Talk:Last universal common ancestor/GA1

GA Review

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Reviewer: David Eppstein (talk · contribs) 05:11, 6 October 2022 (UTC)

Reviewing. A quick skim suggests that the most likely issues to be found here are points where the technical jargon is in need of more explanation (WP:GACR 1a). —David Eppstein (talk) 05:11, 6 October 2022 (UTC)

I've added wikilinks and glosses. Chiswick Chap (talk) 08:13, 6 October 2022 (UTC)

Oops. That's not the most significant issue. Earwig finds that Special:Diff/968988227, by Archaealvirus in July 2020, is a copyvio of [1], and therefore so is most of the present "LUCA's viruses" section, which probably needs a ground-up rewrite (or simple removal, but I think it's a very relevant part of the article). Ironically, the source for the copyvio, a 2020 article cited by the above diff, in turn appears to have copied the first line of their abstract from the Wikipedia article's lead sentence, in the form that it has roughly taken since Special:Diff/765948312 by Greaber in 2017.

User:Chiswick Chap, do you think this can be handled within the timeframe of a GA review, or should I quickfail this to give you the time to do it more slowly and carefully? —David Eppstein (talk) 05:29, 6 October 2022 (UTC)

David, thanks for taking this on, and for the comments. I can certainly do the needed rewriting. Chiswick Chap (talk) 05:38, 6 October 2022 (UTC)

In fact I've done that already, paraphrasing the cited source. Chiswick Chap (talk) 08:11, 6 October 2022 (UTC)

First reading (mostly focused on criterion 1)

Here's a read-through for understandability, clarity, and layout (GACR 1a and 1b). Overall, I think per WP:TECHNICAL that the earlier parts of the article and each of its sections should be readable to someone college-educated with some interest in the sciences but without a specific degree pertaining to this topic. There can be material surveying the state of the art at a specialist level of expertise but it needs to be separated out enough, towards the end of its sections, that it doesn't interfere with understanding by lay readers. I don't think the article in its current state meets that criterion, so attention is needed for more careful and readable and extensive explanations where possible.

Within reason, and especially for the lead, yes.

• Lead, "the latest form ancestral to all current existing life": somewhere in here and in the figure, there is an assumption made that life does not include viruses, which according to life is not universally accepted. Maybe there should be an explicit statement that for the purposes of this article we are only counting cellular organisms as life? The virus section is not currently summarized at all in the lead, and probably should be.

• Added both.

• Re the claim that Patrick Forterre, in a 1999 paper, was the first to use the term "Last Universal Common Ancestor": dubious, from a Google Scholar search. The secondary source for this cites Forterre's 1999 paper and says that the phrase was coined by Forterre, which may be true, but if so it may have been an earlier paper. The Scholar search points to Forterre's 1993 letter https://www.nature.com/articles/362795a0.pdf but I don't see the phrase anywhere there. "The Evolutionary History of Carbamoyltransferases: Insights on the Early Evolution of the last Universal Common Ancestor" by Bernard Labedan, Anne Doyen (doi:10.1201/9781482273045-26) was published with a 1998 date. The phrase also appears in a 1997 paper by Forterre, "Archaea: what can we learn from their sequences?", doi:10.1016/S0959-437X(97)80038-X. I can find references to Lazcano & Forterre, "The last universal common ancestor and beyond", 1996, but not the publication (if it is a publication) itself. However, the earliest verifiable use of the phrase that I can find is earlier and not by Forterre: Gene Stephen Wickham, The molecular phylogenetic analysis of naturally occurring hyperthermophilic microbial communities, Doctoral dissertation, Indiana University, March 1995, ProQuest 304192982 (bottom of p.4).

• edited, added refs.

• Figure, start of "Inferring LUCA's features": technical term "domain monophyly" unexplained and not even linked. What is this?

• reworded.

• The long quote from Weiss et al is also replete with unexplained jargon. I realize it's a quote, but it would help to try to explain some terms.

• Linked some more terms. The rest of the article does its best to explain what Weiss et al. meant.

• Also, how does a tree have a genome? Maybe what they sequenced were only the genomes of the prokaryotes in the trees, skipping any eukaryotes? Why is this a reasonable thing to do when you're trying to find an ancestor of both? What do the "various phylogenetic trees" have to do with the analysis; isn't it just choosing some life-forms and analyzing their genomes, regardless of which of several hypothetical trees they might have been arranged in? Or does "various phylogenetic trees" really mean "various separate branches of the (one) tree of life"?

• Edited. Yes, the trees are all branches; they chose prokaryotes representing different branches of the two major domains, bacteria and archaea. The eukaryotes are close to the archaea and have genes of bacteria as well (symbiogenesis, but that's off-topic here) so they wouldn't help in this analysis.

• "can only be reconstructed with much uncertainty": this implies that it can be reconstructed, but that we are uncertain of the accuracy of the reconstruction. Is that true?

• Yes.

• I guess the later sentence "The cell contained a water-based cytoplasm effectively enclosed by a lipid bilayer membrane." is a reconstruction of gross anatomy, as is "it appears to have been a small, single-celled organism. It likely had a ring-shaped coil of DNA floating freely within the cell", but one has to search to find these; they are mixed in with a lot lower-level structure and not well connected to the starting sentence about gross anatomy that they relates to. And they're written as if it certain; is there much uncertainty about them?

• These things are basically certain, as all cells are like that. There are many pretty-much certain facts of the same kind to list; the DNA organisation does not has much to do with the cell membrane and so forth, so it's not obvious that moving things around would be an improvement. More like the blind men feeling the elephant, really, this bit is cold, smooth, and hard; over here it's like a rope; this bit is flat and flaps about...

• What does "template-dependent" mean?

• Explained.

• What does "the family D" mean?

• Removed.

• What does "expressed via single-stranded RNA intermediates" mean?

• Reworded.

• What does "the catalytic activity of the ribosomes" mean?

• Reworded, linked. The machinery builds proteins.

• What does "an energy intermediate" mean?

• Reworded.

• What does "reduced CO2 and oxidized H2" mean? (actually I did not have to look these up to find out but still they are more unexplained and unlinked technical terms).

• Linked; actually both 'reduced' and 'oxidized' would link to Redox. To be honest, if people come here with no knowledge of chemistry (redox, catalysis) and no knowledge of basic biology (DNA, protein) then this article is going to be a tad difficult whatever we say; we can't explain both sciences in full here. I told Nick Lane his book was a bit difficult (English understatement) and he replied "Difficult is good!"

• "acetyl-CoA pathway chemicals": more unlinked and unexplained technicality. The chemicals whose names follow don't need explanation, but I think they do need wikilinks.

• Linked several. The pathway is linked above (I'm not averse to judicious overlinking, and this is certainly a case where it's justified) and illustrated: I've repositioned the diagram to be right alongside.

• autotrophy, heterotrophic, abiotically produced organic compounds: yet more technical terms.

• Linked and glossed.

• "hot spring habitat": does this mean what I think it does, land-based places where warm water bubbles out of the ground? Searching for "abiotic organic synthesis" suggests that research on this topic focuses on deep sea vents. How does this contradict Weiss?

• Weiss and others have worked extensively on deep sea vents; a rival view is that hot springs on land are more likely. Edited and linked.

• "In rare cases, gene linkage has been identified predating the LUCA, as with the F-ATPase genes.": technical and context-free. What is gene linkage? What would its existence prior to LUCA imply about LUCA? What is F-ATPase?

• Removed as probably off-topic for this article; we're not claiming that LUCA is the first organism, so, sure, there can be facts known about pre-LUCA organisms. Remarkable but another subject.

• "Location of the root": some introduction to what this even means would help, before starting on hypothesis. The root is, by definition, at the base of the tree. What does it mean for it to have a location? Is this really just asking, what was the first split? If so, why are the two sides of the split identified with modern subdivisions, when really they are unions of multiple modern subdivisions? Also, is any of this section really about LUCA, or is it off-topic speculation about life before LUCA? The last two sentences read like specialists reciting memorized arguments to other specialists rather than anything that would inform someone who has not already memorized those arguments.

• Yes, it's rather a techy title. I've boldly renamed it "Root of the tree of life" as somewhat more comprehensible. Nothing in the section is pre-LUCA: LUCA is definitively taken as the root, so the question is what are LUCA's most immediate descendants (i.e., what were the lowest branches in the tree of life). I agree that the second paragraph is about LUCA's features so I've moved it to the earlier section.

• Viruses: the main question I am left with from this section is: are all modern viruses descendants of these "dsDNA viruses in the groups called Duplodnaviria and Varidnaviria"? Do the viruses have a different LUCA that was earlier, with the other groups of viruses that infectedorganisms coextant with LUCA that do not have modern descendants later moving on from them to infect LUCA descendants instead? Or did viruses come from multiple separate later incidents involving the DNA and RNA of living organisms somehow getting transformed into a viral form?

• Probably all of that is off-topic for an article about LUCA. The viruses share the genetic code with cellular organisms but almost no other features, so deductions aren't easy. The groups you named are not ancestral to all modern viruses; these may have split off from cellular lineages at different times, and as the text cited to Krupovic 2020 indicates, that could have been pre-LUCA. To revisit the question at the top, are viruses included among the LUCA's descendants and are they even alive? It's rather TBD/an intentionally tricky exam question, isn't it. No doubt more will be discovered about viral origins.

• "RNA viruses had probably already been out-competed by DNA viruses": so why do we still have them now?

• RNA viruses are rare parasites of bacteria and archaea, but commonly cause disease in eukaryotes. Not sure we should say that in this article as it's not about LUCA as such; it is mentioned in Krupovic 2020.

• viral eukaryogenesis: probably deserves an explanation.

• Removed, again it's basically off-topic.

... and that's all I have time for tonight, so the later GACR criteria will have to wait until next time. —David Eppstein (talk) 06:36, 7 October 2022 (UTC)

Halfway through a source check (mostly focused on criterion 2)

Citations appear consistently formatted as footnotes in Citation Style 1. All look reliable.

• Noted.

The lead figure (a tree of major groups of organisms) is sourced to [1] Woese et al PNAS 1990. That source has a drawing of a tree with a very similar layout, with 19 leaves. Our article has 26 leaves. Where did those extra 7 leaves come from?

• Some Commons editor or other, who obviously thought them an "improvement", yeah right. Removed.

[2] and [8] (both Darwin) are the same source and almost the same page numbers and should be consolidated into one footnote (one is missing a word from its title, the other missing the title-link. A link to an online copy of the original source on each page number, like p. 490, would have been helpful.

• Merged refs, added online link.

[2]a does not source the image from Darwin's notebooks, or its implications

• Removed.

[2]b does source "The idea that all life comes from a single origin" (although Darwin hedges and says "into a few forms or into one") but fails to source "implicit in drawings of the tree of life, as all the branches of such a tree share a common trunk". That page of Darwin says nothing at all about drawings, the fact that they have a trunk, or the fact that their tree-like form implies a single origin.

• Removed.

[2]c is not the correct page number for the Darwin quote sourced to it.

• Fixed.

The worldcat link on [3] Lamarck is useless; a full-text link would have been more useful. And I really doubt that 1994 is the correct publication year for this source. I did find what claims to be a 1994 edition of Lamarck but with no tree drawing on page 649 [2]. There is a vaguely drawn tree on page 737 of that link, the same one reproduced by [4]. However, [4] does not source the claim that Lamarck's tree implies a single origin for life; instead it notes that "It is true that Lamarck envisaged multiple origins of life," and later describes multiple trees for different branches.

• Removed the link, used yours and its page number. The text does not claim that Lamarck proposed a single origin.

I already discussed [5] Wikham [6] Forterre [7] Koonin and they now appear accurately-enough sourced.

• Noted.

[8]a Darwin is there a reason to have the same quote repeated in two successive paragraphs?

• Merged.

[9] Oparin This article is about LUCA, not the origin of life; what is this sentence about Oparin's theories doing here?

• Removed. Chiswick Chap (talk) 08:53, 8 October 2022 (UTC)

[10]abc Weiss ok.

• Noted.

[10]d our article: "Experiments show that acetyl-CoA pathway chemicals used in anaerobic respiration, such as formate, methanol, acetyl entities, and pyruvate all arise spontaneously in the presence of water, carbon dioxide, and native metals"; source: "experiments also demonstrate ... end products and inter- mediates of the acetyl–CoA pathway ... formate, methanol, acetyl moieties, and even pyruvate arise spontaneously ... from CO2, native metals, and water". Too-close paraphrasing?

• Very hard to find other words for the chemicals, nor should it be tried, and the few words in between can't really be paraphrased much further without self-parody. Formatted as direct quotation.

[11]ab Weiss direct quotes

• Noted.

[11]b "basal clade" unexplained jargon

• Linked and glossed.

[11]d we already found out about the hydrothermal vents in the first paragraph of this section; it seems repetitive here

• Merged.

[11]e does source the first part of its sentence, "suggest that life on Earth originated in hydrothermal vents", but I didn't find anything in [11] regarding the second part of the sentence, the alternative hypothesis that life originated elsewhere but then took refuge in the vents from the Late Heavy Bombardment.

• Removed the second part.

[12] Lane [13] Sutherland why does one direct quote have three different sources?

• Removed. These are however good secondary sources on the topic as a whole.

[14]a Wächtershäuser good enough to source this minor point without the other sources

• Removed them.

[14]b sources DNA-to-RNA transcription but not the thymidine-uridine replacement

• Removed, but that's just a gloss on the basic biochemistry of RNA.

[14]c sources RNA-to-protein expression but not the ribosome detailed structure, energetics, and nutrients

• Removed.

[14]d sources bilayer structure but not ion transfer; also sources cell division

• Repositioned ref, mentioned cell division.

[15]a Pace to the extent that this talks about "the "universal" properties currently shared by all independently living organisms" (mostly bottom middle column last page) it uses them as a marker for terrestriality rather than as a way to make inferences about what LUCA would have been like.

• Removed.

[15]bcd not a useful source here

• Removed.

[16] Wächtershäuser appears to focus on a subtly different concept: "a last universal common ancestor (LUCA) with regard to the genetic machinery, but not with regard to the metabolic genes." Our article is about the LUCA as defined by the evolutionary tree, for all genes, earlier than the LUCA studied by [16]. In any case, [16] is never cited separately from the other Wächtershäuser reference, [14], so I'm not convinced it's needed at all as a source.

• Removed.

[17] Camprubí is entirely about the origin of life rather than LUCA, and again appears redundant.

• It discusses LUCA at some length, and has the merit of being a secondary source. I've removed it for now but it may well be worth citing elsewhere.

[18] Garwood this point (that LUCA used DNA) could more clearly be sourced to [14], since [18] talks about LUCA only briefly and in general terms, although it does also source this point. What [18] may be better for is the next point after the footnote, the distinction between the DNA and RNA worlds.

• Added W1998 and moved Garwood down.

[19] Marshall, [20] Koonin ok

• Noted.

[21] Koonin Does not source "If DNA was present, it was composed exclusively of the four modern-day nucleotides": this is a basic and obvious point (presumably the reason [21] doesn't bother saying anything about it) but needs sourcing. This is a good source for the existence of DNAP, though.

• Removed.

[22] Ahmad, [23] Lupas, [24] Martin, [25] Lane ok

• Noted.

[26] Berkemer which of the many conclusions does this source challenge? Which alternatives does it propose? Is it their conclusions or their methods that it challenges?

• Conclusions mainly, though that implies the methods were not sufficient: "Using phylogenetic tree–based approaches of the type used here, only limited information can be gained about the LUCA, leaving specific details on physiology largely speculative. Analysis of proteins such as the reverse gyrase, hydrogenase, and nitrogenase discussed here and elsewhere ... does not support the conclusion of a thermophilic, nitrogen fixing and hydrogen utilizing LUCA." I haven't quoted that in the article as it's going rather far into argumentation, but it's an interesting footnote: I guess we could quote it in the ref if you liked. They don't really try to replace Weiss, just to say that there are holes in the argument. Added a description to the text.

[27] Mulkidjanian this appears to be about the origin of life, rather than the later last-universal point, so it's not clear that the conclusions that it draws about the initial conditions for the origin of life are relevant for a discussion of the (possibly very different) conditions under which LUCA lived (especially given the alternative hypothesis mentioned much earlier that life originated and spread before the Late Heavy Bombardment and then took refuge in marine vents during the bombardment).

• Partly true. It is about the origin of life, but Mulkidjanian et al discuss the LUCA proteins to try to deduce its habitat and by implication that of earlier cells as well. In other words, if they are right about the deduced habitat and way of life, that is LUCA's habitat and way of life.

[28] Gogarten ok

• Noted.

[29] Adam, [30] Weiss probably the sourcing is ok here, but the sentences they source are too jargon-laden and unlinked and unexplained to be digestible

• Edited and linked.

—David Eppstein (talk) 01:11, 8 October 2022 (UTC)

Continuation of second pass, most of the way through

[26] Doolittle and [27] Glansdorff are both used to source dates of 3.5-3.8 Gyr as what was believed in 2000. [26] does source this; [27] is from 2008 and the only clear discussion of dates that I saw, in the first paragraph of "Palaeochemistry and chronology of early eukaryote evolution", is on a more technical point that it says is contentious.

• Removed Glansdorff.

[28] Noffke through [32] Dodd source earliest fossil life being 3.48 to 4.28 Gyr old. They appear to be chronological with Noffke 3.48 Gyr, [29] Ohtomo 3.7 Gyr, [30] Hassenkam 3.7 Gyr, [31] Bell 4.1 Gyr, [32] Dodd 3.77-4.29 Gyr. I'm not sure why our article says 4.28 instead of 4.29 but otherwise all ok, and individually useful as references rather than merely being citation overkill.

• Noted.

[33] Betts adequately sources the entire rest of the paragraph (including the currently unsourced date for the Moon-forming event); consider moving the placement of the footnote a little later.

• Done.

"When the LUCA was first proposed": vague. Does Darwin count as a proposal?

• Fixed, and no, though he led the way towards it.

"leading some scientists to suggest that the LUCA evolved in areas like the deep ocean vents": isn't that what the earlier section "Inferring LUCA's features" states as the current leading hypothesis, in some detail? So why is it used here as if it is a strawman that is no longer believed? I think the actual point being made here is

• People thought (and still think) that LUCA lived only in vents
• People thought that archaea currently live only in vents, but that was found to be incorrect
• The common vent environment was taken as evidence that the first split was between archaea and the rest, and that evidence became weaker when other environments for current archaea were discovered
• In the meantime other stronger evidence for a different split was discovered

I just think that this paragraph makes this point in a confusing way that suggests that we no longer think LUCA lived in vents.

• Reworded.

So far this is all sourced to [35] Xie and [36] Yutin. However, both sources appear to be concerned primarily with technical points that form pieces of that other stronger evidence for a different split; they don't really describe the history of thought on this topic that this paragraph covers. I think they support only the final clause "now believed to be more closely related to the Eukaryota" of the paragraph, but none of the rest. However, the rest of the paragraph is interesting and relevant and worth saving if other sources for it can be found.

• Reworded as above; added source.

[37] Brown through [41] Iwabe are all used only to source the common acceptance of a tree of life in which the first split separates bacteria from archaea+eukaryota. They do source that, but do we really need five technical papers dated from 1989 to 1998 to source that sort of claim? Surely this is the sort of thing a textbook source would be both more convincing (for the wide acceptance part, since one could cherry-pick five technical sources to back some outlandish claims, and with a more recent date) and more accessible to most readers? Given that the remaining sources [42] Valas through [46] Williams of the same paragraph detail alternative hypotheses and are significantly more recent, is the paragraph's claim that the earlier sources describe "The most commonly accepted" hierarchy accurate and well-attested?

• The Bacteria / Archaea split is widely accepted. The Eukaryotes came into being later, likely involving partnerships (symbiogenesis) from both the other groups: but that is off-topic here. Going with Brown here.

"would have become feasible and could have been common": it's ambiguously phrased whether this is referring to becoming feasible earlier than LUCA and common at the time of LUCA, or whether it refers to the time of "the later gene pool of the LUCA's descendants". Our text says Woese made the proposal in 1988 but our source [47] Woese is from 1998 and doesn't mention anything about something happening earlier in 1988; maybe 1988 is a typo? Is Woese's proposal now widely accepted or a fringe outlying opinion?

• It's widely accepted. Fixed the typo.

"formal test": vague. Formal can mean a lot of things. What the article actually proposes is a statistical hypothesis test.

• The exact words used in the cited source. I've quoted them and linked them to the article you suggest.

I notice that this paragraph favors the UK spelling "favour" but that elsewhere the article uses oxidized not oxidised and criticized not criticised, so it is a little schizophrenic about whether it is written in UK or US English. The original spelling "favored" was used consistently from its addition in 2011 [3] until last July, when you changed it to "favoured" ([4]). I think this suggests that "favored" is the status quo ante to which this should be returned.

• Fixed. Chiswick Chap (talk) 08:41, 9 October 2022 (UTC)

Remaining source check and remaining criteria

[16], referenced only as "LUCA". State University of New York, with a retrieval date: come on, you can do better at identifying sources than that. Is it someone's lecture notes? Whose? What broader work is it part of? The State University of New York is a system of some 64 campuses with some 424000 students and you haven't even identified which one this is from, let alone which department or subunit published it.

• Extended citation.

"Martin's 2016 findings": whose? We have no reference to a Martin 2016. And I don't understand how this sentence is supposed to be connected to the rest of its paragraph.

• Removed, it's not needed for the sense of the paragraph.

"When Weiss and colleagues first proposed the LUCA, cladograms based on genetic distance between living cells indicated that Archaea split early from all other living things. This relied on the view that the LUCA and the Archaea lived only in hydrothermal vents.": this all still appears to be unsourced.

• Removed. Weiss et al. did not rely on this, and it's close to circular reasoning.

You answered my question on GA1 about the date typo in "In 1998, Carl Woese proposed" but did not do anything about providing non-primary sources that could attest to the wide acceptance of Woese's proposal. It still reads, within the article, as a random minor suggestion that someone once made, rather than as the standard current consensus.

• Egel 2012 [41] speaks of a "complex collective genome" at the time of the LUCA; this was the theme of the next paragraph, but I've merged the two now. Added Glansdorff 2008 who says directly that LUCA was part of a larger population. Actually it's hard to imagine any biologist supposing that the LUCA was living alone. Chiswick Chap (talk) 09:44, 10 October 2022 (UTC)

Continuing the source check: "It is extremely unlikely that organisms that had descended from separate incidents of cell-formation would be able to complete a horizontal gene transfer without garbling each other's genes": this seems plausible enough, but it does not appear to be sourced by [45] Theobald, which instead suggests a possibility that "multiple populations with independent, separate origins convergently gained the ability to exchange essential genetic material" noting that this possibility is nevertheless consistent with the existence of LUCA. This argument from first principles also appears to be a separate thing than the statistical test of Theobald and should not be described as if it is incorporated into the statistical test. The same goes for the next two sentences: "Further, many more amino acids are chemically possible than the 22 found in protein molecules. These lines of chemical evidence, incorporated into the formal statistical test, point to a single cell having been the LUCA.": I don't see in Theobald anywhere where he mentions or incorporates into his test the possibility of many additional amino acids.

• Removed.

"it was one of many early microbes": Theobald, the supposed source for this claim, is much less definitive on this point, writing only on a slightly different point about a possibility of "population of organisms with different genotypes".

• Removed.

[47] El Baidouri: "phenotype was indeed complex" again seems overly definitive. This source is speculative and appears not even to be a reliable source, as it has not yet gone through peer-review and publication.

• Removed.

[48] Krupovic through [50] Durzyńska: already checked recently in connection with the copyvio incident. No changes needed.

• Noted.

Moving on to the other GACR criteria:

3a: Is it sufficiently broad in its coverage: I think so. It is beyond my expertise to guess at significant aspects of the subject that have been omitted from the article, but the obvious questions (What does LUCA mean and how does it differ from first life? when was LUCA? What was it like? What does this imply about later evolution? How has thought on this subject changed historically?) appear to have been answered. The history of the subject is mostly incorporated throughout rather than separated out, except for a bit of context in the initial "Historical background" section, but I think that's an acceptable editorial decision. No changes needed.

• Noted.

3b: Unnecessary detail. There is a fair amount of quite technical detail, but I think it is all relevant enough to keep. No changes needed.

• Noted.

4: Neutral? This obviously takes some sides in what the scientific consensus is. It appears to be accurate in its assessments, but the insistence on citing only primary research papers and not secondary material such as textbooks (with rare exceptions like [12] Marshall, [16] unidentified web page, [26] Doolittle, [44] Steel) has made it difficult to assess the accuracy of this.

• Noted.

5: Stable? Yes, no edit wars or major disputes evident in the history or talk page. No changes needed.

• Noted.

6: Illustrations? These appear sufficient but not overwhelming, and to cover most of the things that one could reasonably ask to have illustrated. File:Phylogenetic tree of life 1990 LUCA.svg is very similar in layout to its source but the layout is probably uncopyrightable per Commons:Commons:Threshold of originality. I'm skeptical that the licensing of File:Tree Of Life (with horizontal gene transfer).svg would hold up to a deletion discussion without a clearer statement of copyright transfer from its author, but it appears to be a good faith upload that validly has permission from its author, and we don't need to test the more detailed legal niceties now. All other licenses appear valid. After the previous fix to the Darwin notebook caption, all captions appear ok. No changes needed.

• Noted. Chiswick Chap (talk) 08:21, 10 October 2022 (UTC)

A few more small points

Ok, now that reference [16] has been somewhat more fully identified, it appears to be by Walter Jahn [5], a drosophila neurogeneticist and community college teacher. I am not convinced that he is in any sense an "established subject-matter expert in the relevant field" who could pass the exception to our prohibition on self-published sources, and this appears to me to be basically a self-published source. I don't think it's reliable.

• Removed.

Lead: "This includes all cellular organisms; the origins of viruses are unclear but they share the same genetic code as cellular organisms; LUCA probably harboured a variety of viruses.": a bit of a run-on sentence.

• Split.

"Horizontal gene transferr" typo

• Fixed.

—David Eppstein (talk) 01:04, 11 October 2022 (UTC)

Ok, all done now, passing. —David Eppstein (talk) 15:26, 11 October 2022 (UTC)