Darwin's greatest challenge tackled

European Molecular Biology Laboratory ^ | 10/28/2004 | EMBL

[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.

[Junior]

...including one kind that responds to dark.

Dark is just the absence of light. Wouldn't the sensor just be responding to lowered light levels?

[O.C. - Old Cracker]

Since what we are discussing is your eternal destination, then I would say an objective study of the teachings of Jesus Christ are in order. The choice is yours.

Respectfully,

O.C.

[RightWhale]

This is extremely cool. The sensor fires when it gets dark. The other light sensors respond to light. If you want to catch a frog, you must not block its light or it will be [kersplush] gone.

[Dimensio]

Since what we are discussing is your eternal destination, then I would say an objective study of the teachings of Jesus Christ are in order.

Why not an objective studies of the teaching of Krsna?

Why are your unsupported religious claims more credible than the unsupported religious claims of someone else?

[balrog666]

Why are your unsupported religious claims more credible than the unsupported religious claims of someone else?

Funny how these anti-science buffoons cannot properly construct even a single coherent question.

[Texas Songwriter]

I would be happy to discuss Krsna and his teachings. Suffice it to say his teachings are a parenthetical cult of Hinduism. Not a great deal of difference. Budhism is also a cult of Hinduism. We have plowed that ground and it only leads to the void. I ask one question only. I am not trying to be tricky. Will you tell me role of the 1st and 2nd law of thermodynamics as it relates to Origins.

[O.C. - Old Cracker]

Study all the other world religions first and save the teachings of Jesus Christ for last, if you wish.

Jesus Christ said:

Behold, I stand at the door, and knock: if any man hear my voice, and open the door, I will come in to him, and will sup with him, and he with me.
- Revelation 3:20

Jesus Christ is standing at the door of your heart right now. Imagine! The architect of the universe, the One who made you and I, wants to call us friend! It is too great to fathom and I am filled with joy!

[balrog666]

I would be happy to discuss Krsna and his teachings. Suffice it to say his teachings are a parenthetical cult of Hinduism. Not a great deal of difference.

Funny that! All your cults look the same to us too.

Budhism is also a cult of Hinduism. We have plowed that ground and it only leads to the void.

If you say so...

I ask one question only. I am not trying to be tricky. Will you tell me role of the 1st and 2nd law of thermodynamics as it relates to Origins.

Perhaps you could try to undumb-it-down a bit and be a bit more specific. And spurious capital letters are not needed.

[Dimensio]

I would be happy to discuss Krsna and his teachings.

Okay. Why should I believe someone who speaks of Jesus and not someone who speaks of Krsna?

Suffice it to say his teachings are a parenthetical cult of Hinduism.

I'm aware of Krsna and its relation to Hinduism.

Not a great deal of difference.

The study of Krsna is a more specialized field within the study of Hinduism in general.

Budhism is also a cult of Hinduism.

Er, no. Buddhism's early roots are tied to Hinduism, but Buddhism itself is not Hindusim. You'd be able to make a more convincing case for Islam being a "cult" of Judaism.

We have plowed that ground and it only leads to the void.

Huh? What does that mean? How does this relate to my question of why I should believe a Christian over a Vishnuvite?

I ask one question only. I am not trying to be tricky. Will you tell me role of the 1st and 2nd law of thermodynamics as it relates to Origins.

The Origins of what? The Origins of life, the Origins of the planet, the Origins of the solar system or the Origins of the universe?

I suppose that it doesn't matter. In every case, the 1st and 2nd laws of thermodynamics simply meant that during whatever Origins period you want, there was no loss or gain of energy (though there might have been conversion) and the overall entropy of the universe did not decrease.

[Dimensio]

Study all the other world religions first and save the teachings of Jesus Christ for last, if you wish.

Why should I save Christianity for last? Why not go through them in alphabetical order? It would be easier to keep track of things that way.

Jesus Christ is standing at the door of your heart right now. Imagine! The architect of the universe, the One who made you and I, wants to call us friend! It is too great to fathom and I am filled with joy!

Yes, I know that you believe this, but you fail to understand that merely asserting it over and over again isn't going to convince someone who does not already believe as you do.

[O.C. - Old Cracker]

That I believe the teachings of Jesus Christ is not at issue. Jesus Christ presents His case without need of my assistance. All I can tell you is what He has done for me.

If you would know of Him, you must consider His teachings and open the door of your heart. Make yourself available to Him and He will do as he promises in Revelation 3:20. The alternative is to spend an eternity separated from the One who made you. What profit is there in that?

[Dimensio]

Jesus Christ presents His case without need of my assistance.

Yes, of course he does. So does Krsna.

If you would know of Him, you must consider His teachings and open the door of your heart.

Uh-huh. Same with Krsna.

Make yourself available to Him and He will do as he promises in Revelation 3:20.

And I could read Krsna's holy texts also.

The alternative is to spend an eternity separated from the One who made you. What profit is there in that?

Your question requies the assumption of your conclusion. This is a logical fallacy.

[PatrickHenry]

Same with Krsna.

Fool! Zeus is king of the gods. But don't take my word for it. Read the Iliad. The truth is there.

[balrog666]

Zeus is king of the gods.

Only after he killed Uranus!

Nothing to see here - move along, little doggy!

Or something like that.

[PatrickHenry]

Secret message received.

[O.C. - Old Cracker]

All the best, O.C.

[Ichneumon]

"In the beginning...God." 'nuff said.

That makes for a really short biology textbook. A lot of us prefer to know more details about "how things work".

[Ichneumon]

eyeball ping

Okay, that just sounds painful...

[Ichneumon]

Yes, and all those fossilized ape skulls they occasionally find in Africa and the National Geographics staff fawn over, are really our uncles too. NOT!

Are so, actually, but I won't confuse you with the evidence.

[Ichneumon]

Now that's real interesting, a light sensitive cell "evolving" in a dark area.

What "dark area" are you talking about? The article mentioned no such thing, so you might want to explain your non sequitur.

It couldn't be that God was getting it ready, oh perish the thought /sarcasm

If you have evidence for such a hypothesis, feel free to present it. In the meantime, sarcasm is a poor substitute.