Albion

I think GeoTheo did. Poor guy's getting thrown out of his church for his trouble, too. Anybody seen him around recently?

Albion

You'r ejoking, right? Evolution involves adaptation to the environment. The only way this would count as evolution in reverse is if blind fish evolved from sighted fish after exposure to higher levels of light.

Not in the dark, it isn't.

Only if you're of the (usually creationist these days) opinion that evolution is somehow directed toward increasing "perfection" or increasing likeness to humans.

Camaban

Just one of the creationist arguments against the Appendix being useless is that it either plays a small part in either digestion or the immune system.

one or the other.

Oolon Colluphid

The appendix is an outgrowth of the gut and is made of the same tissues, so it’s not surprising that its cells do the same sorts of things that the rest of the intestine does. It is often claimed that it is functionless and so vestigial. But this plays into the creationists’ hands -- all they think they have to do is show it has a function. (They do the same with the coccyx, saying it acts as a muscle attachment. And the way to counter this is the same...) But the point is that the function could be performed far more simply.

The appendix could be involved in digestion... and so is yards more gut. It doesn’t do anything special itself. It could be involved in the immune system... but the Peyers patches in the appendix wall are found throughout the intestine wall. Again, the appendix doesn’t, of itself, do anything special... and crucially, there is nothing in what (little) the appendix does do that requires it to be the shape it is. Yet it is that shape, and it is a shape that makes it very prone to blockage leading to potentially lethal perforation. With either function, just lengthening the gut a tad would produce the same amount of tissue as the appendix contains. And there wouldn’t be a dangerous pocket to worry about.

As I’ve said before, vestigial doesn’t mean useless. It means greatly reduced. So the term assumes evolution. And hence it should be avoided in these discussions. Much better to avoid ‘useful / useless’, and instead relate structure to function. ‘Vestigial’ parts are identified by the fact that they have features of structure which are not related to their function. The appendix doesn’t need to be vermiform; the coccyx doesn’t need to be made of separate vertebrae-like bones that then fuse into a single piece; and so on. They may have uses, they definitely have design irrelevancies.

The creationist might respond that we’re trying to knowing the mind of the designer. But then all design arguments are off: they are doing the same thing when they say that eyes are well designed to see with. I suspect they don’t want to let go of the argument from design that easily .

Cheers, Oolon

Kevin Dorner

No worries... it happens. It's a bit of a pain because it makes it difficult to discuss source material that is hidden behind paid accounts and one is left with only the articles that have been predigested for public consumption. Ah well.

Blinn

Let me reiterate:

pz

All this is obvious to rational people. This still leaves an open question, though: if he thinks blind fish are doomed to starve to death or be unable to breed, how does Vanderzyden think entire species of blind fish manage to survive?

Prediction: he's going to squink madly, flinging out clouds of rhetoric in a vain attempt to obscure the fact that he won't answer a simple question.

Blinn

Strawman. You assume that these fish depend upon sight for reproduction. The Mexican blind cave fish (and the surface dwelling version) are egg scatterers. The male and female swim in close proximity to one another in the water column and drop their gametes. And as I said before, recognition of a conspecific's sex is probably cued by scent and/or pheremones.

Lizard

Originally posted by Vanderzyden:
VZ:
Are you under the impression that individual, seeing fish *suddenly* lose their sight?

It takes generations for natural selection to work. It doesn't happen to an individual, certainly not *suddenly*.

So there wouldn't be a formerly sighted fish swimming around bumping into cave walls saying, "Hey! Who turned the lights out! I can't find my mate! Where'd my eggs go?"

Blinn

How about "adapted"?

That is not what the article says at all. It reads (bold added), This is what you will find in sighted, surface dwelling fish. Lateral line and gustatory systems, which they use, in addition to sight, to go about their habits. Take away light, and they still have means by which to find food, mates, avoid objects in the water column, etc. They do not die for lack of being able to see.

It's not a deficiency if you have other strong sensory systems to rely on and you're on a level playing field with the rest of the individuals in your population, i.e. they're in the dark too.

[ October 14, 2002: Message edited by: Zetek ]</p>