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.
No, I'm not copping out, I just see nothing to gain by having an argument with someone who just wants to argue. If anyone wants to know the truth, I am happy to discuss it with them. If someone wants to argue, find someone who values their time less than I do.
Carbon dating upon which most evolutionary proofs depend remains a problem because it assumes so much but mainly steady state theory.
http://www.christiananswers.net/q-aig/aig-c007.html
Or a forged TANG document.
It cannot be an accident.. Dumping the data of our daily production does seem to force humilty, that is, if you get a look at the data..
BWAAAAAAAAAAAAAAAAAAAAHAHAHHAHA!
Do you really think this idiocy should be taken seriously?
Absolute placemarker.
Evolutionary fanatics have this in common: inability to look at the world other than through the blinders of Enlightenment science.
The "science" that you accept without question leads to dead ends...that's the trouble with evolutionists. Dead ends.
I am a novice in this discussion, and I'm sure this has been beaten to death before, but can someone here explain to me how evolution and the big bang theory are not subject to the lst and 2nd laws of thermodynamics?
How would evolution violate either one?
Frogs have better eyes.
Better than what? ;)
Not to put too fine a point on it, but you're so full of crap your eyebrows stink.
I'll tell you, though. Little is more likely to drive Rightwhale away than someone just assuming natural selection answers what ontological categories are real and what ones are subjective. Frogs have 5 kinds of light sensors, including one kind that responds to dark.
Evolutionists are a law unto themselves.
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