboreal
> Sure--give me a plush grant and five years, and I'll be happy (well,
> not very happy, but at least it would pay) to survey the mechanical
> properties of hair and feathers. You're talking _real work_ here,
> something to which the e-mail medium is not terribly
> adaptable. Plus, after five years and the grant, I would still have
> only a Just So Story--though perhaps a more detailed one.
To quote Beryl Markham (off the top of my head, don't quote me on the
quote :-), "Anything worth doing is going to be hard." In the charter
of this list, it's stated that we're here to talk about scientific
evidence. In the spirit of educating others, I'd like to make sure
that people appreciate that science isn't just about making up
stories. It's about testing ideas. Yes, it's hard. Yes, it isn't
always pleasant. However, its results indicate that it's the best way
to learn about the world (or at least certain aspects of it). If you
don't want to do it yourself, I suggest that you at least use your
intellectual powers to guide others (as you're attempting to do in
your argument over cladistics) rather than act like you know the
answers without having performed any rigorous analysis.
> The question is whether feathered wings would evolve as an aid to
> running--as something whose existence confers an advantage on a
> bipedal cursorial animal--and I just can't see that happening. If
> this were true, why do sprinters and marathoners wear so little
> clothing when they run?
Boy this is fun! It's not often somebody of George's stature tosses
me something so easy to blow away! Human swimmers shave every bit of
hair from their bodies if they want to have any hope of winning
olympic medals. But wow, 25,000 species of fish tell us that you can
swim fast even if you have things growing on your skin. Pinnipeds,
otters and a host of other creatures (including cetaceans which are
NOT completely bald) testify to the same thing. IMHO, you have to
broaden your imagination a bit when thinking about what animals might
or might not develop as adaptations. Humans are poor models for a lot
> Do you really imagine that feathered wings evolved to make a small,
> cursorial animal more maneuverable on the ground?
I'm really up in the air on the whole issue (rim shot). I do think
it's quite possible that feathered wings COULD have evolved that way,
however. They wouldn't evolve that way on a human marathoner. Humans
use their arms to adjust their balance while running, and thus putting
feathers on them would add a lot of air resistance in the absence of
other modifications. Theropods had big tails which were likely much
more effective than our arms would be in the effort to maintain
balance, so they could (at least conceivably) tuck their forelimbs in
to their bodies during most running. Then they could flash those
limbs out to their sides to aid in making tight turns. Using these
forelimbs as air brakes could actually help in this sort of maneuver.
Again, I'm not saying that's the way that it did happen. I am saying
I think you're being too cavalier by dismissing such possibilities.
> But I never _said_ that feathers will help protobirds escape
> predators. It is _climbing into trees_ that does this. The feathers
> help to solve the falling problem once they're _in_ the trees, not
> the escaping problem. Feathers or pre-feathers have nothing to do
> with escape from predators (in the beginning, at any rate).
It doesn't matter. Animals (or rather developmental mechanisms) can't
know in advance that feathers will help protect their bearers from
injury either. I stand by my statement that the argument you're
trying to make against the niche expansion idea is just plain bad.
> I felt my choices were between "several" and "as much as a hundred."
> It's not the pressures, it's the quite considerable amount of very
> specific anatomical change that _Archaeopteryx_ must have
> undergone. I can't imagine that happening overnight.
Oooo, another choice one ;-) Stop it, George, you're spoiling me! I
recommend that you NEVER start an argument with "I can't imagine..."
Argument via lack of imagination is not at all persuasive. Ask Duane
On a tangent:
> Some people, indeed, don't realize that the moon is visible during
> the day;
You can also see stars during the day if you're in a well. Write to
me if you'd like to know why that is...
Greg Paul writes:
] No running animal uses airfoils to extend leaping range or control.
Oooo, it's not just George feeding me! The above isn't a terribly
compelling argument either. If diploducids and their ilk hadn't left
us a bunch of nice fossils, we'd probably say the long horizontal
necks would never evolve because no animal has ever had them. When
you want to demonstrate that an extinct form did something, it IS
compelling to have other examples of animals that did that same thing
(i.e. it proves that your scenario is plausible). If, however, you
want to argue that a particular trait wouldn't evolve, not knowing of
any animals retaining the trait is only mildly suggestive of its
impossibility. There are a lot of animals we don't know about, and
evolutionary biology tells us that the watchmaker appears to be blind
(i.e. just because a particular style of watch was designed once
doesn't mean it has to be designed more than once).
Back to George:
> In BADD phylogeny, "forelimb length 50% or less than hindlimb
> length" is a frequently cited character. What is magic about 50%?
Those who live in glass houses:
> The most primitive animals generally included in Archosauria
> (stem-group definition; Archosauromorpha if you use the crown- group
> definition of Archosauria) are the proterosuchids, which were about
> two or three times the size of _Mesenosaurus_. This is still pretty
> small, but not exactly my idea of "small" in this context.
I'd probably comment on more, but I've got an appointment to rush off
"What it all boils down to, my friend, is that nobody's got it figured
out just yet..."
Mickey Rowe (firstname.lastname@example.org)