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BioLogos’s Fossil Record Page Conspicuously Missing the Cambrian Explosion

The BioLogos website has a static page titled “What does the fossil record show?,” which would naturally lead one to expect that if you read the page, then you’ll learn what the fossil record shows. What’s odd about the page is that the page makes no mention whatsoever of the Cambrian explosion. This is despite the fact that Robert L. Carroll calls the Cambrian explosion “[t]he most conspicuous event in metazoan evolution”:

The most conspicuous event in metazoan evolution was the dramatic origin of major new structures and body plans documented by the Cambrian explosion. Until 530 million years ago, multicellular animals consisted primarily of simple, soft-bodied forms, most of which have been identified from the fossil record as cnidarians and sponges. Then, within less than 10 million years, almost all of the advanced phyla appeared, including echinoderms, chordates, annelids, brachiopods, molluscs and a host of arthropods. The extreme speed of anatomical change and adaptive radiation during this brief time period requires explanations that go beyond those proposed for the evolution of species within the modern biota.

(Robert L. Carroll, “Towards a new evolutionary synthesis,” Trends in Ecology and Evolution, Vol. 15(1):27-32 (2000) (internal citations removed).)

In fact, BioLogos’s fossil record page doesn’t make any mention of the pattern of explosions of new life-forms common throughout the history of life. This is despite the fact that, as one zoology textbook states, both lower and higher taxa tend to appear abruptly, making this one of the more prevalent features of the fossil record:

Many species remain virtually unchanged for millions of years, then suddenly disappear to be replaced by a quite different, but related, form. Moreover, most major groups of animals appear abruptly in the fossil record, fully formed, and with no fossils yet discovered that form a transition from their parent group.

(C.P. Hickman, L.S. Roberts, and F.M. Hickman, Integrated Principles of Zoology, p. 866 (1988, 8th ed.).)

So what exactly does the fossil record show? It certainly shows a number of explosions, and the Cambrian is perhaps the most dramatic of them all. But somehow this entire event–and this entire pattern–is left out of the BioLogos page explaining what the fossil record shows. Instead BioLogos focuses on a few isolated (and questionable) examples of gradual change–exceptions to the standard rule of abrupt appearance.
Why the omissions? Perhaps it’s because, as a 2003 paper in International Journal of Developmental Biology explains, the Cambrian explosion poses a challenge to unguided neo-Darwinian evolution:

the major evolutionary transitions in animal evolution still remain to be causally explained. … As it stands, microevolution does not provide a satisfactory explanation for the extraordinary burst of novelty during the Cambrian Explosion.

(Jaume Baguña and Jordi Garcia-Fernández, “Evo-Devo: the Long and Winding Road,” International Journal of Developmental Biology, Vol. 47:705-713 (2003) (internal citations removed).)

Yet this most conspicuous event in the history of animal life is conspicuously missing from BioLogos’s description of “what does the fossil record show.”

Postscript: I have received some extremely positive feedback on these posts responding to BioLogos (see Part 1, Part 2, and Part 3). I want to make it clear, however, that nothing in these posts has been intended to suggest or imply that anybody has acted dishonestly. These posts are simply a response and correction to what I view as inaccuracies and deficiencies in the BioLogos fossil record page.


Casey Luskin

Associate Director, Center for Science and Culture
Casey Luskin is a geologist and an attorney with graduate degrees in science and law, giving him expertise in both the scientific and legal dimensions of the debate over evolution. He earned his PhD in Geology from the University of Johannesburg, and BS and MS degrees in Earth Sciences from the University of California, San Diego, where he studied evolution extensively at both the graduate and undergraduate levels. His law degree is from the University of San Diego, where he focused his studies on First Amendment law, education law, and environmental law.



BioLogosCambrian ExplosionDarwin's Dilemmasciencetheistic evolution