Correction Needed about the Use of Ernst Haeckel's Vertebrate Embryo Diagrams
and a Discussion of the Evaluation submitted to TEA by the Discovery Institute

Steven Schafersman
2011 July 20

One publisher submitted materials that continue to use the inaccurate vertebrate embryo diagrams of Ernst Haeckel--Rice University. The Discovery Institute's Evaluation of Supplementary Biology and Evolution Materials contains a misleading and error-filled discussion of this topic, but its conclusion that the traditional diagram should not be used is accurate (as has long been known to legitimate, mainstream biologists). Essentially all biology textbooks have not used them for years. Haeckel's diagram was not, however, fraudulent as the DI claims. The most recent scholarly research informs us that Haeckel did not have modern knowledge of the morphology of vertebrate embryos and that knowledge he did have was inadequate in his day for him to be precise. Also, Haeckel corrected some of his drawings when contemporaneous critics informed him of errors. [Note: 2011 July 21 - Rice University has withdrawn its biology submission.]

The other two publishers identified in the DI's Evaluation, Adaptive Curriculum and Holt McDougal, did not use the traditional Haeckel's diagram but instead used re-drawings that look similar but have been updated to be more accurate. Their submissions are not inaccurate or fraudulent as the DI claims. The Adaptive Curriculum (also used in Learning.com) is very similar to Haeckel's but the first stage of the embryos have been differentiated more than Haeckel did. It is acceptable but I would still prefer that it be changed because it still gives the impression of being identical to Haeckel's diagram. The Holt McDougal illustration is completely scientific and acceptable. I will include images of these here later. [Note: 2011 July 22 - Adaptive Curriculum/Learning.com agreed to change its vertebrate embryo discussion and use new images. I will post both the old and new versions here later. Holt McDougal did not change its illustration and was not forced to by the SBOE or TEA.]

The DI evaluation states that "most textbooks still overstate the degree of similarity between vertebrate embryos." This is completely untrue. All vertebrate embryos have several extremely important similarities such as the embryological development of a notochord and pharyngeal pouches (or arches) and grooves (or slits) that illustrate their ontogenetically primitive condition and evolutionary common origin. This includes human embryos and the similarities reveal our own evolutionary origin from more primitive vertebrates. The DI discussion deceptively hides this fact behind a misuse of rhetoric. I strongly feel that a discussion of the fact that human embryos contain a notochord and pharyngeal grooves (formerly termed "gill slits") that disappear during development is extremely strong and easy to understand evidence of human evolution and all publishers should include it.

Good discussions of the truth about Haeckel's embryos are the outstanding 2003 TalkOrigins article on Wells and Haeckel's Embryos by PZ Myers in which he completely exposes the DI's misrepresentations and mistakes (which are unsurprisingly continued in its 2011 Evaluation submitted several weeks ago to the TEA), PZ Meyers' Textbooks and Haeckel Again (Professor Meyers is a developmental biologist and is therefore fully knowledgeable about this topic), this NCSE discussion, and University of Chicago science historian Robert Richards' Haeckel's embryos: fraud not proven that provides the latest scholarly information about the preparation of Haeckel's vertebrate embryo diagram. A good discussion concerning the use of the diagram in biology textbooks is Haeckel and his Embryos by Ken Miller and Joe Levine. The authors substitute photographs to show the important similarities among vertebrate embryos that reveals their evolutionary relationships and most textbooks now do this routinely (or include diagrams drawn directly from the photographs). Perhaps the best resource to investigate this topic is the 2002 paper by Michael Richardson and Gerhard Keuck, "Haeckel's ABC of evolution and development." Richardson's initial paper on the topic is the 1997 There is no highly conserved embryonic stage in the vertebrates: implications for current theories of evolution and development. And of course Wikipedia has an entry on the topic to which one should turn first.

It must be noted here that all of the sections in the DI's Evaluation of Supplementary Biology and Evolution Materials contain an enormous number of either ignorant or deliberate errors, misrepresentations, confusions, misleading descriptions, errors of logic, sophistic misuse of facts, and specious arguments covering important topics in addition to Haeckel's embryos: the Miller-Urey experiment, the phylogenetic Tree of Life, the stratigraphic and fossil record of fossil succession and lineages, Darwin's finches, vestigial organs, and the Peppered Moths. These topics were all first criticized in a pseudoscientific book titled Icons of Evolution by DI Senior Fellow Jonathan Wells and have been repeated almost verbatim in the DI's current Evaluation, which frankly reads as if Wells wrote it himself. Wells' book has been analyzed and refuted in great detail by numerous evolutionary scientists who care about presenting accurate and reliable information about evolution in schools (these can be found on TalkOrigins, Panda's Thumb blog, and the NCSE website. Three good ones are here (also here), here (also here), and here. These authors criticize Wells' treatment of Haeckel's embryo drawings and refute his conclusions, but without the depth found in the linked resources in the preceding paragraph. Wells' answered these critiques with a mystifyingly inadequate defense that simply dismisses his critics without any evidence or even discussion. In 2009 I produced a brief defense of the Tree of Life in my essay News of the Death of the Tree of Life Has Been Greatly Exaggerated. I mention this because the DI's Evaluation speciously quotes the same sources that announce the "death" of the Tree of Life that I refute in my essay, sources that post-date Wells' book. Many evolutionary scientists took the time to refute the claim and I cite them in my essay.

In conclusion, the Discovery Institute's Evaluation of Supplementary Biology and Evolution Materials should be totally ignored as a source of accurate and reliable scientific insight about the evolution content of biology materials for it contains none.


Last updated: 2011 July 22