Giant, fungus-like organism may be a completely unknown branch of life

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.

it's called the wood wide web (seriously)

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.

> 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?

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."

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.

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.

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?

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.

I am Groot. I am Groot? I am Groot.

Protogroots

> This is a major method of how a single study can perpetuate fake science and fake news.

It's a feature, not a bug.

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.

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.)

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?

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.

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.

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".