by Piter Kehoma Boll
As you may have heard, or read, a paper published this month in Nature claims that the famous Ediacaran biota, a set of fossils from the Ediacaran Period (ca. 635-542 Mya) of the Neoproterozoic Era, is not composed by marine creatures, but rather land lichens. Who made this claim? Gregory Retallack, a geologist at the University of Oregon.
Retallack works on this hypothesis since the 1990s and the main evidences presented by him are related to geological features, like the red color of the rock, which according to him would have a terrestrial origin. Another claim is that if those creatures were soft-bodied animals, they wouldn’t have been so well preserved without compaction, as some fossils have tridimensional features.
Well, I am not a geologist and have no knowledge enough to argue about the geological point of view, neither am I an expert in the Ediacaran biota, but as a biologist I think I can share some thoughts.
First, as it seems, Retallack’s ideas are not accepted by most paleontologists. At the beginning, the innovative view of Ediacaran biota as land-dwelling was interesting, but the arguments to support it are not enough and there are still simpler and more possible explanations for the unusual features of the Ediacaran rocks. This didn’t stop Retallack to pursue in his idea, however, and other paleontologists are getting tired to go on reviewing his papers.
Does such a behavior look familiar? It kind of reminds me of Williamson, whom I talked about some time ago, as you can read here.
Just as Williamson insists in his hybridogenesis idea despite all facts pointing to other directions, so Retallack insists in his land-dwelling lichens hypothesis.
Retallack claims that fossils like Dickinsonia and Charnia, despite their bilaterally symmetrical body plan, were lichens. Does anybody know so well symmetrical lichens? And to support this hypothesis, he simply throws any kind of “fungian” explanation for all the fossils, considering the more radially symmetrical ones as bacterial colonies and the more animal-like as simply fungal fruiting bodies. And to explain things like the trace fossils, he talks about land slugs (land slugs during the Proterozoic? Really?) or slime moulds.
But then one might think: does he have any reference to support his ideas? And the answer is: of course, his OWN previous works. There are no other paleontologists claiming the same but himself. It looks just like a case of what I call Williamson’s syndrome.
I’m sure we will find some people supporting his idea, most probably laymen, and they will most certainly use the classical argument “all great scientific discoveries started by being rejected by most of the scientific community”. And I will say that again: Yes, many theories were initially rejected and later proven right, but you cannot forget that many more theories were rejected and later proven wrong. And once you prove that something is wrong or at least highly, highly unlikely, you must think of another possible and more likely explanations and not move on insisting on a fairytale.
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Cobb, M. 2012. The enigmatic Ediacaran biota just got more enigmatic. Or did it? Why Evolution Is True. Available online at <http://whyevolutionistrue.wordpress.com/2012/12/20/the-enigmatic-ediacaran-biota-just-got-more-enigmatic-or-did-it/ >
Retallack, G. 2012. Ediacaran life on land. Nature. DOI: 10.1038/nature11777
Retallack, G. 2007. Growth, decay and burial compaction of Dickinsonia, an iconic Ediacaran fossil. Alcheringa: An Australasian Journal of Palaeontology, 31 (3), 215-240 DOI: 10.1080/03115510701484705
Switek, B. 2012. Controversial claim puts life on land 65 million years early. Nature. DOI: 10.1038/nature.2012.12017