Freethought & Rationalism Archive

Camaban · 10-13-2002, 01:51 PM

Quote:

Consider a construction analogy: The foundation is present, but no "house" it built upon it.

Only an incompetent builder or slightly madman would put in a foundation and have no intentions of putting the house on.

waste of time, money and effort.

Why have the foundations at all?

Blinn · 10-13-2002, 02:14 PM

Quote:

Originally posted by Vanderzyden:
Quite an amazing thing, I think: the creature functions without an eye. If it had "evolved" this way, we would not observe this fish. It would not exist. There would be no living specimens, since the first "eyeless" surface fish would die immediately. In the wild, an animal that requires sight in order to obtain food would die shortly after its vision degraded. If blind offspring are born to seeing parents, they will notsurvive long after birth. So, I find the suggestion of evolving blind fish to be wholly nonsensical. The Darwinist would do well to think through the likely scenarios before postulating such far-fetched schemes.

An unsighted fish above ground may be at a selective disadvantage relative to a sighted fish, but that is not the scenario that we have here. Surface dwelling (sighted) fish moved into caves. Only after they're already living in total darkness (where there is no selective advantage to being sighted) is sight lost.

Vision is important for most fishes, but its usefulness is often constrained by factors such as water clarity, water depth, or temporal activity. I think I'm safe in stating that many, if not most fishes, rely on sight only partially, if it all, in locating food. Olfaction is a much more important sense in that endeavor. And then lets not forget about lateral lines. Fishes and some amphibians have a sensory pores along their head and body which can detect movement in the water around them. Moving from the surface into caves wouldn't be a problem for these fish.

[ October 13, 2002: Message edited by: Zetek ]

Vanderzyden · 10-13-2002, 02:28 PM

Quote:

Originally posted by Kevin Dorner:


Don't think that I wouldn't like to see this changed and to have free access to online scientific journals and papers myself, as it makes it possible to read scientific material directly from the sources without modification, but unfortunately the nature of scientific publishing these days is to proprietize them. There are many scientists also working to change this, but for now we must abide by them being copyrighted and restricted in their redistribution.

OK, Kevin. Thanks, I appreciate that you have taken the time to provide a solid explanation. I will be careful of this in the future.

Please accept my apologies for any inconvenience that I have caused.

Thanks,

Vanderzyden

Vanderzyden · 10-13-2002, 02:35 PM

Quote:

Originally posted by Zetek:

...Surface dwelling (sighted) fish moved into caves. Only after they're already living in total darkness (where there is no selective advantage to being sighted) is sight lost.

What incentive do sighted fish have for moving into an environment where they can't see to find food?

This isn't like the finch beak example, where adapted configurations provide more leverage in eating different food. Rather, your suggestion entails the virtual absence of food. Why would the sighted fish not return back to the light, if only to die attempting to find food that they can see?

Note: additional complications arise when we consider reproduction.

Vanderzyden

[ October 13, 2002: Message edited by: Vanderzyden ]

Coragyps · 10-13-2002, 02:48 PM

One can easily imagine that a population of fish were forced into caves at some point: I doubt that their employer just offered them a transfer. Balmorrhea Lake is about the only natural, permanent lake for hundreds of miles down there - it's fed by a big spring. The cave fish from the study were from even deeper into the Chihuahuan Desert. The whole area was wetter back in the Ice Ages - so I would imagine that some of the playas that are around here now were once permanent lakes. But they are dry now. Whether the caves in which these fish are found are related to the Carlsbad system of caves, I don't know: they may be too far south for that.

Anyway, I don't think fish exactly choose to move into lightless caves.

[ October 13, 2002: Message edited by: Coragyps ]

Blinn · 10-13-2002, 03:01 PM

How the caves came into existence is best deferred to someone with some geology knowledge, but using <a href="http://www.tmm.utexas.edu/sponsored_sites/tss/txcaves.htm" target="_blank">Texas caves</a> as my example, there are at least two scenarios. In some cases, as Coragyps suggests, populations of animals were forced into caves. In other cases, they may have had the option of leaving the cave, but nature abhors an empty niche. There can be advantages to living in caves, for example, predators have a harder time seeing you or there may be less competition for food resources there. By the way, perhaps you've stated this elsewhere, but are you a YEC or an OEC?

What are the reproductive complications?

[ October 13, 2002: Message edited by: Zetek ]

pz · 10-13-2002, 03:36 PM

Quote:

Originally posted by Vanderzyden:
The "well-established fact", as PZ calls it, is not alluded to in the article or the references.

You tracked down all the references in the article, and read them with comprehension? I do not believe you.

Reciprocal induction in eye development is a well-established fact. The experiments have been done over and over again in the last 70 or so years.

Read any basic text in development.

Quote:

The authors do not explicitly mention the signal, nor the mechanism by which such signal might be transmitted.

Of course they didn't. It's old news.

Quote:

As with so many other "facts" that are claimed here, I am not placing much confidence in this one. To make matters worse, PZ again makes these flippant, UNSUPPPORTED claims.

Look up, oh, say, Wolpert et al.'s _Principles of Development_. The story is all there.

I'm not a creationist, so I don't make up stuff like that.

Quote:

I may not fully understand, but I would not be surprised if this signal "stuff" was no more than hand-waving "business"--as you characterize it so well. "Business", indeed. In this particular case, we don't know how such "business" relates to optical embryogenetic development because the authors do not explain it. As with many other aspects of the paper, they gloss over it with four short, introductory instances of the word "signal".

Yes. It's a short paper in Science. Science doesn't publish remedial science for mental munchkins.

Quote:

Nothing of the sort is demonstrated in this paper. Can PZ direct us to the part of the paper which elaborates upon the formation of the flap of skin? All that I read is this "The degenerate eye sinks into the orbit and is covered by a flap of skin." That's it. So, either the authors don't understand what PZ is writing about here, or PZ providing yet more unsubstantiated material. Read the paper again. It says "covered by a flap of skin".

As usual, it is a total waste of time to discuss anything with you.

Go away. Come back to me after you've read

Chow RL, Lang RA (2001) Early eye development in vertebrates. Annu Rev Cell Dev Biol 2001;17:255-96.

and

Jean D, Ewan K, Gruss P. (1998) Molecular regulators involved in vertebrate eye development. Mech Dev 76(1-2):3-18.

These are reviews of the basic embryological and molecular events in eye formation. These are not "handwaving" articles -- they describe very well done, thoroughly replicated experiments that demonstrate the pattern of induction and identify the specific molecules involved.

lpetrich · 10-13-2002, 04:31 PM

[Vanderzyden:
What incentive do sighted fish have for moving into an environment where they can't see to find food?

... your suggestion entails the virtual absence of food. ...

Except that they have other senses that they can use.

Note: additional complications arise when we consider reproduction.

Those other senses can be used here also.

Happy Wonderer · 10-13-2002, 05:06 PM

Quote:

Originally posted by Camaban:


Only an incompetent builder or slightly madman would put in a foundation and have no intentions of putting the house on.

waste of time, money and effort.

Why have the foundations at all?

Actually it is even worse than that from what I understand of the article. The builder:

1) clears and levels the site
2) excavates the foundation and basement
3) hauls off the spoil
4) installs and ties iron rebar to code
5) installs foundation bolts to code
6) installs forms
7) backfills behind forms
8) calls concrete truck, pours concrete
9) waits for concrete to dry
10) removes forms
11) calls a (large) jackhammer crew
12) excavates and hauls concrete spoil
13) brings in loads of fill dirt
14) regrades ground
15) replaces trees and vegetation
16) continues on with the rest of the project

Sounds like one of my projects

(Actually the worst we have done is to decide to add a dormer after getting the upstairs finished as far as the second coat of drywall -- ended up removing most of the drywall, shortening one wall and redoing most of the electrical work.)

HW

Blinn · 10-13-2002, 05:24 PM

Quote:

Originally posted by Vanderzyden:
Note: additional complications arise when we consider reproduction.

Are you implying that blind animals are unable to reproduce? Well, they do, otherwise there wouldn't be any, would there?

I've watched Mexican blind cave fish, Astyanax mexicanus spawn, and they do it quite well without being able to see one another. You may want to read about <a href="http://www.lookd.com/fish/laterallinesystem.html" target="_blank">lateral lines</a>. I've also watched two males of another species of blind cave fish intensly fight with one another. I'd speculate that blind recognition of a conspecfic and its sex would be through olfactory or pheromonal cues.

[ October 13, 2002: Message edited by: Zetek ]

10-13-2002, 02:48 PM	#125
Coragyps Veteran Join Date: Aug 2001 Location: Snyder,Texas,USA Posts: 4,411	One can easily imagine that a population of fish were forced into caves at some point: I doubt that their employer just offered them a transfer. Balmorrhea Lake is about the only natural, permanent lake for hundreds of miles down there - it's fed by a big spring. The cave fish from the study were from even deeper into the Chihuahuan Desert. The whole area was wetter back in the Ice Ages - so I would imagine that some of the playas that are around here now were once permanent lakes. But they are dry now. Whether the caves in which these fish are found are related to the Carlsbad system of caves, I don't know: they may be too far south for that. Anyway, I don't think fish exactly choose to move into lightless caves. [ October 13, 2002: Message edited by: Coragyps ]</p>

10-13-2002, 03:01 PM	#126
Blinn Veteran Member Join Date: Aug 2001 Location: Ohio, USA Posts: 1,162	How the caves came into existence is best deferred to someone with some geology knowledge, but using <a href="http://www.tmm.utexas.edu/sponsored_sites/tss/txcaves.htm" target="_blank">Texas caves</a> as my example, there are at least two scenarios. In some cases, as Coragyps suggests, populations of animals were forced into caves. In other cases, they may have had the option of leaving the cave, but nature abhors an empty niche. There can be advantages to living in caves, for example, predators have a harder time seeing you or there may be less competition for food resources there. By the way, perhaps you've stated this elsewhere, but are you a YEC or an OEC? What are the reproductive complications? [ October 13, 2002: Message edited by: Zetek ]</p>

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10-13-2002, 04:31 PM	#128
lpetrich Contributor Join Date: Jul 2000 Location: Lebanon, OR, USA Posts: 16,829	[Vanderzyden: What incentive do sighted fish have for moving into an environment where they can't see to find food? ... your suggestion entails the virtual absence of food. ... Except that they have other senses that they can use. Note: additional complications arise when we consider reproduction. Those other senses can be used here also.

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