Is there a continuous series of Xs connecting the modern human eye to a state with no eye at all?

It seems to me clear that the answer has to be yes, provided only that we allow ourselves a sufficiently large series of Xs. You might feel that 1,000 Xs is ample, but if you need more steps to make the total transition plausible in your mind, simply allow yourself to assume 10,000 Xs. And if 10,000 is not enough for you, allow yourself 100,000, and so on. Obviously the available time imposes an upper ceiling on this game, for there can be only one X per generation. In practice the question therefore resolves itself into: Has there been enough time for enough successive generations? We can't give a precise answer to the number of generations that would be necessary. What we do know is that geological time is awfully long. Just to give you an idea of the order of magnitude we are talking about, the number of generations that separate us from our earliest ancestors is certainly measured in the thousands of millions. Given, say, a hundred million Xs, we should be able to construct a plausible series of tiny gradations linking a human eye to just about anything! (Kursiv vom Verfasser, unterstrichen immer von mir.)

Considering each member of the series of hypothetical Xs connecting the human eye to no eye at all, is it plausible that every one of them was made available by random mutation of its predecessor?

My feeling is, that provided the difference between neighbouring intermediates in our series leading to the eye is sufficiently small, the necessary mutations are almost bound to be forthcoming.

Considering each member of the series of Xs connecting the human eye to no eye at all, is it plausible that every one of them works sufficiently well that it assisted the survival and reproduction of the animals concerned?

Considering each member of the series of Xs connecting the human eye to no eye at all, is it plausible that every one of them worked sufficiently well, so that "we must suppose that each new state of the instrument to be multiplied by the million, each to be preserved until a better one is produced and then the old ones to be all destroyed?" (Darwin, zitiert p. 58, Absatz X).

Rather oddly, some people have thought that the answer to this question is a self-evident 'no'. For instance, I quote from Francis Hitching's book of 1982 called The Neck of the Giraffe or Where Darwin Went Wrong. I could have quoted basically the same words from almost any Jehovah's Witness tract, but I choose this book because a reputable publisher (Pan Books Ltd) saw fit to publish it, despite a very large number of errors which would quickly have been spotted if an unemployed biology graduate, or indeed undergraduate had been asked to glance through the manuscript. (My favourites, if you'll indulge me just two in-jokes, are the conferring of a knighthood on Professor John Maynard Smith, and the description of Professor Ernst Mayr, that eloquent and most unmathematical arch-critic of mathematical genetics, as 'the high priest' of mathematical genetics.*)

For the eye to work the following minimum perfectly coordinated steps have to take place (there are many others happening simultaneously, but even a grossly simplified description is enough to point up the problems for Darwinian theory). The eye must be clean and moist, maintained in this state by interaction of the tear gland and movable eyelids, whose eyelashes also act as a crude filter against the sun. The light then passes through a small transparent section of the protective outer coating (the cornea), and continous via a lens which focuses it on the back of the retina. Here 130 million light-sensitive rods and cones cause photochemical reactions which transform the light into electrical impulses. Some 1,000 million of these are transmitted every second, by means that are not properly understood, to a brain which then takes appropriate action.

Now it is quite evident that if the slightest thing goes wrong en route - if the cornea is fuzzy, or the pupil fails to dilate, or the lens becomes opaque, or the focussing goes wrong - then a recognizable image is not formed. The eye either functions as a whole, or not at all. So how did it come to evolve by slow, steady, infinitesimally small Darwinian improvements? Is it really plausible that thousands upon thousands of lucky chance mutations happened coincidentally so that the lens and the retina, which cannot work without each other, evolved in synchrony? What survival value can there be in an eye that doesn't see?

This remarkable argument is very frequently made, presumably because people want to believe its conclusion. Consider the statement that 'if the slightest thing goes wrong...if the focusing goes wrong...a recognizable image is not formed'. The odds cannot be far from 50/50 that you are reading these words through glass lenses. Take them off and look around. Would you agree that 'a recognizable image is not formed'? If you are male, the odds are about 1 in 12 that you are colourblind. You may well be astigmatic. It is not unlikely that, without glasses, your vision is a misty blur. One of today's most distinguished (though not yet knighted) evolutionary theorists so seldom cleans his glasses that his vision is probably a misty blur anyway, but he seems to get along pretty well and, by his own account, he used to play a mean game of monocular squash. If you have lost your glasses, it may be that you upset your friends by failing to recognize them in the street. But you yourself would be even more upset if somebody said to you: 'Since your vision is now not absolutely perfect, you might as well go around with you eyes tight shut until you find your glasses again. ' Yet that is essentially what the author of the passage I have quoted is suggesting.

The book goes on to quote Stephen Jay Gould, the noted Harvard palaeontologist, as saying:

We avoid the excellent question, What good is 5 percent of an eye? by arguing that the possessor of such an incipient structure did not use it for sight.

An ancient animal with 5 per cent of an eye might indeed have used it for something other than sight, but it seems to me at least as likely that it used it for 5 per cent vision. And actually I don't think it is an excellent question. Vision that is 5 per cent as good as yours or mine is very much worth having in comparison with no vision at all. So is 1 per cent vision better than total blindness. And 6 per cent is better than 5, 7 per cent better than 6, and so on up the gradual, continous series.

But is the answer yes? It is less obvious, but I think that it is. Not only is it clear that part of an eye is better than no eye at all. We also can find a plausible series of intermediates among modern animals.

It is the sheer number of interlocking parts, all well adapted to seeing and well adapted to each other, that demands a special kind of explanation beyond mere chance. The Darwinian explanation, of course, involves chance too, in the form of mutations. But the chance is filtered cumulatively by selection, step by step, over many generations.

The eye has been a useful example before, so why not again? Think of all the intricately cooperating working parts: the lens with its clear transparency, its colour correction and its correction for spherical distortion; the muscles that can instantly focus the lens on any target from a few inches to infinity; the iris diaphragm or 'stopping down' mechanism, which fine-tunes the aperture of the eye continuously, like a camera with a built-in lightmeter and fast special-purpose computer; the retina with its 125 million colour-coding photocells; the fine network of blood vessels that fuels every part of the machine; the even finer network of nerves - the equivalent of connecting wires and electronic chips. Hold all this fine-chiselled complexity in your mind, and ask yourself whether it could have been put together by the principle of use and disuse. The answer, it seems to me, is an obvious 'no'.

The lens is transparent and corrected against spherical and chromatic aberration. Could this have come about through sheer use? Can a lens be washed clear by the volume of photons that pour through it? Will it become a better lens because it is used, because light has passed through it? Of course not. Why on earth should it? Will the cells of the retina sort themselves into three colour-sensitive classes, simply because they are bombarded with light of different colours? Again, why on earth should they? Once the focusing muscles exist, it is true that exercising them will make them grow bigger and stronger; but this will not in itself make images come into sharper focus. The truth is that the principle of use and disuse is incapable of shaping any but the crudest and most unimpressive of adaptations.

Darwinian selection, on the other hand, has no difficulty in explaining every tiny detail. Good eyesight, accurate and true down to pernickety detail, can be a matter of life and death for an animal. A lens, properly focused and corrected against aberration, can make all the difference, for a fast-flying bird like a swift, between catching a fly and smashing into a cliff. A well-modulated iris diaphragm, stopping down rapidly when the sun comes out, can make all the difference between seeing a predator in time to escape and being dazzled for a fatal instant. Any improvement in the effectiveness of an eye, no matter how subtle and no matter how deeply buried in internal tissues, can contribute to the animal's survival and reproductive success, and hence to the propagation of the genes that made the improvement. Therefore Darwinian selection can explain the evolution of the improvement. The Darwinian theory explains the evolution of successful apparatus for survival, as a direct consequence of its very success. The coupling between the explanation, and that which is to be explained, is direct and detailed.

The lens is transparent and corrected against spherical and chromatic aberration. Could this have come about through thousands of blind independent micromutations, whose first few hundred steps occurring in many dozens of different genes would have had no selection value at all? Also, what selection value could there have been in many later phases of the hypothetical process until some definite advantage was reached for a special creature in a special situation? Can a lens be washed clear by such independent random micromutations, which, of course, couldn't know what clearness was? But this phase granted - will it become a better lens because other thousands of blind micromutations will disrupt its orderly development? (Landel et al. 1988; Kratochvila 1988). Of course not.* Why on earth should it? Will the cells of the retina sort themselves into three colour-sensitive classes, simply because its DNA is bombarded by X-rays and/or other mutagenic agents? Again, why on earth should they? Because neo-Darwinians want to believe it? And how did the focussing muscles and their control centres in the brain arise by thousands of blind, random, and independent micromutational steps? What selection value did the first few thousands of random micromutations in hundreds of different genes have, until some muscles were formed and fastened around the lens for focussing and - the same question again - in the other case of the 12 to 14 muscles for a movable eyeball? But this will not in itself make images come into sharper focus and moving the eyes into the correct directions until these muscles were innervated and co-ordinately controlled from the different interacting centers of the brain showing special complex programs for their tasks in harmony with the overall organisation and environment of the organisms.

The truth is that the principles of mutation and selection are incapable of shaping any but the crudest and most unimpressive of adaptations.

Intelligent creation, on the other hand, has no difficulty in explaining every tiny detail. Good eyesight, accurate and true down to pernickety detail, can be a matter of life and death for animals with complex environmental relations in time and space as birds and others. A lens, properly focused and corrected against aberration, can make all the difference, for a fast-flying bird like a swift, between catching a fly and smashing into a cliff. What good would be 5 per cent of an eye in such a creature? A well-modulated iris diaphragm, stopping down rapidly when the sun comes out, can make all the difference between seeing a predator in time to escape and being dazzled for a fatal instant.

Yes, "it is quite evident that if the slightest thing goes wrong en route - if the cornea is fuzzy, or the pupil fails to dilate, or the lens becomes opaque, or the focussing goes wrong" - then the necessary fast and clear images for survival are not formed. Keeping in mind all these essential tasks, "the eye either functions as a whole or not at all" in such animals in the wild. And how can the following line of reasoning save the situation: "Vision that is 5 per cent as good as yours and mine is very much worth having in comparison with no vision at all. So is 1 per vent vision better than total blindness. And 6 per cent is better than 5, 7 per cent better than 6, and so on up the gradual, continuous series."? In most of these cases the birds would not even have learned to fly.

Any doubtful improvement in the effectiveness of an eye by the necessary thousands of blind, independent and random micromutations needing millions of years to come together would come too late to contribute to the animal's survival in a new predator-prey relationship, in which highly effective seeing capabilities were an essential prerequisite. Either a bird or other animal had the necessary seeing capabilities in the new situation or it would not have survived. Hence none of the not-yet-functioning new mutant genes would have been especially selected and propagated, but all would have been lost in the predator's successful attacks.

Because of these facts and the many others discussed in the present paper, it is not Darwinian selection but only intelligent creation that can explain the origin of complex new synorganised structures and functions, considering the organism as a whole and its relations with the living and non-living environment. Creation explains the origin of successful apparatus for survival, as a direct consequence of successful intelligent and deliberate design. The coupling between the explanation, and that which is to be explained, is direct and detailed.