I believe Intelligent Design is bunk, and that Hitch has it right that its just creationism in a cheap suit. However, blank eye sockets do not disprove creationism unless you are presuming to know the intent of the creator. Its not a stretch to posit that the creator has an aesthetic that includes the overall facial structure that we see conserved across species.

It is the deeper structures, such as the old visual processing centers of the brain (and whatever they may be now) or gene fragments that once coded for light receptor molecules that make the creationist case harder.

Ultimately though, creationism does not need to meet scientific tests because it is a matter of faith not science.

You point out that you believe Intelligent Design is bunk but then state that creationism relies on faith and cannot be disproved.

While we cannot ultimately disprove Intelligent Design (as you say, in many ways it is just creationism in new guise) we can prove that it is not science and should not be taught as such. That is a significant fundamental difference between Intelligent Design and creationism and should be noted as such.

In an interesting way however, blind cave dwellers do put a chink in random natural selection.

Simply put what is the evolutionary advantage to losing ones eyes?

Yes in the dark eyes offfer no advantage, but do they offer a disadvantage to the creatures who have them?

That eyes atrophy, and become useless, and become removed from the genome of a creature doesn't show natural selection, by contrast they suggest that an animals activities and needs may have some control over their genome.

This isn't creationism, it is infact a scientific theory that was popular just before Darwin. That the repeated streatching of their neck lead to girraffes long neck for example.

That a salamander might turn off genes that are useless but are harmless is interesting, and the question of why always presses man to greater scientific curiosity.

It's best not to get too caught up in one theory of the events to suggest only a single outcome.

Charlie107:

Simply put what is the evolutionary advantage to losing ones eyes?

Ask Oedipus.

"Yes in the dark eyes offfer no advantage, but do they offer a disadvantage to the creatures who have them?"

Obviously, yes.

They requires extra energy and brain processing power to operate. If you were stuck in a completely black cavern, you're brain - which is wired to base most of its perception of site - would have a fit, and you would do far worse than creatures who never had to bother with distractions like "seeing".

Briefly stated, having eyes in a lightless environment wouldn't be "harmless". In fact it still takes neural processing power to run the eyes, and to have the entire ocular system going when in fact you will never (or very, very rarely) see anything is a waste of energy, and of the fairly limited brain capacity of a lizard.

It could also be dangerous. I haven't see the show Hitch mentions but I'm guessing the sightless salamanders didn't flinch in the light of the TV cameras. Had they eyes, such light would probably have immediately blinded them. There's no evolutionary advantage to that.

I'm no biologist, but evolution is too efficient to leave such unnecessary organs in place.

Neuro, I agree.

Charlie,

The fact that there are still vestiges after millions of years implies that there is not a strong evolutionary need to lose the eyes. However, growing and maintaining organs and replicating worthless DNA does put the organism at a slight disadvantage. There is a small energy cost from the eye, and so if it does not aid the organism, it will eventually disappear.

In addition, random "noise" would cause any useless but highly ordered system to eventually disappear. A mutation that happened to prevent eyelids from opening, or rods from forming would not be selected against in this population. Since most mutations in the visual system would cause a less perfect system, the tendency would be for the eye to disappear.

By the way, the theory that you are referencing is by Lamarck.

Blueshift

Charlie,

People are "caught up" with evolution because it's an extremely well-established scientific theory. The hypothesis of Lamarckian evolution, of the sort you cited, is simply not how things work, which is why we disregard it. There was vigorous scientific debate on these competing hypotheses ... 100-150 years ago, but it is since settled.

I don't know if this was your intention, but I often hear arguments from evolution deniers that claim scientists are "caught up" with evolution, and simply haven't considered the alternatives. These arguments almost invariably come from non-scientists, and are absolutely incorrect.

As for the question evolutionary advantage of not having eyes; it's about economy, for one part. Making eyes takes energy. Maintaining the neural pathways necessary for vision takes energy as well, and uses valuable cranial space. And what does a salamander brain in a dark cave do with the sensory input from sight? It may not seem like much, but if two similar phenotypes are competing for survival/selection, and one is just a bit more energy efficient, it is the one likely to survive and propagate. Carry that for millions of years, and the probability turns into near certainty.

Perhaps the eyes are an opening into the body which increases the chance of disease and death. You would not need to increase the chance of death much to favor salamanders who lacked as large an eye aperture. After a while, perhaps the salamanders whose eyes had completely covered over would be favored.

Just throwing it out there.

blueshift:

I believe Intelligent Design is bunk, and that Hitch has it right that its just creationism in a cheap suit. However, blank eye sockets do not disprove creationism unless you are presuming to know the intent of the creator. Its not a stretch to posit that the creator has an aesthetic that includes the overall facial structure that we see conserved across species.

It is the deeper structures, such as the old visual processing centers of the brain (and whatever they may be now) or gene fragments that once coded for light receptor molecules that make the creationist case harder.

Ultimately though, creationism does not need to meet scientific tests because it is a matter of faith not science.

By the standard established here, Creationism can never be disproven. Why should aesthetic be the only possible intent of the creator? Maybe his intent is to have deeper vestigial structures, just to fool non-believers into worshiping a Godless evolution? We could posit infinite things a Creator might intend.

But in any case, my understanding of the latest in pure Creationist science is that of "kinds"; that micro evolution does occur, but is limited to the point that speciation does not occur. It goes thus: yes, salamanders lost their eyes, but the blind ones are still salamanders. Their kind hasn't changed.

Creationism is so nebulous, and they don't care about getting the details right. Their only requirement is a Creator, and such can never be "disproven". I think the blind salamander is a useful bit of evidence though, and provides a simple example of evolution that a lay person can easily grasp.

Charlie, there's a clear evolutionary advantage to not having eyes (where there is no need for them): you don't have to spend time or energy to grow and maintain them.

Every single calorie that isn't spent on eyeballs can be put into something else. There's no reason to pour time and effort into an essentially useless appendage.

This can be done without a Lamarckian "response" to the environment. In fact, the Darwinian approach is actually simpler: the blind salamanders had more baby salamanders than the seeing salamanders. Eventually, all the salamanders are blind.

As a side not, there are at least two works of fiction that I can think of that talk about the precarious nature of human intelligence. Considering that 25% of all our calories get funneled into maintaining those big glorious brains of ours, it's not hard to predict that it would only take a relatively small change in our environment to stamp out the advantage that higher level thinking gives us. _Galapagos_ by Kurt Vonnegut and _Evolution_ by Stephen Baxter are both worth checking out.

Samslaw...

Appendix...

Blanchy:

Perhaps the eyes are an opening into the body which increases the chance of disease and death. You would not need to increase the chance of death much to favor salamanders who lacked as large an eye aperture. After a while, perhaps the salamanders whose eyes had completely covered over would be favored.

Just throwing it out there.

That's quite possible. We're most susceptible to infection at our membranous surfaces, interfacing with the outside world. The eye is one of them. Why have this chink in the armor, if there is no function for it?

Sanjait,

Thats correct, Creationism can't be disproven as it is not a scientific theory. So pointing out scientifc facts can never address Creationist philosophy.

Pointing out how well the evidence supports evolution is a different emphasis to the same data, and I think a more worthwhile approach. So, yes as you say the blind salamander is a useful bit of evidence.

The evolutionary advantage of losing an unneeded structure, such as the blind cave salamander's eyes, is that the creature does not have to expend scarce resources to grow the structure. Body mass equals food energy, particularly in embryonic egg stages. A mother salamander with atrophied eye genes could produce more offspring for same energy investment as a non-atrophied eyed gene mother and thus would gain a classic Darwinian reproductive advantage.

Additionally, the neurological structures devoted to eyesight might also be "hijacked" by other neurological or sensory functions that could confer adaptive advantages in the lightless environment. This is purely speculative, but it wouldn't be surprising. Creationists have a point when they point to the shear unlikelihood of evolving new, complex, structures "from scratch"; what they miss is that complex structures arise from both simpler structures and from existing complex structures useful for ones ancestors but not in the species' current environment.

LMoE