Part 3 of a 7-part series with Dr. Eugenie C. Scott: Intelligent Design, Irreducible Complexity, and the Eye. Dr. Scott criticizes claims by proponents of creation science that the vertebrate eye is too complex a mechanism to have evolved by natural sel

John Connolly: So you spoke a little bit about flagella. The other argument that is always drawn up is the Mammalian Eye, so could you maybe dispel that a little bit for us, the idea that the eye is too complex of a system to have evolved, that it must have had some intelligence involved? Eugenie Scott: You know if you read the creationist literature, and I don’t want to wish that on anyone, but if you do you’ll find that they are very fond of quoting a statement that Darwin made on the Origin of Species where, and I haven’t memorized it but it’s something like “It is really quite preposterous to imagine something like the vertebrate eye, it’s so snazzy (he didn’t say snazzy), it’s got all these parts that work together to bring light to the eye and form an image, and nobody would think it would be possible for my natural selection to produce this”, and the creationists all say “see, Darwin himself says that the eye can’t evolve”. But they’ve never really looked at the book because they just keep quoting each other, and if you actually go to the Origin of Species and you find that passage and you continue reading it, the very next sentence is “But I can assure you that that’s not the case, that I can do this” and then he goes on with this wonderful description of how it’s quite possible to take a very simple structure, and with very few modifications improve its ability to assist an organism, in other words in Darwin’s own terms it had adaptive value. And he then does this wonderful thing, which Darwin did all his life of course [as] he was a wonderful naturalist, he went out to nature and he looked at nature and said “there’s something that’s kind of like what I’m talking about”, and if you look at the eye of a snail it’s hardly more than just a slight pigmented spot on the surface of the skin there, but having a pigmented spot does allow you to tell light from dark, so that’s adaptive to a snail; that would actually help a snail get along better, so any ancestral primitive snail or creature that had this light sensitive spot would be at an advantage and so it would live longer and as we say today would pass on its genes more than a creature of the same species that didn’t have that. And then he goes on and says “Well you know here’s another kind of creature, another little invertebrate creature the limpet that has that pigmented spot, but it also has kind of a little bit of an indentation on the skin where that pigmented spot occurs and that’s an advantage; that’s actually better than that snail eye because having an indentation as well as that pigmented spot allows you to get an idea of what direction the light is coming from, so that’s even better than being able to tell light from dark. And by the way, if you look at the physiology of this, being able to tell light from dark is useful for many creatures, I mean lots and lots and lots of organisms, for setting the biological clock for certain physiological reactions that happen. Being able to tell what direction the light is coming from is very useful because that might help you navigate toward food or away from heat or away from other kinds of phenomenon that you might want to avoid or be attracted to, and then Darwin goes on and find another animal, and he points to it as having not only some wiring down here at the bottom and this cup shaped thing, but actually the cup is formed almost to a pinhole, and it’s kind of the equivalent of the old fashioned pinhole cameras that I know people had in the early 20th century. Nobody has them now of course because we’ve all gone far beyond that, but a pinhole camera is a big advantage over just having a cup because a pinhole camera actually can allow an image to focus on the back of the eye. So anyway, he [Darwin] builds up this system step by step by step by step and actually on NCSE’s website we’ve got a little video talking about the evolution of the eye in the same fashion. And then you add a lens and that’s an improvement as well, so what Darwin does is look at the eye, the final product of the vertebrate eye which is a very snazzy kind of organ, it’s really good about getting images to the eye and getting that information to the brain, but he shows you how from very, very simple beginnings there is an adaptive value to each step until you finally build up to the final product. Now what the intelligent design folks want to do is they want us to start there, they want us to start at that final complex snazzy multi-component form and say “[it] couldn’t possibly form by natural causes”, but actually it’s very possible for it to form. And what’s kind of interesting about the eye story is that there were some Swedish scientists (and I am sorry I am having a senior moment, I don’t remember the exact reference) who did some computer modeling for how long would it take, given such and such a mutation rate for changing the surface of the skin and causing the cup forming and the pinhole eye and the formation of the lens from crystalline structures that are already there, and how long would it take to evolve an eye from something like Darwin’s original pigmented patch and it found that it could be done in something like 100 million years or something which, geologically speaking, is a drop in the bucket.

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