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Darwin on Dissimilarities

Explore Evolution focuses excessively on the details of what Darwin argued 150 years ago, rather than informing students about the dynamic field of evolutionary developmental biology. Whether or not Darwin argued that dissimilarities in early development do not cause a problem for evolution is less important than helping students understand how modern scientists view these issues. Explore Evolution fails to explain that the amount of yolk in an egg has adaptive value and is responsible for differences in embryogenesis.

The Earliest Stages

Explore Evolution claims:

both Darwin's and Haeckel's comparisons left out the earliest stages of development.*

Whether this omission was intentional is a matter of some debate.

Accuracy in embryo illustrations

It has been widely noted that a number of the embryos in top row of the Tables 6 and 7 from Haeckel's Anthropogenie (1874) are not realistic representations. However, the assertion by Explore Evolution that Haeckel claimed that top row represented earliest embryos is false. Nor are the book's claims that Haeckel engaged in fraud justified by current historical scholarship.

Haeckel's Drawings

Explore Evolution incorrectly asserts that Haeckel’s Biogenetic Law claims that the earliest stage of embryos are most similar. Haeckel's concept of caenogenesis fully acknowledged that there can be signficant differences between embryos including at the earliest stages of development. This misrepresentation of the Biogenetic Law allows Explore Evolution to set up erroneous claims that Haeckel committed fraud and that the distinctions between the early stages of development of different classes of vertebrates argue against common descent.

Ontogeny & Phylogeny

There is no question that the study of development played an important role in Charles Darwin's thinking on evolution, and that it continues to play an important role in modern evolutionary biology. Ernst Haeckel's early suggestion that ontogeny (development) recapitulates phylogeny (evolution) was far less influential and is rejected by modern biologists.



Carroll, S. (2005) Endless Forms Most Beautiful.

Davidson, E. (2005). The Regulatory Genome.

Richards, RJ. (1990) The Meaning of Evolution.

Richards, RJ. (2008) The Tragic Sense of Life.

Wells, J. (2000) Icons of Evolution.

Wells, J. (2003) "Survival of the Fakest." American Spectator.

Wells, J. (2005) The Politically Incorrect Guide to Intelligent Design and Evolution.


Rather than presenting an account of how embryology is studied in the 21st century, the "Embryology" chapter concludes by exhorting students to pretend they are jurors in a court case against evolution. It's unclear what the charges might be, but it is certain that the students would be diverted from a fair verdict by the chapter's studious avoidance of current science in the field.

Michael Richardson's photographs

Michael Richardson and colleagues in 1997 were instrumental in pointing out the discrepancies between Haeckel's popular diagram and genuine embryos. However, Explore Evolution simply accepts a flawed creationist interpretation of Richardson's work. The claim that the common ancestry of vertebrates requires that embryos be most similar at the earliest embryonic stage was not accepted by Darwin nor Haeckel nor any modern evolutionary or developmental biologist.

Sedgwick's Two Challenges

Explore Evolution asserts that in 1894, Adam Sedgwick challenged Darwin's two claims about embryos, 1) early embryos of related organisms are more similar than adults and 2) the younger the embryos, the greater the resemblance. A comprehensive comparison of vertebrate embryos does not support Sedgwick's challenges about the similarity of embryos.

History of Embryology

Evolutionary developmental biology is a vital and active field of study. High school biology textbooks rarely cover it in detail, so Explore Evolution might have done a service by offering a brief exploration of that modern field. Instead, it focuses on creationist hobbyhorses from the history of biology. Most prominent of these historical arguments is a debate over illustrations by Ernst Haeckel.


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