Evolution’s Witness: book review

SchwabFigure 2.2_600.jpg

Erythropsidium – a protist with a simple eye, or ocellus. Figure 2.2 of Evolution’s Witness. Image � F.J.R. “Max” Taylor, Ph.D.

Who knew? A single-celled organism has a camera eye with a lens. A certain fish has two corneas and controls the intensity of light on its retina by injecting pigmented particles between them. Other animals can shield their rods (the receptors for low intensity) during the day. A conch can grow a wholly new eye. A flatfish has both eyes on the same side of its head, but starts life with bilateral symmetry. A sea snake has a light sensor in its tail to ensure that the tail is hidden under a rock. Some birds cram their corneas through their irises in order to focus on nearby objects under water. The woodcock can see behind its own head - in stereo. Some animals have two foveas in each eye, one for peripheral vision and one for binocular vision.

If you find any of those facts interesting, then you must read the new book, Evolution’s Witness: How Eyes Evolved, by Ivan Schwab, a professor of ophthalmology at the University of California at Irvine. It is a wonderful book, truly encyclopedic, and chock-full of high-quality color photographs and fascinating examples and explanations. Many of the photographs, I suspect, were taken by the author or other people in his own lab, but others were contributed by surprisingly many researchers worldwide. There is practically nowhere where I thought, “I could really use a figure here,” except occasionally when I would have welcomed a line drawing.

I knew about the flatfish before I read the book. I remember once mentioning to a friend of mine, as he was about to eat a dead flounder, that both eyes are found on the same side of the head, and the flounder lies on the bottom and swims with a vertical undulation. He did not believe me, but my wife convinced him that I was not joking (evidently, I have a bad reputation). She in turn did not believe me when I noted that the fry (baby fish) were born with bilateral symmetry and swam normally. Also true. But that is not all: In order to accommodate the metamorphosis to the adult stage, says Schwab, the pathways in the brain have to change, and “[i]t is almost as if the eyes retained their position and the body of the fish rotated beneath them,” so vision, not structure, is apparently paramount. Further, the fry are born with one kind of cone, but the adult flatfish develop rods and three different kinds of cone during their metamorphosis. Armed with color vision, the adults can now change their skin colors slightly to match the color of the background.

The book is organized by geological epoch and shows how eyes evolved from a simple, light-sensitive spot to a dazzling array of eyes based primarily on the compound (or fly’s-eye) lens or the camera eye. What was most interesting to me, though, was how every type of eye evolved to secure its owner’s niche in the environment and also how similar problems were solved over and over with different solutions. Our mammalian ancestors, for example, descended from animals that had four different kinds of cone: red, green, blue, and ultraviolet. Most mammals eventually lost two of the cones, leaving red and ultraviolet. Presumably when primates became diurnal, they developed three-color vision, probably by duplication of the gene for red, and the ultraviolet cones drifted toward blue. They thus solved the three-color problem by taking what was already there and modifying it substantially. Evolution uses what it has, not what it needs or what we might think it wants.

The book is generally clearly written and organized. Explanations are terse and to the point, and make good use of the figures. Many if not most descriptions are by example; the book is interspersed with short, italicized segments describing the optical systems of various organisms. Additionally, a relatively few explanations are set off in boxes. At first, I found this technique confusing, but I very shortly grew to appreciate it. I also enjoyed the occasional witty aside, as when the author describes the eye of a certain copepod, which is found only in the male and is apparently used to recognize the female: “So, although small, this copepod carnivore holds visual secrets with an eye for the ladies.”

I noticed a few minor errors or misstatements in some of those areas in which I actually know something. Diffraction does not occur only when the diameter of an aperture is comparable to the wavelength of light; in fact, all lenses with the same F-number have the same diffraction limit. The lens of the tuna does not exhibit spherical aberration because it is wide open, but because it is a large lens with a long focal length (spherical aberration scales with focal length, whereas the diffraction limit does not). Large eyes do not have greater light-gathering power (though they have greater magnification and therefore greater resolution); light-gathering power depends only on F-number. I would not call a stippled surface aspheric, and unless I misunderstood the context, the stipples must be one-quarter, not one-half, wavelength high. Brewster’s angle is not the critical angle. In one description, I thought scattering was confused with chromatic aberration. None of these quibbles detracts from the usefulness of the book.

I could have used more explanation in a very few places. Why do certain organisms have noncircular pupils? The one explanation of a pupil that closed down to a number of pinholes for depth perception was unclear, at best. How does a colorblind cuttlefish adjust its own color to match the background? Why does the size of the eye vary with speed? How does a fly’s-eye lens form an image?

The technical editor in me notes that the volume is generally well edited. But I did not like mixing full spellings and SI (International System of Units) symbols, as in “100 meters” and “10 cm”; “100 meters,” should have been “100 m.” Likewise, “10 km an hour” should have been “10 km/h,” and “8000/mm2” should have been “8000/mm2.” The SI symbol for the second is s, not sec: you can get no secs in SI. “Ago” is not an SI unit, and “m” stands for “milli-,” so I do not accept the common notation “mya” for “million years ago”; at the very least, the m (for mega-) should have been capitalized. And, finally, the unit of velocity is the knot, not the knot per hour.

The book is extremely well prepared and exceptionally well illustrated with countless photographs - at 22 by 28 cm, practically a coffee-table book. You could get by by reading only the figures and captions, but you would be missing a lot. Yet much of the book was too technical for me, a nonbiologist. In spite of the excellent glossary of terms, I remain baffled by a few of the explanations. For example, I had to resort to the Web to be certain how many axons emerge from a single ommatidium (the photosensitive element in a fly’s-eye lens).

In short, I felt at times like the seventeen-year-old boy who told Umberto Eco that “he understood nothing of the theological arguments, but they acted as extensions of the spatial labyrinth (as if they were the ‘suspense’ music in a Hitchcock film).” No matter; the boy enjoyed Eco’s novel, and I was fascinated by Schwab’s book.


Matt, When you used “encyclopedic” you were spot on target. And with any encyclopedic effort there are, as you point out, some weak points because the author is forced well beyond their personal expertise, or even interests. I thought the opening section on the origin of life was weak, and would have been better left off.

I also had a few questions about the flat fish. I have dissected dozens of specimens from a half dozen species. They all share lateralized skeletal growth, with even the ribs, pararibs, and lateral spinal processes asymmetric. Just checking a California halibut; the half dozen bones of the mouth are symmetric, but everything from there back to the “tail” vertebra are lateralized. The most dramatic are the cranial bones of course. There are fossil data where this growth does not produce fully lateralized adults. I think this is what Schwab meant. But, it is a great book beautifully illustrated.

A collected volume that does as good a job for teeth is Teaford et al. Being the product of many authors, nearly every chapter is the product of an expert. The downside here is they are not that inclined to make it easy for general interest readers to follow. I personally would have liked a chapter on baleen whale evolution. But, I suppose one could argue that that is tooth loss.

Teaford, Mark F., Moya Meredith Smith, and Mark W.J. Ferguson 2006 “Development, Function and Evolution of Teeth” Cambridge University Press

As I recall from an ancient Scientific American article, flounders (I think) have opposite handedness in their asymmetry on opposite sides of the Pacific. stop. google.…google aha


One of the best types of evidence for evolution is the diversity of life. Creationists who live under a rock seem to be under the impression that there are only about one thousand species that were on the ark and have never changed. The actual number is about two million and that’s probably only a small fraction of the species that actually exist and an even smaller fraction of all of the species that have ever existed. There are some truly bizarre species out there. This diversity is exactly what is expected from over four billion years of evolution. If all of these species were created, they were created by an incompetent tinkerer, completely lacking in imagination, who got it wrong most of the time and got is horribly wrong most of the rest of the time. Why anyone would choose to believe such a depressing scenario is not entirely clear. Historical contingency and developmental constraint would seem to be a much better explanation for the diversity observed anyway.

air said:

As I recall from an ancient Scientific American article, flounders (I think) have opposite handedness in their asymmetry on opposite sides of the Pacific. stop. google.…google aha


There are species that have rare “reverse handedness” within the same populations. And IIRC, some that are nearly 50-50.

Just a clarification:

All flatfish swim in the same manner as typical fish due: through bi-lateral undulation of the body and tail (or just tail). Flatfish as adults merely turn their body sideways, so that the same motion is just performed 90 degrees around (just like the rest of the body).


Shouldn’t flounders have finnedness?

Knot per hour could be a unit of acceleration, though. Right?

Rather OT, but I recently heard a local news reporter describe the extent of a wild fire as some impressive number of “square acres”. While “knots per hour” is a perfectly good unit of acceleration, I wondered what 4th dimension a “square acre” might involve. :-)

Chris Lawson said:


Shouldn’t flounders have finnedness?

Technically yes, but, with flounders, it should be eyedness.

This comment has been moved to The Bathroom Wall.

Robert Byers said:

Eyes are a great example for creationists in demonstrating the unlikelyness of evolution and eye investigation could, based on creationist presumptions, lead to healing of eyes.

‘Unlikely’ as in ‘had to fall together all at once PURELY by chance !!1!!!1!!!’ - a model no one but IDiots and creationists even bring up.

Good thing that - IN REALITY - evolution is NOT pure chance. Variants that work tend to stick around, while less effective variants tend to go extinct.

End result - the APPEARANCE of deliberate design.

Evolutionary explanations - being REALITY BASED - have a far better chance of coming up with something useful than the glorification of willful stupidity known as ‘creationism’.

The sole creationist presumption is ‘AN UNKNOWABLE BEING DIDIT !!!1!!!!1!!!! Now sit down, shut up, and stop asking questions !!!!!’

Its not a dazzling array of types of eyes or different eye types for solution to problems. It is as was said largely about compound eye type or camera type. Very limited options after these foundations. If evolution had been at work forever it wouldn’t be that way.

How the frell would YOU know ?

Evolution has not been at work ‘forever’ - merely a few hundreds of millions of years.

Evolution can be very conservative - whatever works is retained. The only way a system would be replaced is either if a BETTER system came up, or an alternate system got extremely lucky for a very long time (ie, neutral evolution)

Such convergence would be unlikely . The great array would of canceled out these two simple foundations.

From what orifice did you pull that idea ?

‘Convergence’ would be unlikely if all eyes developed independently; good thing that in reality we know of something called COMMON DESCENT. Descendants tend to have eyes very similar in structure to their ancestors.

The other diversity is minor changes after the main structure is established.

In other words - EVOLUTION WORKS.

eyes show a common design from a common designer and not from evolutions mind and hand.

RiiIIiiIIIIiiiight ! Upon what do you base that silly assertion ?

The ‘common designer’ being the laws of physics, variations (mutations), and filtering selection.

In other words - EVOLUTION.

most really do just have two eyes as if from a common blueprint.

Also what you’d expect from common descent and evolution as well.

i didn’t know about some of these options in how some eyes or eye sensitive operations do occur in nature. There is room here to figure out bigger equations for how eyesight works and this might lead to healing eyesight.

How eyesight works is fully explainable via evolution - the relatedness of the proteins used in photoreception, the cascades of protein activations, etc.

And just HOW, exactly, does screaming ‘GOD DIDIT !!!!!!1!1!!!’ help figure out anything at all ?

Believing eyes are all evolved types for every occasion denies common laws to eyesight and healing as i see it.

Those ‘common laws to eyesight’ are known as the laws of physics (ie, OPTICS), and biology must adhere to them.

In other words, all those eye types are fully explainable via evolution - variant eyes that don’t work very tell tend to go extinct, while those that work tend to remain in the population.

A good case where different foundations (creationist/Evolutionist) would lead to different confidence in seeking progress in healing eyesight.

Creationists don’t seek anything - since they’ve deluded themselves into ‘thinking’ that they have all the answers, they prefer to sit on their rumps and mumble about how great their unknowable Magical Sky Pixie is.

Science-based endeavors have always paid off eventually; when was the last time a magic-based endeavor ever yielded anything but ignorance, arrogance, and strife ?

How, EXACTLY, would creationist ‘explanations’ or ‘understandings’ help anything at all ?

Blubbering “IT WUZ DEEZINED !!1!!!1!!!” doesn’t explain anything at all unless you know something about the motives and methods of designer.

And your ‘designer’ is conveniently unknowable …

Please do not feed the Byers troll.

Explanation of diversity:


Other evolution vs creation lectures 101-108:


Matt Young said:

Please do not feed the Byers troll.

Thanks, Matt. I suggest that this guidance is a rough paraphrase of Titus 3 (ESV):

10 As for a person who stirs up division, after warning him once and then twice, have nothing more to do with him, 11 knowing that such a person is warped and sinful; he is self-condemned.

I’m in the middle of reading this book. I am an engineer, however, not a research biologist. Very interesting with a few caveats.

Terms and concepts sometimes aren’t explained until pages later, a good editor would have helped. Having read “Animal Eyes” by Land almost seems a necessary primer because this book jumps in with both feet.

The authors are very good at stating that when modern examples of primitive creatures are used the subject creatures are millions/billions of years evolutionarily removed. An author (from style differences I think it is just one) falls down, however, by repeatedly phrasing evolutionary changes as if it was an active individual choice. I know it is easy short hand language but it irritates my to read that some species had to change this, or they developed this trait or structure to deal with some new environment. Wish I had the book with me to quote some examples of this. I’ve not finished the book. There is a lot of very interesting information about eyes of differing evolutionary stages but I’m not sure all the factoids are neatly tied into supporting the premise of the title.

LibLight. said:

Explanation of diversity:


Other evolution vs creation lectures 101-108:


LibLight, we look forward to the ‘scientists’ at Amazing Discoveries as they publish the results of their science experiments in mainstream science peer-review journals. We look forward to Amazing Discoveries presenting their findings at mainstream science meetings/seminars. LibLight, as you may know, science is tentative. Science is more like a journey toward the truth as opposed to an arrival at the truth. If your ‘scientists’ provide the scientific evidence that sways the scientific consensus, anti-evolution views could supplement evolution or even make evolution go the way of the Dodo bird.

Alas, a few of us on on this Pandas Thumb forum - myself included - happen to be former young-earth creationists. Most of us ex-YECs are quite familiar with Amazing Discoveries, AIG, ICR, etc. I grew up on YEC books like The Genesis Flood (Whitcomb & Morris). Even today as an ex-YEC, I often go to ICR’s website to find old Impact articles I remember from my younger years; back then I eagerly awaited Impact articles in the mailbox.

To be sure, former YECs sometimes drop their YEC views reluctantly due to spiritual pain. Some former YECs remain Christians (click here), others leave the faith feeling they were taken for a ride by both pseudoscience and bad theology. In the end, many former YECs have concluded that young-earth creationism serves little purpose other than to provide hollow theological comfort. YECism is virtually useless in the real world, as ex-YECs like Glenn Morton (link here) painfully discovered.

Carl Drews said:

Matt Young said:

Please do not feed the Byers troll.

Thanks, Matt. I suggest that this guidance is a rough paraphrase of Titus 3 (ESV):

10 As for a person who stirs up division, after warning him once and then twice, have nothing more to do with him, 11 knowing that such a person is warped and sinful; he is self-condemned.

KJV gives a different picture

10 A man that is an heretic after the first and second admonition reject; 11 Knowing that he that is such is subverted, and sinneth, being condemned of himself.

Yes, Henry, the KJV version was written in Jacobean English. What a surprise.

Are you one of the extreme loons who think that God talks Jacobean English and the KJV is the true inerrant Bible, on account of you say it is?

Dave Luckett said:

Yes, Henry, the KJV version was written in Jacobean English. What a surprise.

Are you one of the extreme loons who think that God talks Jacobean English and the KJV is the true inerrant Bible, on account of you say it is?

No, I am not.

All right, Henry. But here’s an interesting exercise. The original meaning of the Greek noun “hairetikos” (singular, masculine, accusative) is derived from the verb “haireo”, which means “to choose for one’s self, to prefer.” That is, “hairetikos” would mean one who chooses to go his own way, by extension, one who is factious, divisive. This is most likely the sense in which the Apostle uses it.

But the word “heretic” came to mean something very different for early seventeenth century Protestants. It meant “one opposed to the established doctrines and authority of the Church”.

In your own words, Henry, explain why the translators of the KING JAMES AUTHORISED VERSION of the Bible might want to warn their readers against opposing the doctrines and authority of the (established) Church, rather than using a word that was closer to the Apostle’s likely original intention, and didn’t carry such, er, additional baggage.

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