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#2 Story of 2020: Kimberella Is No Solution to the Cambrian Conundrum

Kimberella
Photo: Kimberella, by Ghedoghedo / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0).

Editor’s note: Welcome to an Evolution News tradition: a countdown of our Top 10 favorite stories of the past year, concluding on New Year’s Day. Our staff are enjoying the holidays, as we hope that you are, too! Help keep the daily voice of intelligent design going strong. Please give whatever you can to support the Center for Science & Culture before the end of the year!

The following was originally published on September 21, 2020.

Editor’s note that introduced the original article: We have been delighted to present a series of posts by paleontologist Günter Bechly on the Ediacaran organism Kimberella. If identified as an animal, it would “predate the Cambrian explosion of bilaterian animal phyla as a kind of ‘advance guard.’” The question is of interest for debates about evolution and arguments about intelligent design raised by Stephen Meyer, among others. Find the full series about Kimberella here.

We can sum up that the current consensus suggests: that Kimberella is indeed a metazoan animal and most probably belongs either in the stem group of Bilateria or maybe has an uncertain position within Lophotrochozoa, but it is not a stem mollusk. Nevertheless, the proper interpretation of many of the structures of Kimberella is still controversial and the alternative possibility that Kimberella could be a coelenterate grade animal cannot be ruled out yet, especially since there is evidence for sclerotization and very diverse body plans in early Cambrian comb jellies (Scleroctenophora) (Zhao et al. 2019), as well as evidence for ancestral bilateral symmetry in Cnidaria (Erwin 2008).

Implications for the Cambrian Explosion

What does this tell us about the Cambrian explosion? Together with the alleged evidence for other Ediacaran bilaterian animals, which we critically discussed in my previous articles, this means that none of the Cambrian animal phyla is represented in the Ediacaran fossil record. This is very significant, because the potential soft-bodied ancestors would surely have been preserved in the numerous Ediacaran fossil localities of the Burgess Shale type (Bechly 2020), or in the Kimberella layers, which after all could preserve the soft-parts of a mollusk-like organism. At best the only two relatively uncontroversial Ediacaran bilaterians, Kimberella and the recently described worm-like Yilingia (Chen et al. 2019Evolution News 2019), could document the existence of just two phyla of Bilateria of uncertain affinity prior to the Cambrian era. However, their unique specializations strongly suggest that they could only represent extinct side branches but could not be directly ancestral to any of the numerous Cambrian animal phyla, and thus do not resolve their enigmatic origin.

Therefore, the latter still appear abruptly out of nowhere. The thousands of fossil links, postulated by Darwin’s theory of evolution, for the transition from a protist choanoflagellate ancestor to the complex body plans of the more than twenty Cambrian phyla of bilaterian metazoan animals, still remain elusive and missing, in spite of suitable fossil localities. Actually, the same problem exists for the so-called Avalon explosion that abruptly generated the diversity of macro-organisms of the Ediacaran biota. Where are all the missing links for the problematic organisms like CharniaDickinsonia, and Kimberella, which would document their gradual and stepwise evolution from protozoan ancestors? 

Honest scientists cannot any longer ignore this substantial conflicting evidence. The fossil record speaks clearly and cries out loud: the history of life on Earth is a history of saltations. There is a reason why scientists called these abrupt appearances “explosions” or even “Big Bangs” of life. Guess which model better fits this evidence, Darwin’s theory of gradually “climbing mountain improbable” (a metaphor offered by Richard Dawkins) or rather intelligent design theory? It is not a difficult choice, unless your world view dictates what kind of theories are allowed.

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