Posted on 11/03/2004 5:11:47 PM PST by general_re
Darwin's greatest challenge tackled
The mystery of eye evolution
Researchers provide concrete evidence about how the human eye evolved
When Darwin's skeptics attack his theory of evolution, they often focus on the eye. Darwin himself confessed that it was 'absurd' to propose that the human eye, an 'organ of extreme perfection and complication' evolved through spontaneous mutation and natural selection. But he also reasoned that "if numerous gradations from a simple and imperfect eye to one complex and perfect can be shown to exist" then this difficulty should be overcome. Scientists at the European Molecular Biology Laboratory [EMBL] have now tackled Darwin's major challenge in an evolutionary study published this week in the journal Science. They have elucidated the evolutionary origin of the human eye.
Researchers in the laboratories of Detlev Arendt and Jochen Wittbrodt have discovered that the light-sensitive cells of our eyes, the rods and cones, are of unexpected evolutionary origin they come from an ancient population of light-sensitive cells that were initially located in the brain.
"It is not surprising that cells of human eyes come from the brain. We still have light-sensitive cells in our brains today which detect light and influence our daily rhythms of activity," explains Wittbrodt. "Quite possibly, the human eye has originated from light-sensitive cells in the brain. Only later in evolution would such brain cells have relocated into an eye and gained the potential to confer vision."
The scientists discovered that two types of light-sensitive cells existed in our early animal ancestors: rhabdomeric and ciliary. In most animals, rhabdomeric cells became part of the eyes, and ciliary cells remained embedded in the brain. But the evolution of the human eye is peculiar it is the ciliary cells that were recruited for vision which eventually gave rise to the rods and cones of the retina.
So how did EMBL researchers finally trace the evolution of the eye?
By studying a 'living fossil,' Platynereis dumerilii, a marine worm that still resembles early ancestors that lived up to 600 million years ago. Arendt had seen pictures of this worm's brain taken by researcher Adriaan Dorresteijn [University of Mainz, Germany]. "When I saw these pictures, I noticed that the shape of the cells in the worm’s brain resembled the rods and cones in the human eye. I was immediately intrigued by the idea that both of these light-sensitive cells may have the same evolutionary origin."
To test this hypothesis, Arendt and Wittbrodt used a new tool for today’s evolutionary biologists – 'molecular fingerprints'. Such a fingerprint is a unique combination of molecules that is found in a specific cell. He explains that if cells between species have matching molecular fingerprints, then the cells are very likely to share a common ancestor cell.
Scientist Kristin Tessmar-Raible provided the crucial evidence to support Arendt's hypothesis. With the help of EMBL researcher Heidi Snyman, she determined the molecular fingerprint of the cells in the worm's brain. She found an opsin, a light-sensitive molecule, in the worm that strikingly resembled the opsin in the vertebrate rods and cones. "When I saw this vertebrate-type molecule active in the cells of the Playtnereis brain – it was clear that these cells and the vertebrate rods and cones shared a molecular fingerprint. This was concrete evidence of common evolutionary origin. We had finally solved one of the big mysteries in human eye evolution."
Source Article
Ciliary photoreceptors with vertebrate-type opsins in an invertebrate brain.
D. Arendt, K. Tessmar-Raible, Snyman, Dorresteijn, J. Wittbrodt
Science. October 29, 2004.
That is not his motivation.
If anyone wants to know the truth, I am happy to discuss it with them.
Apparently *not*, actually, it seems from your evasions when someone attempts to discuss your "truths" with you in depth.
That's a remarkably ignorant statement, since carbon dating has an effective limit of about 30,000 years, and any evolutionary events of interest occurred partly or in whole in the span of time beyond 30,000 years ago.
Furthermore, carbon dating does not "assume steady state theory", it acknowledges and adjusts for varying conditions over time and location.
Are you sure you have the slightest idea what you're talking about?
The followers of Huitzilopochtli, Isis, Odin, Sutekh, Dis, and countless others were just as certain of the truth of their deities too. What makes you so certain that you're right and they were wrong?
Isn't there a chance that you might be really screwed come judgment day when Tezcatilpoca wants to know why you haven't sacrificed any virgins to him lately?
If you were born into a Muslim culture, wouldn't you now be just as firm in your belief that Allah wants you to make war with the infidels?
What makes your faith on any firmer ground than the followers of Hank, for that matter?
You misspelled "have this annoying habit of looking at the evidence and following it where it leads, instead of just accepting whatever eleni121 believes".
Hint: The scientific method, in a nutshell, is about doing frequently reality-checks to make sure that your beliefs actually conform with the real world.
I'm sorry if that annoys you, but it's ironic that you would mistake this method for "blinders", when in fact it is exactly the opposite -- it is about LOOKING with honest eyes at what the world *is*, not what we might *wish* to believe.
And what "dead ends" would those be? If you're going to join the discussion, please contribute more than slogans.
Oh, that's an easy one to answer: evolution and the big bang are indeed subject to the 1st and 2nd laws of thermodynamics.
And anticipating your next question, no, they do not violate either law. Only the creationists are under the impression that they do, but then their "understanding" of thermodynamics is as poor as their knowledge of biology and physics, so this is hardly surprising.
Did you actually have something of substance to add, or is this about the limit of your wisdom on the subject?
No such word. Did you mean "entropy" or "enthalpy" (both apply to thermodyamics).
Everything tends to deteriorate to the most simple form.
No it doesn't, but thanks for grossly misstating the actual laws of thermodyamics.
And your inclusion of the qualifier "tends to" acknowledges that under the right conditions some things *can* increase in complexity, so what was that you were saying about "laws" again?
Macro evolution starts with a primeaval soup, and develops into more complex organisms.
A vast oversimplification, but close enough.
When we are born, we begin to die. Strength becomes weakness. Weakness becomes death.
I'll bet you're a *lot* of fun at parties...
I am just wondering how evolution gets around this fact.
Reproduction -- spin off fresh copies before the old one gives out. Every generation is a new start.
But even leaving evolution itself aside, your misstated "law" is "violated" by bacteria, which are effectively immortal do not "run down" as you incorrectly claim is some sort of "law of nature". So your "law" is obviously faulty.
Albert Einstein stated that he believed this was the one law that could never be gotten around.
He may be right when it comes to the laws of thermodynamics, but no point you've raised in your post qualifies.
In what way?
If you consider the randomness of purine and pyrimadine base sequences to have evolved identically and in such diverse environmental circumstances cannot be explained by logic, empiric observations, or by random chance.
True enough, but since no one declares that they *have* "evolved identically", what are you babbling about here?
It is logical to therefore conclude it is an artilce of your faith.
Only if anyone actually *does* believe that silly thing you said, but since they don't...
It is your constitutional right to believe such,
Why thank you.
but don't besmirch the honorable name of science by adfixing your fantasy to it.
Don't worry, we don't.
You choose self delusion. Your choice.
Oooookay...
You must not have an actual rebuttal.
Excuse me, but what alternative Bible are *you* reading?
According to the usual Bible, no one saw the resurrection, and at most a couple dozen people (the disciples, and a few women) saw someone who might have been the return of Jesus, but by the Biblical accounts not even his closest disciples were immediately convinced that the person they saw after the crucifixion actually *was* Jesus ("they knew him not"). And there are unresolvable discrepancies in the four different accounts of the alleged resurrection.
That's a far cry from an ironclad case.
There are hardly "more than 500 witnesses" as you say, and the few that did supposedly see it weren't all convinced, and don't have a consistent narrative of it.
Finally, there's the issue of how anyone can be sure that the written accounts are even that of actual eyewitnesses, and not a tale written long after based on fables, histories garbled by word of mouth, or stories crafted to gain followers.
Finally, fully 3000 eyewitnesses watched Harry Blackstone Jr. make an elephant vanish in a puff of smoke. Should we worship him too? What people think they see is not always the same as what actually happened.
This is not to say it didn't happen, or that there might not be other reasons to believe in it, but let's not pretend that some ancient written accounts constitute some kind of indisputable evidence.
We don't.
Unless.....something held it all together. SOMEONE not tied to the universe by cause and effect, SOMEONE separate and distinct from the universe, SOMEONE who is not tied to the universe by the 1st and 2nd Laws of thermodynamics, and can reach down into His universe with love(science), compassion(science?), redemption (science?), justice (science?), and forgiveness (science?)
Or not.
Why do you presume that the "something" "holding it all together" is a "SOMEONE" instead of a "something"?
As for cause and effect, there's no indication that it holds at all times under all conditions.
Which one?
I assure you I am not defensive about my deity. I do not see science as an attack on my faith.
Many people are and do.
I simply have not yet seen either of you answer my simple question from your platform of science.So please explain to me what was the very beginning...you know where the universe and all that is in it began.
The answer is not fully known yet (for that matter, in science *no* answer is ever "fully known"), but the answer which seems to be the best candidate for being correct (or closest to correct) is: The false vacuum. The details are beyond what I can impart in a post, but for popularizations of the concept, see for example:
THE INFLATIONARY UNIVERSE: ALAN GUTHFor a few articles (out of many) indicating how the evidence does indeed confirm the correctness of the inflationary big bang view, see for example:
Motion of primordial universe unveiledUniversal Truths: Distant quasars reveal content, age of universe
Tests Suggest Scientists Have Found Big Bang Goo
Deriving Dimensions: Emergence of a 4D World From Causal Quantum Gravity
Sloan Digital Sky Survey: Dark Energy, Inflation, & Neutrino Mass News
Cosmic Microwave Background Radiation's Polarization Detected at Last
By X-Raying Galaxies, Researchers Offer New Evidence of Rapidly Expanding Universe
Once your science convinces me
Of what?
I will be pulled to your side and will advocate what you teach me, if it is truth.
What is your fixation on "before the big bang", especially on a thread about biological evolution? What what "side" are you talking about, and what does "advocating" have to do with any of this?
Oops, meant to ping you to #213...
No, we are, as always, "proving" theories by comparing them to the evidence.
I think a few thousand years ago they could prove turtles held up the earth by how slow the stars moved.
No they couldn't.
Why would you ask for such a dishonest approach to teaching? Currently, the theory portion of evolution is taught as theory, and the factual part of evolution is taught as fact -- as it should be.
Adding Creation into the classroom can bring a needed dose of humility to the impressionable minds.
I was under the impression that science classrooms were for the purpose of teaching *science*, not "humility".
A very primitive form of sight, yes. That's what the evidence indicates.
Why termites?
Huh?
"Measure"? Observation is not always in the form of "measurement", as if by a yardstick.
where does it reside,,does it exist?
In the brain.
I pontificate, can thought be "rational"?
One would hope so, but one is often disappointed.
I do not mean these to be trite considerations.
Then perhaps you should improve the quality of your questions.
I am not angry so please dispense with that notion.
That wasn't the adjective I would have chosen...
So in your view, the Jews are screwed?
Is there empirical evidence to explain it all? Yes. Jesus Christ is the evidence of things not seen.
Um, okay...
I offer you a challenge. Tonight, before you go to sleep, kneel next to your bed, or in a closet, or wherever and with your eyes closed just call on the name of Jesus Christ and ask Him to reveal Himself to you.
Been there, done that, haven't had any epiphanies. Now what?
No he didn't.
That is not an adequet explaination.
Not a problem.
I do not measure it. They can be observed...I assume you refer to electroencephalography and the various types of wave forms that exist.
No, I don't think that's what he refers to.
I still do not know this to be thought. Could you explain this to me please.
Thought is the information processing which takes place in the brain.
I origianally asked to be your student and have you instruct me as to origins and the laws of thermodynamics, scientific facts which I feel both you and I can stipulate are observable and reproducible scientific dictums.
Why do you consider that a fruitful diversion from the topic which started this thread?
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