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.
*cough*
The Lord is not slack concerning his promise, as some men count slackness; but is longsuffering to us-ward, not willing that any should perish, but that all should come to repentance. - 2 Peter 3:9
Don't look for a Damascus road conversion, look instead for Jesus Christ. If you went to search for a treasure that you had good reason to believe existed, would you abandon your search after the first attempt?
You are back...why can't you respond? Darwin got your tongue?
Please explain the origin oftime,space,energy,mattercontinuum which you and I call the universe. Don't tell me hydrogen is made of protons, I will only ask where the protons came from. Please express one centilla scientific honesty if you will not answer my question and say I cannot answer.That would be an honest answer. However if you do know the answer I again,for the 20th time, ask you to explain it to us all.
Please fill in the blanks.....The formation of the world began like this.........................................
I just love it - first there was a simple eye, then it just exploded into the complex universe of vision we have now! Where have we heard this before?
Correct, they couldn't prove it, any more than current evolution theorists can prove evolution. I don't argue that evolution is false, only that it has yet to be proven. Evolution, as with every single scientific paradigm is not able to answer some fundamental questions. Just as with every scientific theory, when the proponents of that theory can't answer the questions they attack the questioners as boobs or idiots. I'm not accusing you of that, but it seems to predominate in the scientific community. If you don't accept evolution as gospel you must be a religious right wing nut who believes in creationism.
And that is the point. Nobody questions his authorship and what he descirbes is considered fairly reliable history.
Now, Caesar’s Gallic War was written about 54 B.C. and survives in only nine or ten good manuscripts. The oldest one is from a time some 900 years later than Caesar’s day.
Compare that to the Bible. There are about 28,000 different documents, written on both papyrus and parchment, which containing all or parts of the New Testament that have survived to our time.
The time gap between original writing and extant copy for most classical Greek works is about 800 to 1,000 years. But some New Testament fragments date back to the 2nd century, and some date back to only 30 years or so after the documents were written.
If you believe Caesar conquered Gaul you may as well believe the Bible.
I will discuss your advocacy of spontaneous generation of life after you explain origin. I thought this model which was propounded by Aristotle was discredited in the 1700's by Needham and Spallanzani. But before you go down that path let us reason together and you explain to me the fill in the blank question I put before.
In post 212 did you deny "cause and effect"? Have you stepped into metaphysics or the supernatural?
In post 213 you stipulated " an answer is not yet fully known, but seems the best candidate....." Is this a dictum of your faith in science. Yes seek the facts, but this has little to do with truth. Facts change , the Truth stay forever.
Err, well, that's not what Darwin said, nor is it what these researchers are saying...
In post 216 you state that science classrooms are for teaching science, not humility. But in your previous post you agreed that science does not have the facts. Please explain.
In post 222 you state in reference to prophecies that they "were bound to come true" in some sense. I presume you allow that conclusion because of your statistical analysis and application. Consider Life. Blue green algae. One of the most simple forms of life we know of. Consider the probability of the spontaneous generation of the protein, mucopolysaccharides, deoxyribonucleic acid sequenced by the hundreds of thousands, to order the organism by pairing the purine and pyrimidine bases spcifically and precisely to propagate the simplest organism. Statistical probability? Quiet a leap of faith.
Post 224 is an interesting theory, but it does not answer the question of origins, PreBigBang or Pre Primordial soup, I believe you often refer to.
Before time....an oxymoron. I believe Mr. Einstein would take issue with that assertion.
There there are numerous contemporaneous references to Caesar and his activities. And they don't contradict one another. Further, his Commentaries on the Gaulic Wars is intact. There are no apparent gaps in the text, and no apocryphal chapters floating around. It was an important work in its day, and it was never lost or out of print. No council was convened to arrive at the official text. It's as absurd to doubt Caesar's life and work as it is to doubt George Washington's (we even know that the cherry tree tale was fake and who faked it). The Bible, and particularly the life of Jesus, has virtually no external contemporaneous references (other than Josephus). Well, we know Herod was real from other sources. But I don't doubt the life and work of Jesus, so I don't really get your point.
I was answering a quesiton posed in Post 59 as to "How do you know that the Bible is accurate."
It's as objectively reliable as any book in antiquity.
Caesar-like placemarker
I gave you solid, objective standards by which to judge the authenticity of Caesar's book. (1) Contemporaneous references to the events about which he wrote. I gave you other objective standards: (2) "no apocryphal chapters floating around" and (3) that no council was convened to arrive at the official text. By those objective standards, I must respectfully disagree.
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