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The evolution of the eye

shunyadragon

shunyadragon
Premium Member
The evolution of the eye from the simplest, light sensitive spot on single cell organisms, to the many variations of the complex eye in higher phyla has been extensively researched from the perspective of both the survival value, and the genetics. The same genes are involved through the whole process.

BBC did a fantastic description of science of this process in evolution in several programs. I may cite these later,

It is an interesting subject from challenges by fundamentalist Christians like those from the Discovery Institute that claim the complexity of the eye cannot be demonstrated by evolution from the simple to the complex.

Here is the first reference:

Source: New perspectives on eye development and the evolution of eyes and photoreceptors. - PubMed - NCBI


New perspectives on eye development and the evolution of eyes and photoreceptors.

Gehring WJ1.
Author information
Abstract
Recent experiments on the genetic control of eye development have opened up a completely new perspective on eye evolution. The demonstration that targeted expression of one and the same master control gene, that is, Pax6 can induce the formation of ectopic eyes in both insects and vertebrates, necessitates a reconsideration of the dogma of a polyphyletic origin of the various eye types in all the animal phyla. The involvement of Pax6 and six1 and six3 genes, which encode highly conserved transcription factors, in the genetic control of eye development in organisms ranging from planarians to humans argues strongly for a monophyletic origin of the eye. Because transcription factors can control the expression of any target gene provided it contains the appropriate gene regulatory elements, the conservation of the genetic control of eye development by Pax6 among all bilaterian animals is not due to functional constraints but a consequence of its evolutionary history. The prototypic eyes postulated by Darwin to consist of two cells only, a photoreceptor and a pigment cell, were accidentally controlled by Pax6 and the subsequent evolution of the various eye types occurred by building onto this original genetic program. A hypothesis of intercalary evolution is proposed that assumes that the eye morphogenetic pathway is progressively modified by intercalation of genes between the master control genes on the top of the hierarchy and the structural genes like rhodopsin at the bottom. The recruitment of novel genes into the eye morphogenetic pathway can be due to at least two different genetic mechanisms, gene duplication and enhancer fusion.In tracing back the evolution of eyes beyond bilaterians, we find highly developed eyes in some box-jellyfish as well as in some Hydrozoans. In Hydrozoans the same orthologous six genes (six1 and six3) are required for eye regeneration as in planarians, and in the box jellyfish Tripedalia a pax B gene, which may be a precursor of Pax6, was found to be expressed in the eyes. In contrast to the adults, which have highly evolved eyes, the Planula larva of Tripedalia has single- celled photoreceptors similar to some unicellular protists. For the origin of photoreceptor cells in metazoa, I propose two hypotheses, one based on cellular differentiation and a more speculative one based on symbiosis. The former assumes that photoreceptor cells originated from a colonial protist in which all the cells were photosensitive and subsequent cellular differentiation to give rise to photoreceptor cells. The symbiont hypothesis, which I call the Russian doll model, assumes that photosensitivity arose first in photosynthetic cyanobacteria that were subsequently taken up into red algae as primary chloroplasts. The red algae in turn were taken up by dinoflagellates as secondary chloroplasts and in some species evolved into the most sophisticated eye organelles, as found, for example, in some dinoflagellates like Erythropsis and Warnovia, which lack chloroplasts. Because dinoflagellates are commonly found as symbionts in cnidarians, the dinoflagellates may have transferred their photoreceptor genes to cnidarians. In cnidarians such as Tripedalia the step from photoreceptor organelles to multicellular eyes has occurred. These two hypotheses, the cellular differentiation and the symbiont hypothesis, are not mutually exclusive and are the subject of further investigations.

© Copyright Original Source
 

shunyadragon

shunyadragon
Premium Member
But, where's the evidence?

Not sure of the question you are asking here. The evidence is in the incremental genetic relationship from the simple light spot to variations in the complex eye. I will cite more in the future from different sources, Some are very detailed in the incremental gene changes and the progressive complexity of the eye.
 
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Kilgore Trout

Misanthropic Humanist
Not sure of the question you are asking here. The evidence is in the incremental genetic relationship from the simple light spot to variations in the complex eye. I will cite more in the future from different sources, Some are very detailed in the incremental gene changes and the progressive complexity of the eye.

But, if you see an eye just lying on the beach, would you assume that it had evolved there, or that someone is walking around with an empty eye socket?

God wins again.
 

Jonathan Ainsley Bain

Logical Positivist
The evolution of the eye from the simplest

The quote degenerates into jargon, and the writer avoids clear-worded reasoning and has not ever heard of the 'paragraph'.
Of course, that neither proves nor disproves the thesis. But it does speak of a disregard for the role of philosophers in bridging
the gap between the esoteric and clear-cut logic.

Perhaps we may attempt a discourse which can bridge this gap?
The eye is an excellent example for explaining genetic theory.

My own position is that something like genetic information
clearly must exist in order for parents to give birth to children - with eyes.
But having written a computer algorithm for a PHD thesis in microbiology,
I am forced to reach the conclusion that the entire manner in which this
occurs is only vaguely understood. And that careerism is 99% of the
essence of microbiology, whereby the more esoteric the jargon, the
easier it is to acquire public funding.

But this need not dissuade us from pursuing the topic.
To the contrary, it should embolden us to unravel the mystery.

But I can never tolerate a process of emperors and their invisible threads
hiding behind ad hominem processes of self-aggrandizement at the expense
of truth.

So let me get the ball rolling:
Before we can discuss genes, we must address the un-empirical
assumption of abiogenesis. Lest I be accused of jargon myself,
abiogenesis is simply the notion that atoms bouncing off each other
eventually results in living organisms with a genes that 'evolve' into eyes.

So, how does the genetic process appear out of a gloop of clay?
 

Jonathan Ainsley Bain

Logical Positivist
Possibly from what are called "replicating molecules": Self-replication - Wikipedia

But it seems that if replicating molecules were simply a result of electromagnetic reactions,
then we would be able to simply provide the correct proportions of 'primeval soup'
and then life would spontaneously come into being. Now I'm sure there are links claiming this,
just as there are links claiming all sorts of things.

But if the life-process were just a result of chemical reactions, then it would be simply a matter
of supplying the correct chemical concoctions into various parts of the body and we would
have bodily immortality. But we do not. No amount of Dr Frankenstein's and billion dollar budgets
has ever managed to increase the lifespan of humanity beyond its 120 years.

Sure we have stopped some types of death: chemical-death that is. But if a body was a machine,
then we should be able to repair it indefinitely. Just like we can do with any other type of machine.

After all, if physical death were the only type of death, then there could never be a justification
for suicide; or even the essence that the Greeks called Thanatos : the desire for death.
 

omega2xx

Well-Known Member
The evolution of the eye from the simplest, light sensitive spot on single cell organisms, to the many variations of the complex eye in higher phyla has been extensively researched from the perspective of both the survival value, and the genetics. The same genes are involved through the whole process.

BBC did a fantastic description of science of this process in evolution in several programs. I may cite these later,

It is an interesting subject from challenges by fundamentalist Christians like those from the Discovery Institute that claim the complexity of the eye cannot be demonstrated by evolution from the simple to the complex.

Here is the first reference:

Source: New perspectives on eye development and the evolution of eyes and photoreceptors. - PubMed - NCBI


New perspectives on eye development and the evolution of eyes and photoreceptors.

Gehring WJ1.
Author information
Abstract
Recent experiments on the genetic control of eye development have opened up a completely new perspective on eye evolution. The demonstration that targeted expression of one and the same master control gene, that is, Pax6 can induce the formation of ectopic eyes in both insects and vertebrates, necessitates a reconsideration of the dogma of a polyphyletic origin of the various eye types in all the animal phyla. The involvement of Pax6 and six1 and six3 genes, which encode highly conserved transcription factors, in the genetic control of eye development in organisms ranging from planarians to humans argues strongly for a monophyletic origin of the eye. Because transcription factors can control the expression of any target gene provided it contains the appropriate gene regulatory elements, the conservation of the genetic control of eye development by Pax6 among all bilaterian animals is not due to functional constraints but a consequence of its evolutionary history. The prototypic eyes postulated by Darwin to consist of two cells only, a photoreceptor and a pigment cell, were accidentally controlled by Pax6 and the subsequent evolution of the various eye types occurred by building onto this original genetic program. A hypothesis of intercalary evolution is proposed that assumes that the eye morphogenetic pathway is progressively modified by intercalation of genes between the master control genes on the top of the hierarchy and the structural genes like rhodopsin at the bottom. The recruitment of novel genes into the eye morphogenetic pathway can be due to at least two different genetic mechanisms, gene duplication and enhancer fusion.In tracing back the evolution of eyes beyond bilaterians, we find highly developed eyes in some box-jellyfish as well as in some Hydrozoans. In Hydrozoans the same orthologous six genes (six1 and six3) are required for eye regeneration as in planarians, and in the box jellyfish Tripedalia a pax B gene, which may be a precursor of Pax6, was found to be expressed in the eyes. In contrast to the adults, which have highly evolved eyes, the Planula larva of Tripedalia has single- celled photoreceptors similar to some unicellular protists. For the origin of photoreceptor cells in metazoa, I propose two hypotheses, one based on cellular differentiation and a more speculative one based on symbiosis. The former assumes that photoreceptor cells originated from a colonial protist in which all the cells were photosensitive and subsequent cellular differentiation to give rise to photoreceptor cells. The symbiont hypothesis, which I call the Russian doll model, assumes that photosensitivity arose first in photosynthetic cyanobacteria that were subsequently taken up into red algae as primary chloroplasts. The red algae in turn were taken up by dinoflagellates as secondary chloroplasts and in some species evolved into the most sophisticated eye organelles, as found, for example, in some dinoflagellates like Erythropsis and Warnovia, which lack chloroplasts. Because dinoflagellates are commonly found as symbionts in cnidarians, the dinoflagellates may have transferred their photoreceptor genes to cnidarians. In cnidarians such as Tripedalia the step from photoreceptor organelles to multicellular eyes has occurred. These two hypotheses, the cellular differentiation and the symbiont hypothesis, are not mutually exclusive and are the subject of further investigations.

© Copyright Original Source

To say something as complex as the eye evolved from some blob they don't even know what it was, is even more absurd and unscientific as saying whales evolved from a land animal.

Genetics refutes both guesses, and without reading your link, I will say dogmatically they did not provide and scientific evidence to support what they said. Now is a good chance to prove me wrong. Cut and paste what they offered as evidence.
 

shunyadragon

shunyadragon
Premium Member
To say something as complex as the eye evolved from some blob they don't even know what it was, is even more absurd and unscientific as saying whales evolved from a land animal.

Genetics refutes both guesses, and without reading your link, I will say dogmatically they did not provide and scientific evidence to support what they said. Now is a good chance to prove me wrong. Cut and paste what they offered as evidence.

Nice dogmatic 'Hand Wave.'
 

shunyadragon

shunyadragon
Premium Member
But it seems that if replicating molecules were simply a result of electromagnetic reactions, then we would be able to simply provide the correct proportions of 'primeval soup' and then life would spontaneously come into being. Now I'm sure there are links claiming this, just as there are links claiming all sorts of things.

But if the life-process were just a result of chemical reactions, then it would be simply a matter of supplying the correct chemical concoctions into various parts of the body and we would have bodily immortality. But we do not. No amount of Dr Frankenstein's and billion dollar budgets has ever managed to increase the lifespan of humanity beyond its 120 years.

Sure we have stopped some types of death: chemical-death that is. But if a body was a machine, then we should be able to repair it indefinitely. Just like we can do with any other type of machine.

After all, if physical death were the only type of death, then there could never be a justification for suicide; or even the essence that the Greeks called Thanatos : the desire for death.

I will try to give this some thought for a response, but unfortunately as is, it is a ramble that does not address the science of the evolution of the eye.
 

ChristineM

"Be strong", I whispered to my coffee.
Premium Member
To say something as complex as the eye evolved from some blob they don't even know what it was, is even more absurd and unscientific as saying whales evolved from a land animal.

Genetics refutes both guesses, and without reading your link, I will say dogmatically they did not provide and scientific evidence to support what they said. Now is a good chance to prove me wrong. Cut and paste what they offered as evidence.


Or god dun it wiv god magic cos i don't read der link. Doh

So cut and paste any evidence you have that contradicts science
 

Skwim

Veteran Member
The quote degenerates into jargon, and the writer avoids clear-worded reasoning and has not ever heard of the 'paragraph'.
Of course, that neither proves nor disproves the thesis. But it does speak of a disregard for the role of philosophers in bridging
the gap between the esoteric and clear-cut logic.
Obviously the abstract wasn't written with the likes of you in mind, but those educated in the subject. And people not only familiar with the subject, but familiar with the writing style.

My own position is that something like genetic information
clearly must exist in order for parents to give birth to children - with eyes.
But having written a computer algorithm for a PHD thesis in microbiology,
I am forced to reach the conclusion that the entire manner in which this
occurs is only vaguely understood. And that careerism is 99% of the
essence of microbiology, whereby the more esoteric the jargon, the
easier it is to acquire public funding.
You do realize why jargon, "the language, especially the vocabulary, peculiar to a particular trade, profession, or group," is jargon don't you? Well maybe not. Science adopts special words (jargon) so as to more efficiently express itself. Instead of having to continually use a sentence or so to explain a concept within a presentation, it gives that concept a name, which then becomes its identifier. So instead of having to say "having the nature of genes in different species that evolved from a common ancestral gene by speciation" a person can simply say "orthologous." Now, if you don't know the word perhaps you're reading above your grade level or above your expertise to understand what's being said anyway.

So let me get the ball rolling:
Before we can discuss genes, we must address the un-empirical
assumption of abiogenesis. Lest I be accused of jargon myself,
abiogenesis is simply the notion that atoms bouncing off each other
eventually results in living organisms with a genes that 'evolve' into eyes.

So, how does the genetic process appear out of a gloop of clay?
It appears this is where the Dunning–Kruger effect is being brought into play. Which calls for
eatpopcorn.gif


.
 
Last edited:

shunyadragon

shunyadragon
Premium Member
So let me get the ball rolling:
Before we can discuss genes, we must address the un-empirical
assumption of abiogenesis. Lest I be accused of jargon myself,
abiogenesis is simply the notion that atoms bouncing off each other
eventually results in living organisms with a genes that 'evolve' into eyes.

OFF TOPIC! This thread addresses only the evolution of a simple form to the complex.

If you wish to discuss abiogenesis it is another thread topic, which I may propose later, or maybe one that exists.
 

omega2xx

Well-Known Member
Or god dun it wiv god magic cos i don't read der link. Doh

So cut and paste any evidence you have that contradicts science

Prove me wrong. Cut and paste the evidence they posted. It would take more than magic for an eye to evolve out of some unknown blob that they can't explain how it originted. Originally called a simple cell. Then DNA was discovered and they had to walk that guess back.

Gullible is as gullible does.
 
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