Doubting Didymus

The point is that, if the creator specifies from the start that one species will not require eyes, he could remove the eye completely rather than just disable it. To have any eye at all there, usable or not, is a waste of material.

No, you missed my point. The NAV system was a better analogy than headlights, as it picks up information and translates it to information, where a headlight does not require input.

The point is that, even if this fish were to obtain eyes later, it could not use them anyway. Therefore, it does not make sense to give the fish part of an optional system that it couldn't use, even if it had it.

Look at some of the pictures again. Particularly Zeteks most recent embyology pictures. The eye has not dissapeared, it has only become reduced and functionless.

I didn't agree with that. You said that humans can see this as a defect, while natural selection could not. Thats all I agreed with. Actually, from the perspective of a darwinist this is not a defect at all, as the organisms net fitness remains the same.

You misunderstood what I meant by 'detriment' in this case. I said "The malformed eyes and purposeless orbits are a detriment to the fish". I was not talking about being blind, I was talking about the waste of resources involved in building the eye, as well as leaving the fish with two large vulnerable holes in its skull, which do not need to be there for any reason.

To simplify:

The fish has vulnerable eyeholes and useless eye cups.

The fish would be improved if it did not have these features.

Therefore, if the fish was designed, the design is not optimal.

MrDarwin

Has this come up yet?

Every cell in the body has a complete set of chromosomes and genes, even though the vast majority of those genes are unnecessary and will never be used by those cells. I'm not talking about "junk DNA", I'm talking about genes that operate only in certain tissues or organs, or only at certain times (e.g., during embryonic development). Only the cells of the gonads, which produce the gametes (sperm and egg) for reproduction, need to have the full set. Most cells in the body are very specialized and have no use whatsoever for the vast majority of genes they contain, yet every time they reproduce, they reproduce each and every one of those genes, even the unneeded ones.

This is not only wasteful of resources (why use up raw materials to make something you don't need?), but also introduces more opportunity for replication errors (which cause diseases like cancer). And unless they occur very early in development (i.e., during the first few divisions of the embryo) these replication errors can't even be considered a source of beneficial mutations; since they occur in somatic cells they cannot be passed on to the next generation.

It would make far more sense for cells to lose the genes they do not need as they become more specialized during embryonic development. This would be easy enough to accomplish by segregating genes for similar functions together on the same chromosome, which can be discarded when not needed (e.g., the genes guiding early embryonic development to differentiate cells into tissues and organs could be dropped once embryonic development is completed).

Coragyps

Wow, MrD - Would you repost that as a new thread? With a few good examples, this could kick some ID/creationist heinie....

MrDarwin

<a href="http://iidb.org/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=58&t=001549" target="_blank">Done.</a>

pz

There is also precedent for this. Cells of the immune system do remodel their genome, throwing out bits and splicing together chunks to make custom immunoglobins. I have a vague recollection that at least some nematodes do something similar, restricting fates of some cells by discarding some genes.

I can also think of a great advantage to differentiation by gene excision: cancer resistance! One of the things that causes cancer is a loss of constraint on the cell by deregulation -- neoplasias are basically de-differentiated, reacquiring the properties of a more generic, pluripotent cell. Excising genes would make this virtually impossible. Cells would be locked into a terminal fate, and any attempt to backtrack to an earlier state would lead to failure as the cell tried to rely on missing chunks of code.

[ since the message I was commenting got moved to a new topic while I was writing it, I've also copied my reply to that new topic ]

[ October 16, 2002: Message edited by: pz ]</p>

Vanderzyden

The fish do not have eyes. There are no useless eyes. Embryonic remnants are present, but no eye organ is present to be functional or not.

Yes, I saw Zetek's example. We must distinguish the fish from the salamander. The salamander uses its eyes early in its life. Only later, when the salamanders return to the caves, do the eyelids fuse. It doesn't appear that the eyes are "reduced".

The holes (orbits) are not vulnerable, since they are covered by a flap of skin. They are no more vulnerable than other body parts. The eye cups are functionally irrelevant, since the fish does not need to see. But we may intelligently surmise that perhaps some embryonic material is left so that the orbit is not fully sunken in.

Utility is not the only benefit (or "good") in a design. Let me ask, DD, what is the use of the extra skin at the end of your nose? It's pure cartilage, having only aesthetic value. Can you say otherwise? If not, then you might consider the attractive benefits that a designer takes into account when developing specifications.


Vanderzyden

[ October 16, 2002: Message edited by: Vanderzyden ]</p>

Mageth

Attractive, as in the naked mole rat?

Albion

The holes may not be vulnerable but the brain is. That's why animals have skulls in the first place, to protect the brain. Why leave a couple of points of extreme vulnerability when the original reason for eye sockets is no longer applicable?

Does anybody know if these holes fill in over time, given enough generations? I assume that growth of the skull over those eye sockets wouldnt' be selected against in blind fish.

Blinn

DD was referring to this:


But regarding the salamander, hatchlings are not obligated to live outside of caves, and many of them don't. They live in darkness from birth until death. If larvae do not need to live outside of caves, why would a designer bother with giving them all functional eyes when only a fraction of the larvae will use them and no adults will ever use them?

In fact, it seems that a designer puts the outside dwelling larvae in a predicament, because it becomes imperative for those larvae to return to caves by the time they begin to metamorphose, as they are destined to lose their sight. If they don't return to a cave, then as a blind salamander, they will almost certainly end up as prey for a sighted predator. Why didn't the designer just build a cave dwelling salamander that retains functional eyes?

Evolution provides an explanation for the ontongentic loss of functional eyes in the grotto salamander; ID does not.

Dr Rick

This is an unscientific ad hoc argument devoid of utility and neither verifiable nor predictive. It is not consistent with the "black box" and "irreducible complexity" arguments that are readily falsefiable and put forward by mainstream ID advocates. It is also not applicable to many other other rudiments or vestiges: there is no attraction in a ruptured and painful human appendix.

Rick