Brian Thomas returns with the Daily (pseudo)Science Update Perfect Molecule for Vision Shows Eyes Were Designed.
He begins by talking about how William Paley attributed the eye to the work of God, while Darwin attributed it to nature. He then says:
The retina contains tiny molecular machines that capture light and convert it into electrochemical signals. New research on how they do this emphasizes exactly why Paley was right.
So we have an isomer of vitamin A, 11-cis retinal, which is part of the above cycle. It’s a molecule with a long chain including a large number of double bonds, all but one of which is trans. The position of the cis bond is what makes the molecule’s name be 11-cis retinal. When the molecule is hit by a photon the cis bond becomes trans and the molecule becomes all-trans retinal.
The question that a paper called Why 11-cis-Retinal? Why Not 7-cis-, 9-cis-, or 13-cis-Retinal in the Eye? sought to answer was, obviously, why the cis bond was in that place. What was the advantage of 11-cis– that caused it to be selected? They state themselves:
One of the basic and unresolved puzzles in the chemistry of vision concerns the natural selection of 11-cis-retinal as the light-sensing chromophore in visual pigments.
Their study concluded that their were, in fact, advantages to using 11-cis– over the alternatives. The puzzle is solved. Right? Right?
Probably – I wouldn’t know if there was another team out to challenge this study’s findings. B.T. does not appear to be disputing that particular himself, but more the natural selection aspect. He says:
Lead author and Emory University chemist Sivakumar Sekharan told PhysOrg, “Our results show that the strong electrostatic interaction between retinal and opsin favors the natural selection of 11-cis– over other cis-isomers.” In other words, the researchers found that only when vitamin A bends at the 11th carbon atom—not the 9th, 10th, or any other—does it receive light and interact with opsin.
His clarification is incorrect – in fact, the advantage lies in the fact that the ‘link’ between Opsin and retinal is most stable when the retinal is 11-cis-. To quote in full the paragraph immediately above the quoted line in the PhysOrg article:
The results of the modeling showed that differences in the electrostatic interactions between the opsin protein and the retinal chromophore played the biggest factor in the natural selection of 11-cis-retinal over the other cis isomers. Due to electric charges, the link between 11-cis-retinal and opsin has a higher stability than the links between other cis isomers and opsin, making it the most favorable choice.
The others work, but not as well – and that is where natural selection comes in. Back to Thomas:
However, their experimental results did not “show” natural selection at all! They merely showed that opsin and 11-cis-retinal fit like a hand in a glove.
What it shows is that there would be selection pressure in favour of 11-cis– over the rest, which is what they said in the quote he gave.
Sekharan also said, “This indeed is very surprising given the fact that, outside the protein environment, 11-cis-retinal is one of the least stable isomers. Apparently, our results on cow, monkey and squid [eyes] demonstrate that organisms everywhere may tend to gravitate towards common selection.”
But their research focus begs the question of who or what “selected” this isomer, and they gave no space to the possibility that an actual person or selector was responsible instead of nature. The surprise comes from the fact that on its own, vitamin A almost never exists in its 11-cis-retinal form. Therefore, natural selection would not have “seen” it. So, how could nature select what it cannot even see?
Quit it with the ‘you need a selector to select‘ business! You don’t.
To make retinal (which you need to make to make vitamin A) you have to break apart a carotenoid which must first be eaten. What could have happened for the evolution of the 11-cis– isomer is that, as the other versions work and are more likely to be around, the system could be built up and the specific isomer used be determined later.
There isn’t really much else to say.
The Bible offers a different source for the eye’s development: “He that planted the ear, shall he not hear? he that formed the eye, shall he not see?” Not only was the Creator fully aware of the laws of optics that William Paley recognized so long ago, but when He formed the eye He also intimately knew the laws of electrostatic interactions, biomolecular stability, and chemical energetics explored in this recent retina research.