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Evolution of the Eye

The eye, contrary to proponents of Intelligent Design is not irreducibly complex (tip to onegoodmove reader Agitated Monk


 

Comments

that video doesn't have anything to do with irreducable complexity. It has to do with how the eye itself would be modified by evolution.

what most "proponents" of intelligent design would say is that the idea that an eye, and the part of the brain necessary to interpret the signals from the light sensitive areas would have to evolve in perfect unison to be useful at all.

I'm not advocating one thing or the other, I'm just saying this video doesn't prove or disprove anything.

interesting stuff though.

SEAN

one good thing about the wholem creationism debate is, that I actually learn a lot about biology through all the educational films popping up right now...

He got it spot on. The way the world really works in infinitely more fascinating and subtle than the religious fairy stories; but a bit to complex for a bush voter to understand....

Those that believe in intelligent design argue that the eye could not have evolved.
Isn't the argument of irreducible complexity such that the parts of the whole would have no function independent of the whole? The fact that light sensitive cells are functionally useful is evidence that the eye is not irreducibly complex based on that definition.

nicely put sean. i wouldnt like to guess what ID proponents might say about this video. i would like to say it is highly dependent on the assumption of macro-evolution. that means it is good for pointing out the shortcomings of said theory.

  1. like you say, having light sensitive skin is perfectly useless and possibly more harmful than anything unless something connects the mutation to the brain.

  2. this process had to work out each stage in much the same way for each divergent species that has eyes like this but belong to different evolutionary paths.

  3. which came first the lens or the narrow opening? if the lens was first what would make it useful (if hes going to add sub-uses for a primitive lens then this demonstration is far too simplistic)? if the narrow opening came first what would make IT useful. nothing related to seeing .. he made that very clear (dim). one of these occurances due to a mutation requires an astronomical statistical probability which isnt even approached by millions of years worth of time, both of them at the same time? impossible.

  4. he mixes up evolutionary progress with basic modern eye function. we already know lenses adjust and focus. thats nothing to do with evolution.

  5. his final comments are that this must be what happened if evolution is to be accepted, i let you be the judge.

oh and:

3b. this progression is presented as simple steps yet the step between the cavity stage and the cavity and eyeball stage is a major one he left out. im sure with further work he could plot every one of the necessary major structural adjustments needed to get from tapeworm to tennis player with a government grant and a 1400 year life extension.

stipe: Is your argument that it is not worth the time or money to study it because it takes too long? I'm confused.

I hope that you were pleased by the discovery of the "missing link" fish fossil a few weeks ago. I know that some folks might become frustrated or confused by a discovery such as this, but for others, it is simply amazing and satisfying. Why does evolution get such a bad rap? I think it's so cool and fascinating! It's only a matter of time before we discover new links, develop new theories, break down old ones, sharpen our knowledge of where we come from... et cetera!

"Scientists Call Fish Fossil the 'Missing Link'" NY Times http://www.nytimes.com/2006/04/05/science/05cnd-fossil.html?ex=1146024000&en=9fbae51db8d0052e&ei=5070

I agree, ubik!! I eat new knowledge voraciously.

Norm- I had to read through your rebuttal twice, but now that I fully understand it, I gotta say, that's a very sound argument. However, it does rely on the assumption that "the parts of the whole would have no function independent of the whole" is the argument of irreducible complexity. Is it, in fact?

Nice find, this clip. I loved the guy's final statement. "the way eye evolution must proceed"

I'm certainly not an expert on the subject, but I believe that is correct. Here is how Behe defines it.

An irreducibly complex structure is defined as ". . . a single system composed of several well-matched, interacting parts that contribute to the basic function, wherein the removal of any one of the parts causes the system to effectively cease functioning." (Behe 1996a, 39)

Unfortunately I wasn't able to view the video (my computer has some trouble with this format for some reason), but I wanted to contribute anyway...

What I wanted to point out was that, first, evolution doesn't necessarily experiment with every conceptual possibility. In fact, the space of possbilities is highly constrained by physics and thermodynamics, which favors stable, high-entropy solutions. While on the surface this may seem like it runs counter to complexity, in some cases it actually helps. For example, think about the way soap bubbles form spheres. This pattern is not selected, but results from the fact that a sphere is an optimum solution to minimize surface tension. Similarly, evolution would not "try" all possible eye shapes. This idea was pointed out by D'Arcy Thompson over a century ago, but was out of favor until recently.

Another "force" that's important as a complement to incremental selection is spontaneous self-organization. This is a process that takes place in complex, locally interactive systems (of which biological systems are a subset) which, as a result of feedback loops, results in "order for free". The famous Belosov-Zhabotinsky chemical reactions are a classic example. The necessary conditions are simple, but when met the result is a beautiful oscillating pattern of ripples and changing colors. Try Wikipedia-ing it.

Anyway, taken together, these two forces drastically reduce the probability space for complexity, countering some (flawed in the first place) arguments by ID folks that the probabilities involved would have been astronomically small.

Another interesting observation: geneticists have discovered a gene (I think it's called Pax6) that has remarkable homology in essentially all animals with eyes and which can be transplanted from fruitfly to mouse (or vice versa), resulting in the growth of an eye in strange places. The kicker is that the eye that develops is species-appropriate even though the genetic material is identical. The point is that genes don't have a direct relationship to phenotype, but interact with the local environment. It's a common fallacy to say that things are "caused" by genes.

Sorry for the rambling and tangential nature of this comment... hopefully it's interesting food for thought.

Although TalkOrigins.org is down at the moment, there is a good explanation of the evolution of the eye in the Creationist Claims page.

Also, recently there was the episode of "The Way of the Master" (Episode 7 The Beauty of a Broken Spirit - Atheism) on One Good Move. It's the one with the banana. There are so many fallacies in that single episode that it amazes me, but unfortunately the people who watch these videos don't notice them because of their ignorance.

(Also, I sent this video in, in case you were wondering)

Ummmm That guy just assumed a light sensitive diode. Where did that come from? ever seen someone with a birth defect that was light sensitive? This is the problem with evolution. They assume away too many things.

While he's at it maybe he can explain we went from asexual reproducing cells to sexual reproduction. Guess they got lucky and a male and female organism evolved at the same time.

My understanding of both biology and evolution is limited. Yet I find the motivating rational behind ID frustrating. Not having concrete evidence of phenomenon doesn't prove of another entity existence.

Colin- Thanks for the thoughtful comment- it's good to get perspective from other branches of science. However, I think talking about thermodynamics is not very useful when it comes to evolution--try, for instance to explain a male peacock with thermodynamics. "High entropy solutions" are of course always favored in physics and chemistry, but they don't have a lot of force in living organisms. It's true that useless limbs and tissue or organs frequently get "bred out" of a species during its evolution, unless that part happens to be sexually attractive, but we humans are still wandering around with tonsils and an appendix and various other things we could do without. The truth is, in my opinion, and this is a point totally missed by ID people, is that the reason living organisms and things like the eye and the immune system (which is WAY more complex) are so unimaginably complex is because there WASN'T a designer. Think, for instance about the computer you're using to type this: It can do more calculations in the next second than you could do given 1000 lifetimes (this is a wild guess, but you see my point). Now, think about how UNIMAGINABLY more complex your brain is (and the body that supports it) than the computer you're typing on. The computer's made of a few kinds of plastic and metals, some chemicals, maybe some glass, maybe some rubber. They can slap it together in a factory. A part breaks? Just open it up and stick another part in. Load another OS, whatever. And yet they can make a computer (20 years ago, no less) that can beat the best player in the world at chess. Now, in no way am I saying that a computer is currently capable of all or even most of the things the brain is, but, what I'm saying is a truly intelligent designer could create a human being that would function at a bare fraction of the caloric cost. And one that would not suffer all the infinite frailties of homo sapiens--frailties that are frequently due to the fact that we are so complex as to be basically unfixable over the long term, at least with current knowledge and technology. Just think about how crude and primitive brain surgery is when compared to the complexity of the brain. It would be the equivalent of trying to maintain your 2006 Toyota Prius for the next 1000 years using nothing but a screwdriver and a hammer. Wondering why we share 60% of our DNA with lettuce? Well, I don't think it has much to do with thermodynamics. And, I hate to break it to Kirk Cameron (he seems like a nice guy) but it sure as #$%! doesn't have anything to do with intelligent design.

Thinknot [good name for you, by the way]:"Ummmm That guy just assumed a light sensitive diode. Where did that come from? ever seen someone with a birth defect that was light sensitive? This is the problem with evolution. They assume away too many things."

False. You made up an argument and tore it down. You're clueless.

"While he's at it maybe he can explain we went from asexual reproducing cells to sexual reproduction. Guess they got lucky and a male and female organism evolved at the same time."

Evolution says nothing of the sort. Be aware that the only way you can dispute evolution is to lie about what it is so that you can refute it. You make me sick.

"This is the problem with evolution. They assume away too many things."

Yeah unlike theism. I mean, the only ontological commitment there is an all powerful extra-dimensional creator of space time which loves us and gave his only son that those that believe in him would not die but would have eternal life. Self-evident, really.

Have you people never heard of sunflowers? Photosensitivity has obvious selective advantages WITHOUT connection to anything like a brain in anything which photosynthesises. From there it should not be too hard to get to mobile photosynthesisers (look at Phytoflagellates) who use these sensors for navigation.

As for the question of sexual reproduction (and consider for a moment the alternate hypothesis is 'the whim of the invisible man in the sky') the major advantage is the boost to defence against pathogens that a reshuffling of protein markers gives. As to how it might evolve, simply imagine an elabouration in gene communicating mechanisms found in bateria).

It seems odd to me that people, wishing to dismiss evolution as a completely natural process, will talk about how horrible the odds are for one system or another to develop without the guiding force of an intelligent creator.

First off, anybody that throws out a probabilistic figure with the claim that "the odds are astronomical" ,is usually guessing, and, secondly, we have proof that highly complex systems can organize themselves out of less complex systems: us.

Colin: "Sorry for the rambling and tangential nature of this comment... hopefully it's interesting food for thought."

I found your post to right on the ball; particularly this part: "Try Wikipedia-ing it." Which, as it happens, seems to be a good to response to this guy: Think not: "Ummmm That guy just assumed a light sensitive diode. Where did that come from? ever seen someone with a birth defect that was light sensitive? This is the problem with evolution. They assume away too many things.

While he's at it maybe he can explain we went from asexual reproducing cells to sexual reproduction. Guess they got lucky and a male and female organism evolved at the same time."

Its the evolutionist that assume to much, right. rolls eyes

Think not- indeed.

Hmm, seems I need to edit my last post a bit.

That first part should read "...people, wishing to dismiss the idea that evolution is a completely natural process

As my powers of language seem, for the most part, to be leaving, I am trying to say that evolution is completely natural, whatever the odds.

argh

Interesting handle "Think not" it does a fine job of defining the author.

asexual

Colin said: "The kicker is that the eye that develops is species-appropriate even though the genetic material is identical. The point is that genes don't have a direct relationship to phenotype, but interact with the local environment."

Potshot, my powers of language seem to be leaving too. That seems to be what happens as we age. Another intelligent design. :(

Thank you for this. I agree with Ubik. The great thing about the naysayers is that it brings out all of these people who know a lot more than I do about evolution and biology, and I end up learning a lot.

Interesting discussion.

Norm: "Interesting handle "Think not" it does a fine job of defining the author."

Good stuff, I was going to touch on that but felt it was to obvious heh. With you %100 percent, maybe this guy is just trying to mess with us? Why else would he have such a name?

Maybe it is how he protects his faith?

"Think not":

Which is better; To assume that something is true, when all available evidence would lead us to that conclusion...

...or, to assume something is true with next to no proof. (Creationism)

Think not: "While he's at it maybe he can explain we went from asexual reproducing cells to sexual reproduction. Guess they got lucky and a male and female organism evolved at the same time."

1) Bacteria, which reproduce asexually, also undergo conjugation in pairs, wherein they exchange precious bodily fluids (i.e., genetic material) with each other. This is not unlike sexual reproduction, but without distinction between "male" bacteria and "female" bacteria.

2) Yeast, which reproduce asexually by budding, are also capable of sexual reproduction, but they are isogamous. Once again, there is no "male" yeast and "female" yeast.

3) Hydra, which reproduce asexually by budding and by regeneration, are also capable of sexual reproduction through the formation of testes and ovaries. Some species of hydra are hermaphroditic whereas others have males and females occurring as distinct individuals.

The above examples should offer some clues as to how sexual reproduction of the sort found in higher organisms may have gradually evolved. Organisms which are able to reproduce both asexually and sexually, such as the yeast and hydra, may have had ancestors which only reproduced asexually. When these ancestors began to evolve sexual reproduction, any initial failed attempts in this regard would not have been disastrous as asexual reproduction would always exist as a fallback option.

Sean, the example above does prove that Intelligent Design and its supporting concept of irreducable complexity is wrong.

According to ID proponents, they claim that the eye is irredicibly complex as it can't have evolved because it's such a complex organ. Remove just one component from the structure of the eye and it will fail.

To them, half an eye is as good as having no eye at all.

The video here shows how "half an eye" or even one-tenth of an eye in the form of a primitive light-sensitive eye spot is useful to an organism and can kickstart the evolution of a more complex eye structure.

Evidently half an eye is still useful for vision when other organisms are concerned.

And based on research, the eye of human beings are only around half complete. Human beings only have half an eye if you consider these points:

  • Humans see in only three colors. Some fish see five. (A very few women are tetrachromats; they have four types of color receptors; Zorpette 2000.)

  • Humans cannot see into the ultraviolet, like bees.

  • Humans cannot see infrared, like pit vipers and some fish.

  • Humans cannot easily detect the polarization of light, like ants and bees.

  • Humans can see only in front of themselves. Many other animals have far greater fields of view; examples are sandpipers and dragonflies.

  • Human vision is poor in the dark; the vision of owls is 50 to 100 times more sensitive in darkness. Some deep-sea shrimp can detect light hundreds of times fainter still (Zimmer 1996).

On a scale of 100, I have to give the eyes of human beings just 50. In this sense we human beings have only half an eye or half of perfect vision and for most of us that's as good as it gets.

More information here:

http://wiki.cotch.net/index.php/Eye_evolution

Why does Inwit have to so patiently explain this? It's not that difficult is it?

Some people has asked why eye spots come from. The answer is easy. They come about as an interaction between an organism and sunlight shining on it.

Take the example of plants. They do have eyes but they will grow towards the direction of sunlight.

Sunlight is more than just light to living organisms. It is also heat and provides even nutrients.

Close your eyes and you can still feel the sun shining on you.

As time goes on, the parts of the living beings that are more sentive to light will adapt further to totally focus on its tasks, which leads to light-sensitive eye spots:

• Dinoflagellates are single cells, but they have eyespots that allow them to orient toward light sources (Kreimer 1999). • Starfish and flatworms have eyecups; clustering light-sensitive cells in a depression allows animals to more accurately detect the direction from which the light is coming from.

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Intelligent Design is dead wrong on their arguments for eyes. If any of them raise the Eye as irreducibly complex, kindly remind them of moles.

Moles live their lives underground without light. However, they are still born with eyes, which cannot see.

Why would God make eyes for moles if they don't need it?

The answer? Evolution is at work here. Moles gradually adapt to their environment by focusing more on their senses on identifying vibrations while their eyes become redundant.

I see evolution at work. See?

Mitch, hopefully I helped clear your concerns.

Everytime Intelligent Design proponents claim that evolution lies on something, you just need to focus on that thing to find out that ID is the one lying.

ID people are not strong on research and are often looking for bo-brianers to refute evolution.

Why would they do that if they believed God gave us a brain?

But if they were evolved to do away with it, I guess I have nothing further to say.

Cheap shot indeed. I'll apologise for that.

But fun though : >

Kes, you are too intellectual and educated for most people to even begin to understand what you are saying.... I loved this>> "ID people are not strong on research and are often looking for bo-brianers to refute evolution."

Again, I appreciate all of you who research these concepts and share what you have learned with the rest of us.

Thank you.

Hi Jo, you damned me with faint praise but I just read and question too much, besides the fact that I can be really catty i.e. the cat in me likes to flex its claws now and then.

All of which combines to form a truly disagreeable and disreputable ruffian...

... who is also appalled and utterly ashamed at his typos as he keeps on forgetting to do a cut and paste of his postings from a Word document after doing a spell check. It should be:

"ID people are not strong on research and are often looking for NO-brianers to refute evolution."

Were my last few posts here too complicated? I tried to keep them as simple as I could.

Btw, inwit, when you refer to the Hydra, are you referring to this:

http://en.wikipedia.org/wiki/Hydra_%28genus%29

sigh... "No-brainers"

Who gives a damn about every stupid little typo? So it was a no-brainer, and not a bo-brainer? Darn it, and "bo-brainer" sounded so cool.

Jo ann, thanks again. I guess I need to spend more time typing on a real typewriter, rather than on word with its spell check feature. I normally print out what I wrote to eliminate typos as I can be more thorough that way.

Btw, inwit, when you refer to the Hydra, are you referring to this: http://en.wikipedia.org/wiki/Hydra_%28genus%29

Yeah, that's the one.

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i can see why people here might start to get tired of intelligent design, but really, those people (think not and i think a couple others) are just asking questions. theres no need to attack them for that.

But why doesn't the banana have eyes...??

On the subject of hermaphrodites, ogm readers might want to check out this remarkable paper (pdf file) that appeared in Nature a few years ago on how a mutation in a single gene gave rise to reproductive isolation, and thence speciation, in some hermaphroditic snails. This single gene controls whether the snail shells are right-handed or left-handed; and right-handed snails have difficulty mating with left-handed snails. (Caution: contains graphic images of copulating snails.)

That paper should be digested in conjunction with this snippet of a Feynman lecture that Norm posted last year, another example of chirality in Nature—this time in biological molecules, not organisms—being linked to evolution.

Hey guys,

thanks for being patient with me and kindly explaining things.

after I left the first comment I got in my car and as I was driving out of the parking ramp at school I realized that I hadn't thought at all about what the definition of irreducable complexity actually is and had pretty much got it wrong.

so I apologize for my hasty reply.

I'm almost ashamed to admit to being a Christian here. It seems like there is a lot of animosity. That simply by saying that I am a believer I am suddenly a simpleton who wants to have moral rule over everyone.

Unfortunately, you are mostly right to make that assumption because many of the people who claim to be Christians and have lots of money and video cameras ARE simpletons who want moral rule over everyone. But as Bill Maher so eloquently put it, "they aren't Christians at all."

Anyway, my point is this: As a Christian, I don't care if you believe in evolution or not. There is definitely a ton of evidence for it. And the idea of it doesn't threaten me at all.

I'll tell you the problem I've always had with it is the organ-brain thing ... especially with the eye.

If you have a creature who all the sudden developed a few light sensitive cells (aren't all cells light sensitive anyway?) that creature would need nerve endings to transmit the signal to the brain, and once those signals got to the brain, it would need to be able to interpret the signals as "sight".

So it's a three part process. All of these parts would need to come into existence almost simultaneously ... wouldn't they?

SEAN

Hi Sean,

You're making the common mistake of skipping steps. It helps if you think about very simple organisms like the flatworm as a starting point. For light sensitive cells to connect to their nervous system is not so complex. Since mammals evolved from very primitive forms of life, and eyes evolved step by step along the way, by the time they exist in mammals they are much more complex.

It's common problem when humans think about evolution to overlook that massive change happens in tiny incremental steps over hundreds (or thousands, or millions) of years. For bird feathers to change color might only take a few generations, while the existence of the human eye might take thousands of generations (from bacteria to human beings took a long time)... but both physical structures and changes in the structures are the product of adaptation. Some changes simply require more time and more intermidiary steps.

I don't really know if early creatures would have really had a brain, or centralized nervous system.

A mutation that caused special cells to develop that were more sensative to light than usual would then be free to develop anywhere on a creatures body, easily tapping into any sort of nerve.

This would give a creature more knowledge of the outside world, thusly giving it more powers of replication and passing its "knowledge" on to further generations.

Being a christian does not make you a simpleton, although many true simpletons happen to be religious.

As long as you don't educating yourself about reality, I don't have a problem if you want to call yourself a christian. However, you must understand that true christianity holds to scripture, and scripture says that god created man in one day... and there is no reason to take it any way but literally.

It is only when Scripture comes in conflict with true knowledge about reality(i.e. Creationism vs. Evolution) that religious people feel that they need to understand the Bible in a way that allows things like "how do we know what a 'day' is to god?" or various ways of understanding how Noah fit all those animals on the Ark, et cet. ad nauseum.

Just keep on reading, don't believe in something unless it has evidence backing it up, and you should be (mostly) free from ridicule.

right .. sorry. i think im a bit out of my depth on this subject. ill come back one day if i get a clue and resist regurgitating other peoples theories ...

Sean

As a layman, I have limited knowledge of evolution and how it really works. But in regards to this "organ-brain" thing... common sense tells me to ask this question: Doesn't everything evolve with cooperation from the brain? (Or some sort of central nerve factory) All of our various parts, not just eyes, have nerve endings that our brain is connected to. I assume that these various fleshy tools and organs and extremities did not evolve separately-- doesn't the brain at least partly dictate what they do?

Is this a rational assumption? It seems common sense to me. I don't see any "three part process." All of our collective parts are indebted to the brain that makes them work. I assume that organ evolution happens because of this symbiotic relationship with the brain. I'm totally speculating, but it sounds rational to me.

I guess that we run into problems when thinking about the function of something like the appendix! But some scientists would say that it is probably a "vestigial remnant," and its original function has been lost over time...

This is the great thing about science and evolution and exploring the cosmos. Nothing is set in stone. We study observable things. We develop theories based on evidence. Sometimes the theories are so solidly backed up by evidence that they are practically indisputable. But there is always that window open in which some new discovery can be made and change everyone's minds. I love that about science. You don't have that kind of freedom with religion or creationism or "intelligent design."

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Behe (who coined the term irreducible complexity) specifically points to the development of the eye as NOT an example of irreducible complexity. Take a look at this... http://www.arn.org/docs/behe/mb_mm92496.htm

I'm not saying I agree or disagree, just trying to clarify.

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Ok, I did a little more reading and it looks like others pushing ID are claiming the eye as an example of irreducible complexity. So I am simultaneously right and wrong. Don't tell the cat

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Two things:

First, in response to clownfish, I think you might have overinterpreted my comments about thermodynamics. I didn't mean to suggest that thermodynamics alone could explain evolution, just that there are physical laws that constrain the space of possibilities. That is, natural selection is of course a central force, but it's not going to play with the vast space of possibilities that is often cited as evidence against complexity through evolution. I brought up bubbles to point out that symmetry generally arises without specific selection. Although you could imagine an eye that has all sorts of weird bumps on it (which probably wouldn't be that useful for focusing and distributing light), that's not going to be tried. Instead, the progression from flat to concave to spherical is more or less a one-dimensional one.

Regarding the peacock, although the pattern appears very complex and beautiful, it's also quite regular. It's not as if natural selection would treat the peacock's tail as a panel of pixels, adjusting each pixel independently. Because the local environment for each cell greatly influences its differentiation, the genetic "program" for the peacock's tail need not be as complex as the tail itself appears. That's precisely self-organization in action.

Second, I wanted to say a couple things about the co-evolution of the eye itself and the neural system that "interprets" the signal from the eye. It's true that they'd have to develop in concert, but why wouldn't they? Each limits the other, such that an organism that had a sophisticated eye without sufficient neural machinery, or vice versa, would potentially be no better off than an organism that had neither. The implication is that there would never be a point where the two were too discrepant, because any significant discrepancy would produce enormous selective disadvantage.

And now, to tie these two threads together... I've already pointed out how physics reduces the dimensions along which selection operates, and suggested how this could apply to the eye. Something similar is true of the brain. The brain performs vastly many functions, but the variety of physical components is much smaller. There are many, many types of neurons, but not nearly as many as there are brain functions. Critically important for complex functionality is the pattern of connections formed by neurons. A lot of the wiring is nudged by biology, but a lot of it can be accomplished through learning as well. With regard to the visual system, the patterns of light that fall on the eye have a lot of structure in them to begin with. Large (with respect to photoreceptors), coherent objects move as units in the environment, constituting highly reliable statistical structure. It might not take much in the way of fundamental building blocks to get that structure to be transferred to the neural wiring; perhaps something like Hebbian associative learning could get us a lot of the way. What I'm suggesting is that it might not be necessary to have a dedicated genetic program for wiring visual cortex at all -- a lot of the work could be done in the course of experience. What would be selected for is the comparatively simpler fundamental building blocks, that we see working the same way in many brain systems, not just visual ones.

I really think that no matter how many pieces of the fossil record are uncovered and no matter how many "missing links" are reported in the NYT and how many evolutionary mock-ups and models (like the eye clip above) scientists go to the trouble of creating, no hard core (or even soft core) creationist will really believe in evolution. Funny thing about missing links is that when you find one missing link, you suddenly have created empty slots for two MORE missing links. Evolution is probably never going to be definitively demonstrated in the lab either--any more than anyone is going to definitively demonstrate in the lab that the Holocaust really took place. Things that don't happen right before people's eyes (like an apple falling and hitting you on the head) have to be proved by inference and a patchwork of evidence. And when you're trying to prove something by that method that a large segment of society has a vested interest in remaining UNproven, you're going to find that there are just too damn many holes to plug in that patchwork. You're fighting an interesting but ultimately impossible fight. I was thinking about thermodynamics last night after reading Colin's post way up on this page. And so I called a friend of mine who's an astronomer (no, really) and we were talking about those laws. He told me that he'd recently heard a well-respected physicist sum up the laws of thermodynamics: The First Law of Thermodynamics Is: You Can't Win. And the Second Law of Thermodynamics Is: You Can't Even Break Even. And I was thinking how brilliant that is (never mind depressing) and how well it applies to these kind of arguments we have with creationists. It's cynical, but sometimes I just think, why bother? I imagine that if I was Kirk Cameron and trying to sway an atheist by telling him about the eternal damnation he faces by breaking the Ten Commandments, I would find it extremely frustrating that this atheist took the Ten Commandments about as seriously as he took the "Do Not Remove" warning label on a blanket.

I agree this is all very interesting for discussion, but I think it's fruitless trying to prove evolution to these people. Personally, I think you can't really grasp the beauty and inevitability of evolution until you grasp the incredible process by which DNA replicates itself. Understand that, and you understand that evolution is not a "theory" or "hypothesis". You'll understand that evolution is not some amalgamation of unbelievable coincidences and infinitesimal likelihoods. Instead, you'll understand that the possibility of evolution NOT taking place is like the possibility of erecting a giant white wall stretching across a world full of graffiti artists and coming back a billion years later to find it without any marks. Evolution is just a process. It goes on all the time, all around us, for as long as there's been life. Saying evolution doesn't happen is just like saying that societies do not rise and fall, that relationships do not begin and end, that no one ever dies in a car wreck, that outfielders never miss a fly ball, that no one ever meets anybody on the bus, and that the world never changes.

Colin- Sorry, I wasn't very clear with what I meant in my first post about the male peacock--I wasn't suggesting that evolution couldn't devise something so complex; I was just suggesting that explaining the male peacock's overall appearance by the idea that everything tends toward entropy (at least with the literal interpretation of the second law, which assumes no outside input of energy, like the sun) would be a very difficult path to explain. But I'm a biology guy by profession and not a physics guy, so I can't say anything very intelligent about physics. As you can see from my other post (right below your second), you got me thinking. Thanks.

inwit, the discussion here is kinda getting out of my league. Here's probably my last 5 cent coin as foof for thought?

If a person who is born colour blind trains his eyes to be able to differentiate colours anyway, can you see that as evolution?

I keep thinking that there are actually 2 parts of the evolution debate.

One part deals with evolution as it occurs at the biological level where the organism are born with the changes it inherited from its common ancestor and progeny. Darwin called this macro-evolution.

The second part deals with induced evolution due to changes in the physical environment, which necessitated biological changes. This is referred to as micro-evolution.

The ID people has been gunning against macro-evolution, while ignoring micro-evolution. I'm not sure how their ends are served by this.

However, we can use macro-evolution to knock on Intelligent Design in the case of the penguin, panned by some as natures's most poorly designed creature:

www.huffingtonpost.com/kimberly-brooks/penguins-kill-intelligentb5676.html

With micro-evolution, Adelia penguins were able to make changes to survive, NO thanks to any designer:

http://animals.about.com/b/a/218016.htm

snak, you're right about Behe not claiming the eye as an example of irreducible complexity. His favorite is the Flagellum. Kenneth Miller handed him his ass on that one at the Dover trial. He does a great job of explaining it in this video

Ken Miller on Intelligent Design

www.youtube.com/watch?v=JVRsWAjvQSg

Clownfish:

In the interest of full disclosure, I'm not a physics guy either, though I can see how you might get that from my first post. My background is in cognitive science.

I know you weren't suggesting that natural selection couldn't develop a peacock's tail -- quite the opposite actually. My point was that it didn't have to do it alone, but had help from local interaction.... which I guess is physics in some sense, but also biology. Just not at the evolutionary level.

You being someone who understands evolution, I know I don't need to convince you about its power, but I think it's interesting that there are other natural forces in play that are often overlooked because biologists tend to focus on selection alone as the source of complexity. That's all I was trying to say. If it manages to persuade someone who had a hard time understanding evolution, so much the better.

And because I'm long-winded, a general comment about entropy and the second law... as you point out, it's not the case that the earth is a closed system -- we have the sun. There's also evidence that subsystems (organisms for example) can decrease internal entropy by trading it with their surroundings. Overall, net entropy can increase, but it's redistributed in the process. Check out the Wikipedia article on "self-organization" for a brief and accessible discussion of the topic.

This video is from the excellent PBS documentary called Evolution.

There are a whole lot more video snippets at the PBS website.

http://www.pbs.org/wgbh/evolution/index.html

For me the most interesting one is the Religion section... interesting because as a New Zealander I'm amazed and astounded at the need to have this in a documentary about science. It's a non-issue back home.

You can get the Evolution DVD on Amazon somewhere... and the book is fascinating... much more than a paper version of the DVDs - an excellent reference in its own right.

"If a person who is born colour blind trains his eyes to be able to differentiate colours anyway, can you see that as evolution?"

Not in the Darwinian sense, as there would be no way to pass that acquired ability on to their offspring through their genes. (C.f. Lamarckism.)

To take another example, Newton and Leibniz acquired the ability to do calculus but there was no way for this ability to be passed on to their offspring genetically. However, they could and did pass that knowledge on to other persons in their society, and similarly on down through successive generations. This is an example of psycho-social or cultural evolution, a term coined by Huxley.

Also, kes, I think your usage of the terms microevolution and macroevolution may be non-standard. See item 3 in 15 Answers to Creationist Nonsense, an excellent resource.

"[...] The First Law of Thermodynamics Is: You Can't Win. And the Second Law of Thermodynamics Is: You Can't Even Break Even. [...]"

There is also a gag restatement of the Third Law: You can't even get out of the game. But we shouldn't these restatements literally. For instance, you can break even, entropy-wise, for isentropic processes (e.g., during the adiabatic expansion and compression stages of the Carnot cycle) and for closed systems in thermodynamic equilibrium.

Thomas Pynchon had his own take on this in his short story "Entropy":

"Callisto had learned a mnemonic device for remembering the Laws of Thermodynamics: you can't win, things are going to get worse before they get better, who says they're going to get better."

Pynchon takes a great deal of poetic license, as is his wont.

okay. so Darwin was presented with the same question: how does an eye become an eye when a partial eye isn't useful or how does a bettle wing become a wing when a short stub doesn't help you fly or glide?

the logical flaw that opponents of evolutionary biology (as well as many students of evolutionary biology) is to put the final cause before the process. the term in the logic of Evolutionary Biology is "functional change in structural continuity"

this means that the selective pressure at one point may be very different then at another and different forces may be a work once light-sensitive cells form a cup then when a focal point starts to develop clear lenses. the lenses were not inherrent in the early developments and they woulnd't have made any sense anyway,

You're welcome, kes. The "15 Answers to Creationist Nonsense" article from Scientific American is also available as a pdf file. This version is illustrated and has a list of additional resources on the last page.

Thanks! Have you read the recent issue of New Scientist?

Evolution gets busy in the urban lab

http://www.newscientist.com/channel/life/mg19025483.700

user-pic

"This is the problem with evolution. They assume away too many things.

While he's at it maybe he can explain we went from asexual reproducing cells to sexual reproduction. Guess they got lucky and a male and female organism evolved at the same time"

It seems to be simple logic to me to look for examples that already exist naturally. For the evolution of the eye, an interesting animal to look at is the Tuatara. It has a light sensitive spot that is connected to an outswelling in it's pineal gland, seems perfectly reasonable to me to assume that an animal that can sense it's surroundings in this way has an enormous evolutionary advantage.

For an example of the transition from asexual to sexual reproduction the common snail may be a good example. It is able to produce both asexually and sexually, but tends to favour sexual reproduction, where possible, for the evolutionary advantages this method produces. If it is unable to reproduce sexually it can reproduce asexually. The question arises "why don't more animals have both male and female sexual organs, surely this would provide a survival advantage?" Again this body design has significant overheads in terms of growth and energy expenditure, and if an animal is more mobile perhaps the survival advantage of asexual reproduction is reduced.

I can assure you that whatever example you may think you have of an organism or body part that seems to defy evolution, there will be a logical chain of events that exists, or has existed in the past that has lead to the selection of this example for survival or reproductive purposes.

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