Evidence record

Why did complex cells appear only once?

Every sentence on the exploration belongs to at least one claim below. Each says what kind of statement it is, what it rests on, what the evidence does not establish, and how far it was checked. Nothing here is a score, and none of it is a verdict on a belief or a theory.

Last checked 24 September 2026.

A judgement, not a fact: 10
Partly checked: 11
Source checked: 37
Presented as open: 1

If something here is wrong, misquoted, out of date or unfair, write to support@unknownoceans.com and give the claim number, which does not change.

What the question takes for granted

A question in evolutionary biology about a single event. That every living eukaryote shares one ancestor is established; why the step happened once, and whether once means it was hard, is argued between named researchers and is where the page spends its time.

Complex cells appeared only once
Established
Established in the sense the page uses: every known eukaryote descends from one common ancestor. Whether other attempts happened and left no descendants is not something the evidence can see.
Happening once means the step was hard
Open
Lane and Martin read the single origin as the mark of a steep barrier. Booth and Doolittle argue the singularity rhetoric lacks statistical support. The page presents this as its open question.

How the question is labelled

Claim: The singular event

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The page’s title. It follows from claims 4 and 6: every known eukaryote descends from one origin. Whether that single origin reflects a hard step is left open in claims 66 to 68.

Claim 1 · checked 24 September 2026 · AI-assisted audit

Claim: Complex cells

Kind: Framing. Signposting. It asserts nothing a source could check.

The question

Claim: Every plant, animal and fungus descends from one merger between two microbes.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
Mitochondrial Evolutionabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Research in cells or tissue · Review of the field
The source reads: the endosymbiont hypothesis–the idea that the mitochondrion evolved from a bacterial progenitor via symbiosis within an essentially eukaryotic host cell–has assumed the status of a theory
Supports
Asgard archaea illuminate the origin of eukaryotic cellular complexityabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Research in microbes · Observational study: associations, not causes
The source reads: Current data support scenarios in which an archaeal host cell and an alphaproteobacterial (mitochondrial) endosymbiont merged together, resulting in the first eukaryotic cell.
Qualifies
Mitochondrial Evolutionabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Review of the field
The source reads: the organelle itself is increasingly viewed as a genetic and functional mosaic, with the bulk of the mitochondrial proteome having an evolutionary origin outside Alphaproteobacteria

What this does not establish

The review was read as an abstract. The merger is the origin of the mitochondrion; Gray notes that most of the mitochondrial proteome has origins outside the bacterial group the mitochondrion came from, so “two microbes” names the merger, not the source of every gene.

Later work looked for

Crossref and Europe PMC, 2018 on, "eukaryogenesis gene ancestries", "mitochondrial origin alphaproteobacteria": Martijn and others (2018) place the mitochondrial ancestor just outside sampled alphaproteobacteria, and Bernabeu and others (2026) find gene contributions from several microbial partners; neither undoes a single archaeal-bacterial merger as the origin of the mitochondrion.

Claim 3 · checked 24 September 2026 · AI-assisted audit

Claim: In four billion years it does not appear to have happened twice.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
The energetics of genome complexityabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in cells or tissue · Review of the field
The source reads: The eukaryotic cell arose from prokaryotes just once in four billion years, and otherwise prokaryotes show no tendency to evolve greater complexity.
Qualifies
Eukaryogenesis, how special really?abstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Argument
The source reads: we question several of the usual claims about the specialness of eukaryogenesis

What this does not establish

Once is a count of surviving origins. An origin that left no descendants would not be seen.

Claim 4 · checked 24 September 2026 · AI-assisted audit

Claim: Bacteria and archaea have been evolving for billions of years, and apart from one event they show no tendency to evolve greater complexity.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
The energetics of genome complexityabstract; p. 929, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in cells or tissue · Review of the field
The source reads: The eukaryotic cell arose from prokaryotes just once in four billion years, and otherwise prokaryotes show no tendency to evolve greater complexity ... Virtually every ‘eukaryotic’ trait is also found in prokaryotes, including nucleus-like structures

What this does not establish

Prokaryotes do show nucleus-like structures, as the same paper says. The one event is the origin of the eukaryotic cell, which the next sentence describes.

Corrected

24 September 2026. Previously: “Bacteria and archaea have been evolving for billions of years without producing anything like a nucleated cell.” Lane and Martin, the page’s own source, list nucleus-like structures among the eukaryotic traits found in prokaryotes; “anything like” overstated it.

24 September 2026. Previously: “Bacteria and archaea have been evolving for billions of years without producing a nucleated cell.” The sentence said prokaryotes had never produced a nucleated cell, which contradicts the same source: Lane and Martin say the eukaryotic cell arose from prokaryotes once in four billion years, and that otherwise prokaryotes show no tendency to evolve greater complexity. It now says that.

Claim 5 · checked 24 September 2026 · AI-assisted audit

Claim: The eukaryotic cell appears once, apparently through one cell taking another inside it.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
Mitochondrial Evolutionabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Research in cells or tissue · Review of the field
The source reads: the endosymbiont hypothesis–the idea that the mitochondrion evolved from a bacterial progenitor via symbiosis within an essentially eukaryotic host cell–has assumed the status of a theory
Supports
The energetics of genome complexityp. 929, introduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in cells or tissue · Review of the field
The source reads: All eukaryotes share a common ancestor, which arose from prokaryotes just once in four billion years. Genomic chimaerism points to the origin of eukaryotes in an endosymbiosis between prokaryotes

What this does not establish

The review supporting the field-level reading was read as an abstract. The page’s “apparently” is fair: how the partner got inside is itself argued (claims 59 to 62).

Later work looked for

Europe PMC, 2016 on, "eukaryote without mitochondrion": Karnkowska and others (2016) describe Monocercomonoides, which lost its mitochondrion secondarily; consistent with one origin.

Claim 6 · checked 24 September 2026 · AI-assisted audit

Claim: Whether that step is hard, and why, is an open question

Kind: Open question. Something the page says is not known.
Review: Presented as open. The page says this is unresolved, and the review found that it is.

Context
Eukaryogenesis, how special really?abstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026
The source reads: whether, despite widespread acceptance that eukaryogenesis was “special,” any such notion has more than rhetorical value

Corrected

24 September 2026. Previously: “Why that step is so hard is an open question” The page’s own last section asks whether once means hard, and Booth and Doolittle question it; the summary had taken the hardness as given.

Claim 7 · checked 24 September 2026 · AI-assisted audit

Claim: with one quantitative answer on the table and a quantitative challenge to it.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
The energetics of genome complexityabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in cells or tissue · Model
The source reads: Prokaryotic genome size is constrained by bioenergetics.
Supports
Membranes, energetics, and evolution across the prokaryote-eukaryote divideIntroduction, third paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in cells or tissue · Review of the field
The source reads: we present a quantitative summary of the relative bioenergetic costs and benefits of the modified architecture of the eukaryotic cell

Corrected

24 September 2026. Previously: “with one quantitative answer on the table.” Lynch and Marinov’s rebuttal is itself quantitative, and the page reports it; “one quantitative answer” made the energy argument sound unopposed.

Claim 8 · checked 24 September 2026 · AI-assisted audit

Claim: For roughly half of its history, life was single cells without nuclei.

Kind: Historical claim. A statement about the past that historical evidence can test.
Review: Source checked. The cited passage was read, and it says this.

Supports
The energetics of genome complexityabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: The eukaryotic cell arose from prokaryotes just once in four billion years
Supports
Membranes, energetics, and evolution across the prokaryote-eukaryote divideIntroduction, second paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: despite having more than two billion years to impose their presumed superiority, eukaryotes have not driven prokaryotes extinct
Context
Isolation of an archaeon at the prokaryote-eukaryote interfacefinal section
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: the vast amount of time (roughly 2 billion years) that separates this modern-day organism from the organism that evolved into the last eukaryotic common ancestor

What this does not establish

Both dates are round estimates: about four billion years of life and a little over two billion of eukaryotes. “Roughly half” is as precise as they allow.

Corrected

24 September 2026. Previously: “Life spent most of its history as single cells without nuclei.” The page’s sources give life about four billion years and eukaryotes more than two billion, which is about half, not most.

Claim 9 · checked 24 September 2026 · AI-assisted audit

Claim: Counted by cells, it still is.

Kind: Present-day figure. A count, survey or report finding, as the named source gives it.
Review: Source checked. The cited passage was read, and it says this.

Supports
Membranes, energetics, and evolution across the prokaryote-eukaryote divideIntroduction, second paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: Prokaryotes dominate eukaryotes both on a numerical and biomass basis

What this does not establish

Lynch and Marinov state it citing earlier estimates, which were not read here. The page claims only the count of cells.

Later work looked for

Europe PMC, 2017 on, "bacteria and archaea abundance Earth": Flemming and Wuertz (2019) put bacteria and archaea at about 1.2 × 10^30 cells; nothing that changes their numerical dominance.

Corrected

24 September 2026. Previously: “It is still mostly that.” Says by what measure, which the source gives as number of cells.

Claim 10 · checked 24 September 2026 · AI-assisted audit

Claim: Then, once, a cell acquired another cell that became the mitochondrion,

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
Mitochondrial Evolutionabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Research in cells or tissue · Review of the field
The source reads: the endosymbiont hypothesis–the idea that the mitochondrion evolved from a bacterial progenitor via symbiosis within an essentially eukaryotic host cell–has assumed the status of a theory
Supports
The energetics of genome complexityp. 929, introduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: All eukaryotes either possess mitochondria, or once did and later lost them

What this does not establish

The field-level review was read as an abstract.

Later work looked for

Europe PMC, 2018 on, "mitochondrial origin": nothing that disputes the endosymbiotic origin; Martijn and others (2018) revise only where among the proteobacteria it sits.

Claim 11 · checked 24 September 2026 · AI-assisted audit

Claim: and most of what is large enough to see descends from that event.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Membranes, energetics, and evolution across the prokaryote-eukaryote divideabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: The evolution of the eukaryotic cell marked a profound moment in Earth’s history, with most of the visible biota coming to rely on intracellular membrane-bound organelles.
Qualifies
The energetics of genome complexityFigure 1 legend
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Although the prokaryotes are 5–20 times larger than the eukaryote (see scale bars), they lack true complexity.
Giant bacteria such as Epulopiscium and Thiomargarita are among the exceptions “most” allows for.

Corrected

24 September 2026. Previously: “and everything large and visible descends from that event.” Lynch and Marinov say “most of the visible biota”; Lane and Martin picture giant bacteria larger than a protist.

24 September 2026. Previously: “and nearly everything large enough to see descends from that event.” Lynch and Marinov say most of the visible biota came to rely on the organelles; “nearly everything” went beyond that.

Claim 12 · checked 24 September 2026 · AI-assisted audit

Claim: Not from that kind of event: from that event.

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The page’s emphasis on claim 6: every known eukaryote shares one common ancestor, rather than several lineages each acquiring mitochondria.

Claim 13 · checked 24 September 2026 · AI-assisted audit

What happened

Claim: What happened

Kind: Framing. Signposting. It asserts nothing a source could check.

The evidence for one origin

Claim: The evidence for one origin

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: Mitochondria carry their own genome, and read through that genome the organelle is of unquestioned bacterial ancestry, from inside one bacterial phylum.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
Mitochondrial Evolutionabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Research in cells or tissue · Review of the field
The source reads: Viewed through the lens of the genome it contains, the mitochondrion is of unquestioned bacterial ancestry, originating from within the bacterial phylum α-Proteobacteria (Alphaproteobacteria).

What this does not establish

Read as an abstract. Gray calls the group a phylum; the abstract also says most of the mitochondrial proteome comes from elsewhere.

Later work looked for

Europe PMC, 2012 on, "mitochondrial origin alphaproteobacteria": Martijn and others (2018) place the mitochondrial ancestor in a proteobacterial lineage branching just before sampled alphaproteobacteria; still inside one phylum, so the sentence stands.

Claim 16 · checked 24 September 2026 · AI-assisted audit

Claim: The endosymbiont account of where it came from has the standing of a theory rather than a hypothesis.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
Mitochondrial Evolutionabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Research in cells or tissue · Review of the field
The source reads: the endosymbiont hypothesis–the idea that the mitochondrion evolved from a bacterial progenitor via symbiosis within an essentially eukaryotic host cell–has assumed the status of a theory

What this does not establish

Read as an abstract. The review’s wording, attributed to it.

Later work looked for

Europe PMC, 2012 on, "endosymbiotic origin of mitochondria": nothing that reopens it.

Claim 17 · checked 24 September 2026 · AI-assisted audit

Claim: All known eukaryotes either have mitochondria or descend from ancestors that did, including the ones that have since lost them.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
The energetics of genome complexityp. 929, introduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in cells or tissue · Review of the field
The source reads: All eukaryotes either possess mitochondria, or once did and later lost them

What this does not establish

Known eukaryotes. Lane and Martin name a primitively amitochondriate eukaryote as something that would falsify their account; none has been found.

Later work looked for

Europe PMC, 2010 on, "eukaryote without a mitochondrial organelle": Karnkowska and others (2016) found a eukaryote with no mitochondrion at all, and conclude it lost one; consistent.

Claim 18 · checked 24 September 2026 · AI-assisted audit

Claim: There is no surviving lineage of nucleated cells that never had one.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
The energetics of genome complexityp. 929 and p. 933
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in cells or tissue · Review of the field
The source reads: All eukaryotes either possess mitochondria, or once did and later lost them ... Any primitively amitochondriate eukaryote would too.

What this does not establish

Among lineages sampled so far.

Later work looked for

Europe PMC, 2010 on, "amitochondriate eukaryote": the best-known case since, Monocercomonoides (Karnkowska and others, 2016), is read by its authors as a secondary loss.

Claim 19 · checked 24 September 2026 · AI-assisted audit

Prokaryotes are not simple, and they did not do this

Claim: Prokaryotes are not simple, and they did not do this

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

A heading summarising claims 21 to 23.

Claim 20 · checked 24 September 2026 · AI-assisted audit

Claim: Bacteria and archaea have been under selection for billions of years and hold most of the biosphere’s metabolic diversity.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Membranes, energetics, and evolution across the prokaryote-eukaryote divideIntroduction, second paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: Prokaryotes dominate eukaryotes both on a numerical and biomass basis (Whitman et al., 1998; Lynch, 2007), and harbor most of the biosphere’s metabolic diversity.
Supports
The energetics of genome complexityp. 929, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: boundless biochemical ingenuity, prokaryotes have not evolved morphological complexity beyond the rudimentary level seen in cyanobacteria or planctomycetes in four billion years of evolution

Corrected

24 September 2026. Previously: “Bacteria have been under selection for billions of years, occupy every environment on the planet, and have invented photosynthesis, nitrogen fixation, and an enormous range of chemistry.” The list carried no citation that says it. Narrowed to what the page’s sources state, and made to include archaea, which the section heading covers.

Claim 21 · checked 24 September 2026 · AI-assisted audit

Claim: Nearly every trait thought of as eukaryotic turns up somewhere among them: nucleus-like structures, internal membranes, giant size, a dynamic cytoskeleton, even endosymbionts.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
The energetics of genome complexityp. 929, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: Virtually every ‘eukaryotic’ trait is also found in prokaryotes, including nucleus-like structures ... internal membranes ... giant size ... dynamic cytoskeleton ... and even endosymbionts

Corrected

24 September 2026. Previously: “” Replaces the uncited list of bacterial inventions with the case the cited paper actually makes for prokaryotes not being simple.

Claim 22 · checked 24 September 2026 · AI-assisted audit

Claim: Except through that one merger, they have not produced a eukaryotic cell.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
The energetics of genome complexityabstract; p. 929, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: The eukaryotic cell arose from prokaryotes just once in four billion years ... Bacteria made a start up virtually every avenue of eukaryotic complexity, but then stopped short.

Corrected

24 September 2026. Previously: “They have not invented the eukaryotic cell.” The eukaryotic cell did come from prokaryotes, once, by merger (Lane and Martin); the flat denial contradicted the page’s own account.

Claim 23 · checked 24 September 2026 · AI-assisted audit

Claim: If there is a barrier, it is not a lack of time, of numbers, or of evolutionary inventiveness.

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Follows from claims 21 to 23: four billion years, vast numbers and wide inventiveness have not produced a second origin. Lane and Martin make the same move against population-size explanations.

Context
The energetics of genome complexityp. 929, second paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: But why do prokaryotes with small population sizes not tend to become eukaryotic?

Corrected

24 September 2026. Previously: “Whatever the barrier is, it is not a lack of time, of numbers, or of evolutionary inventiveness.” Whether there is a barrier at all is the page’s open question (claims 66 to 68); the sentence had assumed it.

Claim 24 · checked 24 September 2026 · AI-assisted audit

Why it is hard

Claim: Why it is hard

Kind: Framing. Signposting. It asserts nothing a source could check.

The energy argument

Claim: The energy argument

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: Nick Lane and William Martin put a number on the problem in 2010.

Kind: Historical claim. A statement about the past that historical evidence can test.
Review: Source checked. The cited passage was read, and it says this.

Supports
The energetics of genome complexityabstract; journal date 21 October 2010
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Model
The source reads: permitting a remarkable 200,000-fold expansion in the number of genes expressed

Claim 27 · checked 24 September 2026 · AI-assisted audit

Claim: Bacteria generate energy across their cell membrane,

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
Membranes, energetics, and evolution across the prokaryote-eukaryote divideResults, “Energy production and the mitochondrion”
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in cells or tissue · Review of the field
The source reads: In prokaryotes, the F0F1 ATP synthase (the molecular machine that transforms ADP to ATP in the process of chemiosmosis) and the electron transport chain (ETC) components (which create the chemiosmotic proton gradient) are restricted to the cell membrane
Supports
The energetics of genome complexityp. 930
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in cells or tissue · Review of the field
The source reads: as prokaryotes respire over their plasma membrane

Later work looked for

How cells make energy; not a finding later work revises.

Corrected

24 September 2026. Previously: “Bacteria generate energy across their outer membrane,” Both sources place it at the cell (plasma) membrane. Many bacteria also have an outer membrane, which is not where respiration happens.

Claim 28 · checked 24 September 2026 · AI-assisted audit

Claim: so the power available per gene falls as a genome grows: a larger bacterium has more volume to supply and proportionally less membrane to supply it from.

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
The energetics of genome complexitypp. 930-931
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in cells or tissue · Model
The source reads: If bacterial gene number is scaled up to the size of the average protist (20,000 genes) the metabolic power per gene falls ... Because ATP synthesis scales with plasma membrane ... area but protein synthesis scales with cell volume, larger prokaryotic cells are energetically less efficient
Cuts against
Membranes, energetics, and evolution across the prokaryote-eukaryote divideResults, “The energetic costs of building and maintaining a cell”
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in cells or tissue · Review of the field
The source reads: The pattern observed in bacteria is inconsistent with the view that surface area limits the rate of energy production

Other readings

Lynch and Marinov find that bacterial biomass production does not fall with cell size the way a surface-area limit predicts.

Corrected

24 September 2026. Previously: “so the power available per gene scales badly as a genome grows: a larger bacterium has more genome to support and no more membrane to support it with.” A larger bacterium does have more membrane; the argument is that membrane grows with surface and demand with volume (Lane and Martin, p. 931).

Claim 29 · checked 24 September 2026 · AI-assisted audit

Claim: Mitochondria move the energy-generating membrane inside, in many copies (200,000 in a large amoeba), each keeping a small genome of its own for running it.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
The energetics of genome complexityp. 931
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in cells or tissue · Review of the field
The source reads: Taking an average mitochondrial genome of 30 kb in 200,000 mitochondria (as in large amoebae ... Mitochondria that generate ATP by oxidative phosphorylation always retain a core genome that encodes proteins of the respiratory electron-transport chain

Later work looked for

How mitochondria are organised; not a finding later work revises.

Corrected

24 September 2026. Previously: “Mitochondria move the energy-generating membrane inside, in hundreds or thousands of copies, each with a tiny genome of its own dedicated to running it.” Replaced an unsourced range with the figure the paper uses.

Claim 30 · checked 24 September 2026 · AI-assisted audit

Claim: On that account the rearrangement permitted a 200,000-fold expansion in the number of genes a cell can express, which is what pays for a large genome and the complexity it encodes.

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
The energetics of genome complexityabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in cells or tissue · Model
The source reads: The endosymbiosis that gave rise to mitochondria restructured the distribution of DNA in relation to bioenergetic membranes, permitting a remarkable 200,000-fold expansion in the number of genes expressed. This vast leap in genomic capacity was strictly dependent on mitochondrial power, and prerequisite to eukaryote complexity

What this does not establish

A calculation from average metabolic rates and genome sizes; the paper’s own Table 1 note says values differing by one or two orders of magnitude may not be meaningfully different.

Other readings

Disputed by Lynch and Marinov (claims 34 and 35).

Claim 31 · checked 24 September 2026 · AI-assisted audit

Claim: It is an elegant argument

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The page’s judgement, not a finding.

Claim 32 · checked 24 September 2026 · AI-assisted audit

Claim: and it is disputed.

Kind: Disputed. A contested point, where the page reports a side or the disagreement.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Cuts against
Membranes, energetics, and evolution across the prokaryote-eukaryote divideabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: there is no reason to think membrane bioenergetics played a direct, causal role in the transition from prokaryotes to eukaryotes

Other readings

Lane and Martin hold the energy account; Lynch and Marinov reject it; the exchange continued in 2025 (claims 36 to 38).

Claim 33 · checked 24 September 2026 · AI-assisted audit

Claim: Michael Lynch and Georgi Marinov compiled measurements of the membranes and the costs and found no eukaryotic advantage to explain: the outer surfaces of a cell’s mitochondria add up to roughly the area of its cell membrane, and their inner membranes to two to five times that, not a vast multiple; and the costs of building and running a cell scale with its volume with no break between bacteria and eukaryotes.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Membranes, energetics, and evolution across the prokaryote-eukaryote divideResults, “Energy production and the mitochondrion”
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in cells or tissue · Review of the field
The source reads: the total outer surface area of mitochondria per cell is generally on the order of the total area of the plasma membrane, with no observed ratio exceeding 5:1 ... the ratios of inner (including the internal cristae) to outer membrane areas ... are 5.0 (SE = 1.1), 2.4, 2.5, and 5.2
Supports
Membranes, energetics, and evolution across the prokaryote-eukaryote divideResults, “The energetic costs of building and maintaining a cell”
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in cells or tissue · Review of the field
The source reads: as there is no discontinuity in scaling between prokaryotes and eukaryotes, these results suggest that a shift of bioenergetics from the cell membrane in prokaryotes to the mitochondria of eukaryotes conferred no directly favorable energetic effects

What this does not establish

A compilation from published studies of a small number of species; the authors note uncertainties in their packing-density estimates. Martin disputes the cost model the scaling rests on (claim 37).

Later work looked for

Crossref, 2017 on, "Lynch Marinov bioenergetic cost mitochondria": Martin (2025) disputes the cost model and Lynch (2025) replies; page updated to report both.

Corrected

24 September 2026. Previously: “Michael Lynch and Georgi Marinov measured the membranes and the costs and found no eukaryotic advantage to explain: mitochondrial surface area is roughly the area of the cell membrane rather than a vast multiple of it, and the cost of a gene falls with cell volume in bacteria and eukaryotes alike.” They compiled published data rather than measuring; the equal-area finding is for the outer mitochondrial membrane, with the inner two to five times larger; and the paper’s scaling finding is continuity across the divide, not a falling cost per gene.

Claim 34 · checked 24 September 2026 · AI-assisted audit

Claim: On their reading membrane bioenergetics played no direct, causal role in the transition, and the eukaryotic cell plan may have emerged partly by non-adaptive processes in a small population passing through a long bottleneck.

Kind: Hypothesis. A proposed explanation, not an established one.
Review: Source checked. The cited passage was read, and it says this.

Supports
Membranes, energetics, and evolution across the prokaryote-eukaryote divideabstract; Discussion
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in cells or tissue · Review of the field
The source reads: there is no reason to think membrane bioenergetics played a direct, causal role in the transition from prokaryotes to eukaryotes ... a plausible scenario is that the full eukaryotic cell plan emerged at least in part by initially nonadaptive processes made possible by a very strong and prolonged population bottleneck

Other readings

Lane and Martin argue the reverse (claim 31), and in 2025 Martin argued the cost accounting behind this reading is wrong (claim 37).

Corrected

24 September 2026. Previously: “On their reading the mitochondrion was not a prerequisite for a large genome.” Replaced a paraphrase the paper does not make with its own conclusion and the alternative it proposes.

Claim 35 · checked 24 September 2026 · AI-assisted audit

Claim: The dispute is live.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Energetics and evolution: Response to MartinIntroduction, second paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Argument
The source reads: one specific area in which debate has come to the forefront concerns the idea that the origin of the mitochondrion was the single causal event enabling the emergence of all things eukaryotic

Corrected

24 September 2026. Previously: “” Currency: the page ended the dispute on the 2017 paper, and a published exchange in 2025 continues it.

Claim 36 · checked 24 September 2026 · AI-assisted audit

Claim: In 2025 Martin argued that the cost model Lynch and Marinov had built on overstates the energy needed to make an amino acid up to 200-fold, and that the first mitochondria could have doubled their host’s supply of ATP under conditions he sets out.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
ATP requirements for growth reveal the bioenergetic impact of mitochondrial symbiosisabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Argument
The source reads: The more recent model contains, however, a severe and previously unrecognized error that systematically overestimates the ATP cost of amino acid synthesis up to 200-fold. ... the first mitochondrial endosymbionts could have easily doubled the host’s available ATP pool, provided

What this does not establish

Martin’s conditions are that genes for growth on amino acids moved from the symbiont to the host, and that the host was an autotroph using the acetyl-CoA pathway. He is a co-author of the energy argument.

Corrected

24 September 2026. Previously: “” Currency: the published reply to the rebuttal the page reports.

Claim 37 · checked 24 September 2026 · AI-assisted audit

Claim: Lynch replied that the criticism rests on a misreading of the methods.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Energetics and evolution: Response to Martinabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Argument
The source reads: Here, it is shown that this conclusion is based on an erroneous interpretation of the methods previously employed by a diversity of authors and that the downstream arguments are conceptually flawed.

What this does not establish

Lynch’s response was read in full. Which side has the accounting right is not something this audit can settle, and the page does not say.

Later work looked for

Europe PMC, 2025 on, "Martin Lynch ATP": Martin replied again in 2026 ("Demand-only energetics at 120 ATP per glucose"), read as an abstract only; the exchange continues, which the page says.

Corrected

24 September 2026. Previously: “” Currency: the reply to Martin, so the page reports both sides.

Claim 38 · checked 24 September 2026 · AI-assisted audit

Claim: Two readings of the same event

Kind: Framing. Signposting. It asserts nothing a source could check.

Corrected

24 September 2026. Previously: “Two readings of the same singularity” The second column questions whether the event was a singularity; the caption had assumed it.

Claim: Energy was the barrier

Kind: Hypothesis. A proposed explanation, not an established one.
Review: Source checked. The cited passage was read, and it says this.

Supports
The energetics of genome complexityp. 932
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in cells or tissue · Model
The source reads: This critical redistribution of DNA in relation to bioenergetic membranes seems to be the fundamental hurdle en route to complexity.

Other readings

Lynch and Marinov’s reading, in the next column.

Claim 40 · checked 24 September 2026 · AI-assisted audit

Claim: Power per gene is set by membrane area against genome size

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
The energetics of genome complexityp. 931
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in cells or tissue · Model
The source reads: larger prokaryotic cells are energetically less efficient ... a eukaryotic gene commands some 200,000 times more energy than a prokaryotic gene

Other readings

Lynch and Marinov find no evidence that membrane area limits ATP synthesis.

Claim 41 · checked 24 September 2026 · AI-assisted audit

Claim: Internalising the membrane lifts the ceiling by orders of magnitude

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
The energetics of genome complexityp. 929
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in cells or tissue · Model
The source reads: Mitochondria increased the number of proteins that a cell can evolve, inherit and express by four to six orders of magnitude

Other readings

Lynch and Marinov: inner mitochondrial membrane is two to five times the outer, not orders of magnitude more than the cell membrane.

Claim 42 · checked 24 September 2026 · AI-assisted audit

Claim: Predicts that the merger had to come first and the complexity after

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
The energetics of genome complexityp. 933
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in cells or tissue · Model
The source reads: mitochondria are prerequisite to complexity. It follows that the host for mitochondria was a prokaryote
Qualifies
Complex archaea that bridge the gap between prokaryotes and eukaryotessection “A ‘complex’ archaeal ancestor of Eukarya”
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in microbes · Observational study: associations, not causes
The source reads: the emergence of cellular complexity was already underway before the acquisition of the mitochondrial endosymbiont

Other readings

Spang and others read the Lokiarchaeum genome as showing complexity already underway before the merger.

Claim 43 · checked 24 September 2026 · AI-assisted audit

Claim: Something else was, or nothing

Kind: Hypothesis. A proposed explanation, not an established one.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
Membranes, energetics, and evolution across the prokaryote-eukaryote divideDiscussion
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in cells or tissue · Review of the field
The source reads: if the establishment of the mitochondrion was a key innovation in the adaptive radiation of eukaryotes, the causal connection does not appear to involve a boost in energy acquisition
Supports
Eukaryogenesis, how special really?abstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Argument
The source reads: we question whether premises of existing theories about the uniqueness of eukaryogenesis and the greater evolutionary potential of eukaryotes have been objectively formulated

What this does not establish

Booth and Doolittle were read as an abstract only.

Other readings

Lane and Martin’s reading, in the first column.

Corrected

24 September 2026. Previously: “Something else was” The column’s last point, and Booth and Doolittle, allow that there was no barrier at all.

Claim 44 · checked 24 September 2026 · AI-assisted audit

Claim: Measured mitochondrial membrane area is not the vast multiple the argument needs

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Membranes, energetics, and evolution across the prokaryote-eukaryote divideResults, “Energy production and the mitochondrion”
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in cells or tissue · Review of the field
The source reads: the data are inconsistent with the idea that the mitochondrion engendered a massive expansion in the surface area of bioenergetic membranes in eukaryotes

Claim 45 · checked 24 September 2026 · AI-assisted audit

Claim: The cell plan may owe more to drift in a small, bottlenecked population than to power

Kind: Hypothesis. A proposed explanation, not an established one.
Review: Source checked. The cited passage was read, and it says this.

Supports
Membranes, energetics, and evolution across the prokaryote-eukaryote divideDiscussion
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Argument
The source reads: a plausible scenario is that the full eukaryotic cell plan emerged at least in part by initially nonadaptive processes made possible by a very strong and prolonged population bottleneck

What this does not establish

Offered by Lynch and Marinov as plausible, not demonstrated.

Corrected

24 September 2026. Previously: “The hard step may be the merger itself rather than what it paid for” The column had no source for the old point, and Lane and Martin themselves place the difficulty in the merger. Replaced with the alternative Lynch and Marinov actually propose.

Claim 46 · checked 24 September 2026 · AI-assisted audit

Claim: Once may just be small numbers: rare events happen once

Kind: Hypothesis. A proposed explanation, not an established one.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
Eukaryogenesis, how special really?abstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Argument
The source reads: scientific and popular rhetoric extolling this event as a singularity lacks rigorous evidential and statistical support

What this does not establish

Booth and Doolittle argue that the case for singularity is unsupported; they were read as an abstract, and a sample of one cannot confirm this reading either.

Claim 47 · checked 24 September 2026 · AI-assisted audit

Which came first

Claim: Which came first

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: One account has a host cell that was already complex, with a dynamic cytoskeleton, engulfing a bacterium.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Complex archaea that bridge the gap between prokaryotes and eukaryotesclosing discussion
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in microbes · Observational study: associations, not causes
The source reads: the emergence of cellular complexity was already underway before the acquisition of the mitochondrial endosymbiont ... it seems plausible that the archaeal ancestor of eukaryotes had a dynamic actin cytoskeleton and potentially endo- and/or phagocytic capabilities, which would have facilitated the invagination of the mitochondrial progenitor
Supports
Membranes, energetics, and evolution across the prokaryote-eukaryote divideDiscussion, last paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: a recent analysis suggests that the origin of the mitochondrion postdated the establishment of many aspects of eukaryotic cellular complexity
Supports
The energetics of genome complexityp. 929 and p. 933
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: If phagocytosis offered the decisive advantage ... Although conventional wisdom holds that the origin of complexity was key to the acquisition of mitochondria
Lane and Martin describe this account in order to argue against it.
Context
Mitochondrial Evolutionabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Review of the field
The source reads: particularly raising the question of whether the mitochondrion originated after the eukaryotic cell arose, as assumed in the classical endosymbiont hypothesis

What this does not establish

The cytoskeleton and the capacity to engulf are inferred from genes in an archaeal relative, and Spang and colleagues call them plausible, not observed.

Corrected

24 September 2026. Previously: “One account has a host cell that was already complex, with a nucleus and a cytoskeleton, engulfing a bacterium.” No source read carries a nucleus in the host on this account: Gray's review, the one support for it, was read only as an abstract that does not name one. Spang and colleagues, read in full, carry a dynamic cytoskeleton and a capacity to engulf; the sentence now names only that.

Claim 49 · checked 24 September 2026 · AI-assisted audit

Claim: Another has a simple archaeal host and has the complexity arriving afterwards, paid for by the new energy supply.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
The energetics of genome complexityp. 933
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Model
The source reads: mitochondria are prerequisite to complexity. It follows that the host for mitochondria was a prokaryote

Claim 50 · checked 24 September 2026 · AI-assisted audit

Claim: Genomic evidence places the host among the Asgard archaea, a superphylum named in 2017,

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
Asgard archaea illuminate the origin of eukaryotic cellular complexityabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Research in microbes · Observational study: associations, not causes
The source reads: Here we describe the ‘Asgard’ superphylum, a group of uncultivated archaea ... Asgard archaea affiliate with eukaryotes in phylogenomic analyses
Supports
Isolation of an archaeon at the prokaryote-eukaryote interfaceabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in microbes · Observational study: associations, not causes
The source reads: Current data suggest that eukaryotes may have emerged from an archaeal lineage known as ‘Asgard’ archaea

What this does not establish

The naming paper was read as an abstract.

Later work looked for

Europe PMC, 2017 on, "Asgard archaea eukaryotes phylogenomics": Eme and others (2023) place eukaryotes within the Asgard archaea, as sister to the Hodarchaeales in the Heimdallarchaeia; narrows it further without contradicting the page.

Claim 51 · checked 24 September 2026 · AI-assisted audit

Claim: uncultivated then and cultured since,

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
Asgard archaea illuminate the origin of eukaryotic cellular complexityabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Research in microbes · Observational study: associations, not causes
The source reads: a group of uncultivated archaea
Supports
Isolation of an archaeon at the prokaryote-eukaryote interfaceabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in microbes · Experiment
The source reads: Here we report the decade-long isolation of an Asgard archaeon related to Lokiarchaeota from deep marine sediment.

What this does not establish

The naming paper was read as an abstract.

Later work looked for

Europe PMC, 2020 on, "Asgard archaeon culture": Rodrigues-Oliveira and others (2023) report a second enriched culture, of a Lokiarchaeum; consistent.

Claim 52 · checked 24 September 2026 · AI-assisted audit

Claim: whose genomes are enriched for proteins formerly considered specific to eukaryotes.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
Asgard archaea illuminate the origin of eukaryotic cellular complexityabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Research in microbes · Observational study: associations, not causes
The source reads: Asgard archaea affiliate with eukaryotes in phylogenomic analyses, and their genomes are enriched for proteins formerly considered specific to eukaryotes

What this does not establish

Read as an abstract.

Later work looked for

Europe PMC, 2017 on, "Asgard eukaryotic signature proteins": Rodrigues-Oliveira and others (2023) find such proteins make up 5% of one cultured Asgard genome; consistent.

Claim 53 · checked 24 September 2026 · AI-assisted audit

Claim: That has narrowed the question without closing it.

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Follows from claims 43 and 59 to 62: the Asgard genomes suggest some complexity came first, while the cultured relative is internally simple.

Claim 54 · checked 24 September 2026 · AI-assisted audit

The host’s relatives have been found

Claim: The host’s relatives have been found

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
Isolation of an archaeon at the prokaryote-eukaryote interfacefinal paragraph of the main text
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in microbes · Experiment
The source reads: we have isolated and cultivated the closest archaeal relative of eukaryotes to date

Later work looked for

Europe PMC, 2020 on, "Asgard archaea closest relatives of eukaryotes": Eme and others (2023) confirm eukaryotes nest within Asgard archaea.

Corrected

24 September 2026. Previously: “The host has been found” What was found are living relatives of the host, separated from it by roughly two billion years (Imachi and others); the host itself is not available to find.

Claim 55 · checked 24 September 2026 · AI-assisted audit

Claim: In 2015 a group sequenced DNA from sediment about fifteen kilometres from a hydrothermal vent field in the Arctic and assembled a composite genome of an archaeon nobody had cultured, named Lokiarchaeum.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
Complex archaea that bridge the gap between prokaryotes and eukaryotesResults; Methods, “Sampling site and sample description”
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in microbes · Observational study: associations, not causes
The source reads: A 2-m long gravity core (GC14) was retrieved from the Arctic Mid-Ocean Ridge during summer 2010 (approximately 15 km north-northwest of the active venting site Loki’s Castle ... yielding a 92% complete, 1.4 fold-redundant composite genome (‘Lokiarchaeum’) of 5.1 Mbp

Later work looked for

A dated discovery; later Asgard work (claims 51 to 53) builds on it.

Corrected

24 September 2026. Previously: “In 2015 a group sequenced DNA from sediment near a hydrothermal vent in the Arctic and assembled the genome of an archaeon nobody had cultured, named Lokiarchaeum.” The paper gives the distance and calls the genome a composite, assembled from environmental DNA.

Claim 56 · checked 24 September 2026 · AI-assisted audit

Claim: It carries genes for proteins previously considered exclusive to eukaryotes, including components of the machinery eukaryotic cells use to reshape their membranes and to engulf things.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
Complex archaea that bridge the gap between prokaryotes and eukaryotesabstract; Results
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in microbes · Observational study: associations, not causes
The source reads: genomes encode an expanded repertoire of eukaryotic signature proteins ... a significant part of the predicted proteome (175 proteins or 3.3%) was most similar to eukaryotic proteins (Fig. 2c) and revealed a dominance of proteins, which in eukaryotes are involved in membrane deformation and cell shape formation processes, including phagocytosis

Later work looked for

Europe PMC, 2015 on, "Lokiarchaeota eukaryotic signature proteins": later Asgard genomes enlarge the list (Zaremba-Niedzwiedzka and others, 2017); nothing reverses it.

Corrected

24 September 2026. Previously: “the machinery cells use” The source describes what these proteins do in eukaryotes, not what they do in Lokiarchaeum.

Claim 57 · checked 24 September 2026 · AI-assisted audit

Claim: That placed the host of the merger within a specific group of archaea,

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Complex archaea that bridge the gap between prokaryotes and eukaryotessection “A ‘complex’ archaeal ancestor of Eukarya”
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in microbes · Observational study: associations, not causes
The source reads: a novel, deeply rooting clade of the archaeal TACK superphylum, which in phylogenomic analyses of universal proteins forms a monophyletic group with eukaryotes

Corrected

24 September 2026. Previously: “That places the host of the merger within a specific group of archaea,” Past tense, because the 2015 result has since been refined (claim 51).

Claim 58 · checked 24 September 2026 · AI-assisted audit

Claim: and suggested to its discoverers that the host already had some of the equipment to take another cell inside.

Kind: Hypothesis. A proposed explanation, not an established one.
Review: Source checked. The cited passage was read, and it says this.

Supports
Complex archaea that bridge the gap between prokaryotes and eukaryotessection “A ‘complex’ archaeal ancestor of Eukarya”
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in microbes · Observational study: associations, not causes
The source reads: it seems plausible that the archaeal ancestor of eukaryotes had a dynamic actin cytoskeleton and potentially endo- and/or phagocytic capabilities, which would have facilitated the invagination of the mitochondrial progenitor
Qualifies
Isolation of an archaeon at the prokaryote-eukaryote interfacemain text, final section
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in microbes · Experiment
The source reads: we suggest that the physical manifestation of this endosymbiosis was probably independent of phagocytosis

Other readings

The team that cultured a relative in 2020 thinks the merger probably did not involve phagocytosis (claim 62).

Corrected

24 September 2026. Previously: “and suggests it already had some of the equipment required to take another cell inside.” Spang and others offer this as plausible; the 2020 culture argues against phagocytosis, so it is attributed rather than stated.

Claim 59 · checked 24 September 2026 · AI-assisted audit

Claim: A relative was finally grown, alongside a partner microbe, after a twelve-year effort: an anaerobic coccus about half a micron across that takes fourteen to twenty-five days to double.

Kind: Experimental result. What an experiment or trial found, under its own conditions. A result in animals, cells or a simulation is not a result in people.
Review: Source checked. The cited passage was read, and it says this.

Supports
Isolation of an archaeon at the prokaryote-eukaryote interfaceabstract; main text, isolation and characterisation
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in microbes · Experiment
The source reads: enabling us to obtain a pure co-culture of the target archaeon MK-D1 and Methanogenium after a 12-year study ... The doubling time was estimated to be approximately 14–25 days. ... small cocci (approximately 300–750 nm in diameter (average, 550 nm)) ... is an anaerobic, extremely slow-growing, small coccus

What this does not establish

One strain, grown with a methanogen partner. The twelve years run from bioreactor enrichment to a final seven years of laboratory culture.

Later work looked for

Europe PMC, 2020 on, "Asgard archaeon culture": Rodrigues-Oliveira and others (2023) grew a second Asgard archaeon, dividing every 7 to 14 days; the page’s figures are for the first and remain correct for it.

Corrected

24 September 2026. Previously: “A relative of it was finally cultured after twelve years of trying, an anaerobic coccus half a micron across that doubles in a fortnight to a month.” The paper gives 14 to 25 days, not up to a month, and the culture is a co-culture with a partner.

Claim 60 · checked 24 September 2026 · AI-assisted audit

Claim: It showed no organelle-like structures inside, only long, branching protrusions,

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
Isolation of an archaeon at the prokaryote-eukaryote interfaceabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in microbes · Experiment
The source reads: the isolate has no visible organelle-like structure. Instead, Ca. P. syntrophicum is morphologically complex and has unique protrusions that are long and often branching.

Later work looked for

Europe PMC, 2020 on, "Asgard archaea cytoskeleton": Rodrigues-Oliveira and others (2023) image an actin cytoskeleton in a second cultured Asgard archaeon; it does not report organelles either.

Corrected

24 September 2026. Previously: “” The culture’s main finding about the host question, which the page had left out.

Claim 61 · checked 24 September 2026 · AI-assisted audit

Claim: and the team that grew it suggests the host drew its partner in with structures like those rather than by phagocytosis, a conjecture they say needs more evidence.

Kind: Hypothesis. A proposed explanation, not an established one.
Review: Source checked. The cited passage was read, and it says this.

Supports
Isolation of an archaeon at the prokaryote-eukaryote interfacemain text, final section
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in microbes · Experiment
The source reads: we suggest that the physical manifestation of this endosymbiosis was probably independent of phagocytosis ... in which the host archaeon engulfed the metabolic partner using extracellular structures ... however, further evidence is required to support this conjecture

What this does not establish

A proposal built on one cultured strain that is some two billion years removed from the host.

Corrected

24 September 2026. Previously: “” Reports the rival reading to claim 59 from the paper the page already cites.

Claim 62 · checked 24 September 2026 · AI-assisted audit

Whether it is rare

Claim: Whether it is rare

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: Not once of its kind. Once.

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Restates claim 13: one ancestral event, not one kind of event.

Claim 64 · checked 24 September 2026 · AI-assisted audit

Whether once means hard

Claim: Whether once means hard

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: A single occurrence in four billion years is consistent with an extremely improbable step and also with an ordinary step whose first success prevented any second one, because the incumbent occupies the niche.

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The page’s own reasoning about what one occurrence can show. It asserts only that both readings fit the count, not which is right.

Claim 66 · checked 24 September 2026 · AI-assisted audit

Claim: Distinguishing those is hard with one planet to go on, which is the same limitation that runs through every question about how likely life’s major transitions are.

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The page’s judgement. Booth and Doolittle show that evidence from this planet bears on how special the event was, which is why the sentence says hard rather than impossible.

Context
Eukaryogenesis, how special really?abstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026
The source reads: the criteria by which we judge eukaryogenesis to have required a genuinely unlikely series of events 2 billion years in the making are being eroded by discoveries that fill in the gaps of the prokaryote:eukaryote “discontinuity.”

Corrected

24 September 2026. Previously: “Distinguishing those requires more than one planet, which is the same limitation that runs through every question about how likely life’s major transitions are.” Booth and Doolittle argue from evidence on this planet; “requires” overstated the limit.

Claim 67 · checked 24 September 2026 · AI-assisted audit

Claim: Austin Booth and Ford Doolittle make the narrower version of the point: the rhetoric calling eukaryogenesis a singularity lacks rigorous evidential and statistical support.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
Eukaryogenesis, how special really?abstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Argument
The source reads: scientific and popular rhetoric extolling this event as a singularity lacks rigorous evidential and statistical support

What this does not establish

Read as an abstract. Lane and Martin published a reply in PNAS the same year, “Eukaryotes really are special, and mitochondria are why”, which could not be read here.

Corrected

24 September 2026. Previously: “the rhetoric calling eukaryogenesis a singularity has never had statistical support behind it.” Brought back to the paper’s own wording, which is narrower than “never had”.

Claim 68 · checked 24 September 2026 · AI-assisted audit

What was read

Mitochondrial EvolutionMichael W. Gray, Cold Spring Harbor Perspectives in Biology 4 · NCBI PMC record PMC3428767 via E-utilities, which carries the abstract only; the publisher does not allow the full text in XML and its PDF host refused this environmentAbstract only, 24 September 2026 · Copyright; quoted briefly
The energetics of genome complexityLane and Martin, Nature · Nature 467, 929-934, the published PDF as uploaded to ResearchGate by Nick Lane on 17 December 2014 (copy hosted with Complexity Explorer course materials); abstract and editor’s summary also read on nature.comRead in full, 24 September 2026 · Copyright; quoted brieflyThe body text and Table 1 were read; the reference list was not checked.
Membranes, energetics, and evolution across the prokaryote-eukaryote divideLynch and Marinov, eLife · Europe PMC full text, PMC5354521Read in full, 24 September 2026 · CC BY 4.0The equations do not survive the XML conversion; the supplementary material was not read.
ATP requirements for growth reveal the bioenergetic impact of mitochondrial symbiosisWilliam F. Martin, Biochimica et Biophysica Acta: Bioenergetics · Europe PMC full text, PMC7617979 (author manuscript); the arXiv version 2503.16962 was also readRead in full, 24 September 2026 · Author manuscript; quoted briefly
Energetics and evolution: Response to MartinMichael Lynch, Biochimica et Biophysica Acta: Bioenergetics · Author manuscript, NCBI PMC12990190 via E-utilitiesRead in full, 24 September 2026 · Author manuscript; quoted briefly
Eukaryogenesis, how special really?Booth and Doolittle, PNAS · NCBI PMC record PMC4547297 via E-utilities, abstract only; the publisher’s site refused this environmentAbstract only, 24 September 2026 · Copyright; quoted briefly
Asgard archaea illuminate the origin of eukaryotic cellular complexityZaremba-Niedzwiedzka and others, Nature · nature.com abstract and editor’s summary; the repository copies listed by Unpaywall (OSTI, Wageningen) did not serve the text hereAbstract only, 24 September 2026 · Copyright; quoted briefly
Isolation of an archaeon at the prokaryote-eukaryote interfaceImachi and others, Nature · Europe PMC full text, PMC7015854Read in full, 24 September 2026 · CC BY 4.0Supplementary notes and videos were not read.
Complex archaea that bridge the gap between prokaryotes and eukaryotesSpang and others, Nature · Europe PMC full text, PMC4444528 (author manuscript)Read in full, 24 September 2026 · Author manuscript; quoted brieflySupplementary tables and discussion were not read.