Textbooks and Haeckel again


[When I started this weblog, one of the hot topics in the Creationist Wars was Jonathan Wells, a Moonie who had trained as a developmental biologist and written a screed against evolutionary biology titled Icons of Evolution. This book purported to document serious flaws in some of the major examples of evolutionary biology, although what it actually did was parrot old creationist arguments and get much of the science wrong. One of the subjects he focused on was the pharyngula—the embryonic stage that exhibits a common morphology across all vertebrates. This fascinating developmental period has an unfortunate history, in that Ernst Haeckel published some fraudulent drawings of it, and also made exaggerated claims about it. One of Wells’ strategies was to condemn every biology textbook that illustrated homologies in pharyngula stage embryos, tarring them with the broad brush of Haeckelism. This got to the point where he was absurdly damning books that even included photos of embryos, and one of the things I’ve tried to do is document the way he misrepresents science teaching.]

I got a request to document some of Wells’ claims from his execrable book, Icons of Evolution. Specifically, Wells chastises several textbook authors for using modified versions of Haeckel’s drawings:

Starr & Taggart, 10th ed and this was mentioned in
Well’s testimony, p. 315, “slightly simplified version of
Haekel’s original fraudulent drawings”

Raven & Johnson, Biology, 6th ed

“modified version … exaggerates actual similarities” p. 450

I don’t have all of the textbooks he describes, but I do have the 5th and 9th editions of the above books, and I suspect the figures haven’t changed. Below, I’ve scanned in several of the figures that Wells finds objectionable, and for the most part, they aren’t bad at all, and actually make useful pedagogical points. I suspect that the real reason Wells and other creationists dislike them is that they reveal deep homologies that support evolutionary explanations of the origins of animal diversity.

Here’s figure 20.7 from Starr & Taggert’s Biology: The Unity and Diversity of Life, 9th edition:

Copyright © 2001 Brooks/Cole

That is clearly a reworked version of the Haeckel/Romanes diagram; the fish in particular isn’t very accurate, and there is very little detail. It’s not very good, and doesn’t do a good job of illustrating the point. 20.7b, though, salvages the figure—that is a nice illustration of the homologous layout of the aortic arches.

And here is figure 20.18 from Raven & Johnson’s Biology, 5th edition:

Copyright © 1999 McGraw-Hill Companies, Inc.

I think this is very nice. These aren’t from Haeckel; these are clearly drawn from real animals. They show the variations that do exist between these animals, for instance in the degree of flexure, the presence of limb buds, and differences in relative size of various structures. There is some exaggeration—for instance, I’ve never seen a photo of a human embryo in which all of those branchial arches are as clearly delineated as that—but that’s the purpose of a drawing. The purple tint isn’t objectionable, since that’s purely to indicate where the structures are.

Another, Guttman’s Biology, 1st edition:

Copyright © 1999 McGraw-Hill Companies, Inc.

This discussion earned Guttman an “F” from Wells, for using Haeckel’s drawings, and for citing the similarity of early embryos as evidence for common ancestry. Of course, what this textbook is actually doing is discussing the history of this concept, and explaining how the idea has changed from its erroneous 19th form into its current non-recapitulationist version—which makes using Haeckel’s figure quite reasonable. It’s not perfect (I itch to change that last line to “…must resemble the larval cnidarian ancestor”), but these three short paragraphs treat the issue with more honesty and sophistication than Wells’ whole book.

Now here’s something a bit sad, from Campbell-Reece-Mitchell’s 5th edition of Biology:

Copyright © 1999 Benjamin/Cummings

That’s the best of the four shown here! It’s a pair of good photos (although Wells doesn’t like photos, either—they are “misleading”), that accurately illustrate the point of embryonic homology.

So what’s sad about it? The photos are not present in the 6th edition. The 5th came out in 1999, Wells’ book is from 2000, the 6th is copyright 2002. I hope that is just a coincidence and that Benjamin Cummings (the publisher) had some other good reason for expunging an illustration than criticism from a creationist. I notice that the third edition has even better photographs of embryos; it’s odd that the presentation of this one small subject has been given progressively less attention from Campbell over the years. Rather than creationist pressure, it may be that the increasing amount of information on homologies in vertebrate embryos has made it difficult to do it justice in an introductory textbook.

Here at UMM, we use the textbook Life: The Science of Biology by Purves et al. in our introductory courses. It says nothing about Haeckel or a conserved phylotypic stage at all…but what it does have is an entire short chapter on “Development and Evolutionary Change”. Instead of vertebrates, it uses the example of crustaceans to illustrate how embryonic similarities are useful indicators of homology, and discusses deeper molecular relationships, such as the Hox genes, that unite animal life. It’s strongly pro-evolution, so I’m sure Wells would find some criterion to give this textbook an “F”, anyway.

One thing I have noticed over the last 5 years, though, is an increase in the amount of material on evolution and development in college biology texts. Wells’ book, if it had any influence at all, has not had the effect he might have expected; it’s much more likely, though, that the expansion of evo-devo related content has been a consequence of the success and growing importance of the evo-devo research program.


  1. Ronpar says

    Just so you know, I pulled my Campbell-Reece 7th edition down of the shelf and the figure is back in (22.15, p449). The caption is changed to read:

    “Anatomical similarities in vertebrate embryos. At some stage in their embryonic development, all vertebrates have a tail located posterior to the anus, as well as pharyngeal (throat) pouches. Descent from a common ancestor can explain such similarities.”

    Campbell-Reece also include an “evolution connection” at the end of the problems for each chapter (something that was also in the 6th edition).

  2. A.H. says

    Calling pharyngeal arches ‘gill slits’ or ‘gill pouches’ has always been a pet peeve of mine. It often leads to a misconception about nature of these structures during development and early vertebrate development in general. It is unfortunate to see arches refered to as gill slits in biology textbooks especially when better terminology exists.

  3. BW says

    As to the Campbell images:

    They are back in the 7th edition on page 449.

    I had the priviledge to work closely with Neil for a number of years. I really can’t say why they are missing from the 6th ed. but I can say that any number of factors play into such a decision. I can assure you that Well’s critiques had nothing to do with the decision made. Page real-estate is a very limiting factor. You do find an ever increasing emphasis on evo-devo in these books–just not in the discussion of Darwin’s development of “One long argument.”

    In fact, I worked with Neil on a high school edition, Exploring Life, that included the same images. I can tell you high school texts are under different and more intense pressures than college texts. This book was produced at the very height of Well’s notoriety–between the 5th and 6th editions as you mention. We felt that it was essential to include actual photographs in the high school version specifically to counter Well’s claims.


  4. Harry Eagar says

    The thing that strikes me so forcibly by your comparisons is how VERY much more advanced introductory textbooks are than when I was in school 40 years ago.

    I felt the same a couple years ago when my wife was taking introductory chemistry. The material would have been considered an advanced course for majors only back at Cow College.

    What I conclude is that boomers like myself who have not made any effort to renew their basic science education in recent years should be considered to be illiterates.

  5. PaulC says

    I suspect that the real reason Wells and other creationists dislike them is that they reveal deep homologies

    I would put the period right there. The real reason the fundies get their knickers in a knot about biology in general is that it reveals deep homologies between humans and other living things. Evolution is just the issue that they attack because it’s hard to contemplate the scale of time and population needed; thus, there is some room for spreading their FUD. On the other hand, photos of embryos are difficult to deny, so it’s in their interest to minimize the significance of something that would cause anyone with common sense and functioning eyes to conclude that we’re really not so different.

    No doubt, they’d prefer something like, oh:

    And God said, Let us make man in our image, after our likeness: and let them have dominion over the fish of the sea, and over the fowl of the air, and over the cattle, and over all the earth, and over every creeping thing that creepeth upon the earth.

    See? We’re made in God’s image. We’re the ones with dominion over everything else. If you start pointing out homologies, next thing you’ll be saying we’re basically another animal–notable for brain size, tool use, and language, but not substantially different.

    Fundies and other kinds of conservatives hate this idea because it pulls out the entire underpinnings of their program, which is based on privilege and hierarchy.

    I got caught up in a thought today before reading PZ’s posting, but it seems tangentially relevant here. I’m not a biologist, but it seems to me that it’s funny to see people announce their incredulity at the evolution of specific organs (the eye, the human brain) in multicellular animals, when the most remarkable thing is the eukaryotic cell, which has existed much longer. Once you have one of those, the rest is just gravy–or software if you don’t mind loose analogies.

    I assume the IDers aren’t going to start promoting vitalist theory as an explanation for all the things we don’t understand yet about development (in their hearts who can say what they believe?). So they’d have to accept the premise that you take a single cell and get all kinds of different results just by inserting a strand of DNA whose informatic content would fit easily on a DVD ROM.

    Imagine you had a device that could be anything you wanted just by upgrading the firmware. A cuisinart food processor? You got it! A race car? You got it! An airplane? You got it! The eukaryotic cell is very roughly such a thing. It’s not too loose to say it is a von Neumann universal constructor, since von Neumann himself based the abstraction of a constructor on the question of self-reproduction in living things.

    But the cell has been around a lot longer than all multicellular features we ooh and ah about. Some of them, like the optics of the human eye are a good bit less remarkable than the cell: i.e., we know how to build excellent optics ourselves, but we haven’t come close to building a true self-replicating machine. It’s true that having a cell is not the same as having the genes needed to grow it into a multicellular animal, but it’s still rather breathtaking to think of it having the potential to develop into all the complex living things we observe. I can honestly say that at some level I’m incredulous that you can take a single cell and get an octopus, an elephant, or a human just by giving it some DNA to encode some proteins. I believe it’s true because it is repeatable, but I have difficulty grasping it intuitively (I imagine a developmental biologist can do a better job at that, but nobody has a complete play-by-play).

    The only thing fundies have left to debate is whether you need an “intelligent content provider” to supply the firmware for your eukaryomatic universal cell thingy. Honest, it must suck to be left with these tiny scraps of an argument. A Dembski born a couple hundred years ago could have written thick treatises on the elan vital, but today all he has left is to misapply some technical results from optimization theory (NFL theorems). Again, it must suck to be Dembski.

  6. Hyperion says

    Incidentally, Campbell’s 5th edition was also uite clear in stating that Haekel’s thesis that “embryology recapitulates phylogeny” has long been discarded by biologists, and then goes on to mention the basics of evo-devo and then shows those pictures.

    So even leaving aside Well’s contention that they use inaccurate pictures, this should also destroy his argument that biology texts support Haekel or that they try to cover up his errors.

  7. vandalhooch says

    I just pulled down the latest Johnson and Raven text. It is copyrighted 2006 (not sure of the edition number. There is no image of embryos at all!

    The only mention of embryos as evidence for evolution is this paragraph:

    “Most scientists believe that the evolutionary history of organisms is also seen in the development of embryos. At some time in their development, all vertebrate embryos have a tail, buds that become limbs, and pharyngeal (fuh RIN jee uhl) pouches. The tail remains in most adult vertebrates. Only adult fish and immature amphibians retain pharyngeal pouches (which contain their gills). In humans, the tail disappears during fetal development, and pharyngeal pouches develop into structures in the throat.” pg. 286

    In my experience with 10th grade students, this paragraph without a picture or diagram becomes the equivalent of Charlie Brown ‘teacher talk’.

    I’m so glad that I chose Miller and Levine’s as our new text. There is a decent discription of embryological evidence with text clearly written to refute Wells! As a coincidence, I just issued the books today and the students were very enthused. They spent about 15 minutes just perusing the pages and sharing page numbers of cool photos. I also got a lot of pointed and thoughtful questions, even some from the students who have not been doing well in class.

    Just thought I would share.
    BTW: I will definitely be going into deeper depth of the embryological connections during lecture, complete with images.

  8. Ed Darrell says

    1. Wells’ criticisms of Haeckel were a key point in the Texas process of high school biology textbook approval. David Hillis at UT got at least one publisher to agree to substitute photos for drawings Wells complained about — but we keep hearing rumors that the publishers were approached by the creationist majority on the Texas State Board of Education and asked secretly to get rid of the drawings, and to make other, science-unfriendly, ID-friendly changes. Keep up the demand for real stuff in your states, please. (The 2003 public discussions are still on-line, in the archives at the Texas Education Agency website.)

    2. Remember the chicken and human embryo photos you posted a couple of days ago? There is stuff on several very conservative religious blogs claiming you suggested eating human embryoes, or that at a minimum you denigrated the value of human life.

    Go see Joe Carter’s blog, for example: http://www.evangelicaloutpost.com/archives/001794.html

    It becomes clear reading those things that there is genuine fear among creationists, and among anti-abortion advocates, that real science will persuade people to views contrary to theirs.

    It’s as if the creationists are saying they can’t afford to let the truth make people free, you know: That’s why creationists support Wells and want to keep the drawings and photos out of high school biology books.

  9. *AndreA* says

    Amen sister!! jessica is soo right.. have you guys ever thought about this.. okay so like we have some of the same bodily structures as a freaking ape.. maybe its cuz we came from the same PERSON!!!!!!!!!! if you beleive in Evolution then you should seriously think about reading the Bible.. Jesus has a lot to say to you =))

  10. says

    Isn’t it strange how two people show up suddenly, testify for each other with a superfluity of exclamation points, and share amazingly similar attitudes? Maybe it’s because Jesus created you both.

    It’s also cool how Jesus gave both of you the same IP address.

  11. Jason says

    Well at least Jesus/God knows what is truly in AndreA/Jessica’s heart.
    She’s a liar, has born false witness, and in her idealic world should be pulled into the town square and stoned.

    Now back to the science.

    Wouldn’t it be better worded (and accurate) to say;
    “Ontogeny recapitulates embryonic phylogeny”?
    Let me know if I have this right…

    Any similarity in structure between two embryos reflects similar phenotopic body plan development derived from similar genetic expression and timing of this expression. Any differences between embryos later on in development are the result of genetic changes and the timing of such expression during these later stages.

    The closer the embryos look during later stages (say man and chimp), are the result in recent historical genetic changes that cause develomental changes towards the end of the embryonic cycle. (genetic changes that impact early embryonic development will more likely result in cataclysmic effects on the embryo and thus not be passed on.)

    The more different embryos look during later stages (say man and chicken), are the result of more ancient changes. Such changes, that at the time of their divergence, more likely impacted late embryonic development (the speciation event) but since then has been compounded upon by even more genetic divergence and perhaps lengthier embryonic development, typical of more modern animals, particularly mammals.

    So, Haekel was wrong but it is not wrong to use comparative embryology as evidence for evolution. Creationists can’t tell the diffence between the two concepts. This phenomenon is similar to the “Peppered Moths on tree trunks” fiasco.

  12. Randy says

    To Jessica and Andrea,
    You ought to read the Bible; the whole thing, cover to cover, front to back. If more fundies actually read the entire Bible, there’d be fewer fundies. Too few fundies realize that their supernatural, infallible, compilation of the Word of God is entirely the work of men. Indeed, the very version most commonly used among fundies (and isn’t it funny that there even are versions?), The Revised Standard Version (sometimes called the Revised American Standard), derived from the King James, is, in fact, derived from Martin Luther’s German translations in the 1500s. In other words, 1,500 years of scribal and typesetting convention, translation, and editing separate their magic book from the life of the man they supposedly worship — 1,500 years of a time when their own dogma demands that the Word of God was closed and complete.
    Jessica and Andrea, you are idolators and heretics. You worship the Book, an idol, and substitute worship of the Book, its every little jot and tittle, for worship of the God supposedly at the center of your religion.
    How sad.