Hi everyone. Back again. Looking at the paper by Steele et al., titled, Cause of Cambrian Explosion - Terrestrial or Cosmic?, the following paragraph leaps out:
Evidence of the role of extraterrestrial viruses in affecting terrestrial evolution has recently been plausibly implied in the gene and transcriptome sequencing of Cephalopods. The genome of the Octopus shows a staggering level of complexity with 33,000 protein-coding genes more than is present in Homo sapiens (Albertin et al., 2015). Octopus belongs to the coleoid sub-class of molluscs (Cephalopods) that have an evolutionary history that stretches back over 500 million years, although Cephalopod phylogenetics is highly inconsistent and confusing (see Carlini et al., 2000; Strugnell et al., 2005, 2006, 2007; Bergmann et al., 2006). Cephalopods are also very diverse, with the behaviourally complex coleoids, (Squid, Cuttlefish and Octopus) presumably arising under a pure terrestrial evolutionary model from the more primitive nautiloids. However the genetic divergence of Octopus from its ancestral coleoid sub-class is very great, akin to the extreme features seen across many genera and species noted in Eldridge-Gould punctuated equilibria patterns (below). Its large brain and sophisticated nervous system, camera-like eyes, flexible bodies, instantaneous camouflage via the ability to switch colour and shape are just a few of the striking features that appear suddenly on the evolutionary scene. The transformative genes leading from the consensus ancestral Nautilus (e.g. Nautilus pompilius) to the common Cuttlefish (Sepia officinalis) to Squid (Loligo vulgaris) to the common Octopus (Octopus vulgaris, Fig. 5) are not easily to be found in any pre-existing life form – it is plausible then to suggest they seem to be borrowed from a far distant “future” in terms of terrestrial evolution, or more realistically from the cosmos at large. Such an extraterrestrial origin as an explanation of emergence of course runs counter to the prevailing dominant paradigm.
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The paper from Albertin et al. doesn’t back up Steele et al.'s claim that octopuses have 33,000 more protein-coding genes than humans do. Instead, Albertin et al. write that based on their research they “predicted 33,638 protein-coding genes” after sequencing the Octopus bimaculoides genome. The number of protein-coding genes in the human genome is 19,000 to 20,000, so that means octopuses have 14,000 more protein-coding genes than we do.
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In any case, the notion that the number of protein-coding genes corresponds in any way with an organism’s complexity is debunked in a 2008 paper by Leslie Pray, titled, Eukaryotic Genome Complexity (Nature Education 1(1):96). Pray points out that the number of genes in an organism’s genome “has nothing to do with the organism’s complexity,” and lists several organisms which have more protein-coding genes than we do: among them the laboratory mouse, Mus musculus (30,000 protein-coding genes), the rice plant Oryza sativa (51,000) and the protozoan parasite and STI Trichomonas vaginalis (60,000).
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The claim that scientists believe that there was a lineage leading “from the consensus ancestral Nautilus (e.g. Nautilus pompilius) to the common Cuttlefish (Sepia officinalis) to Squid (Loligo vulgaris) to the common Octopus (Octopus vulgaris, Fig. 5)” is flat-out wrong, as Carnall points out in his critical review:
Nautilus, especially the one living species referred to, is absolutely not ancestral, definitely not consensus ancestral to common cuttlefish etc. They’re modern representatives of a long-lived-more-diverse-in-the-past group but ain’t nothing primitive or ancestral about them. The broader group, Nautiloidea, maybe, but there is a lot that needs resolving about stem coleoid relationships. The simplification here is misleading.
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Steele et al. haven’t done their homework on cephalopod phylogenetics: the papers they cite are more than ten years out-of-date (Carlini et al., 2000; Strugnell et al., 2005, 2006, 2007; Bergmann et al., 2006). They never even mention the article published in 2017 by Tanner et al., titled, Molecular clocks indicate turnover and diversification of modern coleoid cephalopods during the Mesozoic Marine Revolution (Proceedings of the Royal Society B, 15 March 2017, Volume 284, issue 1850), which provides an up-to-date phylogeny. Incidentally, Tanner et al. describe Nautilus as a “sister group to coleoids,” not an ancestor.
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Steele et al. also get their chronology wrong: they seem to think that octopuses appeared suddenly about 270 million years ago, with all of their modern features:
Thus the possibility that cryopreserved Squid and/or Octopus eggs, arrived in icy bolides several hundred million years ago should not be discounted (below) as that would be a parsimonious cosmic explanation for the Octopus’ sudden emergence on Earth ca. 270 million years ago.
Wrong on two counts. For starters, the oldest known octopus fossil is not 270 million years old but 296 million years old, as Wikipedia points out. Second, as Tanner et al. point out, the really interesting features possessed by modern cephalopods evolved much later, during the Jurassic period. Here’s how the Daily Mail summarized their findings (Mysterious genetic origins of the squid, octopus and cuttlefish revealed: Creatures had a common ancestor 100 million years ago by Harry Pettit, 1 March 2017):
‘We found that cephalopods evolved during a time of great ecological change, due to competition with fish and their predators,’ study lead-author Al Tanner, a molecular biologist at the University of Bristol, told MailOnline.
'Cephalopods shifted from being slow, armoured organisms into rapid jet-propelled oceanic species, able to compete with fish.
'Their ancestors, the heavily-shelled ammonites and belemnites, probably went extinct because their predators evolved to defeat their armour, and so were easy pickings compared to the increasingly-swift squid, and increasingly well-hidden octopuses.
The period that the octopus, squid and cuttlefish split from their common ancestor was known as the ‘Mesozoic Marine Revolution’ and occurred around 100 to 160 million years ago, the researchers claim.
Or as Tanner et al. put it in their article:
Decabrachian coleoids are nektonic predators with streamlined morphology, high metabolic rates and shoaling behaviour; adaptations in common with teleost fishes [43]. The majority of modern teleost groups radiated during the Jurassic and Cretaceous [44], concomitantly with the origin of most modern coleoids as revealed by our molecular estimates and the fossil record. The scenario in which Mesozoic ecological shifts are exhibited in teleost fishes, chondrichthyans (sharks and rays), and shelled invertebrates as investigated by Vermeij [10] can be extended to cephalopods (figure 4). In the face of high-metabolism, robust predators and niche-competitors, the cephalopods may have responded in kind to these evolutionary pressures. We hypothesize that the cephalopods evolved into the forms we are familiar with today, while shelled groups fell into extinction owing to the shifts in predation in this time period. The Mesozoic Marine Revolution can thus be viewed as the final stage in the shift from Palaeozoic ecologies into the modern structure of marine ecosystems, where (at least in the nektonic realm), agility superseded passive defence.
So Steele et al. are looking at the wrong time period.
- Figure 5 in Steele et al. is totally inconsistent with the rest of their paper, as it depicts octopus evolution as follows: Squid + Virus = Octopus. Carnall comments:
WHY IS “SQUID” + VIRUS = OCTOPUS? That’s not even what they’re arguing here and nobody thinks that modern ‘squid’ evolved into octopuses.
- The weirdness of the octopus genome is simply due to the fact that not many genomes of related creatures have been sequenced yet. As Carnall explains:
To put this into context, to date there has only been one complete-ish cephalopod genome sequenced and assembled, that of Octopus bimaculoides in 2015 (Albertin et al. 2015). This is worth bearing in mind when we contemplate the ‘weirdness’ of the genome given that, as yet, there’s very little in the way of comparators in this whole group.
- Skepticism is warranted regarding the thesis propounded by Steele et al… To quote Carnall:
I have so many questions. 1) How did fertilised “Octopus” eggs get into space and does this mean they are coming back? 2) There are a handful of cephalopod species that can be bred in captivity and raised to adulthood, I think extra terrestrial bolides etc. are kind of a harsher environment than that so how that work? 3) If these “Octopuses and/or Squid” are laying eggs on bolides are they living in space or are they living on bolides or are they living on other planets and laying eggs like terrestrial cephalopods which are then somehow getting transported to space? 4) What about the octopuses evolving from squid plus viruses? Did we forget about that? 5) Are you defining likely and plausible as it could happen but extremely extremely remotely and with much better evidence than given here? 6) If we can go back to viruses again, isn’t it ever so slightly more plausible that viruses are living on bollides in cryostasis rather than actual fertilised eggs? 7) Why on fairly arbitrary grounds are cephalopods chosen? There are likely other better candidates you could weave a way more convincing story around if that’s the intention.
My overall verdict: a thumbs-down.