Eyeing a common origin (where even Darwin didn’t manage to tread)
He made sense of something Darwin was at pains to speculate about, but couldn’t quite argue persuasively. Professor Walter Gehring’s discovery of the Pax-6 gene, the supreme master control gene’s role in the formation of the eye, is now widely regarded as the surprising confirmation of the single origin of an organ as perfect as this, which the author of the evolutionary theory had passionately postulated but found especially hard to defend. Creationists had traditionally seized on that particular soft spot in Darwin’s argument, whereas neo-Darwinists had preferred to allow for many independent evolutions of the eye instead: after all, an insect’s compound eye, which consists of many individual eyes with individual lenses, is so different from a human’s camera eye, or from a scallop’s mirror eye, that the intuitive assumption was they must have evolved separately. But Professor Gehring, who is working at the Biozentrum of Basel University within the EU-financed “Cells into Organs” research project, believes that Darwin was absolutely right all along. He has found out there is the same underlying genetic basis in the eye of all animal species and he is now aiming to apply his own discovery to fight macular eye degeneration. How does your discovery impact on Darwin’s evolutionary theory? Darwin was especially concerned about eye evolution. In his “Theory of the Species”, he devoted an entire chapter to difficulties with his theory, which makes it an extremely honest book. His hypothesis was that there must have been a very early evolution of a prototype eye which consisted of two cells only, one photoreceptor cell and one pigment cell. This would allow its carrier to have directional vision, because the pigment cell shields the light from one side, so it can come through the other side. What Darwin didn’t know was that this prototype actually still exists in nature: my Japanese colleagues have found that a flatworm in a mountain lake of Hokkaido has such a prototypal eye. What are the actual implications of such a prototype? Darwin also said clearly you cannot explain these prototypes already by selection, because this works once the organ is already effective, in this case when the animal can see. So before the prototype is there, the prototype cannot be selected, and this was overlooked by the neo-Darwinists, because this means that the formation of a prototype must be an extremely rare event, and only once the prototype is formed, then evolution can set in. The neo-Darwinists presumed instead that the eye must have evolved between 40 and 60 times, but they didn’t realize this would have been very contrary to Darwin’s theory, because it’s so unlikely. So your own interpretation of the Pax-6 gene story very much supports Darwin. Absolutely. When we made the discovery that the same master control genes were involved in the formation of the eyes in mice and flies and later on in all other animals, it was clear that there was only one original prototype and that all other eyes were derived by descent from it, even though they look very different. So my own monophyletic hypothesis of this single origin of the eye is very much supporting Darwin’s theory. The neo-Darwinists’ idea of a 40 to 60 times independent evolution is actually against him as it would have ruined his argument. Not only that. We actually found the prototype eye, which Darwin had only speculated about. Just the same way you induced a compound eye in a fruit fly, will one day be possible to induce a lens eye in a human to cure blindness? Well, that should theoretically be possible but practically very difficult and I wouldn’t want to be involved in it anyway. Growing an eye, say, on the side of the head would be fraught with dangers, not to mention the fact that you wouldn’t know how to connect it to the brain. I don’t want to create replacement parts, but do disease prevention instead, as in the case of macular eye degeneration. You can certainly use a Pax-6 gene from a fruit fly to induce an eye in a frog, but of course in order to regenerate a retina in a person you would want to use human Pax-6, the patient’s own. How would you want to regenerate a retina? If the patient has lost his retina, you might be able to restore it by giving it a Pax-6 shot. You could inject the protein, RNA or DNA into the eye, via a harmless virus carrier most people have. But I would prefer to use the protein, as it would be safer, even if you had to re-inject it at intervals. I am aware there are also some other very fascinating possibilities to use these primitive “opsin” molecules, light sensitive ion channel which you can insert into a mouse’s retina. This approach, not by my team, might be quite realistic and relatively close to success.