Oolon Colluphid

Fair enough. I wastrying to keep it simple, y’know! Sure, mate selection matters... where it can happen. There ain’t a lot of sexual selection going on among asexual species... which is most of ’em!

And the point of course is that they may be chosing whom to mate with, but they don’t chose which bits of their DNA get altered!

Oolon

[ August 19, 2002: Message edited by: Oolon Colluphid ]</p>

Jonesy

has it been proven anywhere that any living oprganisms replicate and that the copy is not a perfect replication? Is there any link to such a proof?

In any case, even though all you say may be true, I'm still having a problem with the idea that, no matter how many mutations/selections occurred, this could've led to very complex structures, like the human eye for example.

Basically, I cannot understand how, even given billions of mutations, you could get the super-complex,multi-function human eye. The complexity makes me difficult to understand how it could just randomly form (over time). Any other links as to this? I feel I need to be logically, (rather than with difficult theory) persuaded. I need some strong logical argumentation/reasoning why its ok to say that 'billions of changes, accidental in nature' could have produced 'very complex living things'. I've read many things by behe, dembsky,k. miller and I still can't be convinced that purely random processes could result in a human being, no matter how long it takes.

The odds to me seem too low of this happening. But if you have any good links that could logically explain to me why it's really possible, please provide them (anything would do)

note that I'm not religious in any way, and I need some final piece of argumentation that could convince me of the evolution type as put forward by Darwin and elaborated by dawkins and others.

seanie

Oh dear.

Anyone volunteer to explain the birds and the bees?

hyzer

"purely random processes"

T - you keep writing this . . . . and I know that it has been explained numerous times. I'd like to see one of your posts acknowledge that evolution is NOT A PURELY RANDOM PROCESS.

Writer@Large

But ... that may lead to breeding ...

--W@L

Mageth

has it been proven anywhere that any living oprganisms replicate and that the copy is not a perfect replication? Is there any link to such a proof?

Look in the mirror. Do you look just like your mommy and daddy?

Dr Rick

<img src="graemlins/banghead.gif" border="0" alt="[Bang Head]" />

Sci_Fidelity

Translation: I can't see how this could happen, therefore it didn't.

Your incredulity has no bearing on the truth of the matter. And again, it is NOT a random process.

Doubting Didymus

How the eye evolved without design:

Start with a single light sensitive cell (if you really want, we can get into the evolution of this cell later).

If an organism were born with TWO photocells, it would survive much better, producing a population of multi-photocelled organisms. This continues for a while, each new photocell requiring only a tiny mutation and suppliying a significant survival bonus.

At this stage, we are thinking of something like a starfish, which has photocells in its skin.

This organism cannot yet 'see', but it can tell when it is nighttime, or detect the shadow of a predator.

Next, any organism with a slight depression in its photocellular surface would be able to cut out some of the incidental light, giving it a very slight ability to direct its 'vision'. Organisms with slightly deeper depressions will be even better.

After a time, the depression becomes a cup. No big jumps have been required so far, and the eye will be something like a mollusk eye. It is a cup with a protective gel coating. It was produced by each organism occasionally giving birth to a slightly cuppier child, which would be much more likely to survive.

Next, the cup would slowly, generation by generation, close over. This will provide the selection advantage of being able to cut out more and more light. After many generations, the cup is a ball, coated in gel, with only a fairly small hole. This gives a unique ability to focus. Have you ever looked through a pinhole in a piece of cardboard? Again, no large jumps, and the eye will look like a snail eye. (I think its snails who have eyes like this).

Next, eyes that have more gel coating will be better protected, and be better able to focus light. Thus, the ball becomes filled with more and more gel coating (this may happen alongside the earlier evolution).

Where the gel touches the eyes opening, a convex bulging bubble will naturally be formed, like if you squeese gel toothpaste just up to the tube opening, a small dome shape forms. This would have the incidental function of focusing the light even better. Organisms whose bulge is a better shape are more likely to leave descendants.

How did the lens evolve? Well, there are some species of fish whose lense is not the rock solid thing it is in our eye. Rather, the lens of certain fish is a very thick glob of the eyes jelly filling. Lenses would heve evolved from those organisms with thicker globs at the front of the eye, giving an enhanced focus.

At this stage we have a working fish eye, where we started with starfish skin. No large jumps are required, and all intermediate forms are functional and have modern counterparts.

Read dawkins' "climbing mount improbable" for a more detailed version of the lineage I proposed here.

Oolon Colluphid

Okay Thiaoouba. Maybe we’re getting somewhere. What you’ve got there is the Argument from Personal Incredulity. But, just cos you can’t imagine it don’t mean it ain’t so.

Do you honestly think -- have you even ever given it any thought? -- that if things like eyes were a problem for evolution, biologists might not have noticed this by now? Just wondering.

I can’t be bothered to rewrite what I’ve previously written (aka stolen wholesale from Dawkins ), so here’s a cut ‘n’ paste from these two archived threads:

<a href="http://iidb.org/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=3&t=001531&p=" target="_blank">http://iidb.org/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=3&t=001531&p=</a>

<a href="http://iidb.org/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=3&t=001471&p=2" target="_blank">http://iidb.org/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=3&t=001471&p=2</a>

Please read this carefully, as Dawkins and I have tried to explain how mutation plus selection(s) ( @ W@L) cut through the problem of complexity, by smearing out the luck needed over lots of generational small steps.

I’ve summed this lot up to you earlier in this thread, but here’s the fuller version. If you still don’t get it, then I refer you to the books mentioned.

********

Complexity is at the heart of the question. It is what we really mean by the fantastic quality of natural design, the amazing improbability of these things coming about by chance. The power and beauty of natural selection is that it can explain organised complexity. To repeat, because it is so important: Darwinism cuts through the statistical probability problem.

Theologian William Paley’s watchmaker analogy is one of the best-known formulations of the ‘argument from design’, the improbability of life’s organised complexity. Just as a watch has its watchmaker, it seems obvious that anything as well designed for its function as the human eye (or any other example you can think of) must have had a designer. It is simply too improbable that such things could come about by chance.

Sir Fred Hoyle, for instance, has expressed this view with respect to large molecules such as enzymes. He has been quoted as saying that the spontaneous formation by ‘chance’ of a working enzyme is like a hurricane blowing through a junk yard and assembling a Boeing 747. There’s not just a very large number of parts, but they must be precisely arranged.

The number of possible arrangements is phenomenal. I don’t want you to think I’m underestimating this. The inherent ‘improbability’ of protein molecules - that is, the probability that they’d spontaneously come into existence by chance - is rather easier to calculate than that for eyes, or bombardier beetle defence mechanisms, or whatever. The permutations are calculated by simple multiplication. Isaac Asimov did this for the protein molecule haemoglobin, and called the result the haemoglobin number. It has 190 noughts. That’s the number of ways the parts could be arranged such that the result would not be haemoglobin.

Of all the possible arrangements of the parts of an organism (or 747), only a TINY number of them actually ARE functioning organisms. This can be thought of as a quasi-mathematical ‘space of all possible arrangements (see below, and also Dennett’s <a href="http://www.amazon.com/exec/obidos/ASIN/068482471X/ref=ase_internetinfidelsA/103-2194675-5705437" target="_blank">Darwin’s Dangerous Idea</a> or Dawkins’ <a href="http://www.amazon.com/exec/obidos/ASIN/0393315703/ref=ase_internetinfidelsA/103-2194675-5705437" target="_blank">The Blind Watchmaker</a>, Chapter 3, ‘Accumulating small change’, where he calls it ‘animal space’ ). As Dawkins has famously (well it got into a quotations dictionary!) put it, however many ways there are of being alive, there’s a vastly greater number of ways of being dead.

(Incidentally, positing a creator as the designer just shifts the problem. Any god capable of designing a machine as complicated as a bombardier beetle, let alone capable of forgiving sins, answering prayers, performing minor -- strangely, these days VERY minor -- miracles, and everything else he’s credited with, must be at least as complex as what he’s created. And complex is just another way of saying improbable, in need of explanation. By Fred Hoyle’s analogy, God should be seen as the ultimate self-assembling 747.)

It is extremely obvious therefore that it’s extremely improbable these things could come about by chance.

It ought to be grindingly, creakingly, crashingly obvious that if Darwinism were a theory of chance, it wouldn’t work. You don’t have to be a mathematician to calculate that it would take from here to infinity for an eye or a haemoglobin molecule to self-assemble by sheer luck, though perhaps you have to be a physicist or astronomer to think that’s what Darwinism claims. Far from being a difficulty peculiar to Darwinism, the phenomenal improbability of DNA or spiders’ webs or bats’ sonar or bombardier beetles is precisely the problem that ANY theory of life must solve, and that Darwinism, uniquely, does solve.

It solves the problem by breaking the improbability up into many many tiny parts and smearing out the luck required over thousands or millions of years, or generations. Tiny (ie by definition, not very improbable) changes, and keeping only the ones that work.

Several ways have been used to model this random-variation-plus-non-random-selection, in order to show its power to cut through the improbability of design. Most I’ve seen are computer models -- useful for their speed and ability to generate randomness, but it has also been demonstrated in real life, for instance in antibody genes in the laboratory. Below is my take on explaining it -- inevitably not as good as some of the other ways, because I wanted to find analogies of my own. I don’t actually think mine are as good as the others, but this is plagiaristic enough already!

Also, this is an attempt to compress several whole chapters from various sources into a few paragraphs. If you do still doubt it, go read the originals! Here goes.

Back in the early-mid seventies there was a board game called Master Mind. Coloured pegs, six colours, one person chooses four pegs as a code, his opponent has to work out the code -- which colours and in what order, according to how each attempt is marked. Now, by simple probability multiplication, there are 6x6x6x6 = 1296 combinations. The chance of getting the code by just guessing -- random choosing -- is 1 in 1296. Not much chance.

In fact, the board only had ten try lines, and I remember being able to get it in six tries, on average. That is of course because the tries were marked. Once you have what you think is a correct colour/position, you keep it. You don’t, as you’d have to with random tries, throw it out and hope to get it again by luck. This is cumulative selection, and it is immensely powerful.

Unlike the games players, natural selection doesn’t have an end point in mind, but the power of cumulative selection is the same. If a random change is an improvement, if it confers extra survivability (or more accurately, breedability) in the environment in which it finds itself, then it stands a greater chance of finding itself in future generations than the unmodified version does.

The point is that although the changes are random, survival and reproduction are very much NON-RANDOM. Natural selection is a quintessentially non-random process.

It is also an algorithmic process, repeated mechanically again and again, with each generation’s differential, non-random survival and reproduction - due to inherited variation (some are better than others) - being down to how well adapted to that environment each organism is. A novel advantage spreads through the population over time (incidentally, the genetic definition of evolution, and a well-documented fact), simply because it out-breeds the competition. Eventually it becomes the standard version. And against the background of this version, any new advantageous variation will be selected for. So the whole thing ratchets forward toward better and better adaptation. Natural selection causes genes to pick their way, step by tiny step, through ‘animal space’, by only allowing the working versions of parts-arrangements to continue with the game.

For example, leg length is a heritable trait, non-random in its effects. In an environment containing, say, antelopes with the advantage of slightly longer legs, those antelopes with slightly shorter legs (who are therefore a little slower) are more likely, on average, to end up in the bellies of lions. The genes for longer legs therefore, naturally and inevitably, spread through the population simply because those with it leave more descendants, and so do their offspring. Ultimately the less well adapted genes die out, out-competed. This is what is known as selection pressure, and it too is well documented, in the wild, in the laboratory, and demonstrated by computer models.

No wonder we do see such marvellous adaptations! Everything alive today comes from a long line of successful breeders. Or put the other way, not one organism alive today had an ancestor that died young or otherwise failed to reproduce. Many of the ancestors’ contemporaries did fail, but they left no descendants! That is an awful lot of history contained in an organism, of collective ‘being good at getting to reproduce’, of cumulative selection.

Try thinking of a series of sieves, dozens, hundreds, thousands of sieves. What comes out at the end of all that sieving has whatever it takes to get through sieves. Whatever is alive today has what it takes to be alive in its particular environment, thanks to the cumulative effect of all its ancestors being good at it.

Changes have to be small. Organisms, like Boeing 747s, are phenomenally complex machines. If you make a large random change, the odds are overwhelming that the result will be an overwhelming ballsup. This is because most random changes will be for the worse, and any PARTICULAR large change is statistically less probable than a particular small one, in the ‘space of all possible arrangements’. The more steps away you are aiming, the more POSSIBLE arrangements there are, so the chances of hitting on a particular one by chance drop rapidly.

For simplicity, imagine a creature with one chromosome ten genes long, and three possible versions ('alleles') for each gene. With three alleles, there are just three versions of the creature with only different Gene As. But there are nine versions of a creature with different Genes A and B (3x3); twenty seven versions (3x3x3) of one with different Genes A, B and C, and so on. A big genetic change, say, a change to six of its genes, has 729 possible arrangements, so the chances of jumping, in a single step, to a PARTICULAR arrangement is 1 in (3x3x3x3x3x3), ie 1 in 729. Living things have rather more genes, and chromosomes.

However, the chances of a random change causing just one of the six mutations we want are one in three. And the chances of the next step are also only one in three. Provided each step is advantageous, it is not all that unlikely.

If your computer is playing up, a gentle-but-firm thump might jog it back to life. If you make a large random change to its innards with a screwdriver, call the help number, and they can have a good laugh.

With all of this in mind, let’s see if something as amazing as a human eye could, in principle at least, evolve?

1. Could it have arisen in a single chance step?

No, of course not, for the reasons above. The odds are many times greater than the number of atoms in the universe.

2. So, could it have arisen from something VERY SLIGHTLY different from itself, something that we might call X?

The answer to this must be a clear yes, provided only that the difference we have in mind is sufficiently small. X is defined as something very like a human eye, sufficiently similar to it that the human eye could have arisen by a single alteration to X. Just a tiny change. If you’re still answering no, try an even smaller difference, say, clarity of the lens, number of rod or cone cells, or strength of the muscles that pull the lens to focus the image.

Now having found an X such that the answer to question 2 is yes, we apply the same logic to X itself. By this reasoning we have to conclude that X could have arisen in a single chance step from X’. Obviously we can then trace X1 back to something else slightly different from it, X2, then X3, and so on. With enough Xs we can derive the human eye from something very different from itself. Provided we take only small-enough steps, the journey must be logically plausible.

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

The answer must surely logically be yes, provided only that we allow ourselves a SUFFICIENTLY LARGE series of Xs. If you consider 1,000 Xs too few, try 10,000. Or if you need to, allow yourself 100,000. Obviously the available time imposes an upper limit on this game, for there can only be one X per generation. So, has there been enough time? We can’t be precise as to how many generations would be necessary, but we do know that geological time is awfully long. Just to give you an idea, the number of generations separating us from our earliest ancestors is certainly measured in the thousands of millions. Given, say, a hundred million Xs (at a generation time of one per year - faster than an elephant but slower than a mouse - that’s only a third of the way back through the known history of life), we should be able to construct a plausible series of tiny gradations linking a human eye to just about anything!

4. Could all of these Xs be plausibly produced by random mutation of its predecessor?

This is actually a question about embryology; mutation has to work through modifying existing embryological processes, some of which are more amenable to change than others. But as above, the smaller the change, the more embryologically plausible it is. Remember that we are talking minor quantitative changes in existing processes, and that however complicated the status quo may be at any given generation, each mutational change in the status quo can be very small and simple. So we can say that that at worst, the frequency of mutational availability could slow down the rate of improvement.

5. Considering this series of Xs, is it plausible that they each worked sufficiently well to assist the survival and reproduction of the animals concerned?

Oddly, some people have thought the answer to this is no. The eye and all its elements are supposed to have to function perfectly to work at all. For instance, Hitchins 1982, ‘The Neck of the Giraffe, or Where Darwin Went Wrong’ claims (though it is a common claim among creationists) that if the eye isn’t moist, the lens clear, focusable and without aberration, if the cornea is fuzzy, and so on, then a proper image isn’t formed. “What survival value is there in an eye that doesn’t see?”
Presumably people WANT to believe this sort of argument. “If the slightest thing goes wrong ... if the focusing goes wrong ... a recognisable image is not formed” says Hitchins. Think about that. The odds must be 50/50 that you’re reading these words through glass lenses. (If not, ask someone you know who is!) Take them off and look round. Would you agree that a recognisable image is not formed? The odds are about 1 in 12 that you’re colour-blind. You may be astigmatic. Perhaps without glasses your vision is but a misty blur. Would you therefore agree that, because a recognisable image isn’t formed, you might as well go around with your eyes tight shut until you can put your glasses on again?

Hitchens and co. also state, as though it were obvious, that the lens and the retina cannot work without each other. On what authority? My late uncle in Florida, back in the seventies, had cataract operations on both eyes, removing the lenses. Without his glasses, he wouldn’t have been able to shoot the cottonmouth on his lakeside lawn that was heading my way. (I was only five at the time, so I don’t know how much of a threat it posed, but still.) Nevertheless, he seemed quite sure that lensless eyes were better than none at all. Even with lensless eyes, you can tell if you are about to walk into a wall, or a person. If you were a wild creature, you could detect the approach of a predator, and from which direction. In a primitive world where some creatures had lensless eyes and others no eyes at all, the ones with lensless eyes would have all sorts of advantages. To paraphrase the saying, in the land of the blind, the very partially sighted man is king - until someone with slightly better vision comes along!

You will often hear (even from people who should know better, like Stephen Jay Gould) questions like what use is 5% of a wing? The trite but accurate answer is that is precisely 1% better than a 4% wing in breaking your fall rather than your neck if you misjudge a jump from one branch to another. Gould’s point is that the ‘wing’ in question may have started out as something else, feathers to keep warm, an extra-stretchy bit of underarm skin, etc. But as above, it may also have been useful as a wing, or at least a fall-breaker. There are many gliding mammals and lizards that show how this works. And the thing about surface area of wings/gliding membranes is that it is a smoothly variable quantity - a smooth series of Xs.

What about camouflage/mimicry? 5% ‘looking like a stick’? Well it could be that a 5% stick insect fools a bird with 5% vision, that the two have developed together in an arms race. This probably is the case with, eg, the speed of gazelles and cheetahs. However it is more likely that mimicry evolved under the watchful gaze of eyes approximately as good as they are today. Another answer would be that perhaps different predators latch onto different features - one species detects black insects but not brown; another is fooled by shape but not colour, etc.

But I think the problem is best solved by realising that, however good eyes are, there are distances or angles of view or light levels under which even the best eyes can be fooled. On a trip to our local zoo recently we looked in the Tropical World. There are all sorts of rather well camouflaged stick insects there. If I stare at one six inches from my nose, I’m not fooled. If I were walking through a forest at night, I would not stand a chance of seeing it. If I were searching by crawling along on all fours, maybe I’d see it, maybe I wouldn’t. The point is that many an insect’s life was saved by even a slight resemblance to a stick, when a bird happened to go by it in the rain, or at dusk, or too far away, or failed to spot it out of the corner of its eye. And the thing about distance and light levels and angle-viewed-at is that they are all smoothly variable, from the best conditions to the worst.

*******

So, how could eyes evolve? There are clues from all over the animal kingdom. (Note that these are living creatures, not ancestors, but they show that plausible intermediates do actually work in real life and are valuable to their owners.) Below is a (very) rough outline, highlighting the major steps, and showing that there aren’t any major steps, if you see what I mean! (Bear in mind too that we are not, of course, talking about a nice completely formed but eyeless human skull; the rest of the organism developed along the way too!)

A single photocell (I won’t go into their origins other than to say there are smooth transitions to them -- any coloured pigment, by definition of being coloured, absorbs some light and reflects others; many chemicals are coloured...) can only react if it is struck by a photon, ie if there is light around. Two photocells stand a better chance of picking up photons than one, especially when they are rarer, that is, in lower light levels. Three are better than two at this. There is a smooth continuous series of improvements, from single photocells to multiple photocells to a sheet if photocells.

Now, any slight curvature of this sheet of cells, due perhaps to where on the creature it happens to be mounted, will automatically mean that not all light will be picked up, only that on the lit side of the curve, where the photocells are pointing. And there is a smooth series of improvements leading from this slight curvature to a cup, each with an increased accuracy of direction-sensing.

Cup eyes like this are common in the animal kingdom. Limpets, bristleworms, clams and flatworms all have them. (Flatworm eyes, incidentally, evolved separately, as shown by its photocells being inside the cup whereas the others have them round the outside.)

Because light rays bounce off an object in lots of directions, a cup eye cannot form what we would call an image. There are too many ‘images’ coming from the object, all overlapping. However, the more you can enclose the cup, the more of these extraneous ‘images’ are cut out. Initially this is just more and more accurate direction-sensing, but it incidentally produces an ‘image’ of sorts. There is, of course, a smooth series of graded improvements, each with a greater deepening and enclosing of the cup. The more you close over the top of the cup, the more you can sharpen the image. Marine snails have this deep cup arrangement.

If you close over the top enough, you end up with a pinhole camera. The smaller the pinhole, the sharper the image produced. The strange relative of the extinct ammonites, Nautilus, bivalve molluscs such as mussels, ragworms, and the gastropod mollusc called an abalone all have pinhole camera eyes.

There are two problems with a pinhole eye. An extremely small hole ought to produce an extremely sharp image. But such a hole cuts out the absolute amount of light the eye can pick up (and also causes diffraction of the light entering through it). You can have a dim but sharp image or a bright but fuzzy one, not both. But fortunately there is a way of producing a simultaneously bright and sharp image. It is called a lens.

An interesting thing about transparent substances is that they bend light as it enters and leaves them. The amount of bending is measured by the refractive index of the substance. Any curved transparent object can act, accidentally and automatically, as a crude lens.

Now, many living creatures at the level of eye sophistication so far mentioned, eg bivalve molluscs, have a lining layer of transparent material over the photocells to protect them. Often this fills the cup or camera, and is then known as the vitreous mass. There is a smooth series of changes increasing the thickness of a protective lining to a vitreous mass filling a camera eye. And the same goes for clarity of the medium. As lenses, none of them would have Mr Carl Zeiss worried. But any blob of jelly with a slight convex curvature would be an improvement on an open pinhole. And slight, crude improvements are all we require to get started.

The biggest difference between a good lens and a vitreous mass is that, for best results, it should be detached from the retina, as we may as well call it, and separated by some distance. The gap needn’t be empty; it could be filled by more vitreous mass. All that is required is that the lens has a higher refractive index than what’s behind it. There are several ways this could be achieved. For instance, sawfly larvae form their lens by a thickening of the cornea, the transparent outer layer of the eye. Mayflies have a lens composed of a mass of transparent cells behind the cornea. Or an area of higher refractive index could condense out of the vitreous mass. Of course, degree of refractive index is a thing open to gradual change, a series of Xs. A graded index lens is probably easier to produce by modifying embryological processes - “a smidge more of jelly type B towards the top” -- than it is for human optical glass manufacturers! What you end up with is a fish-type eye.

Computer modelling has shown that this pathway from sheet of cells to a fish eye is not only plausible, but probable -- and quick. Almost too quick, so that it makes me wonder what’s holding evolution back! In fact, the variations in eye designs in unrelated orders of creatures has led experts such as Michael Land to the conclusion that eyes have evolved separately over forty times!

How about focusing? Well it could be done in a number of ways, and animals do. The lens can be moved forward and back, as in a photographic camera. Snakes, frogs, chameleons and fish do this. Or the lens can be pulled so its diameter alters and the light enters and leaves at different angles for closer and further objects. Any muscle in the vicinity of the eye which, in contracting, distorts or moves the lens, could be co-opted into aiding focus. Same goes for moving the eyeball. Pupils are no more of a problem either. They are useful to control the amount of light entering the eye, and also the ‘depth of field’ that’s in focus. But initially, any variability in the light aperture will do. Pupils do not have to be circular - cattle, goats, snakes and octopuses have vertical or horizontal slits, while even expensive cameras have crude polygons. So any - possibly originally accidental - ability to alter the aperture would be advantageous. Variability, and its control and response time, are all series of smooth gradual Xs.

One further point: the above account of necessity lays the development out as if the improvements happened one bit at a time, but this is not essential. For instance, the vitreous mass could thicken and become clearer while the cup is deepening to a pinhole. The only rule is that two or more different improvements are diminishingly likely in the SAME GENERATION, for the probability reasons above. Genes are selected according to their fitness in a particular environment, and this environment includes the rest of the genes in the series of organisms they find themselves in. Genes for sharper teeth are selected for in an environment including genes for the digestion of meat, being quick to accelerate after prey, and behaviour such as creeping up on it. So individual elements of use in a particular way of life can develop in unison towards better adaptation of the whole organism. Just not lots of changes at once.

********

One final thought, taken from my ‘poor designs’ list (which Thia hasn’t bothered to comment on). Is it not odd that the designer, having given the nautilus a very good pinhole camera eye, did not bother to give it a lens too?

Here’s a nautilus, for no better reason than I think they’re wonderful!



Cheers, Oolon