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Evans et al. (2021): All Four Examples Debunked

Photo: Tribrachidium, by Captmondo, CC BY-SA 3.0 , via Wikimedia Commons.

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.

Harsh Criticism

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.


  • Bechly G 2018. Why Dickinsonia Was Most Probably Not an Ediacaran Animal. Evolution News September 27, 2018.
  • Bechly G 2020a. Did Cloudinids Have the Guts to be Worms. Evolution News January 7, 2020.
  • Bechly G 2020b. Ancestor of All Animals in 555-Million-Year-Old Ediacaran Sediments? Evolution News March 26, 2020.
  • Bechly G 2020c. The Myth of Precambrian Sponges. Evolution News May 26, 2020.
  • Bechly G 2020d. Namacalathus, an Ediacaran Lophophorate Animal? Evolution News July 9, 2020.
  • Bechly G 2020e. Namacalathus, Alleged Ediacaran “Animal,” Fails to Refute Abrupt Cambrian Explosion. Evolution News July 10, 2020.
  • Bechly G 2020f. Was Kimberella a Precambrian Mollusk? Evolution News September 3 – 21, 2020. [14 part article series]
  • Bechly G 2021a. Resurrecting Namacalathus as an Ediacaran Animal. Evolution News January 18, 2021.
  • Bechly G 2021b. Namacalathus Revisited — Not Much to See. Evolution News January 19, 2021.
  • Bernstein J 2021. Research shows we’re surprisingly similar to Earth’s first animals. UC Riverside News March 8, 2021.
  • Budd GE, Jensen S 2017. The origin of the animals and a ‘Savannah’ hypothesis for early bilaterian evolution. Biological Reviews 92(1), 446–473. DOI: 10.1111/brv.12239.
  • Clites EC, Droser ML, Gehling JG 2012. The advent of hard-part structural support among the Ediacara biota: Ediacaran harbinger of a Cambrian mode of body construction. Geology 40(4), 307–310. DOI: 10.1130/G32828.1.
  • Conway Morris S 1990. Late Precambrian and Cambrian Soft-Bodied Faunas. Annual Review of Earth and Planetary Sciences 18, 101–122. DOI: 10.1146/annurev.ea.18.050190.000533.
  • Darroch SAF, Smith EF, Laflamme M, Erwin DH 2018. Ediacaran Extinction and Cambrian Explosion. Trends in Ecology & Evolution 33(9), 653–663. DOI: 10.1016/j.tree.2018.06.003.
  • Dockrill P 2021. Humans Have Surprising Similarities to Strange Creatures From 550 Million Years Ago. ScienceAlert 9 March 2021.
  • Droser ML, Tarhan LG, Gehling JG 2017. The Rise of Animals in a Changing Environment: Global Ecological Innovation in the Late Ediacaran. Annual Review of Earth and Planetary Sciences 45, 593–617. DOI: 10.1146/annurev-earth-063016-015645.
  • Dzik J 2003. Anatomical Information Content in the Ediacaran Fossils and Their Possible Zoological Affinities. Integrative and Comparative Biology 43(1), 114–126. DOI: 10.1093/icb/43.1.114.
  • Erwin DH, Laflamme M, Tweedt SM, Sperling EA, Pisani D, Peterson KJ 2011. The Cambrian Conundrum: Early Divergence and Later Ecological Success in the Early History of Animals. Science 334(6059), 1091–1097. DOI: 10.1126/science.1206375. [the description of Triradialomorpha is only found in the Supporting Online Material]
  • Evans SD, Droser ML, Erwin DH 2021. Developmental processes in Ediacara macrofossils. Proceedings of the Royal Society B 288: 20203055, 1–10. DOI: 10.1098/rspb.2020.3055.
  • Fedonkin MA 1981. Belomorskaya biota venda (dokembrijskaya besskeletnaya fauna severa Russkoy platformy) [The White Sea Biota of the Vendian: Precambrian Non-Skeletal Fauna of the Northern Russian Platform]. Trudy Akademii Nauk SSSR 342, 196 pp. [In Russian]
  • Fedonkin MA 1982. Precambrian soft-bodied fauna and the earliest radiation of invertebrates. Third North American Paleontological Convention Proceedings 1, 165–167.
  • Fedonkin MA 1983a. [Organic world of the Vendian]. Itogi Nauki Tekhniki Viniti an SSSR [Transactions of the Institute of Scientific and Technical Information, Series Stratigraphy and Paleontology] 12, 1–128. [In Russian]
  • Fedonkin MA 1983b. Promorphology of Vendian Radialia as a key to understanding the early evolution of Coelenterata. p. 6 in: Fourth International Symposium on Fossil Cnidaria. Abstracts, Washington, D.C.
  • Fedonkin MA 1984. Promorphology of Vendian Radialia. pp. 30–58 in: Ivanovsky AB, Ivanov AB (eds). Stratigraphy and Paleontology of the Most Ancient Phanerozoic. Nauka, Moscow.
  • Fedonkin MA 1985a. Besskeletnaya fauna venda: Promorfologicheskij analiz. [Non-skeletal fauna of the Vendian: Promorphological analysis]. pp. 18–69 in: Sokolov BS, Ivanovski AB (eds). Vendskaya sistema, Tom 1. [The Vendian System, Volume 1]. Nauka, Moscow. [In Russian]
  • Fedonkin MA 1985b. [Systematic description of Vendian Metazoa]. pp. 70–106 in: Sokolov BS, Ivanovski AB (eds). Vendskaya sistema, Tom 1. [The Vendian System, Volume 1]. Nauka, Moscow. [In Russian]
  • Fedonkin MA 1985c. Precambrian metazoans: the problems of preservation, systematics and evolution. Philosophical Transactions of the Royal Society B 311(1148), 27–45. DOI: 10.1098/rstb.1985.0136.
  • Fedonkin MA 1986. Precambrian problematic animals: their body plan and phylogeny. pp. 59–67 in: Hoffman A, Nitecki MH (eds). Problematic fossil taxa. Oxford Monographs on Geology and Geophysics, Vol. 5. Oxford University Press, New York, 276 pp. 
  • Fedonkin MA 1987. Vendian non-skeletal fauna and its relation to metazoan evolution. Transactions of the Paleontological Institute 226. Nauka, Moscow, 176 pp. [in Russian].
  • Fedonkin MA 1990. Non-Skeletal Fauna of the Vendian: Promorphological Analysis. Chapter 1 pp. 7–70 in: Sokolov BS, Ivanovski AB (eds). The Vendian System. Vol. 1 Paleontology. Springer-Verlag, Berlin, 383 pp. [Translation of Fedonkin 1985a]
  • Fedonkin MA 1992. Vendian Faunas and the Early Evolution of Metazoa. Chapter 4 pp. 87–129 in: Lipps JH, Signor PW (eds). Origin and Early Evolution of the Metazoa. Springer Science / Plenum Press, New York, xiv+570 pp. DOI: 10.1007/978-1-4899-2427-8_4.
  • Fedonkin MA 2003. The origin of the Metazoa in the light of the Proterozoic fossil record. Paleontological Research 7(1), 9–41. DOI: 10.2517/prpsj.7.9.
  • Fedonkin MA, Cope JCW 1985. Precambrian metazoans: The problems of preservation, systematics, and evolution. Philosophical Transactions of the Royal Society of London Biological Sciences 311(1148), 27–45. DOI: 10.1098/rstb.1985.0136.
  • Fedonkin MA, Ivantsov AY 2007. Ventogyrus, a possible siphonophore-like trilobozoan coelenterate from the Vendian Sequence (late Neoproterozoic), northern Russia. pp. 187–194 in: Vickers-Rich P, Komarower P (eds). The Rise and Fall of the Ediacartan Biota. Special Publications 286, Geological Society, London. DOI: 10.1144/SP286.14.
  • Fedonkin MA, Gehling JG, Grey K, Narbonne GM, Vickers-Rich P 2007. pp. 241-242, 261, 273 in: The Rise of Animals: Evolution and Diversification of the Kingdom Animalia. John Hopkins University Press, Baltimore, 326 pp. [Google Books]
  • Gee H 2000. p. 134 in: Shaking the Tree: Readings from Nature in the History of Life. University of Chicago Press, 411 pp. [Google Books]
  • Gehling JG 1987. Earliest known echinoderm – a new Ediacaran fossil from the Pound Subgroup of South Australia. Alcheringa 11(4), 337–345. DOI: 10.1080/03115518708619143.
  • Gehling JG 1991. The case for the Ediacaran fossil roots to the Metazoan tree. Memoirs Geological Society of India 20, 181–224. [ResearchGate with PDF]
  • Gehling JG, Narbonne GM, Anderson MM, 2000. The first named Ediacaran body fossil, Aspidella terranovica. Palaeontology 43(3), 427–456. DOI: 10.1111/j.0031-0239.2000.00134.x.
  • Giribet G, Edgecombe GD 2020. The Invertebrate Tree of Life. Princeton University Press, Princeton, NJ, 608 pp. [Google Books]
  • Glaessner MT 1962. Pre-Cambrian Fossils. Biological Reviews 37(4), 467–494. DOI: 10.1111/j.1469-185X.1962.tb01331.x.
  • Glaessner MF 1984. The Dawn of Animal Life: A Biohistorical Study. Cambridge, UK: Cambridge University Press, Cambridge, 258 pp. [Website]
  • Glaessner MF, Daily B 1959. The Geology and Late Precambrian Fauna of the Ediacara Fossil Reserve. Records of the South Australian Museum 13, 369–401, pls xlii–xlvii. [BHL]
  • Glaessner MF, Wade M 1966. The late Precambrian fossils from Ediacara, South Australia. Palaeontology 9(4), 599–628. [Website with PDF]
  • Grazhdankin D 2014. Patterns of Evolution of the Ediacaran Soft-Bodied Biota. Journal of Paleontology 88(2), 269–283. DOI: 10.1666/13-072.
  • Hall CMS 2015. Paleoecology of Tribrachidium: New Data From the Ediacaran of South Australia. M.Sc. thesis, University of California Riverside, viii+40 pp. [PDF]
  • Hall CMS, Droser ML, Gehling JG, Dzaugis ME 2015. Paleoecology of the enigmatic Tribrachidium: New data from the Ediacaran of South Australia. Precambrian Research 269, 183–194. DOI: 10.1016/j.precamres.2015.08.009.
  • Hall CMS, Droser ML, Clites EC & Gehling JG 2018. The short-lived but successful tri-radial body plan: a view from the Ediacaran of Australia. Australian Journal of Earth Sciences. DOI: 10.1080/08120099.2018.1472666.
  • Ivantsov AY, Fedonkin MA 2002. Conulariid-like fossil from the Vendian of Russia: a metazoan clade across the Proterozoic/Palaeozoic boundary. Palaeontology 45(6), 1219–1229. DOI: 10.1111/1475-4983.00283.
  • Ivantsov AY, Fedonkin MA (in press). Reinterpretation of the Vendian genus Ventogyrus as a trilobozoan coelenterate, Onega River, north of the Russian Platform. Journal of Paleontology. [This paper is referenced in Ivantsov & Fedonkin 2002 but was apparently never published, but later published as Fedonkin & Ivantsov 2007]
  • Ivantsov AY, Leonov MV 2008. The imprints of Vendian animals – unique paleontological objects of the Arkhangelsk region. [ResearchGate with PDF]
  • Just J, Kristensen RM, Olesen J 2014. Dendrogramma, new genus, with two new non-Bilaterian species from the marine bathyal of southeastern Australia (Animalia, Metazoa incertae sedis) – with similarities to some medusoids from the Precambrian Ediacara. PLoS One 9(9), e102976, 1–11. DOI: 10.1371/journal.pone.0102976.
  • Keller BM, Fedonkin MA 1977. New organic fossil finds in the Precambrian Valday series along the Syuz’ma River. International Geology Review 19(8), 924–930. DOI: 10.1080/00206817709471091.
  • Kiessling W 2003. [unpublished data quoted in PaleoDB]
  • Kouchinsky A, Bengtson S, Gershwin L-A 1999. Cnidarian-like embryos associated with the first shelly fossils in Siberia. Geology 27(7), 609–612. DOI: 10.1130/0091-7613(1999)027<0609:CLEAWT>2.3.CO;2.
  • Kouchinsky A, Bengtson S, Feng W, Kutygin R, Val’kov A 2009. The Lower Cambrian Fossil Anabaritids: Affinities, Occurrences and Systematics. Journal of Systematic Palaeontology 7(3), 241–298. DOI: 10.1017/S1477201909002715.
  • Laflamme M, Darroch SAF, Tweedt SM, Peterson KJ, Erwin DH 2013. The end of the Ediacara: Extinction, biotic replacement, or Cheshire Cat? Gondwana Research 23(2), 558–573. DOI: 10.1016/j.gr.2012.11.004.
  • Matz MV, Frank TM, Marshall NJ, Widder EA & Johnsen S 2008. Giant Deep-Sea Protist Produces Bilaterian-like Traces. Current Biology 18(23), 1849–1854. DOI: 10.1016/j.cub.2008.10.028.
  • McMenamin MAS 1998. The Garden of Ediacara. Columbia University Press, New York, xii+295 pp. [revised edition 2000, 324 pp.]
  • McMenamin MAS 2016. Dynamic Paleontology: Using Quantification and Other Tools to Decipher the History of Life. Springer, Switzerland, xii+251 pp. [Website]
  • Narbonne GM 2005. The Ediacara Biota: Neoproterozoic Origin of Animals and Their Ecosystems. Annual Review of Earth and Planetary Sciences 33, 421–442. DOI: 10.1146/annurev.earth.33.092203.122519.
  • O’Hara TD, Hugall AF, MacIntosh H, Naughton KM, Williams A, Moussalli A 2016. Dendrogramma is a siphonophore. Current Biology 26(11), 457–458. DOI: 10.1016/j.cub.2016.04.051.
  • Paul CRC 1979. Early echinoderm radiation. pp. 415–434 in: House MR (ed). The Origin of Major Invertebrate Groups. Systematics Association Special Volume 12, Academic Press, New York, x+515 pp. 
  • Rahman IA, Darroch SAF, Racicot RA, Laflamme M 2015. Suspension feeding in the enigmatic Ediacaran organism Tribrachidium demonstrates complexity of Neoproterozoic ecosystems. Science Advances 1(10), e1500800, 1–8. DOI: 10.1126/sciadv.1500800.
  • Retallack GJ 2013. Ediacaran life on land. Nature 493, 89–92. DOI: 10.1038/nature11777.
  • Runnegar B 1989. Proterozoic evolution of Metazoa. pp. 733-735 in: Abstracts, 28th International Geological Congress, Washington, D.C., USA, July 9-19, 1989, Vol. 2.
  • Schopf JW, Klein C (eds) 1992. The Proterozoic Biosphere: A Multidiscplinary Study. Cambridge University Press, Cambridge, 1348 pp. [Google Books]
  • Seilacher A 1999. Biomat-Related Lifestyles in the Precambrian. Palaios 14(1), 86– 93. DOI: 10.2307/3515363.
  • Seilacher A, Grazhdankin D, Legouta A 2003. Ediacaran biota: The dawn of animal life in the shadow of giant protists. Paleontological Research 7(1), 43–54. DOI: 10.2517/prpsj.7.43.
  • Serezhnikova EA 2014. Skeletogenesis in Problematic Late Proterozoic Lower Metazoa. Paleontological Journal 48(14), 1457–1472. DOI: 10.1134/S0031030114140123.
  • Solon Hall CM 2015. Paleoecology of Tribrachidium: New Data From the Ediacaran of South Australia. M.Sc. thesis, University of California, Riverside, viii+40 pp. [PDF]
  • Solon CM, Droser ML, Gehling JG, Dzaugis ME 2014. Paleoecology of Rugoconites and Tribrachidium: New Data from the Ediacaran of South Australia. The Paleontological Society Special Publications, Vol. 13: 10th North American Paleontological Convention, Abstract Book, 2014, 46–47. DOI: 10.1017/S2475262200010984.
  • Tang F, Bengtson S, Wang Y, Wang XL, Yin CY 2011. Eoandromeda and the origin of Ctenophora. Evolution & Development 13(5), 408–414. DOI: 10.1111/j.1525-142X.2011.00499.x.
  • Taylor, W.L., Almond, J.E., Jensen, S., Högström, A.E.S., Gresse, P., Harrison, B., Agić, H., Høyberget, M., Ebbestad, J.O.R., Meinhold, G., Palacios, T. 2017. Possible trilobozoans with internal structures from the Late Ediacaran Nama Group, Northern Cape, South Africa. Abstracts of the International Symposium on the Ediacaran-Cambrian Transition (ISECT), June 15-29, 2017, Memorial University, St. Johns, Newfoundland. [Website]
  • Valentine JW 1992. The Macroevolution of Phyla. pp. 525–553 in: Lipps JH, Signor PW (eds). Origin and Early Evolution of the Metazoa. Plenum Press, New York, xiv+570 pp. DOI: 10.1007/978-1-4899-2427-8_16.
  • Val’kov AK 1987. Biostratigrafija nizhnego kembrija vostoka Sibirskoj platformy (Yudoma-Oleniokskij region). [Biostratigraphy of the Lower Cambrian of the eastern Siberian Platform (Yudoma-Oleniok region)]. Nauka, Moscow, 136 pp. [In Russian].
  • Van Iten H, Leme JDM, Simoes MG, Marques AC, Collins AG 2006. Reassessment of the phylogenetic position of conulariids (?Ediacaran–Triassic) within the subphylum Medusozoa (Phylum Cnidaria). Journal of Systematic Palaeontology 4(2), 109–118. DOI: 10.1017/S1477201905001793.
  • Wade M 1969. Medusae from uppermost Precambrian or Cambrian sandstones, central Australia. Palaeontology 12(3), 351–365. [Website with PDF]
  • Wade M 1972. Hydrozoa and Scyphozoa and other medusoids from the Precambrian Ediacara fauna, South Australia. Palaeontology 15(2), 197–225. [Website with PDF]
  • Wang Y, Wang X, Huang Y 2008. Megascopic Symmetrical Metazoans from the Ediacaran Doushantuo Formation in the Northeastern Guizhou, South China. Journal of China University of Geosciences 19(3), 200–206. DOI: 10.1016/S1002-0705(08)60039-4.
  • Xiao S & Laflamme M 2008. On the eve of animal radiation: phylogeny, ecology and evolution of the Ediacara biota. Trends in Ecology and Evolution 24(1), 31–40. DOI: 10.1016/j.tree.2008.07.015.
  • Zakrevskaya M, Ivantsov A 2020. Ontogenetic transformations and re-interpretation of Ediacaran Trilobozoa. Abstracts of the JpGU-AGU Joint Meeting 2020, B-PT05-02, Japan Geoscience Union. [Website with PDF]