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.
The law of enthropy is readily observable. Everything tends to deteriorate to the most simple form. Macro evolution starts with a primeaval soup, and develops into more complex organisms. When we are born, we begin to die. Strength becomes weakness. Weakness becomes death. I am just wondering how evolution gets around this fact. Albert Einstein stated that he believed this was the one law that could never be gotten around.
To believe what you believe makes the Apostle Paul seem to be an unbeliever. 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. It is logical to therefore conclude it is an artilce of your faith. It is your constitutional right to believe such, but don't besmirch the honorable name of science by adfixing your fantasy to it. You choose self delusion. Your choice.
You must have a gastrointestinal pain or an itch.
After graduating with a degree in Biology and Chemistry, spending 3 years working on my masters degree in Pleistocene Paleontology (my dissertation was "Identification of Pleistocene Fossils for McFaddin Beach,Texas" , Obtaining my medical degree, and spending 5 years in a general surgical residency...After all that schooling I have concluded that you,sir, have made the most cogent statement in this entire thread. I wish all of our fellow freeper could have this assurrance. We must not give up on them.
Resurrection observed by more than 500 eyewitness. And they were not squid or octopus.
If you deny the 1st and 2nd laws of thermodynamics, then you can never get the first molecule or atom or subatomic particle produced. If the makeup of the universe has always been present the according to the 2nd law (entropy) it requires that all particle, subatomic elements would not defy the law of entropy and wouold therefore be washed out into a cosmic ocean of nothingness approaching absolute zero,completely vacuous. 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?)
Yes, now we are proving theories with other theories. I think a few thousand years ago they could prove turtles held up the earth by how slow the stars moved.
My point exactly.
"There is an absolute truth and His name is Jesus Christ of Nazareth."
The only Truth here. All else is conjecture and wishful thinking.
All that Creationists ask is that Evolution be taught as a theory not fact. Adding Creation into the classroom can bring a needed dose of humility to the impressionable minds.
Yes, I do. Read Matthew,Mark,Luke, John. It's all right there. Where do you read your theological prescriptions?
Mr. Dimensio , please go back to origins and explain to me where I am wrong...with your own science. I am more than willing to have a discourse with you. Let me be your student. Convince me.
There seems a lot of assumptions and conditions in those sentences.
These people are implying the ability of sight developed before fish, amphibians and insects branched off. Why termites?
Mr. Dimensio, in rereading your remarks I focused on the phrase "rational thought". I wonder, can you explain to me from a scientific reference point, of course, what is thought,,,how do you measure it? where does it reside,,does it exist? I pontificate, can thought be "rational"? I do not mean these to be trite considerations. I am not angry so please dispense with that notion. In fact I am quiet elated , especially at the results of the past few days, as I am sure you are.
The second law applies only to closed systems - the earth is not a closed system. In order to decrease entropy, you apply energy, which we get from the big hot thing you see in the daytime sky. ;)
Inductive logic is your friend.
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