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.
Is there empirical evidence to explain it all? Yes. Jesus Christ is the evidence of things not seen. He transcended space and time in order to save us. All he wants is for us to accept the gift of salvation He offers. In order to accept Him as our Savior and Lord, we must first recognize that we are not the center of the universe, He is. Coming to grips with our own mortality and finiteness is impossible without His aid.
Jesus Christ said to Saul of Tarsus, "Saul, Saul, why persecutest thou me? it is hard for thee to kick against the pricks." Acts 26:14
All of my preaching is worthless, because I was not converted by preaching but by Jesus Christ's love for me. Seek Him out with all sincerity and He will reveal Himself to you. He loves you so much that He died for You. He wants to share His kingdom with You. I may sound like a nut, but what have you to lose by just seeking Him out?
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. I am not saying He will appear in your presence, although He may (I don't know anyone living who has had such an experience), but the real work He accomplishes is on the inside of us. We are much more than flesh and bone, and it is the inner man who lives inside this coat of flesh that He wants to change. What have you to lose? And if the words of Jesus Christ are true, think what you have to gain.
Did you say the brain perceives neurochemical reactions in the brain? That is not an adequet explaination. I do not measure it. They can be observed...I assume you refer to electroencephalography and the various types of wave forms that exist. I still do not know this to be thought. Could you explain this to me please. And no, it was just an after thought. 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. I was not trying to distract you.
Is the solar system a closed system? How about the Milky Way? How about this constellation? How about the universe?
Where did that big hot thing in sky come from?
Here's a bit of evolutionary history about Darwin. Englishmen evolved from a piece French mold.
Please explain what was going on before life began on earth. Go back, I believe you say 5.5 billion years, and take me back from there. Before organic evolution began. I am confused as you can see.
Technically, that's the only one you listed that is a closed system. Of course, nothing precludes local decreases in entropy even in closed systems.
Where did that big hot thing in sky come from?
Here you go...
So we agree that the 1st law of thermodynamics is truth. But then you just made an exception to the fact of the law of entropy. I simply adhere to observable science and you adjust you "facts" which are not observable nor reproducible. That is faith. You are so entitled to your faith, but you are not entitled to dispose of the 1st and 2nd laws of thermodynamics apart from your faith or metaphysics.
Bump
Thought you might find this interesting.
He is not required to give you evidence of his assertion. He asserts he takes his belief on faith, evidence not seen. You,however, have risen above these lowly levels to assert the holy grail of science, which we all agree require evidence. So please spell it out scientifically for Mr. Ole Cracker and me. We are not as enlightened as you. We await your reply.
Ummm, well, I was talking about the second law, not the first - the first law merely states that energy is conserved, and doesn't directly implicate entropy. Did you want to take a moment to review before continuing?
I believe he stated that the universe was the only closed system. He then stated the Law of entropy did not apply universally to it. That is an exception to the rule or to the law of entropy.
You are correct. I incorrectly prescribed the 1st law and meant to say the 2nd law (entropy). Thank you. See we can be nice.
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