Side Comments on Evolution of the Eye

Why not start with the question did the eye evolve? The other question is circular.

A couple teasers, because I just love every time I come across such statements, as they provide continuing evidence that Darwinism is not dead.

The example of the eye proves that even a complex organ can evolve by intermediate steps that are all adaptive (p. 50).

As discussed in Chapter 4, the eye seems to have evolved by a series of small changes, each of which was advantageous (p. 52).

These quotes are from a book by Alan R. Rogers, The Evidence for Evolution. There’s even a section on how easy it is to evolve an eye. :slight_smile:

Kimura killed it off quite a few decades ago.

Alan made circular reasoning an art form :rofl:

Perhaps we could just stick with snail eyes?

Yet if we knew only about the anatomy of their eyes, no one would think all snails were relatives. (p 46).

…the various kinds of eyes in modern snails cannot be traced back to a single ancestral eye. They are independent inventions (p 47).

  • Rogers, Alan R. The Evidence for Evolution

Note the reversion to pure Darwinian thinking.

Apparently not.

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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