PZ Myers. 2003 Sep 17. Textbooks and Haeckel, again. <http://pharyngula.org/index/weblog/textbooks_and_haeckel_again/>. Accessed 2008 Dec 04.

Posted on M00o93H7pQ09L8X1t49cHY01Z5j4TT91fGfr on Wednesday, September 17, 2003

Textbooks and Haeckel, again

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 5^th and 9^th editions of the above books, and I suspect the figures haven't changed.

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

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, 5^th edition:

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, 1^st edition:

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 19^th 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 5^th edition of Biology:

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 6^th edition. The 5^th came out in 1999, Wells' book is from 2000, the 6^th 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.