Editor’s note: We are delighted to present here Part 7 of “A Precambrian House of Cards,”a series by Dr. Bechly. Find the full series at this link. This post concludes the series. An extensive References section appears at the end.
Tribrachidium is anything but similar to us. It could hardly be more alien. We have no clue what it was or how it lived. Trilobozoans are multicellular Eukaryonta of uncertain relationship and thus cannot support the case of the new study. With all their four examples of alleged Ediacaran animals debunked, Evans et al. (2021) have built their house on sand and their study does not stand up to scrutiny.
In the press release from U.C. Riverside (Bernstein 2021), one of the authors, Dr. Mary Droser, said, “Our work is a way to put these animals on the tree of life, in some respects … And show they’re genetically linked to modern animals, and to us.” This revealing statement demonstrates what this exercise in evolutionary make-believe and circular reasoning is really all about: placing the enigmatic Ediacaran organisms in Darwin’s tree of life just by assuming that they were animals (also to explain away the conundrum of the Cambrian explosion), and then simply postulating that they had a similar genomic makeup to modern animals and us. How about first establishing your crucial assumptions instead? What happened to good scientific practice in the La La Land of current evolutionary biology?
I am not alone in my harsh criticism. Professor Gregory Retallack at the University of Oregon, a renowned specialist on Ediacaran fossils, could not resist commenting on this new study. Writing at the Facebook group The Ediacaran Period, here is what he had to say on March 8, 2021:
This study guesses what the genes were based on the assumption they were marine animals, but what if they were not animals or marine?…On the first page the authors write ‘we assume that these taxa were animals.’ Does it make a difference if the assumption is mere or just an assumption?…Thus the report caption should read “Research assumes we’re surprisingly similar to the first animals.”
Retallack (2013), who arguably is a dissenter among Ediacaran specialists, thinks that Tribrachidium was a terrestrial fungal fruiting body and that Dickinsonia was a terrestrial lichen, thus both were neither marine nor animals. Be that it as it may, the wide disparity of different interpretations at least shows that the evidence is totally ambiguous and does not allow a clear identification of an affinity with any particular group of modern organisms.
Circular Reasoning and a Cunning Claim
Evans et al. (2021) seem to have been well aware of the circular reasoning in their argument. They therefore cunningly claimed that “Developmental characters are interpreted exclusively from fossil evidence, independent of phylogenetic classification.” However, this is simply not true. Cellular and tissue differentiation as well as polarity and symmetry are not restricted to animals but also occur in other multicellular organisms, and multicellularity originated many times independently (e.g., in fungi, green plants, red and brown algae). Nevertheless, they inferred the animal genetic modules for axial polarity, musculature, immunity, nervous system, and multicellularity for the selected Ediacaran organisms even though we don’t know if they were animals. They inferred the animal genetic module for left-right symmetry in Dickinsonia and Ikaria even though Dickinsonia has no bilateral symmetry but the glide symmetry unique to Ediacaran organisms (Bechly 2018), and Ikaria is just represented by featureless rice-grain shaped impressions that at best have axial polarity (Bechly 2020b). Even if Ikaria should be the maker of the Helminthoidichnites traces, such traces are even today produced by large marine protozoans (Matz et al. 2008) and thus not indicative of animals with muscles and nervous system. The only somewhat reasonable case could be made for Kimberella, but even here a non-bilaterian coelenterate grade affinity could not yet be excluded (Budd & Jensen 2017, Bechly 2020f), so that the attribution of “bilaterian specific regulatory elements, including β-catenin, distal enhancers, Notch/Delta and Nodal signalling” is rather daring.
Evans et al. (2021) nevertheless conclude: “Although diverse bilaterian body plans do not appear until the Cambrian, bilaterians and gene regulatory elements critical for their later success were represented in the Ediacara Biota.” Sorry, but there is no convincing evidence for that!
A Precambrian House of Cards
Building far reaching hypotheses on highly ambiguous evidence and poorly based assumptions is unfortunately a common theme in modern evolutionary science, and with this study the authors have truly created a Precambrian house of cards. Their fantasy collapses as soon as the underlying assumption of an animal relationship of the concerning Ediacaran fossils is removed. This reminds me of the wonderful last book by the recently deceased author Tom Bethell, which was appropriately titled Darwin’s House of Cards. It is warmly recommended reading, an antidote against the prevailing Darwinian hyperbole, which is especially rampant in modern paleontology.
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