Re: Flightless Bird Evolution

Everett Hickey wrote:

First off... I'm not trying to attack science, evolution, or any of the
other subjects that this newsgroup has a hair-trigger about. :)

"John Harshman" <jharshman.diespamdie@xxxxxxxxxxx> wrote in message
news:8ikNf.55484$dW3.53679@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Everett Hickey wrote:


"Augray" <augray@xxxxxxxxxxxx> wrote in message
news:mev8029j4oiek1l98ftalbpd80il8u0p6t@xxxxxxxxxx


On Tue, 28 Feb 2006 09:54:09 -0600, "Everett Hickey" <everett@xxxxxxx>

I just wish more opinions on the details were less absolute.

Why?


Even when we
have unassailable reasons behind accepted (or even largely-accepted)

ideas,

it's not at all uncommon for something new, eventually, to force a
readjustment of our basic assumptions. Dinosaurs provide some of the

best

examples of this - most of the biggest mistakes were well supported,
logical, assumptions based on what we knew... and of course, we were

right

at the time.

Could you give examples?


A good bit of this falls into the realm of debatable ideas being stated too
strongly by authors (often by non-researchers who heard it from elsewhere)
in books and articles over the past decades...

If they're debatable, they're not all that well supported or right at
the time. So are you backing off your original claim?

but one example is the
(long-since negated) idea that the larger dinosaurs (brontosaurs,
brachiosaurs, etc) were semi-aquatic, because known biomechanics (before
there was a name for it) showed that such an animal could not support itself
without boyancy. There were many reasons for them to think it at the time,
but once we knew more about biomechanics the solution was fairly simple. Of
course, entire generations grew up with the old idea as a given fact.

Though not entire generations of paleontologists, as far as I can tell.
The whole underwater thing was more in artists' reconstructions than
anything else.

Iquanadon's initial descriptions had a single readily-noticable trait that
later turned out to be off. Again, there were good reasons (at the time) to
reconstruct it that way, but later information (and more people looking at
it) eventually modified it.

Are you talking about the thumb spike being on the end of the nose? If
so, what were the good reasons?

The idea of endothermic dinosaurs, that
dinosaurs weren't reptiles, that they could be fast and agile, etc - all
just a natural part of a science growing more mature. However, before we
had that data, assumptions based on earlier perceptions were handed out as
fact with great confidence.

By whom?

People have learned from past mistakes, and it's fairly clear (at least I
think it is) that we're generally closer to the mark on most areas of
paleontology than we ever were before, but it's hard to tell the difference
sometimes between assertiveness for the sake of brevity, and assertiveness
out of absolute confidence that the current models are, where largely or
near-universally accepted, essentially fact. A model being supported by
later findings does make it stronger, but even a model composed out of
ignorance of later facts can "work" well before being scrapped - look at the
earlier models of the atom. They gave us everything we needed for the
basics of lasers, fission weapons, x-rays, but were eventually replaced by
later, more refined versions that bore little resemblance except for the
basics. However, the Bohr model was so purvasive that it was being taught
as "THE" model in high schools as late as the 90's (possibly even today).

It's a pretty good model. At any rate I don't see the relevance.

That's one thing I like about DNA comparisons. Even I am hard-pressed

to

worry about assumptions getting in the way of that kind of hard data.

I'm afraid that's only because you don't know all that much about DNA
comparisons. There are all manner of potential pitfalls. They're often
different pitfalls from what we find in morphological data, but they
exist nonetheless.

That's entirely possible. In genetics, I'm mostly concerned with how short
a time we've delved this deep... but if we find a sequencial relationship
in two species, that seems to me to be a stronger link than any
morphological similarity. We might misinterpret what we see, but it seems
to give us less room for debate. That's a little farther out of my
understanding, though, as I understand DNA better as a chemical than as a
sequence.

Since I do molecular systematics, I'm tempted to agree with you. There
are advantages to molecules. But there are disadvantages too. It's not
black and white. The big advantages are that 1) you can get thousands of
molecular characters in the time it takes to examine one morphological
character, and there are always more where that came from, and 2) you
can hope to model the evolution of DNA sequences in ways that aren't
totally useless, including assumptions of neutrality. The big
disadvantages are 1) there are only 4 bases with no hope of recognizing
homoplasy a priori and 2) sequence evolution never stands still.

Though I guess it could be said that seperate points of divergence

are...

extremely improbable, without something rather extrordinary to say
otherwise. :)

And that's all we can ever say in science, isn't it?


Exactly. There is nothing wrong with it, but the sureness of some types of
still-arguable statements, in a number of fields, usually feels wrong to me.
You can't get very far qualifying each statement, but I'm also usually
cautious using accepted theory as if it were fact, to refute another
statement. If had a wild, unsubstatiated, or uneducated idea about how
galactic cores were constructed, I would never correct them by describing
current models as my refutation. I know many who would, though. I might
try to compare their idea to currently accepted ideas, but I don't consider
interpretations of data to have the same importance as the data itself (at
least in cases where the results can be duplicated)

If we liked, we could get into a discussion of what, if anything, is the
difference between data and interpretation, or fact and theory. But
let's not. I am ready to call any sufficiently well tested theory a
fact, and any sufficiently strongly supported inference a certainty. If
all we're arguing about is whether X is sufficiently supported, then
only the evidence is relevant. If it's something else, then I suspect
it's a semantic quibble.

Then again, in my professional life I'm often accused of being too
qualitative... I don't like to give a deffinite yes or no response unless
I'm dead certain, have tested my results on the largest scale I can manage,
and have worked through every contingency I can imagine... and even then
I'll retract a deffinite answer the moment anything raises a question. My
boss calls me Heisenberg. Just so you know what kind of mindset I have. :)

Getting back to the concrete subject, none of the alternatives to
monophyly of modern birds, with that ancestor being a flyer, is remotely
tenable. So I'm willing to go with that as certain. Perhaps you would
too if you knew more about it.

.

Relevant Pages

  • Problem installing DBI
    ... CPAN: File::HomeDir loaded ok ... The next questions deal with Module::Build support. ... Do you want to use a different command for './Build install'? ... 4/130 skipped: various reasons ...
    (comp.lang.perl.misc)
  • Re: A new paradigm
    ... First I use a 3rd party btree handler for several reasons - cross platform ... Therefore all our programs use a standard common area ... but no one in the rest of the market seemed interested. ... people just shifting where they're buying their features and support ...
    (comp.databases.pick)
  • my numerous saint wont slam before I waste it
    ... if Rifaat suddenly drives the cottage? ... The drives, reasons, and ... Just now Fahd will date the contrast, ... He'll be assuming in support of confident ...
    (sci.crypt)
  • Re: topless bathing now allowed at all public swimming pools in Denmark at all times
    ... Again, I'm not saying that I agree with this, I'm ... Equality is equality, period. ... There can be many reasons for the ... since I can't believably say that I support their ...
    (uk.rec.naturist)
  • Re: Effect size with no control group?
    ... My only reason for doing the paired t-test ... on the reasons for this. ... When I see a patent that proclaims that certain data is ... lamp post for support. ...
    (sci.stat.consult)
Loading