It’s quite a strange article.
Here are two very interesting updates to my recent articles at Evolution News on alleged Ediacaran animals and the Cambrian Explosion.
When I read this first sentence, I assumed the article would be about some recent papers that had been published that added to the discussion of the topics of his previous articles (both from 2018). He’s writing in 2021, after all. Turns out the two updates are a response to a comment I made here on PS in 2018 (a month after his article came out in September), and a paper that came out in 2018. Why Bechly is responding 3 years later is a bit beyond me, but he seems to think it’s important.
In my article (Bechly 2018b) about the iconic and enigmatic Ediacaran organism Dickinsonia , I showed why in spite of new biomarker evidence presented by Bobrovskiy et al. (2018), Dickinsonia is unlikely to be an animal. Such evidence-based skepticism is of course not greatly appreciated in Darwinist circles and provoked a response.
At the Peaceful Science forum, an anonymous atheist and self-professed blogging graduate student (evograd 2018), who obviously lacks sufficient expertise as well as some reading comprehension, criticized my article with a red herring quibble about two of six references that Bobrovskiy et al. quoted (which I actually never disputed), while ignoring all real arguments. Just read my article and compare it with his criticism to decide for yourself if it has any merit. Anyway, this young know-it-all then triumphantly proclaimed:The relevant context here is that the authors were specifically testing the animal affinity for Dickinsonia against other hypotheses of a lichen fungi affinity or a giant protist affinity. By ruling out lichen fungi and giant protist affinities, the only remaining plausible option is that Dickinsonia is an animal.
First, can we just appreciate the fact that Bechly decided to write half an article responding to a short, innocuous comment made 3 years prior by an anonymous grad student on a pretty niche forum? Either I really got under his skin for some reason or he’s scraping the bottom of the barrel for content to write about. Anyway, on with the content…
Bechly says I criticized his article “with a red herring quibble about two of six references that Bobrovskiy et al. quoted (which I actually never disputed), while ignoring all real arguments.” My comment was obviously not intended to be a thoughout critque of Bechly’s entire article - I’m not an expert on Ediacaran animals, so I just commented on something I noticed in the article that seemed incorrect. In a sense, then, his charge that I “ignored all real arguments” is true, but that doesn’t detract from the comment I made. The “red herring quibble about references” isn’t a red herring at all, it’s a substantive criticism of Bechly’s article.
Specifically, I had an issue with the section of Bechly’s article titled “Incomplete Homework”, where he criticized the authors of a study for “not doing their homework” on the subject of cholesterols in organisms other than animals. In short, the case he made went like this: “The authors claim Dickinsonia is an animal becuase they identified cholesterol in it and they say cholesterol is only found in animals, but look at all these papers that show non-animals producing cholesterol! The authors clearly didn’t do their homework!”
The problem with this argument, as I pointed out in my comment in 2018, is that the authors actually discussed the subject of non-animal cholesterols in their paper, citing some of the very same papers that Bechly did to try and prove their ignorance! I quoted the following passage from the paper to show this:
Using the remarkable steroid patterns of the fossils, it is possible to test the position of dickinsoniids on the phylogenetic tree. Lichen-forming fungi only produce ergosteroids, and even in those that host symbiotic algae, ergosteroids remain the major sterols (29, 30). Dickinsonia contained no or a maximum of only 0.23% ergosteroids, conclusively refuting the lichen hypothesis (7). The groups of rhizarian protists that include gigantic representatives (Gromiidae, Xenophyophorea, and other Foraminifera) and their retarian relatives all produce a complex mixture of sterols, with cholesteroids comprising 10.3 to 78.2% of the mixture, ergosteroids 4.9 to 43.0%, and stigmasteroids 7.2 to 60.1% (table S4). Moreover, rhizarian protists may produce C30 sterols (24-n-propylcholesteroids) that can form a notable (up to ~20%) proportion of their total sterol content (31). By contrast, in most Dickinsonia and Andiva extracts, C30 steroids were below detection limits. Thus, the steroid composition of dickinsoniids is markedly distinct from steroid distributions observed in Rhizaria, rendering a protozoan affinity of these fossils extremely unlikely. All animals—with rare exceptions, such as some demosponges and bivalve molluscs—are characterized by exclusive production of C27 sterols (32, 33). The closest relatives of metazoans, Choanoflagellatea and Filasterea, produce 90 to 100% and 84 to 100% of cholesterol, respectively, and contain up to 16% ergosteroids (34–36). Although the sterol composition of some choanoflagellates and filastereans falls within the range observed for Dickinsonia and Andiva, they are unlikely precursor candidates because these groups are only ever represented by microscopic organisms, leaving a stem- or crown-group metazoan affinity as the only plausible phylogenetic position for Dickinsonia and its morphological relatives.
In order to put that quote in context so it made more sense to the readers, I said the following directly underneath it in my 2018 comment:
The relevant context here is that the authors were specifically testing the animal affinity for Dickinsonia against other hypotheses of a lichen fungi affinity or a giant protist affinity. By ruling out lichen fungi and giant protist affinities, the only remaining plausible option is that Dickinsonia is an animal. The only other option is that the cholesterols are some kind of contaminants from other organisms.
I was summarising the argument the authors made in the quoted passage from the paper to make it easier to understand how Bechly was misrepresenting them. He was claiming that the authors were wholly unaware of the existence of non-animal cholesterol, and that was how they concluded that Dickinsonia must be an animal. The passage shows that their reasoning is much more nuanced - they recognise that other organisms produce cholesterols but argue that Dickinsonia couldn’t be a member of these other groups (e.g. rhizarian protists) for other reasons (e.g. Dickinsonia had a radically different steroid composition compared to rhizarian protists).
Bechly entirely ignores my criticism of him strawmanning or misunderstanding the authors on this point (he dismisses it as a “red herring”), and instead chooses to focus on my summary of the author’s argument, saying I’m a “young know-it-all” who made a “triumphant proclamation”. His response to my summary is:
The problem is, this is simply false. Do not take my word for it, but that of paleontologist Professor Gregory Retallack, who is a renowned specialist on Ediacaran biota. In response to the article by Bobrovskiy et al. he wrote a comment to the journal Science (Retallack 2018) titled “Dickinsonia steroids not unique to animals.” In this comment Retallack explains that the biomarkers found in Dickinsonia fossils are fully compatible with an affinity to lichenized glomeromycotan fungi. If there are even such alternative candidates among living organisms, this may well have been even more the case in the extinct Vendobionta, which have been proposed as an independent Ediacaran kingdom of life by Seilacher (1992). The very alien body plan of Dickinsonia with glide symmetry definitely supports such a Vendobionta hypothesis rather than an animal affinity (McMenamin 1998/2000).
Again, this feels like a point that might have been worth making back in 2018, and seems strange to direct towards me specifically, 3 years later. Once again, the point of my 2018 comment wasn’t that the conclusion of the original authors was unassailable, but simply that Bechly had misrepresented them. That said, the original authors actually promptly responded to both of Retallack’s criticisms, pointing out, for example, that contrary to what he claimed, Dickinsonia is unliklely to have an affinity with Glomeromycota because the latter doesn’t actually produce cholesterol. To a non-expert like me, this response seems adequate to dismiss Retallack’s criticisms, so Bechly seems not to have a leg to stand on here either.