Prototaxites, an ancient treetrunk-mushroom-like organism that preceded land plants about 400M yr ago. Its fossils contained plantlike lignin instead of funguslike chitin or chitosan.
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.
Who knews the scope and breadth of the reach of Al Gore, internet inventor, conceiver of the series of tubes paradaigm. Perhaps he has a tube all the way back 400 million years ago amongst his tube series
> with eukarya containing all multicellular organisms within the four kingdoms of fungi, animals, plants and protists.
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.
> The exact list is up for debate, and currently undergoing change.
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?
Children can memorize all 50 US state capitals, they can memorize a handful of scientific names. If we really wanted to, we could teach them a much more accurate view of the tree of life. Also, I don't think the four-kingdom system has been taught in schools for a while? I went to high school in the late 90s and it wasn't taught then.
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.
I strongly disagree. It's necessary to teach oversimplified things to small minds, even oversimplified to the extent of being incorrect.
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.
To be fair, "functional analysis is infinite dimensional linear algebra" is a saying for a reason, that's an intuition a good professor should have given you. Mine gave me it so well, I still see no difference between R^n and a Hilbert space! (on the dangers of intuitions)
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.
> To be fair, "functional analysis is infinite dimensional linear algebra" is a saying for a reason, that's an intuition a good professor should have given you. Mine gave me it so well, I still see no difference between R^n and a Hilbert space! (on the dangers of intuitions)
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).
I'm torn on this one, because there's no way I can accept "lies-to-children are for their own good", but on the other hand I'd hate to be overburdened with information about Peanut maximums or the Ophthalmic supergroup when all I wanted to know was how to do division or what kind of thing a mushroom is.
Once you accept that a model of reality is always somewhat incorrect you kind of stop seeing this as "lies". Reality is infinitely complex, a model however is finite and therefore understandable.
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.
There are very many pithy sayings to this effect, most famously "All models are wrong, but some are useful" (perhaps by George Box, but I can't find this exact phrase attributed to him)
Even Von Neumann said "truth is much too complicated to allow anything but approximations."
It's not hard. "It's sort of like that, but the details are complicated and you'll learn them later if you want" is a perfectly fine answer.
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".
I was learned enough in school to know when teachers were “teaching” something oversimplified. They uniformly acknowledged that when asked, until one didn’t. That one didn’t care about the nuance and insisted I give the “expected” answer when asked and ruined my attitude in school for years (not the only event, but it didn’t help). Obviously I’ve never forgotten her.
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.
Had this experience more than once, but the one that comes to mind:
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.".
From my limited experience (being a child and raising one child) I would say that the problem is more that we (as adults) pretend that the simplified thing is the whole picture.
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.
When I moved to the US in 3rd grade, I was marked wrong for putting negative numbers as answers on a math test. The correct answer was "You can't subtract a larger number from a smaller number".
I had a similar experience, but was fortunate that the teacher took me aside and explained that I was right but they were teaching a simplified version. In hindsight that was really a helpful approach.
I suspect that the best approach would be not to "get ahead", but rather see this realisation develop naturally and help it along the way. It's hard to get critical thinking if everything is already criticized before you even come.
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.
Doing this would create a nice opportunity to teach the right and wrong ways to move the needle in scientific discourse (e.g. don't start by holding a press conference about cold fusion).
Graduation could mean an overthrowing of the known-wrong models. Congratulations, here are the next known-wrong models. Now prove these wrong.
I love your point that avoiding oversimplifications leads to disaster. It explains why I struggle to have a purist mindset while also unable to explain why things go poorly sometimes.
It's necessary to teach oversimplified things to small minds, even oversimplified to the extent of being incorrect.
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.
I'm a huge cladistics fan, but insisting that "animal" isn't a useful term is pretty out there, IMHO. Certainly we can (and do!) teach cladistics in high school biology, but does your ideal world have baby books titled with one of the mentioned names...?
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.
I'm not arguing that animal isn't a useful term, but if you're dividing eukaryotes into the major groups, it's not one of them.
> 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.
Interesting, thanks for elaborating! Still not sure I understand sadly, but maybe it’s just different worldviews on how to play language games. Like, you say we don’t need to teach nuance, and that animal is a useful term — but then what does it denote, if not a group of creatures?
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.
> animal vegetable mineral also seems to have held up okay…? It’s a culinary thing
Interesting - Linnaeus (and possibly contemporaries and predecessors) were maybe biased too look at the world through eating: The hunted, the grown, and the mined.
Why not go the other way, what are you missing if you don’t learnt four kingdoms. Why should that be taught at all.
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:
Well in very practical terms, it gives you a way to name things you see in the forest, to figure out what is edible, and to understand what has a sentience of its own, similar to yours.
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.
There is much more to figure out what is edible and what is not. Considering shrooms alone, it is much more "complicated", so much that there are specialists for that, even, but I agree, could be an useful skill, but not for people who do not even leave the city, I think.
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.
I didn’t say there wasn’t. My point is that explaining to kids why they can pick a strawberry from the forest floor, but leave the fly agaric where it is, despite being the same color, is hard enough without going into the phylogenetic peculiarities.
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.
The reality of normal people and parents is that a different basic classification is warranted:
- 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.)
The four kingdoms system is taught because it is useful; not for science, but for everyday communication.
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.
> 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.
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.
People gain understanding when we relate things to their frame of reference. Kids have very limited life experience and their frame of reference is very low. Introducing new concepts that are not relatable would create huge gaps in real understanding.
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.
Except encryption is nothing like a lock, and "stealing data" is a problematic term, as it's stretching the concept of theft way past its common meaning - it's using the term "stealing" in the exact same way people saying "software piracy is stealing" are. So that's already providing completely twisted mental model to kids. And it stems in big part from trying to pass one specific application as an answer to what the thing is.
(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.
Substitution is a new concept for kids. Not something they can readily understand. So you need to explain that in terms of a game. Kids know what secrets are. But from their point of view, why even talk about it if it is secret? Why can't we go to another place and talk secretly? Why do we need to talk secrets in public using substitution? Since they do not see obvious need for it in their daily life and there are workarounds for it, they do not get why there is a need for substitution.
By the time we explain all these to them, they would have already lost interest, or context and would easily forget the whole thing.
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.
Encryption might not even need much any explanation, just using familiar terms: kids come up with "secret languages" all the time between friends and siblings.
> Kids know what secrets are. But from their point of view, why even talk about it if it is secret? Why can't we go to another place and talk secretly? Why do we need to talk secrets in public using substitution?
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.
>>Don't overly simplify things for small minds, it creates a false picture and it kills the imagination.
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 :).
> 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.
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.
But... but... every cell has one spherical nucleus, one spherical chloroplast for plants or spherical mitochondria for animals, and a host of other features depicted in this helpful diagram that you're going to have to copy from memory.
Yes I agree. 4 humors were enough for medieval europe, they're good enough for me!! Who can remember all this complicated 'germ theory of disease' liberal junk?! There must be hundreds of these supposed 'germs' out there! No sir, no thank you!
At which point started to be important in science that “public can understand”? I think if something is a better explanation for the reality, we ahould go for it, even if it is difficult for the public.
Disclaimer: in this case I have absolutely no idea what is better. But the rationale seems wrong.
Pretty sure anyone who knows anything about viruses would say they are alive. Or at least as alive as parasitic nano archaea with genomes smaller than the viruses living right next to them... The philosophical way to look at it is humans aren't alive in the space between planets they live inside these little hard shells, then when they get to a planet they go wild using all the other resources around them made of biomass. Viruses are just this, their biome isn't the wider one you participate in instead they are sub-cellular life, in the same way you are sub-planetary life. Humans don't make the oxygen atmosphere on the planet themselves, they parasitize this feature of planets from other life. In the same way viruses use cellular machinery.
> Pretty sure anyone who knows anything about viruses would say they are alive
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.
I feel like what trips people up is the abstraction layer.
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.
When classifying living beings, a single classification criterion is not good enough.
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.
I dunno you can mostly solve for this, look at the majority share of the genome in a compartment with a single membrane contained by the outer membrane (by definition for endosymbiogenesis), with the DNA molecules containing the highest quantity of coding gene content. That's the thing you do the cladistic descent on. Just because I'm carrying a load of bacterial symbionts that are better at digesting wheat doesn't make me a different species to humans who mostly eat rice. That I eventually carry those as an endosymbiont then eventually just a sack of genes doesn't really change who' was the boss in this situation, or who I'm able to reproduce with that entire time as a species either. Symbiogenesis is very much like this, look at Hatena arenicola if you want to see this emerging to see how it interacts with descent. This is really the difference between understanding reproductive relationships specifically, vs wider ecology. I agree that symbiogenesis is like this weird one where its both only going to happen through other ecological relationships and then reproduction. But there really is a clear cut time one turns into the other, with the fate of one of those organisms of the combination "winning" even though profoundly altered. Symbiodinium is probably another good example, it has loads of ecological partners and little remnants of all of those histories in its genetic material and organelle arrangement. But its still an obvious species, with all the other oddball dinoflagellates that act and look like it also appearing to have some common descent from something much simpler and eukaryotic.
As a programmer symbiogenesis is a mixin or interface not a class.
It is not that simple, because a large part of the genes that originally belonged to the mitochondria or to the chloroplasts have been transferred into the nucleus and they are now completely integrated into it, even if evolution trees will show that those genes have a different history than the remainder of the nucleus.
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.
One of the great wonders of clustering algorithms is that no matter what k > n you choose, you can construct k clusters. Then we can argue about the clusters and about k. It is said that when Humanity discovers the One True K, the taxonomy will disappear and be replaced by a different one.
I saw this on bsky a few days ago and was fascinated, so glad to see it made its way here! I had this question that went unanswered, so hopefully there's some experts/fellow musers here:
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?
When you feed off decaying matter, hosting a colony of bugs which go out daily, bring back food and leave waste all around your environment sounds like a pretty good strategy when you don't have any way to move to better pastures?
"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
One reason to grow upward is also just the need for oxygen. Mushrooms do this too - they tend to colonise and begin to fruit in high CO2 concentrations, but eventually want to escape it. And you can see the negative side effects of not being able to do this in mushrooms too (if the CO2 is too intense they grow too fast relative to their thickness [trying to reach air] and become nasty and stringy looking)
If I remember correctly, there was this hypothesis that these things were covered by symbiotic algae so the idea is that they grew tall to increase the photosynthesis of their symbiotic organism (so kind of a giant lichen). But I can't find the source anymore, and I think that there isn't much evidence of any photobiont.
> Prototaxites did not contain chitin, a major building block of fungal cell walls and a hallmark of the fungal kingdom. The Prototaxites fossils instead appeared to contain chemicals similar to lignin, which is found in the wood and bark of plants. ... best considered a member of a previously undescribed, entirely extinct group of eukaryotes
So these are the ancestors of Groot? or Ents? and all manner of "animated trees"?
Acknowledging this is a pre-print, but it is _wild_ that we can do this kind of analysis on a species that went extinct nearly a third of a billion years before the first hominids emerged. Every now and again I'm reminded of just how far we've extended our sensorium as a species.
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.
Perhaps its a Ediacaran biota remnant, that had very diverse groups some of which could be misclassified because the consensus is against Ediacaran relics existing past their period.
This was an interesting read, and reminded me how paleo-biology is the closest thing to exobiology we've got. Looking at the different biomes that emerged on planet earth over a billion years feels equivalent to looking at a thousand different planets at the same time. Basically a thousand chance to see what that 'megayear' produced, life wise.
> All life on Earth is classified within three domains — bacteria, archaea and eukarya — with eukarya containing all multicellular organisms
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?
Cyanobacteria are an example of prokaryotes that, while not truly multicellular, may at times exhibit similar behavior.
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.
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.)
> Both archaea and bacteria, in the three-domain model referenced in the article, are prokaryotes.
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".
I wasn't trying to refute it; I was adding information: The quote didn't mention or imply that there are also single-cell eukaryotes, so I added that detail.
I think prokaryotic bacteria can form biofilms which seems like one step on the road to multicellularity, but that's more like a community, and iiuc most biofilms these days at least contain eukaryotic yeasts. I don't know of any actually-properly-multicellular prokaryotes, but maybe I need to read up?
Is there a point in Earth’s history where if you were to visit you’d find it was just a fungus planet, with no other form of life? Could there have been fungal type creatures that lived, died, and left no trace?
Blue-green algae have colonized fresh water and all moist spaces on the continents billions of years before the appearance of fungi and of the terrestrial green plants. They were accompanied by the ancestors of several groups of heterotrophic bacteria, e.g. Firmicutes and Actinobacteria (the Gram-positive bacteria), which had developed abilities like making spores that could survive dryness and be spread by wind, like also fungi would do later.
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.
Discussions about classifying the domains of life aside, this article implies that there was, or could have been entire domains that are now extinct. Is this the case?
That's really hard to answer without tackling the classification question head on. Do you mean groups that "would have" been considered a domain if humans had been around at the time? Or groups that are in some sense different from other domains to the same degree those domains are from each other?
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.
In my draft reply, I was going to add "is this even the right question", meaning "is the taxonomy more of a human construct than a natural one". It seems the answer is yes.
>Or groups that are in some sense different from other domains to the same degree those domains are from each other?
I'm not a biologist, and especially not a microbiologist, so you should take what I say with a decent chunk of salt. That said, microbes are so wildly diverse that that version of the question sounds a lot like "are there any big extinct clades of microbes", which, I don't know, microbes are pretty persistent. But probably.
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.
Depends on how wide your definition on "domain" is. Most of the dinosaur lineages have gone extinct, it's not too wild an assumption to assume the same is true for entire lineages of other species. So the safe answer to your question is "probably, yes".
Prototaxites, an ancient treetrunk-mushroom-like organism that preceded land plants about 400M yr ago. Its fossils contained plantlike lignin instead of funguslike chitin or chitosan.
https://www.biorxiv.org/content/10.1101/2025.03.14.643340v1
https://en.wikipedia.org/wiki/Prototaxites
hilarious:
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.
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> Upon examining the internal structure of the fossilized Prototaxites, the researchers found that its interior was made up of a series of tubes
Who knew the internet evolved millions of years ago?
it's called the wood wide web (seriously)
Scientists are so adorable
Who knews the scope and breadth of the reach of Al Gore, internet inventor, conceiver of the series of tubes paradaigm. Perhaps he has a tube all the way back 400 million years ago amongst his tube series
https://www.pellcenter.org/did-al-gore-invent-the-internet/
I love the idea that fungi house the Polises of Greg Egan.
> with eukarya containing all multicellular organisms within the four kingdoms of fungi, animals, plants and protists.
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.
> The exact list is up for debate, and currently undergoing change.
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?
Children can memorize all 50 US state capitals, they can memorize a handful of scientific names. If we really wanted to, we could teach them a much more accurate view of the tree of life. Also, I don't think the four-kingdom system has been taught in schools for a while? I went to high school in the late 90s and it wasn't taught then.
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.
I strongly disagree. It's necessary to teach oversimplified things to small minds, even oversimplified to the extent of being incorrect.
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.
To be fair, "functional analysis is infinite dimensional linear algebra" is a saying for a reason, that's an intuition a good professor should have given you. Mine gave me it so well, I still see no difference between R^n and a Hilbert space! (on the dangers of intuitions)
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.
> To be fair, "functional analysis is infinite dimensional linear algebra" is a saying for a reason, that's an intuition a good professor should have given you. Mine gave me it so well, I still see no difference between R^n and a Hilbert space! (on the dangers of intuitions)
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.
A small note on Bourbaki:
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).
I'm torn on this one, because there's no way I can accept "lies-to-children are for their own good", but on the other hand I'd hate to be overburdened with information about Peanut maximums or the Ophthalmic supergroup when all I wanted to know was how to do division or what kind of thing a mushroom is.
Once you accept that a model of reality is always somewhat incorrect you kind of stop seeing this as "lies". Reality is infinitely complex, a model however is finite and therefore understandable.
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.
I think the problem comes in when you have adults teaching kids a simplified model who don't actually understand that is what they are doing.
It is not always conveyed well that they are learning a simplified model, or using an analogy. That's when kids feel lied to.
There are very many pithy sayings to this effect, most famously "All models are wrong, but some are useful" (perhaps by George Box, but I can't find this exact phrase attributed to him)
Even Von Neumann said "truth is much too complicated to allow anything but approximations."
It's not hard. "It's sort of like that, but the details are complicated and you'll learn them later if you want" is a perfectly fine answer.
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".
I was learned enough in school to know when teachers were “teaching” something oversimplified. They uniformly acknowledged that when asked, until one didn’t. That one didn’t care about the nuance and insisted I give the “expected” answer when asked and ruined my attitude in school for years (not the only event, but it didn’t help). Obviously I’ve never forgotten her.
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.
To bring that back into the tech/business world:
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.
It wouldn't be so nice if it was oversimplified and incorrect to the extent that the child realizes it doesn't add up.
Had this experience more than once, but the one that comes to mind:
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.".
From my limited experience (being a child and raising one child) I would say that the problem is more that we (as adults) pretend that the simplified thing is the whole picture.
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.
When I moved to the US in 3rd grade, I was marked wrong for putting negative numbers as answers on a math test. The correct answer was "You can't subtract a larger number from a smaller number".
I had a similar experience, but was fortunate that the teacher took me aside and explained that I was right but they were teaching a simplified version. In hindsight that was really a helpful approach.
I got into an argument with my science teacher in 4th or 5th grade about whether rivers could flow north, because on a globe, north is up.
I suspect that the best approach would be not to "get ahead", but rather see this realisation develop naturally and help it along the way. It's hard to get critical thinking if everything is already criticized before you even come.
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.
Doing this would create a nice opportunity to teach the right and wrong ways to move the needle in scientific discourse (e.g. don't start by holding a press conference about cold fusion).
Graduation could mean an overthrowing of the known-wrong models. Congratulations, here are the next known-wrong models. Now prove these wrong.
Thankfully at very young ages where this is required, that level of critical thinking is very far off
I love your point that avoiding oversimplifications leads to disaster. It explains why I struggle to have a purist mindset while also unable to explain why things go poorly sometimes.
It's necessary to teach oversimplified things to small minds, even oversimplified to the extent of being incorrect.
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.
What's your point then?
All minds alike, big and small, benefit from simplification. I was replying to a comment that specifically referenced "small minds", that's all.
I'm a huge cladistics fan, but insisting that "animal" isn't a useful term is pretty out there, IMHO. Certainly we can (and do!) teach cladistics in high school biology, but does your ideal world have baby books titled with one of the mentioned names...?
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.
I'm not arguing that animal isn't a useful term, but if you're dividing eukaryotes into the major groups, it's not one of them.
> 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.
Interesting, thanks for elaborating! Still not sure I understand sadly, but maybe it’s just different worldviews on how to play language games. Like, you say we don’t need to teach nuance, and that animal is a useful term — but then what does it denote, if not a group of creatures?
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.
> animal vegetable mineral also seems to have held up okay…? It’s a culinary thing
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.)
Why not go the other way, what are you missing if you don’t learnt four kingdoms. Why should that be taught at all.
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:
Well in very practical terms, it gives you a way to name things you see in the forest, to figure out what is edible, and to understand what has a sentience of its own, similar to yours.
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.
There is much more to figure out what is edible and what is not. Considering shrooms alone, it is much more "complicated", so much that there are specialists for that, even, but I agree, could be an useful skill, but not for people who do not even leave the city, I think.
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.
I didn’t say there wasn’t. My point is that explaining to kids why they can pick a strawberry from the forest floor, but leave the fly agaric where it is, despite being the same color, is hard enough without going into the phylogenetic peculiarities.
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.
I agree.
The reality of normal people and parents is that a different basic classification is warranted:
- 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.)
> That covers about all the biology regular people see, to the extent they care about.
Insects and spiders are feeling left out.
That insects and mammals are both Animalia can be nonintuitive for preschoolers.
Parazoa (e.g., sponges), radially-symmetrical creatures (jellyfish, corals, etc.), acoelomates (flatworms, I think), pseudocoelomates (nematode parasites, roundworms), echinodermata (sand dollars, sea urchins, etc), lophotrochozoans (molluscs, some worms, many more).
A 19th century breakdown by Cuvier, influential for a long time, was: Vertebrates, arthropods, molluscs, radiates. (I don't know where worms fit.)
> That insects and mammals are both Animalia can be nonintuitive for preschoolers.
Insects and mammals both walk around. Plants and shrooms don't. Can't get more obvious than that for a kid.
The four kingdoms system is taught because it is useful; not for science, but for everyday communication.
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.
> 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.
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.
People gain understanding when we relate things to their frame of reference. Kids have very limited life experience and their frame of reference is very low. Introducing new concepts that are not relatable would create huge gaps in real understanding.
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.
Except encryption is nothing like a lock, and "stealing data" is a problematic term, as it's stretching the concept of theft way past its common meaning - it's using the term "stealing" in the exact same way people saying "software piracy is stealing" are. So that's already providing completely twisted mental model to kids. And it stems in big part from trying to pass one specific application as an answer to what the thing is.
(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.
Substitution is a new concept for kids. Not something they can readily understand. So you need to explain that in terms of a game. Kids know what secrets are. But from their point of view, why even talk about it if it is secret? Why can't we go to another place and talk secretly? Why do we need to talk secrets in public using substitution? Since they do not see obvious need for it in their daily life and there are workarounds for it, they do not get why there is a need for substitution.
By the time we explain all these to them, they would have already lost interest, or context and would easily forget the whole thing.
> Substitution is a new concept for kids.
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.
Encryption might not even need much any explanation, just using familiar terms: kids come up with "secret languages" all the time between friends and siblings.
> Kids know what secrets are. But from their point of view, why even talk about it if it is secret? Why can't we go to another place and talk secretly? Why do we need to talk secrets in public using substitution?
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.
>>Don't overly simplify things for small minds, it creates a false picture and it kills the imagination.
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 :).
> 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.
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-...
But... but... every cell has one spherical nucleus, one spherical chloroplast for plants or spherical mitochondria for animals, and a host of other features depicted in this helpful diagram that you're going to have to copy from memory.
Would you also propose we skip over the Bohr model of the atom and teach Schrödinger to ten year olds?
went to school till 2012, highly esteemed US high school, was still taught then
May as well add this to the above: https://en.wikipedia.org/wiki/Songline (large amounts of knowledge can be transferred just fine)
> it creates a false picture and it kills the imagination.
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.
Yes I agree. 4 humors were enough for medieval europe, they're good enough for me!! Who can remember all this complicated 'germ theory of disease' liberal junk?! There must be hundreds of these supposed 'germs' out there! No sir, no thank you!
> Who can understand and remember that?
Anybody who is interested in it
At which point started to be important in science that “public can understand”? I think if something is a better explanation for the reality, we ahould go for it, even if it is difficult for the public.
Disclaimer: in this case I have absolutely no idea what is better. But the rationale seems wrong.
We can and, IMHO, should do both. Scientists explaining physical realities, such as gravity, don't use advanced mathematics - it would be pointless.
And then there are viruses, which don't show up on the tree of life at all because there's no consensus that they even constitute "life."
Pretty sure anyone who knows anything about viruses would say they are alive. Or at least as alive as parasitic nano archaea with genomes smaller than the viruses living right next to them... The philosophical way to look at it is humans aren't alive in the space between planets they live inside these little hard shells, then when they get to a planet they go wild using all the other resources around them made of biomass. Viruses are just this, their biome isn't the wider one you participate in instead they are sub-cellular life, in the same way you are sub-planetary life. Humans don't make the oxygen atmosphere on the planet themselves, they parasitize this feature of planets from other life. In the same way viruses use cellular machinery.
This guy agrees with you:
https://www.youtube.com/watch?v=mgS1Lwr8gq8
> Pretty sure anyone who knows anything about viruses would say they are alive
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.
I thought "has a metabolism" (consumes food and produces waste) was the one viruses didn't fit with.
That as well. They also don't respond to their environment.
Men like me also don't replicate by ourselves. Does that mean that we are not alive?
Humans though, can create more humans, but viruses can't create more viruses without using the machinery within a cell that it compromises.
If humans create oxygen with a machine, is that parasitic?
I feel like what trips people up is the abstraction layer.
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.
When classifying living beings, a single classification criterion is not good enough.
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.
Glad to see diamond inheritance being a problem in other fields
It's not a problem, it's a feature.
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.)
They should rewrite biology in Rust.
Just to stay on topic, Rust Language was named after fungus. “over-engineered for survival”
I dunno you can mostly solve for this, look at the majority share of the genome in a compartment with a single membrane contained by the outer membrane (by definition for endosymbiogenesis), with the DNA molecules containing the highest quantity of coding gene content. That's the thing you do the cladistic descent on. Just because I'm carrying a load of bacterial symbionts that are better at digesting wheat doesn't make me a different species to humans who mostly eat rice. That I eventually carry those as an endosymbiont then eventually just a sack of genes doesn't really change who' was the boss in this situation, or who I'm able to reproduce with that entire time as a species either. Symbiogenesis is very much like this, look at Hatena arenicola if you want to see this emerging to see how it interacts with descent. This is really the difference between understanding reproductive relationships specifically, vs wider ecology. I agree that symbiogenesis is like this weird one where its both only going to happen through other ecological relationships and then reproduction. But there really is a clear cut time one turns into the other, with the fate of one of those organisms of the combination "winning" even though profoundly altered. Symbiodinium is probably another good example, it has loads of ecological partners and little remnants of all of those histories in its genetic material and organelle arrangement. But its still an obvious species, with all the other oddball dinoflagellates that act and look like it also appearing to have some common descent from something much simpler and eukaryotic.
As a programmer symbiogenesis is a mixin or interface not a class.
It is not that simple, because a large part of the genes that originally belonged to the mitochondria or to the chloroplasts have been transferred into the nucleus and they are now completely integrated into it, even if evolution trees will show that those genes have a different history than the remainder of the nucleus.
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.
As an unscientific layperson this was a riveting analysis, thanks for interesting reading.
From what I've gathered it's been pretty clear for a while now that archea is basal to eucarya, meaning humans are archea.
One of the great wonders of clustering algorithms is that no matter what k > n you choose, you can construct k clusters. Then we can argue about the clusters and about k. It is said that when Humanity discovers the One True K, the taxonomy will disappear and be replaced by a different one.
I saw this on bsky a few days ago and was fascinated, so glad to see it made its way here! I had this question that went unanswered, so hopefully there's some experts/fellow musers here:
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?
When you feed off decaying matter, hosting a colony of bugs which go out daily, bring back food and leave waste all around your environment sounds like a pretty good strategy when you don't have any way to move to better pastures?
Isn't this a long time before insects and such though?
Wikipedia says:
"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
One reason to grow upward is also just the need for oxygen. Mushrooms do this too - they tend to colonise and begin to fruit in high CO2 concentrations, but eventually want to escape it. And you can see the negative side effects of not being able to do this in mushrooms too (if the CO2 is too intense they grow too fast relative to their thickness [trying to reach air] and become nasty and stringy looking)
If I remember correctly, there was this hypothesis that these things were covered by symbiotic algae so the idea is that they grew tall to increase the photosynthesis of their symbiotic organism (so kind of a giant lichen). But I can't find the source anymore, and I think that there isn't much evidence of any photobiont.
> Prototaxites did not contain chitin, a major building block of fungal cell walls and a hallmark of the fungal kingdom. The Prototaxites fossils instead appeared to contain chemicals similar to lignin, which is found in the wood and bark of plants. ... best considered a member of a previously undescribed, entirely extinct group of eukaryotes
So these are the ancestors of Groot? or Ents? and all manner of "animated trees"?
I am Groot. I am Groot? I am Groot.
Protogroots
Protomolecule.
Allows for Protozombies [as seen on TV]?
It's fine as long as it also allows for warp gates.
Acknowledging this is a pre-print, but it is _wild_ that we can do this kind of analysis on a species that went extinct nearly a third of a billion years before the first hominids emerged. Every now and again I'm reminded of just how far we've extended our sensorium as a species.
Oh, that? That’s just Bob. He helps out around the busy season sometimes. Didn’t know this much about his family, though—neat!
The article about the study writes: `The study has not yet been peer-reviewed.`
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.
> This is a major method of how a single study can perpetuate fake science and fake news.
It's a feature, not a bug.
Clickbait is a bug tagged with WON'T FIX
We should, but we don't.
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.
Perhaps its a Ediacaran biota remnant, that had very diverse groups some of which could be misclassified because the consensus is against Ediacaran relics existing past their period.
This was an interesting read, and reminded me how paleo-biology is the closest thing to exobiology we've got. Looking at the different biomes that emerged on planet earth over a billion years feels equivalent to looking at a thousand different planets at the same time. Basically a thousand chance to see what that 'megayear' produced, life wise.
> All life on Earth is classified within three domains — bacteria, archaea and eukarya — with eukarya containing all multicellular organisms
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?
Cyanobacteria are an example of prokaryotes that, while not truly multicellular, may at times exhibit similar behavior.
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.
> Single cell eukaryotes also exist.
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.)
> Both archaea and bacteria, in the three-domain model referenced in the article, are prokaryotes.
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?
> 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.
I wasn't trying to refute it; I was adding information: The quote didn't mention or imply that there are also single-cell eukaryotes, so I added that detail.
Not everything is an argument or attack.
I know that you weren't trying to refute it, and I know that it's not 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.
I see. Communication is tricky.
I think prokaryotic bacteria can form biofilms which seems like one step on the road to multicellularity, but that's more like a community, and iiuc most biofilms these days at least contain eukaryotic yeasts. I don't know of any actually-properly-multicellular prokaryotes, but maybe I need to read up?
Is there a point in Earth’s history where if you were to visit you’d find it was just a fungus planet, with no other form of life? Could there have been fungal type creatures that lived, died, and left no trace?
No, non-fungi single celled organisms have existed at all times that fungi have existed on earth.
Blue-green algae have colonized fresh water and all moist spaces on the continents billions of years before the appearance of fungi and of the terrestrial green plants. They were accompanied by the ancestors of several groups of heterotrophic bacteria, e.g. Firmicutes and Actinobacteria (the Gram-positive bacteria), which had developed abilities like making spores that could survive dryness and be spread by wind, like also fungi would do later.
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.
Discussions about classifying the domains of life aside, this article implies that there was, or could have been entire domains that are now extinct. Is this the case?
That's really hard to answer without tackling the classification question head on. Do you mean groups that "would have" been considered a domain if humans had been around at the time? Or groups that are in some sense different from other domains to the same degree those domains are from each other?
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.
In my draft reply, I was going to add "is this even the right question", meaning "is the taxonomy more of a human construct than a natural one". It seems the answer is yes.
>Or groups that are in some sense different from other domains to the same degree those domains are from each other?
This.
I'm not a biologist, and especially not a microbiologist, so you should take what I say with a decent chunk of salt. That said, microbes are so wildly diverse that that version of the question sounds a lot like "are there any big extinct clades of microbes", which, I don't know, microbes are pretty persistent. But probably.
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.
Depends on how wide your definition on "domain" is. Most of the dinosaur lineages have gone extinct, it's not too wild an assumption to assume the same is true for entire lineages of other species. So the safe answer to your question is "probably, yes".
It's likely simply a fungus that used lignin instead of chitin. It went instinct when fungus learned to attack lignin.
You never did like my mother.
I wonder what it tastes like
I'm still trying to wrap my head around nitroplasts, another newfound plastid.
[dead]
Common Side Effects, here we come.
There’s one of them at the back of my fridge.
Pretty sure this was a major plot point of the latest resident evil game.