Dawkins on the Human Eye: Reality Check, Please?
For those of you who can't get enough of Richard Dawkins interviewing "Darwinian medicine" advocate Randolph Nesse, there's a Part 2! Here, Dawkins presses Dr. Nesse for a better example of an unintelligently designed feature of the body than the one he gave in Part 1 (the human forearm). This time Dr. Nesse offers the human eye, observing that with its counterintuitive wiring that results in a (virtually unnoticeable) blind spot, "It's the perfect example of why the body is not designed."
Dawkins guffaws in appreciation:
I think it was Helmholtz, the famous German psychologist, who said that if an engineer had given him the human eye, he'd have sent it back.Reality check, please? Hermann von Helmholtz is indeed cited to that effect in Dawkins's book The Greatest Show on Earth. I remember coming across the comment when I was reading the book and thinking, of Helmholtz, "What an ass that guy must have been!"
Think about it. To date, engineers have indeed tried to develop a visual prosthesis -- an artificial or bionic eye -- but without much success. The best that's been accomplished is experimental devices with the potential of allowing a blind person to see a simple array of dots or lights, which he then needs to interpret as, for example, a doorway or another person, a shape, light versus dark.
Scientists at Carnegie Mellon, Cornell and MIT are working on it, and good luck to them. The journal Ophthalmology reported back in April that a medical products company in California, Second Sight, has achieved positive but modest results with its Argus II Retinal Prosthesis System:
Subjects performed statistically better with the system on versus off in the following tasks: object localization (96% of subjects), motion discrimination (57%), and discrimination of oriented gratings (23%). The best recorded visual acuity to date is 20/1260. Subjects' mean performance on orientation and mobility tasks was significantly better when the system was on versus off.Visual acuity of 20/1260! That's better than nothing (as the results of the international trial also showed). But it's not very good vision! Yet if some future biotech genius were to step forward with his plans for successfully building a functioning prosthesis like our human eye, capable of delivering 20/20 vision even with a minor blind spot, allowing 40 million or so blind people around the world to see better than Richard Dawkins currently does (he wears glasses), Dawkins following Helmholtz would send him packing? Please, give me a break. What nonsense.
Even as Richard Dawkins kicked him out the door, our optical engineer would be celebrated as among the greatest medical innovators ever, enjoying worldwide fame and tremendous riches on top of it.
Nesse goes on, by the way, to explain why we rarely perceive our blind spot. For that you can thank an involuntary eye movement, called nystagmus, a sort of jiggling:
If it wasn't for the eye jiggling constantly just a little bit, that blind spot would always be in the same spot and you'd never see anything there. But because the eye moves slightly you end up getting a complete coverage of your field of vision.In other words, for a typical healthy person, there's effectively no blind spot to speak of. Well done, natural selection!