Side Comments on Evolution of the Eye

No. That’s like thinking that humans evolved from modern apes. :wink:

But you will find arguments for eye evolution that use just that sort of reasoning. They look at extant eyes, look for ones that they can classify as “simple” and find ones that might be a little more complex, a little more like a human eye, put them into a sequence, and declare that’s a plausible scenario for how eyes evolved.

If course we all know that all extant eyes are equivalently evolved. No extant eye is ancestrally primitive. But it’s a simple thing to pretend that they are. You are right to remain skeptical.

Eyes evolved independently many times. It follows that it must be easy to evolve an eye.

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Darwinism is dead.

image

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@mung that is a cartoon of the argument, displaying your ignorance more than anything else. Ask elucidating questions instead of shutting down the conversation. Here are two examples to help you along.

@T_aquaticus you say that darwinism is dead, so how do you square that with presenting a sequence of selectable steps? How is that different than darwinism?

@T_aquaticus Ive seen scientist place extant eyes into a sequence and say that is how things evolved. How would explain the reasoning behind this? Extant are not the ancestral eyes, so how does that effect the reasoning?

@mung, until you can answer those questions at the same rigor and coherence as Evolutionary scientists, your critique of their reasoning has zero value here.

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I am not saying that all features are either selected for or against. I am also not saying that all changes in phenotype that increase in frequency within a population are adaptive.

I have always read those scenarios as a possible evolutionary pathway, not as an evidenced pathway. It is only meant to answer the question of how eyes could evolve, not how they did evolve. Within our little world of debate, it would answer Behe’s question of how IC systems could evolve.

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I absolutely do not understand this comment. Are you saying that I cannot critique an argument until i can rigorously answer how an eye evolved?

Some links that may be of interest:

http://www.bem.fi/book/28/28.htm

http://www.pigeon.psy.tufts.edu/avc/husband/avc4eye.htm

https://genome.cshlp.org/content/14/8/1555.full

I have a quote but i haven’t been able to verify where it came from:

The more complex a system is, the greater the number of parts that must be sustained in their proper place, and the lesser the tolerance for errors; therefore, a high degree of regulation and control is required.

A nod to this was given in the aforementioned book by Alan Rogers:

In solving one problem, the new design has caused another (p 40).

While both Eakin and Vanfleteren/Coomans assumed a common origin of photoreceptors with subsequent evolutionary change, von Salvini-Plawen & Mayr (1977; see also von Salvini-Plawen 1982) regarded photoreceptors as so diverse and so scattered in distribution that they might have evolved several times in parallel, between 40 and 65 times.

  • Andreas Schmidt-Rhaesa. The Evolution of Organ Systems

@swamidass

The general types of photoreceptors can be arranged into an order of increasing complexity and ‘visual potential’. Simple photoreceptors are thereafter flat spots which can only detect differences in light intensity. More advanced are cup-shaped shaped photoreceptors, which can additionally detect the direction of light (see Land 1991 for a more detailed account). When the cup becomes deeper and the tissue closes except for a small pore, a camera lucida eye is formed which can project an image onto the sheet of pigment cells. The presence of a lens is a further optimization of this system (see, e.g., Goldsmith 1990, Wolken 1995, Land & Nilsson 2004, Warrant & Nilsson 2006 for further details). It has to be tested whether such a ‘logical’ and physical order of photoreceptors does really mirror evolution.

  • Andreas Schmidt-Rhaesa. The Evolution of Organ Systems

I’m actually trying to see things from the other side and not argue about the logic.

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In few instances has the phylogenetic sequence of photoreceptor evolution been clarified; in its place, we can recognize grades of complexity among unrelated animals that show the adaptive feasibility of each stage.

  • Douglas Futuyma

Salvini-Plawen and Mayr (1977) estimated that at least 15 lineages have independently evolved eyes with a distinct lens. The evolution of eyes is apparently not so improbable!

  • Douglas Futuyma

@Mung, you are not a scientist. @Michael_Callen has asked to understand this from the mainstream scientific point of view. That is the purpose of this thread. Do you plan to respect this or not?

I appreciate your comments @Mung … I guess that I’m really trying to understand the evolution of the eye from the perspective of one who is convinced that it happened… and not trying to defeat it at all… MIke

Let’s take these in reverse order.

As a guest here, I will respect your wishes. All you needed to do was ask, something which you had not done. I have had zero interaction with @NLENTS in this thread.

Only just now are you explaining the purpose of this thread. It was started based on a joke! And it was not stated that the thread would be restricted to only certain individuals in order to hear only what @NLENTS had to say. .

What does the fact that I am not a scientist have to do with anything? I’ve certainly read plenty of what scientists have to say on the subject. I am not ignorant nor is my presentation of what scientists say ignorant. @T_aquaticus does a good job of presenting the party line. You seemed fine with me questioning his logic and reasoning and just didn’t care for my tone. Is it my tone or the fact that I dare question?

I still would like an explanation of your earlier comment.

What on earth do you mean?

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That is fair @mung. Let me think about it. I should have been clearer about the purpose here. Let me think about it, and get back to you, along with an answer to your last question. Thank you for your patience.

@moderators help me out if you can.

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I think that everyone here is making comments that are suitable for the site and appropriate for the thread… I have suggested to @Mung and one other that my purpose in this discussion (for which you, Joshua, set the stage with Nathan from several weeks back) was not to debate the evolution of the eye, but rather to understand from an outsider’s perspective how people in the evolutionary biology realm see this as happening, what they know about the process, and why the evidence is compelling to them.

So for me, I have no objection to the other comments and questions, except that, as you tried to point out, my line of questioning was for a specific purpose. I think that spinning off the objections to another thread might be appropriate??

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Yes, it’s your tone. When 99% of the scientific community is of one opinion and you are of the other, that should humble you in your inquiry (to say the least). I’m not saying you don’t have the right to question us, but remember that we study this stuff day in and day out and we know it really well. When you are incredulous and insulting to our body of work while not even having the credentials or authority to be so, yes, it pisses us off.

I’m sure that there are many things that you know better than I. If I asked questions about that, I’d sit back and listen and learn. If I disagreed, I’d so humbly, respectful of the fact that you know more. Your approach is the opposite of that. You take pot-shots. And then you take what could be interesting questions and wrap them in attempted condescension. It makes you look petulant and immature. And it makes someone like me, who has otherwise chosen to dedicate large amounts of time to educating the public, want to just ignore you as someone not capable of (or not interested in) grownup conversations about science. YOU are why so few scientists are willing to spend any time on public engagement.

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For the record, I am not anti-evolution and I accept universal common ancestry including shared ancestry between humans and other primates. Just because someone raises questions it does not make them anti-evolution. My questions should not be interpreted as expressing doubt as to whether or not evolution took place. I firmly believe that it did.

I will create another thread on eye evolution where I will try to make it clear that I am addressing arguments presented to the public and why I find fault with the argument, not the evidence.

My comments on eye evolution are not related to anything Nathan has written on the subject. I have totally different authors in mind and regret if any of my comments on eye evolution in this thread were taken as an attack on anything Nathan has written. That was not my intent.

I sincerely hope that @NLENTS will continue discussion with others such as @Michael_Callen. I would not want to interfere with something that others find productive.

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You’re about the 50th person on various E/C discussion boards to make that same observation, but the approach never changes.

Okay, I’ve had a chance to think about it.

What I am saying is that no one should take your argument seriously until you can demonstrate you rigorously understand how mainstream science understands the evolution of the eye. If you think it is wrong, you have to understand the evidence and the argument as well as the expert. You have to understand and demonstrate your understanding of the argument.

Questions are great. We welcome questions. I’m not okay with dismissive and disrespectful retorts. Here is a key clue to look for.

Whenever a person of note joins a conversation, get out of the way. @NLENTS is a scientist, a published author, and we are honored to have him here. He will only stay if we treat him with respect. The same is true for ID proponents (@Agauger and @bjmiller) and scientists from RTB (@AJRoberts) and YEC organizations (if they come).

Let me be the first to admit that I get exasperated at time and can say things too harshly. That much is obvious. What may not be clear is that I do a lot of work behind the sciences (and even publicly) to mend fences. I am also a legitimate player here. There is a big difference between me, a scientist and known voice in the conversation, and an anonymous poster. When you (or others) create problems, I have to clean up the mess and drives away legitimate people we all want to hear.

We all are enjoying seeing real dialogue between leading voices in the conversation here. That is the goal. It is not a platform for recycling the same rhetoric back and forth. We are not a debate site. So help us create the conditions for real dialogue, especially when you see person of note join a thread.

If we get good at this, and find better ways of structuring the rules here, we are going to see more and more interesting conversations here, unfolding in real time. Help make that possible.

That being said, I did not state the rules of the thread. When I made them clear, you responded immediately. Thank you. Sorry, also, that it wasn’t clear. Now you know. If you see similar situations unfold in the future, hopefully you know now how to recognize them and help guide things in the right direction.

Sound good?

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