So these are the ancestors of Groot? or Ents? and all manner of "animated trees"?
In fact, it is likely that blue-green algae have appeared for the first time on continents, either in fresh water or moist rocks, and only much later they have spread into marine environments, which had been previously dominated by anoxygenic phototrophic bacteria, which were oxidizing sulfur, iron or manganese, not water. The transition to oxidizing water is likely to have been necessary for the spreading of the blue-green algae on continents, where the fresh water had only a very small content of substances that could be oxidized unlike seawater, which at that time was rich in hydrogen sulfide and in Fe(II) and Mn(II) ions. When the blue-green algae have expanded back into the oceans, that must have been after the oxygenation of the atmosphere has modified the composition of the oceans, by precipitating most of the iron and manganese and oxidizing sulfide to sulfate, which would have deprived the anoxygenic phototrophic bacteria of their food.
Then, in the oceans, at some point in time a blue-green alga has become symbiotic with the ancestor of red algae and green algae, which have then dominated for many hundred million years the oceans, before the much later appearance of other phototrophic groups, like diatoms and brown algae. Multicellular red algae and green algae already existed in the oceans around one billion years ago, when no other multicellular eukaryotes existed.
When the fungi have appeared through a transition to a terrestrial lifestyle, that could happen only if on land they could find great amounts of dead living matter, which had been produced by blue-green algae. It is not known for sure whether fungi have appeared a long time before the first terrestrial green plants or about the same time, but it seems that already for the most ancient terrestrial green plants, symbioses with fungi that enhanced the absorptive capabilities of their roots have been important. For aquatic plants, roots had only a fixation function, not the function of absorbing nutrients, so perhaps symbiosis with some already existing terrestrial fungi might have been necessary, not optional, for the first terrestrial green plants, until better absorbing roots have evolved.
So for a long time in the history of the planet, the drier parts of the land would be barren, but wherever there was moisture you would find mats or crusts of blue-green algae, with associated heterotrophic bacteria and viruses.
Then, probably not earlier than the Cambrian, there would be also fungi, and even later the first moss-like terrestrial green plants would appear.
This bugs me so much. The four-kingdom system should have died out decades ago, it's absurdly wrong. For one thing, fungi and animals should be together (opisthokonts) if you're dividing eukaryotes into the major groups. If you consider genetics, there's no such thing as "protists", they're just a whole bunch of small things that were grouped together because we didn't know otherwise.
It's more like, Archaeplastida, Excavata, SAR supergroup, Amoebozoa, and Opisthokonta at the moment. The exact list is up for debate, and currently undergoing change. There's plenty of weird things like Hemimastigophora and we're not really sure where they fit yet.
My strong impression is that even the roots of the tree are debated, with competing models that often change.
> The four-kingdom system should have died out decades ago
First, hopefully not! :) Second, I think it's used because it's the last stable model. Third, it's a model that the public can understand - theres no point in even trying to use "Archaeplastida, Excavata, SAR supergroup, Amoebozoa, and Opisthokonta" unless you are an expert in phylogenics or evolution. Who can understand and remember that?
It's strange to see people promoting it online in 2025. If adults want to remain ignorant, so be it, but at least teach children the truth. Let them know that life is incredibly complicated, it's a mystery we're still solving, and they could be the ones to help figure it out. Don't overly simplify things for small minds, it creates a false picture and it kills the imagination.
More personally speaking: what am I missing out by using the four kingdoms? Like, how could that possibly ever backfire in a way that slightly impacts my life negatively, or impedes the scientists studying genetic lineages? There's basically infinite science to "remain ignorant" of, I don't see any justification for an elitist attitude on this nuance in particular.
One obvious reason it should not be taught, if it is wrong then it kills curiosity and imagination by giving us a neat story we think is true. In a way it has the same negative effect religion can have but to a smaller degree. Why does the earth exist, because god made it kills all spirit of enquiry. This is the same problem I have with the big bang. This is another theory that kills inquiry. Similar example:
I don’t mean to be snarky, but it seems like you’re very removed from the reality of normal people and parents out there.
However, they should know the basics such as "not eating potatoes (or its parts) that are green", and so forth, since that is something you run into even if you never leave the city. Food spoilage in general would be useful to teach, but that is the job of the parents, I would say. That said, my teachers in elementary school always used to tell me that they are our second parents. I can see where they were coming from.
Starting with animals (things that can think like you), plants (things that eat light), fungi (underground webs that bloom above ground), and bacteria (very small things that are sort-of alive, and can both be good for you or make you sick), makes things so much easier and is probably all you need to know for a while.
- Humans are what they are;
- Animals are what they are;
- Plants and fungi of the kind you can gather in the forest, and anything else that is macro-scale but doesn't run or swim around, are just "plants";
- Bacteria, viruses, fungi of the other kind, archaea and even single-cellular organisms that could have negative impact on you, are all just "bacteria" or "microorganisms" or "pathogens";
- "Plants" breaks down into "trees", "grasses", "bushes", "shrooms", "flowers", and that's about it;
- "Animals" breaks down into "fish", "reptiles", "birds", "mammals";
That covers about all the biology regular people see, to the extent they care about.
Now, if you're teaching people the biological categorization, any one you will pick will be different from the daily experience of an ordinary person. Like, for practical reasons, whales and dolphins are fish (they look like every other fish and swim in water, and you hunt them with ships), and tomato is a vegetable (you don't put it into a fruit salad), and all that looks like grass is grass (despite genetics telling that some grasses are really just very tiny trees, or some trees are genetically just really big grass, etc.).
Point being, if you're going to teach them a biological categorization, that's already distinct from "normie everyday life" categorization, so you may just as well pick one that's current and useful in biology.
(And once again, this is another case of a non-issue that turns into issue only because people are unable to comprehend and teach the distinction between "is" and "can be thought of as"; the fact that categories are invented by people, are not facts of nature; that their only job is to be useful, and you can have many classification systems for the same thing, useful in different contexts.)
Insects and spiders are feeling left out.
That insects and mammals are both Animalia can be nonintuitive for preschoolers.
A 19th century breakdown by Cuvier, influential for a long time, was: Vertebrates, arthropods, molluscs, radiates. (I don't know where worms fit.)
Insects and mammals both walk around. Plants and shrooms don't. Can't get more obvious than that for a kid.
> More personally speaking: what am I missing out by using the four kingdoms? Like, how could that possibly ever backfire in a way that slightly impacts my life negatively, or impedes the scientists studying genetic lineages?
Sure, where does kelp fit in? How about slime molds?
Also, I'm not suggesting we teach children all the nuance of phylogeny. I'm suggesting we don't teach a version that we've proven to be objectively wrong.
Eventually, the four-kingdoms system will go away, and it will sit next to the "animal, vegetable, mineral" system in the annals of scientific history.
To me, this discussion should center around utility — “objectively wrong” is assumed to apply to basically everything we ever say on some level (what are the chances we happen to live at the End of Science?) so I hesitate to adopt such a binary framework. In this light, taking a stand against “animal, plant, fungus”—which sums up an overwhelming majority of how laypeople interact with the world—seems of dubious value.
Re:examples, kelp are plants and slime molds are molds, and therefor fungi. Boom. Does that capture 100% of their characteristics on a genetic level? Presumably not (and TIL kelp are technically like flexible coral colonies, not vascular plants)! Is it more useful for 99.9% of usage than “they’re their own things, somewhat unlike anything else”? Definitely, yes.
P.s. animal vegetable mineral also seems to have held up okay…? It’s a culinary thing AFAIK, not an exhaustive list of all objects.
Interesting - Linnaeus (and possibly contemporaries and predecessors) were maybe biased too look at the world through eating: The hunted, the grown, and the mined.
(Completely speculative, of course.)
It's unlikely you understand relativistic mechanics unless you learn and practice Newtonian for a few years, then many people stop there and never go for relativism.
It's unlikely you understand Peano axioms without first spending years just working with numbers, completely disregarding the formal foundations. Then many people stop there and never study the formal math.
It's unlikely you understand electron configurations and orbitals without first imagining electrons orbiting the nucleus like earth is orbiting the sun. And even that part you won't understand until you master the false concepts of "sunrise" and "sunset".
You can't climb the ladder without stepping on the first step. I've been studying for many years, observing people around me, I also did a fair share of teaching myself. The purist approach that avoids oversimplifications inevitably leads to disaster. There are maybe 1-2 kids in the class who can "jump the ladder", the rest are left on the ground helpless and confused.
Another curious observation: when I found myself in that role of a kid jumping the ladder in a purist class, I did that by secretly building a false ladder of my own. When professor said "Banach space" I would imagine Euclidean or Hilbert spaces and would get correct intuition half the time. The other half I would remember and use it to understand the difference. Most of others suffered dearly, unable to grasp anything at all, seeing the glass bead game instead of vectors and functions. And we were 20 years old back then, not even that small.
Every time someone told me: "this is a simplified version to give you a basic understanding and later you will be able to learn more accurate versions" that was tremendously helpful and sometimes it sparked my curiosity and motivated me to look stuff up myself.
I mean we should get ahead of the realisation that it doesn't add up.
This can work with your kids though but I don't know if it can be effectively scaled to a school class. Maybe on a few dedicated play/discovery sessions, not on a regular basis.
Graduation could mean an overthrowing of the known-wrong models. Congratulations, here are the next known-wrong models. Now prove these wrong.
In high school chemistry, the teacher was reviewing what we should remember from lower school about atoms & molecules (single bonds, double bonds, slots available for single atoms of different elements). I asked something like "If the model we were using treats the bonding sites on every atom of every element as equal, but says that some molecules are either rarer than others or not known to occur in nature, doesn't that mean the model is incomplete or incorrect?". She instantly shook her head with annoyance and said sternly "No.".
A big difference between a lie and a simplification is whether the other party knows it's a simplification. Communicating that is independent of specific simplification you use, and it's sometimes as easy as saying "is mostly like" / "sorta" instead of "is".
One thing I adore about this community is the broad acceptance of “I don’t know” and “it depends” as the starting point for answers.
My personal rule for being an expert/consultant is to be very willing to say "I don't know, but I can find that out for you", and define that as my real expertise: know how to find out things.
Technology stacks, programming languages, all of those things come and go. The skill to pick up whatever is needed is long-term better.
We value models for their simplicity, for their ability to disregard secondary and tertiary details to allow comprehension and prediction of primary effects.
Then the only question is: which level of the simplicity/correctness trade-off is appropriate in given circumstances? When teaching kids or even a non-professional adults, the appropriate level is often very heavy on the "simplicity" side. Adding more complexity results in less overall understanding, so a net-negative effect in the end.
It is not always conveyed well that they are learning a simplified model, or using an analogy. That's when kids feel lied to.
Even Von Neumann said "truth is much too complicated to allow anything but approximations."
This reminds me of a short lived stretch in French mathematical education, the "Bourbaki years". For those unaware, Nicolas Bourbaki was "a dozen mathematicians in a trench coat" who, in the early 20th, reformed mathematics from the ground up, their work is notoriously opaque (to some, perhaps a revelation to others), if rigorous. It served as inspiration for ambitious mathematics education reforms in the 60s and 70s.
Some of the things my father had to contend with:
- naive set theory and non-10 basis arithmetic in primary school (age 7)
- set theory in early middle school (ages 10/11), maps over sets, so I imagine things like injectivity and bijections. "[...] a different approach of arithmetic, computations often replaced by a more abstract theoretical approach": I wonder how that went in the classroom
- general Algebra introduced at 15yo, groups, rings, fields, vector spaces; 16yo mostly linear algebra (vector spaces, linear mappings etc; in true French fashion I'll bet they didn't see many 2x2 or 3x3 matrices that year)
I'm quoting Wikipedia "Mathématiques modernes" here, my father only told me of the last point himself. Though I do have his notebooks from early higher ed, they had general topology before metric space topology, for example, in year 1 or 2 (probably 1, because how can you do anything before you know topology...). It was all like this, a theory that builds on itself and you can't skip any steps. A finite dimensional space is a particular case of an infinite dimensional one, so you start with the latter. Backwards from how things were constructed and are understood by people.
The fact these reforms survived about 10 years and have been completely reverted is testament that this approach probably doesn't work.
That's the thing: not only he didn't share this intuition, he actively prohibited people from bringing it up in the class because it can lead to mistakes.
The program was to start with most generic cases (Banach spaces, metric spaces) and prove whatever is provable there, then continue adding assumptions one by one and proving stronger and stronger theorems. I think we've reached Hilbert spaces by the end of the year and that was a gotcha moment for many students (wait, these vectors were functions the whole time?), but it was too late. Everyone failed miserably at proving or understanding all the preceding theorems because without the intuition it turns into a game of symbols with no structure or hope. The only recourse were those bootleg analogies from finite spaces and Fourier analysis that a few students knew or came up with.
The "New Math" you mention above gives a good frame of reference. A beautiful curriculum that's almost impossible to understand unless you already learned math the normal way -- a formally incorrect and inconsistent but reliable way.
I also made similar mistake myself when I tried to teach the C language to 12 y.o kids without saying the dreaded "just write it like that, you'll understand later". That experiment failed completely but I only understood why two years later when I myself was subjected to the functional analysis course. Or I think the complete realization came to me even later, with the C language experiment and the functional analysis story becoming pieces of the same puzzle.
Alan Sokal's famous and brilliant hoax Transgressing the Boundaries: Toward a Transformative Hermeneutics of Quantum Gravity had a hilarious footnote that read (my highlighting):
> Miller (1977/78, especially pp. 24-25). This article has become quite influential in film theory: see e.g. Jameson (1982, 27-28) and the references cited there. As Strathausen (1994, 69) indicates, Miller's article is tough going for the reader not well versed in the mathematics of set theory. But it is well worth the effort. For a gentle introduction to set theory, see Bourbaki (1970).
Please get off your elitist horse. "Small minds" has nothing to do with it, it is mostly a matter of topic specialization. You even acknowledge this yourself in the next few paragraphs.
Also, as attested by another current front page story (https://news.ycombinator.com/item?id=43470138), it's incorrect even when talking about children.
All minds alike, big and small, benefit from simplification. I was replying to a comment that specifically referenced "small minds", that's all.
Yes we should have this firm stance and accept nothing less especially when it come to something fundamental such as the Theory of Evolution. It's a shame that some scientists are even promoting that human come from monkey while the fact that from Darwin own observation was that monkey and human probably share the same ancestor not human come from monkey and even that's debatable. They even create a false picture that now become a "universal truth" printed on people shirts and kind of accepted as truth as far as layman and kids are concerned [1]. But now even the one making the picture is regretting it but the damaged has already been done. Einstein once mentioned "Everything should be made as simple as possible, but not simpler". By making things simpler than simpler (pun intended), we are creating distortion and falsehood that can take years and perhaps centuries to be fixed, and just ask the "flat earth" crowd.
[1] On the Origins of “The March of Progress”:
https://sites.wustl.edu/prosper/on-the-origins-of-the-march-of-progress/
For example, explaining encryption as a lock to prevent thieves from stealing data is much more understandable to kids than going into actual definition of encryption. Lock is something concrete that they have seen, while encryption is an abstract concept hard to grasp.
(What is a car? It's like extra legs for your butt, that can run very fast and carry multiple butts.)
You can get much closer to the truth by explaining encryption as a trick to make words understandable only to those who know the trick. You can play a substitution game with your kids, explain how you and them could agree that when one says "snake" it means "I", etc. and so "snake eats green grass" means "I am very hungry", and that you'll understand them but no one else will, etc.
At any given age, kids are as likely to understand secrecy as they're to understand why locks exist, so it's really just a choice of not using a bad and confusing analogy.
By the time we explain all these to them, they would have already lost interest, or context and would easily forget the whole thing.
Connect this to surprise gifts and birthday invites. Or another thing that resonates with them.
Explaining locks and their purpose ain't any easier. Just yesterday, my daughter asked me why I'm locking the extra set of doors we're normally keeping open, and when I told her about the just-issued warning about burglaries in our area, well, there's a lot of context to explain before a 5yo gets why locking the doors is the right thing to do in this scenario.
I mean, there's always a lot of explaining to do with kids anyway. So far, I've never had trouble giving them real explanations and letting them know when they're simplified.
Children learn substitution with language. Hand signs and words are substituted for the objects, feelings and actions they know inherently. It’s tempting to apply adult context on children but it’s a mistake.
We use a similarly flawed model every day: fruit and vegetables. What's in one group or the other is based on vague similarities and is mostly arbitrary, but it's still useful to split the huge category of "edible plant parts" into more manageable chunks.
Anyone familiar with apples and pears will likely see an orange and say it's a fruit. Likewise anyone familiar with cats and dogs will see a boar and think "animal", not "plant" or "fungus". A genetics-based assessment would be more "correct", yes, but impossible on a walk or in the store.
Primary school teachers, from my experience, have a tendency to present things as "the truth" and accept no deviation from their own word. I think changing that would be a good step in fostering creativity in children, much more than skipping less-accurate models.
This is completely wrong. Those categories aren't any smaller, in a practical sense, than the combined category "plants". The gain in manageability is zero.
The reason we divide the categories that way is that we put them to different purposes, not that they'd be too large if combined.
this reminds me of a certain voting population that think male and female are very simple XY and XX things and nothing else exists.
unfortunately a lot of people take dumbed down models and mistake the map for the terrain.
I'm not sure there's a cure for it - I have cousins who went through the same schooling and came out with very different abilities to generalise.
I think we can all agree that in pedagogy and teaching, you have to start simplified; then it becomes a more productive discussion on what constitutes over simplifying, rather than a binary "do or do not over simplify". We can and absolutely should be open about complexity of the world, but at the same time be aware that average person goes through between 8 and 16 years of education (with important outliers on either side of the bell curve), and trying to fit all complexity and all the knowledge on day one generally does not lead to productive results.
The first lesson of the biology in this area I think is not so much "there are these and precisely these 4 or 7 or 9 fixed and immutable categories of life", but... "life can be categorized, and living creatures that look different actually have similarities". There's wonder, and insight, and enlightenment right there that's probably going to stick longer for vast vast vast majority of people, than the specifics of whether there were 4 or 7 or 9 categories. Heck, we changed number of planets and our understanding of "planet" remained the same :).
Anybody who is interested in it
Disclaimer: in this case I have absolutely no idea what is better. But the rationale seems wrong.
Whilst I don't doubt that, viruses don't abide by typical definitions of life that would include self-replication. Obviously, they do replicate, but not by themselves.
Viruses are abstracted on top of other living things in the same way that animals are abstracted on top of plants, in that they both require the lower layer of abstraction for their basic survival.
One classification criterion is descendance from a common ancestor, i.e. cladistic classification.
In many cases this is the most useful classification criterion, because the living beings grouped in a class defined by having a common ancestor share a lot of characteristics inherited from their common ancestor, so when using a name that is applied to that class of living beings, the name provides a lot of information about any member.
However there are at least 2 reasons which complicate such a cladistic classification.
One is that the graph of the evolution of living beings is not strictly a tree, because there are hybridization events that merge branches.
Sometimes the branches that are merged are closely related, e.g. between different species of felids, so they do not change the overall aspect of the tree. However there are also merges between extremely distant branches, like the symbiosis event between some blue-green alga (Cyanobacteria) and some unicellular eukaryote, which has created the ancestors of all eukaryotes that are oxygenic phototrophs, including the green plants.
Moreover, there have been additional symbiosis events that have merged additional eukaryote branches and which have created the ancestors of other eukaryote phototrophs, e.g. the ancestor of brown algae.
After any such hybridization event, there is the question how you should classify the descendants of the hybrid ancestor, as belonging to one branch or to the other branch that have been merged.
For some purposes it is more useful to classify all eukaryote phototrophs based on the branch that has provided the main nucleus of the hybrid cell, and this is the most frequently used classification.
For other purposes it is more useful to group together all the living beings that are oxygenic phototrophs, including various kinds of eukaryotes and also the blue-green algae, and divide them based on the evolution tree of their light-capturing organelles, i.e. the chloroplasts.
This is also a valid cladistic classification, because all oxygenic phototrophs, both eukaryotes and prokaryotes, are the descendants of a single common ancestor, some ancient phototrophic bacteria that has switched from oxidizing manganese using light energy, to oxidizing water, which releases free dioxygen.
Even when there are no branch merges due to hybridization, there remains the problem that in the set of descendants from a single ancestor there are some that are conservative, so they still resemble a lot with their ancestor, and some that are progressive, which may have changed a lot, so they no longer resemble with their ancestor.
In this case, using the name of the entire group provides very little information, because most characteristics that were valid for the ancestor may be completely inapplicable to the subgroups that have become different. In such a case, defining and using a name for the paraphiletic set of subgroups that remains after excluding the subgroups that have evolved divergently may be more useful in practice than using only names based on a cladistic classification. For instance the use of the word "fish" with its traditional paraphiletic meaning, i.e. "vertebrate that is not a tetrapod", is very useful and including tetrapods in "fishes" is stupid, because that would make "fish" and "vertebrate" synonymous and it would require the frequent use of the expression "fishes that are not tetrapods", whenever something is said that is correct only for vertebrates that are not tetrapods, or of the expression "bony fishes that are not tetrapods", for things valid for bony fishes, but not for tetrapods.
While in many contexts it is very useful to know that both fungi and animals are opisthokonts, and there are a few facts that apply to all opisthokonts, regardless whether they are fungi, animals or other opisthokonts more closely related to fungi or more closely related to animals, the number of cases when it is much more important to distinguish fungi from animals is much greater than the number of cases when their common ancestry is relevant.
Animals are multicellular eukaryotes that have retained the primitive lifestyle of the eukaryotes, i.e. feeding by ingesting other living beings, which is made possible by cell motility.
Fungi are multicellular eukaryotes that have abandoned the primitive lifestyle of the eukaryotes, and which have reverted to a lifestyle similar to that of heterotrophic bacteria, just with a different topology of the interface between cells and environment (i.e. with a branched multicellular mycelium instead of multiple small separate cells).
This change in lifestyle has been caused by the transition to a terrestrial life, which has been accomplished with a thick cell wall (of chitin) for avoiding dehydration, which has suppressed cell motility, making impossible the ingestion of other living beings, the same as for bacteria. Moreover the transition to a bacterial lifestyle has also been enabled by several lateral gene transfers from some bacteria, which have provided some additional metabolic pathways that enable fungi to survive when feeding with simpler substances than required by most eukaryotes, including animals.
So even from a cladistic point of view, fungi have some additional bacterial ancestors for their DNA, besides the common opisthokont ancestor that they share with the animals.
Animals are unique among eukaryotes, because all other multicellular eukaryotes have abandoned the primitive lifestyle of eukaryotes, by taking the lifestyles of either heterotrophic or phototrophic bacteria. However for both other kinds of lifestyle changes there are multiple examples, i.e. besides true fungi that are opisthokonts there are several other groups of fungous eukaryotes that are not opisthokonts, the best known being the Oomycetes. There are also bacteria with fungal lifestyle and topology, e.g. actinomycetes a.k.a. Actinobacteria.
If we will ever explore other planets with life, those living beings will not have a common ancestor with the living beings from our planet, but nevertheless it will still be possible to classify them based on their lifestyle in about a half of dozen groups that would be analogous to animals (multicellular living beings that feed by ingestion, so they must be mobile or they must have at least some mobile parts), fungi (multicellular beings that grow into their food, absorbing it after external digestion), oxygenic phototrophs, anoxygenic phototrophs, chemoautotrophs, unicellular equivalents of animals and fungi, like protozoa and heterotrophic bacteria, viruses.
These differences in lifestyles are more important in most contexts than the descendance from a common ancestor.
So while it is useful to have the name Opisthokonta for the contexts where fungi and animals and their close relatives must be included, it is much more frequent to need to speak separately about fungi and other fungous organisms on one hand, and animals on the other hand.
I agree that the term "kingdom" is obsolete when used in the context of a cladistic classification of the living beings.
Perhaps it should be retained for a non-cladistic classification of the living beings, based on the few fundamental lifestyles that are possible, and which would remain valid even for extraterrestrial living beings.
Or rather, it's only a problem when you insist on rigid perspective that makes it a problem.
(The real problem is that so many people insist on viewing things as trees, when their natural shape is directed graph.)
As a programmer symbiogenesis is a mixin or interface not a class.
So even if you want to use only the DNA inside the nucleus for a cladistic classification, that does not produce a tree of evolution, but only a directed graph of genetic information flows, with many important hybridization events. While initially mitochondria and chloroplasts were just symbionts, like the useful bacteria in the human gut, eventually that symbiosis has become a full hybridization, with mixing and integration of the genetic information.
The official cladistic classification produces a tree from the directed graph of the evolution by cutting the branches that are considered to be less important.
Sometimes this is indeed the best choice, but there are contexts in which the genetic information brought through the minor branches is actually that which determines most of the importance of an organism in an ecosystem.
E.g. in many contexts the most important feature of a living being is whether it is an oxygenic phototroph due to inheriting genetic information from some blue-green algae, i.e. that it is a primary producer in the ecosystem, and not the features that depend on which is the exact eukaryotic group from which most of its nucleus has been inherited. For instance, it is more frequently useful to group together brown algae with red algae (whose chloroplasts share a common ancestor), than to group brown algae with some non-phototrophic stramenopiles (which share a common ancestor for most of the nuclear DNA), with which they share only inherited characters that need an electron microscope for detection.
Single cell eukaryotes also exist. Is it strictly true that there are no multicellular prokaryotes (what they call bacteria) or archaea? No exceptions at all?
Yes, "with eukarya containing all multicellular organisms" does not mean "all eukarya are multicellular organisms" it means "multicellular organisms are a subset of eukarya".
> Is it strictly true that there are no multicellular prokaryotes (what they call bacteria) or archaea?
First off, "prokaryotes (what they call bacteria)" is incorrect. Both archaea and bacteria, in the three-domain model referenced in the article, are prokaryotes.
Second, correct, everything understood as a multicellular organism -- as distinct from colonies of unicellular organisms -- is composed of cells with nuclei, classified in eukarya in the three-domain model.
(There is a newer proposed two-domain model which disposes with Eukarya as a top-level domain, folding it under Archaea; in that model, clearly, there are multicellular Archaea.)
I suppose it depends on which model you use, and as discussed they seem to vary and be in flux right now, but the three domain model I learned was prokaryotes, archaea, and eukaryotes - the first two being different domains.
> Yes, "with eukarya containing all multicellular organisms" does not mean "all eukarya are multicellular organisms" it means "multicellular organisms are a subset of eukarya".
We agree. I don't grasp your point?
your original comment didn't refute the quote, but one needs to squint hard to see that you didn't refute it.
Not everything is an argument or attack.
> with eukarya containing all multicellular organisms
Single cell eukaryotes also exist
My point is that your statement here looks like a refutation to most, even though I know you did not intend it to be.
They can form colonies and, within groups that share walls, specialize into different functions such as photosynthesis or nitrogen fixing behavior. This enables the colony to adapt to changing conditions that, while still made up of individual organisms, collectively appear to function similarly to a single multicellular one.
With that said, there aren't any examples of truly multicellular organisms within either domain. Just as an ant colony is not a single organism, cyanobacteria colony specializations are not examples of organs.
Who knew the internet evolved millions of years ago?
Why grow up if you don't need photosynthesis?
From my perusal of The Literature (AKA an amazing Wikipedia article + the paper discussed in this link), we have a few strong theories about the prototaxites:
1. They fed off decaying matter in the soil through a vast network of mycelia/roots, and didn't photosynthesize.
2. They grew large, trunk-like protrusions, but without any branches or leaves (that were fossilized, at least). Like, way, way taller than the bugs, moss, and short weird proto-grass around at the time.
3. These protrusions were regularly burrowed into by aforementioned bugs, which surely was a major health risk.
4. Even before this analysis, they've always been something of an oddball compared to contemporary life -- so everything's on the table, so to speak.
Given those facts, I'm pretty stumped as to what evolutionary pressures might have driven them to grow upwards. At first I considered spore (seed?) dispersal, but mushrooms seem to get along just fine without towering above everything else, and I don't think wind speeds were way lower or anything. Anyone here have any better guesses?
"evidence of arthropod boreholes in Prototaxites has been found from the early and late Devonian, suggesting the organism survived the stress of boring for many millions of years.[30] Intriguingly, boreholes appeared in Prototaxites long before plants developed a structurally equivalent woody stem, and it is possible that the borers transferred to plants when these evolved"
and for Arthropods:
"The evolutionary ancestry of arthropods dates back to the Cambrian period."
which is about 100 million years before the Devonian
also:
"The oldest known arachnid is the trigonotarbid Palaeotarbus jerami, from about 420 million years ago in the Silurian period.[82][Note 3] Attercopus fimbriunguis, from 386 million years ago in the Devonian period, bears the earliest known silk-producing spigots"
so there could have been all sorts of weird and wonderful bugs burrowing into Prototaxites I guess
We should just stop reading the article then and there. This is a major method of how a single study can perpetuate fake science and fake news.
It's a feature, not a bug.
People want the news now. They don't want to wait for it to be peer reviewed, or even cursorily checked. There is an infinite maw for information, and it has already consumed every single known fact.
If you want science, you'll wait a month, because it's not actually urgent. These species waited hundreds of millions of years and it'll still be there in a few weeks.
If you want entertainment, you want it right this instant. And that's what LiveScience exists to do.
So you really should have stopped reading as soon as you saw the URL.
Whether we tag something as a domain also depends on its abundance and/or visibility. I bet if you take dug into microorganisms, you'd find tons that are as different from plants and animals as plants and animals are fun each other. But they all tend to get lumped in as "protists" or something because... we kinda don't care. I wouldn't be surprised if we somehow found out there were a lot of extinct critters in equivalent situations.
>Or groups that are in some sense different from other domains to the same degree those domains are from each other?
This.
As for macroscopic life, there are some Ediacaran critters like rangeomorphs and tribrachidium that (to my knowledge) are not conclusively associated with any existing domain. So who knows about those guys.
https://www.biorxiv.org/content/10.1101/2025.03.14.643340v1
https://en.wikipedia.org/wiki/Prototaxites
John William Dawson, a Canadian scientist, studied Prototaxites fossils, which he described as partially rotten giant conifers, containing the remains of the fungi which had been decomposing them. This concept was not disputed until 1872, when the rival scientist William Carruthers poured ridicule on the idea. ... Dawson fought adamantly to defend his original interpretation until studies of the microstructure made it clear that his position was untenable, whence he promptly attempted to rename the genus himself, calling it Nematophyton ("stringy plant"), and denying with great vehemence that he had ever considered it to be a tree.