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Author Topic:   Evolution of the eye? The myth goes on...
NosyNed
Member
Posts: 8996
From: Canada
Joined: 04-04-2003


Message 31 of 189 (58248)
09-27-2003 11:17 PM
Reply to: Message 27 by Joralex
09-27-2003 8:39 PM


Please see my answer to this post in "Is it science" "Separation of Church and State"

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NosyNed
Member
Posts: 8996
From: Canada
Joined: 04-04-2003


Message 32 of 189 (58249)
09-27-2003 11:25 PM
Reply to: Message 29 by Joralex
09-27-2003 10:05 PM


Since you are hanging your god on ignorance of how the eye could evolve what will you do if someone shows extant organisms that make clear how a more complex eye could get there step by step?
Will that prove that god doesn't exist? Of course not so I won't be facitious.
However, more seriously,exactly what step is it that you think is impossible. Are you suggesting that an organism with an eye spot and no brain is not possible or would not have any advantage? Do you base this on the fact that human beings would not have much use for an eye if the brain regions which process it's signels into "vision" were not functioning? Please explain in more detail.
[This message has been edited by NosyNed, 09-28-2003]

This message is a reply to:
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Zhimbo
Member (Idle past 6011 days)
Posts: 571
From: New Hampshire, USA
Joined: 07-28-2001


Message 33 of 189 (58250)
09-27-2003 11:34 PM
Reply to: Message 16 by Joralex
09-27-2003 10:29 AM


quote:
"I'm saying that there are deeper, more fundamental issues at stake and you keep insisting on the mere surface of the matter"
Gosh, let us know what they are! That would sure show us the evilutionist's folly!

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Coragyps
Member (Idle past 734 days)
Posts: 5553
From: Snyder, Texas, USA
Joined: 11-12-2002


Message 34 of 189 (58251)
09-27-2003 11:46 PM
Reply to: Message 29 by Joralex
09-27-2003 10:05 PM


ALL of this infrastructure (1, 2, 3, 4 and more) - however primitive you may want to imagine it - had to be in place simultaneously for, if not, then the 'light-sensitive spot' would have been as useful as a lead balloon (figuratively speaking).
You're starting, it appears, with a possibly multicellular eukaryote as your "beginning," but there are phototactic bacteria. These have - and I'm going to tell you one of the "fairytales" you like so well until/if I can dig up some more background - a local concentration of a chemical like bacteriorhodopsin. When light strikes a molecule of this, its actual shape changes - from cis tp trans around a particular double bond, in the case of the mammalian analogue. This change affects the shape of the protein associated with the rhodopsin. This mechanical change in shape pushes on something else, and in some Rube Goldberg fashion, something else happens......
And over the first billion years of phototactic bacterial evolution on earth, some of the trillions of bacteria had a "something else" happen that helped them out - the reaction to the light was "useful" in finding nutrients, or avoiding getting eaten - and that chemical chain of reactions got kept. Daughter bacteria with the change found a niche where they did well, in other words.
The first "eye" can be very simple, indeed, compared to what we think of as an eye. Trilobites, in fact, had quite elaborate eyes, no doubt with a history that we may never find in their shell-free ancestors. Eyes themselves don't fossilize too well. Trilobite eyes are well-known only because each lens is a little calcite (~limestone) crystal. And from early Cambrian to late trilobites, there is amazing variation in just how fancy these eyes are.

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Zhimbo
Member (Idle past 6011 days)
Posts: 571
From: New Hampshire, USA
Joined: 07-28-2001


Message 35 of 189 (58259)
09-28-2003 2:30 AM
Reply to: Message 29 by Joralex
09-27-2003 10:05 PM


Light sensitive spots typically occur in species that are transparent, or partially so. Thus, light sensitive chemicals, not in any structure, could provide information. Many single-celled organisms show this.
Furthermore, many naturally occuring chemicals are light sensitive, so there's no special problem with the first occurence of light-sensitive chemicals - their original purpose need not have been "visual". There is no "channel" necessary; passive diffusion is all that's necessary for chemical signalling (say, increase or decrease of activity levels with changes in lighting conditions).
So, no structure analogous to a detector is necessary, no channel is necessary, no processor need be formed that doesn't already exist. All you need to get things started is for an adaptive effect of a photochemical change. Once the photochemical reaction is in place, all the other features are free to come on board, one at a time.
The light sensitive spot is a convenient starting point for discussing the eye, but there's little problem in coming up with simpler systems.
------------------
"Colorless green ideas sleep furiously." - Chomsky
[This message has been edited by Zhimbo, 09-28-2003]

This message is a reply to:
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Replies to this message:
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Rei
Member (Idle past 7012 days)
Posts: 1546
From: Iowa City, IA
Joined: 09-03-2003


Message 36 of 189 (58262)
09-28-2003 3:47 AM
Reply to: Message 29 by Joralex
09-27-2003 10:05 PM


Joralex - first, allow me to thank you for actually stating what your current contention with the evolution of the eye is, apart from personal incredulity.
Despite what you've been portraying, if we want to talk about the simplest light-sensitive tissues, we have to look no further than the lowly Euglena - and millions of other unicellular creatures. In the euglena, the light-sensitive proteins are found in a structure called the stigma. The proteins responsible belong to a family of proteins known as rhodopsins, which are a specific class of opsins.
There are four types: H+ pump, Cl- pump, sensory rhodopsins, and photorhodopsins. The latter is activated by light. They are all quite similar in structure, and appear to be the result of DNA replication and subsequent mutation - and yet, each one is used for a different purpose. For example, sensor rhodopsins are used for signal transmission.
It seems quite clear that a duplicated gene for a sensor rhodopsin for a reaction to a certain stimulus that would be beneficial to react to light in the same manner, had a gene duplication and subsequent mutation (which is very, very common). Making things simpler, sensor rhodopsins tend to react to stimuli from other rhodopsins, meaning that they can use the exact same stimulus mechanism for the photorhodopsins.
The evolutionary mechanism is not only obvious, it is pretty much expected that such mutations would occur.
------------------
"Illuminant light,
illuminate me."

This message is a reply to:
 Message 29 by Joralex, posted 09-27-2003 10:05 PM Joralex has replied

Replies to this message:
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Joralex
Inactive Member


Message 37 of 189 (58276)
09-28-2003 9:20 AM
Reply to: Message 32 by NosyNed
09-27-2003 11:25 PM


Since you are hanging your god on ignorance of how the eye could evolve what will you do if someone shows extant organisms that make clear how a more complex eye could get there step by step?
"Hanging my God on ignorance of how the eye could evolve"? Hardly! It isn't "ignorance" - go back and read my argument - and this is just one of a myriad of reasons that support my belief in the God of the Bible.
Will that prove that god doesn't exist? Of course not so I won't be facitious.
Nor will I. This wouldn't "prove" or disprove God's existence.
The issue here, however, is evolution as a viable alternative.
However, more seriously,exactly what step is it that you think is impossible.
Did you understand the argument? It's not about a "step". It's about the fact that even if it were granted that a light-sensitive spot one day appeared, this woud be completely useless without the additional infrastructure.
Do you understand the argument?
Are you suggesting that an organism with an eye spot and no brain is not possible or would not have any advantage?
NOT, "and no brain". A minimum infrastructure is absolutely necessary or else a 'light-detector' serves absolutely no purpose. Do you understand?
Do you base this on the fact that human beings would not have much use for an eye if the brain regions which process it's signels into "vision" were not functioning? Please explain in more detail.
See above and please think about it - it's not that difficult to comprehend. Here's a bit more :
What is a 'light-sensitive spot'? Think about it.
Any conceivable light detector works on the principle of energy transfer from a photon to some other particle (usually an electron). Photosynthesis, for example, employs the energy of photons to achieve excitation levels (the electron attains a higher energy state). This energy is stored via a complex process as potential energy that is available for use later on.
In light detection the same principles must be employed. Either an electron is taken to another energy level and remains there or it drops down to a lower lever emitting a photon in the process. Regardless of how it happens, this is not "sight". Sight is achieved only after the energy provided by the photon is transmitted to a suitable decoding mechanism.
In short, an infrastructure is necessary and without this infrastructure ANY eye - no matter how simple - is completely and totally useless.
That's the crux of the argument. Now, what evolutionary theory provides for the simultaneous emergence of an eye (or a light-sensitive spot) AND this necessary infrastructure?
Joralex

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Joralex
Inactive Member


Message 38 of 189 (58280)
09-28-2003 9:40 AM
Reply to: Message 34 by Coragyps
09-27-2003 11:46 PM


You're starting, it appears, with a possibly multicellular eukaryote as your "beginning," but there are phototactic bacteria.
Yes, I know but I do believe you've missed the main point of the argument. To wit : anything, even inert (lifeless) matter, reacts to light. Thus, your example of how these bacteria "found a niche" due to their light sensitivity doesn't address the crux of the matter.
This crux is that what I refer to as the infrastructure had to develop simultaneously in the more complex organisms (multicellular eukaryotes and beyond) since the light detection must be transmitted, decoded and then acted upon if it were going to serve any purpose at all. This requires both hardware and software components within the organism and if any of these components is missing then you may as well have nothing. For instance : I give the organism the light detector, the physical 'brain' for processing the information and the 'software' to carry out that processing but I will not give it the 'channel' ("optic nerve") for the signal to travel from the light detector to the processing center. See what I mean?
These have - and I'm going to tell you one of the "fairytales" you like so well
You know I do.
until/if I can dig up some more background
I wish you luck - I've studied this rather intensly and 'fairytales' is all that I've been able to find (not surprisingly).
The first "eye" can be very simple, indeed, compared to what we think of as an eye. Trilobites, in fact, had quite elaborate eyes, no doubt with a history that we may never find in their shell-free ancestors. Eyes themselves don't fossilize too well.
Yes, I spoke of this in my earlier post.
Trilobite eyes are well-known only because each lens is a little calcite (~limestone) crystal. And from early Cambrian to late trilobites, there is amazing variation in just how fancy these eyes are.
"Fancy" / complex!! The complexity of the neural connections and processing requirements are staggering and yet these are supposed "early" eyes, evolutionary-speaking. Wonders never cease.
Joralex

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Joralex
Inactive Member


Message 39 of 189 (58285)
09-28-2003 9:59 AM
Reply to: Message 35 by Zhimbo
09-28-2003 2:30 AM


Light sensitive spots typically occur in species that are transparent, or partially so. Thus, light sensitive chemicals, not in any structure, could provide information. Many single-celled organisms show this.
Yes, but that's not the point.
Furthermore, many naturally occuring chemicals are light sensitive, so there's no special problem with the first occurence of light-sensitive chemicals - their original purpose need not have been "visual".
Also true but also not the point. Fact is, even inert (lifeless) matter reacts to light.
There is no "channel" necessary; passive diffusion is all that's necessary for chemical signalling (say, increase or decrease of activity levels with changes in lighting conditions).
Untrue! Chemical signalling IS a communications channel in itself. Besides, the chemical signal must be transmitted, received, decoded, and then acted upon. This is the minimum infrastructure that I have been alluding to. Sorry, Zhimbo, but you have not dispensed with the argument at all.
So, no structure analogous to a detector is necessary,
Are you sure you understand the physics of light detection?
no channel is necessary,
Answered above.
no processor need be formed that doesn't already exist.
Yes, it must exist simultaneously with the signal - what else is the processor going to process?
All you need to get things started is for an adaptive effect of a photochemical change. Once the photochemical reaction is in place, all the other features are free to come on board, one at a time.
No, no, no - you need to think a little harder! The photochemical reaction is completely and utterly useless to the organism as "sight" without the means to employ the information that the photons provide. You can't have your cake and eat it too, Zhimbo.
The light sensitive spot is a convenient starting point for discussing the eye, but there's little problem in coming up with simpler systems.
A "little problem".... I'll say!
I think that you've not understood the crux of the argument. This crux is that what I refer to as the infrastructure had to develop simultaneously in the more complex organisms (multicellular eukaryotes and beyond) since the light detection must be transmitted, decoded and then acted upon if it were going to serve any purpose at all. This requires both hardware and software components within the organism and if any of these components is missing then you may as well have nothing.
For instance : I'll let you give the organism the light detector, the physical 'brain' for processing the information and the 'software' to carry out that processing but not the 'channel' ("optic nerve") for the signal to travel from the light detector to the processing center. Result = zilch! See what I mean?
Joralex

This message is a reply to:
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Replies to this message:
 Message 43 by Zhimbo, posted 09-28-2003 1:17 PM Joralex has replied

  
Joralex
Inactive Member


Message 40 of 189 (58287)
09-28-2003 10:26 AM
Reply to: Message 36 by Rei
09-28-2003 3:47 AM


Joralex - first, allow me to thank you for actually stating what your current contention with the evolution of the eye is, apart from personal incredulity.
"Personal incredulity" my eye! Tell me that you have a machine that generates energy with no input and I'll tell you that you're full of hot air - would that be considered 'personal incredulity'? Same difference!
Despite what you've been portraying, if we want to talk about the simplest light-sensitive tissues, we have to look no further than the lowly Euglena - and millions of other unicellular creatures. In the euglena, the light-sensitive proteins are found in a structure called the stigma. The proteins responsible belong to a family of proteins known as rhodopsins, which are a specific class of opsins.
There are four types: H+ pump, Cl- pump, sensory rhodopsins, and photorhodopsins. The latter is activated by light. They are all quite similar in structure, and appear to be the result of DNA replication and subsequent mutation
Hold it right there - that is your assumption. I would say that they were created specifically for their purpose. Let's continue...
- and yet, each one is used for a different purpose. For example, sensor rhodopsins are used for signal transmission.
Okay...
It seems quite clear that a duplicated gene for a sensor rhodopsin for a reaction to a certain stimulus that would be beneficial to react to light in the same manner, had a gene duplication and subsequent mutation (which is very, very common).
"Clear"? Not at all! I would say that the rhodopsins were each created to perform their respective functions. Now, 'prove' me wrong...
Making things simpler, sensor rhodopsins tend to react to stimuli from other rhodopsins, meaning that they can use the exact same stimulus mechanism for the photorhodopsins.
This is all very fascinating (and known) but how does it address my argument?
The evolutionary mechanism is not only obvious, it is pretty much expected that such mutations would occur.
Whoa... hold them there horses right there!!
"The evolutionary mechanism is obvious", you say? I see absolutely nothing "obvious" about it UNLESS a person is predisposed to believe in evolution. Is that what you are - predisposed?
The issue here was 'sight' (the 'eye'). My thesis is that a photoreceptor (call it whatever you wish) is essentially a photon detector (the physics are not that hard to understand). Photon detection must then be communicated somehow and this requires transmission (somehow) and then the signal must be somehow processed and then acted upon. Without this complete infrastructure in place there is no "sight" to speak of.
So how did evolution manage to produce the first "seeing" multicellular eukaryotic system and beyond given that this multi-element infrastructure had to be there simultaneously with the 'eye'?
Joralex

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 Message 36 by Rei, posted 09-28-2003 3:47 AM Rei has replied

Replies to this message:
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 Message 46 by sidelined, posted 09-29-2003 1:25 AM Joralex has replied

  
JonF
Member (Idle past 167 days)
Posts: 6174
Joined: 06-23-2003


Message 41 of 189 (58291)
09-28-2003 11:32 AM
Reply to: Message 29 by Joralex
09-27-2003 10:05 PM


Ah, you have nothing new to say either.
Carry on.

This message is a reply to:
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NosyNed
Member
Posts: 8996
From: Canada
Joined: 04-04-2003


Message 42 of 189 (58300)
09-28-2003 1:07 PM
Reply to: Message 40 by Joralex
09-28-2003 10:26 AM


You've lost track of your arguement Joralex, at least I think you have. You are now saying that the mechanisms described, including the duplicated and modified genes were created explicitly that way. And you say this is your "proof" god did it. Or at least you're saying we can't prove god didn't do it.
That wasn't the original issue if I have it straight. You were claiming that evolution could not manage to do this. Now you are shown some of the details down to the genetic underpinnings and you decide that we can't prove god didn't do it.
Well, you haven't been able to prove that natural processes didn't do it. In which case you've done no damage to any naturalistic arguements.
You may continue to believe that god did it. You are free to believe what ever you want. Others will believe that god allowed it to occur in the fashion the scientists have described. Still others will see no need for god in the picture at all.
Science as a discipline will not have anything to say about god's existance. Just that if s/he does exist then s/he has made it appear that things have unfolded in a certain way. Since society as a whole wishes to avoid picking and choosing between conflicting religious views society chooses to leave the religious elements out of things that don't need them imposed.
We have demonstrated here that your choosen example has no need to have a god solution imposed.
[This message has been edited by NosyNed, 09-28-2003]

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Zhimbo
Member (Idle past 6011 days)
Posts: 571
From: New Hampshire, USA
Joined: 07-28-2001


Message 43 of 189 (58303)
09-28-2003 1:17 PM
Reply to: Message 39 by Joralex
09-28-2003 9:59 AM


quote:
This crux is that what I refer to as the infrastructure had to develop simultaneously in the more complex organisms
And I just explained how that's untrue, but either I wasn't clear or you didn't read carefully. Or both.
quote:
I'll let you give the organism the light detector, the physical 'brain' for processing the information and the 'software' to carry out that processing but not the 'channel' ("optic nerve") for the signal to travel from the light detector to the processing center. Result = zilch! See what I mean?
If you take an advanced organism and remove a crucial component, of course it doesn't work. You're thinking backwards.
I can give you organisms with detectors, but no brain or "channel". In these animals, light detection exists, but isn't used. (You concur that even lifeless matter can be light sensitive). I can give you organisms with detectors that have chemical effects. No brain needed. No further channel needed other than the chemical effects of the detectors.
If you have that second case, the nervous system can develop for reasons other than vision (indeed, motor control seems far more fundamental than vision with regards to the nervous system). No "channel" necessary for all parts to be useful.
However, probably some nervous system structure could be sensitive, downstream of the detectors, to overall light levels (in mammals it's the suprachiasmatic nucleus). This is very primitive vision. Indeed, with such an organism we're probably long since past the point where the detector is cup shaped, and can give directional information. Such creatures now exist.
All of these are organisms missing one or more of the components you list as "necessary"; living examples of all of them exist today. Thus, your argument that all of your components must exist for any one of them to be useful is invalid.
It may be true, depending on how you define "vision", that all components are necessary for true "vision"; but it is NOT true that each component is useless without all the others.
It isn't helpful to think of highly specialized creatures, and removing parts. Think of simple creatures, and adding simple parts, as I have done.
quote:
Chemical signalling IS a communications channel in itself. Besides, the chemical signal must be transmitted, received, decoded, and then acted upon.
That sounds complicated. Tell me, when I add vinegar and baking soda, and a chemical reaction occurs, how much "infrastructure" is necessary?
That's as complicated as I'm talking about to start with. Light causing a change in a molecule, which causes a change in a another molecule.
Is this far from "vision"? Of course, that's the whole point. It's a tiny incremental step that might lead to vision, a process you're claiming is impossible in principle.
[This message has been edited by Zhimbo, 09-28-2003]
[This message has been edited by Zhimbo, 09-28-2003]

This message is a reply to:
 Message 39 by Joralex, posted 09-28-2003 9:59 AM Joralex has replied

Replies to this message:
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Rei
Member (Idle past 7012 days)
Posts: 1546
From: Iowa City, IA
Joined: 09-03-2003


Message 44 of 189 (58350)
09-28-2003 5:58 PM
Reply to: Message 40 by Joralex
09-28-2003 10:26 AM


Joralex, you didn't address the mechanism.
The fact is that if a sensor rhodopsin gene gets duplicated and incurs a mutation that changes it to a photorhodopsin instead, the sensor rhodopsin will automatically carry the signals from the photorhodopsin. In short, if we have a sensor rhodopsin targetted to react to some already extant stimulus mechanism, for which it would be good to have the same reaction to light, the above-described duplication and mutation would be beneficial to the organism.
Example: Lets say you have a predatory bacteria that eats photosynthetic bacteria. The photosynthetic bacteria will inherently be clustered toward the surface, and that is where this bacteria would want to be. Lets say that it has a sensory protein in the front, and a flagellum in the back; if the sensor gets activated, the flagellum immediately starts swimming to push the bacteria forward so that it can consume its prey. Well, what happens if a sensor rhodopsin in the front replicates and the replica mutates, as is commonly observed in the lab to occur to genes? It is likely that the same transport proteins that affect the sensor rhodopsin will affect the photorhodopsins, putting them in the front with the sensor rhodopsins. What would this do? Well, when the front side was toward light, it would be more likely to activate and cause the flagellum to swim. If it was away from the light, the light would have to filter through the organism first, making it less likely to activate (depending on its location, it may have further chemicals impeding light). While the mechanism could do with plenty of incremental enhancements, it would work and be advantageous off the bat.
This is just an example; I could rattle off 100 possibilities - the key is, if there is any stimulus mechanism already in place for which it would be advantageous to react the same way to light, this mutation would immediately be beneficial to it - it would immediately have a proper light-response mechanism.
Would you rather discuss the neural response in higher animals?
------------------
"Illuminant light,
illuminate me."

This message is a reply to:
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Replies to this message:
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DC85
Member (Idle past 379 days)
Posts: 876
From: Richmond, Virginia USA
Joined: 05-06-2003


Message 45 of 189 (58403)
09-28-2003 11:42 PM
Reply to: Message 40 by Joralex
09-28-2003 10:26 AM


"Miracles"? You mean like the 'miracle' where once-upon-a-time life emerged from lifeless chemicals and then started down a road towards complexity and diversity? You mean 'miracles' like that,
Here we go again! I am tired of this! NOT all Evolutionists are Atheist!(really very few are) And I am tired of that being assumed! Get that out of your mind if you want to continue. That seems to be a Problem you have with evolution when Evolution never says a god didn't create life

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