Is this a serious statement? If so, wouldn't it be incompatible with the theory of evolution? Would an alien taxonomy of human binary numbers not be a legitimate tree?
What is a cat? It's a small furry quadruped in family Felidae.
- Exception: cats may be quite large (lions, tigers).
- Exception: cats may have no fur (sphinx cats).
- Exception: cats may have fewer than four legs (e.g. due to injury).
Even questions that seem like they should be quite easy to settle, like "are these two gulls of the same or different species?", might be impossible to define formally due to things like <https://en.wikipedia.org/wiki/Ring_species>.
With the specific example of "no such thing as a tree", the category of plants that humans call "trees" isn't a genetically coherent group. Lots of different types of plants have woody stems and bark and leaves, and you can't group together all the things humans call trees without also including things that we definitely don't.
That said, taxonomic groupings can have both wide consensus and be useful, can't they? (Hand on chin... monotremes? hominids??)
Any complex-phenomena that is modeled with with a simplification will have places where that simplification fails. But models can still be highly useful, you just need to choose an appropriate level of abstraction, accept and manage any tradeoffs with exceptions, and move to better paradigm if one emerges.
Sort of like how word/semantic clustering works in LLMs.
This obviously isn't a fully formed idea, but it might make creating taxonomies easier? Taxonomic clusters? Something like that.
The idea is that our taxonomy selects a group named "trees", but there's little internal coherence in that group, which probably results in more online hilly wars in the plant-loving communities than we the laypeople can think of.
See also: is Pluto a planet?
1. There is a coherent parent-child relationship
2. Children have only one parent
3. Children have no lateral relationships with other children
4. Relationships are mediated through parents, not e.g. grandparent-child directly.
5. We can coherently differentiate between different children
etc.
All of these are assumptions that greatly simplify analysis and therefore useful in any situations, but almost always fail in some way on closer inspection.
More generally we go to the saying "all models are wrong, some are useful."
It's possible that he's additionally making a double entendre about abstract tree structures.
OK... technically it's almost everything you think is a berry isn't. But it sure feels like it's everything.
What exactly do you mean by "our taxonomy". There's no plant order, family, or genus called trees. It's just a common plant form. Do you just mean some people's personal mental model?
Someone else already linked to ring species. In microbiology, the definition of species is "stop asking, we agreed to stop fighting about that, no, really, la-la-la-la." Horizontal gene transfer between species is ubiquitous.
In the end I started talking about populations occupying a niche in a specific place at a specific time, and very cautiously tracing properties among linkages of those. But I'm also the one who kept insisting to my labmates that a gene is not a locus of DNA.
It does not in fact require a specific number of clearly delineated categories of organisms where all individual organisms are in one and only one category.
That part is a human invention to try to make sense of the world, rather than part of the mechanics of the world itself. The categorization is probably a necessary invention to try to make sense of the world in a scientific systematic way, and is also inevitably a broken inconsistent subjective biased over-simplified map of the territory.
Voodoo categorisation and dynamic ontologies in the world of OER: https://web.archive.org/web/20190505064655/https://blog.mood...
Ontology is Overrated: Categories, Links, and Tags: https://web.archive.org/web/20070119210402/http://www.shirky...
https://www.science.org/content/article/ancient-virus-may-be... https://www.discovermagazine.com/planet-earth/mammals-made-b...
It would be incompatible with viewing some past views of the mechanisms of evolution as complete; the “theory of evolution” beyond broad outline is something of a moving target that accommodates things like the ways in which taxonomies are approximate abstractions that aid in discussion rather than exact descriptions of reality.
That said, some categories are real, precise, and useful, like integers vs reals vs complex numbers.
Carcinization is a good example: it makes lots of things crab-like, so from a surface taxonomic point of view a flattop crab, a coconut crab, and marbled crab are all pretty crabby. But they're completely different evolutionary lineages, and only one of them is a "true crab".
Where evolution gets less tree-like is MGEs (https://en.wikipedia.org/wiki/Mobile_genetic_elements) as some of them can move between branches.
Yes, exactly. "All taxonomies are don't broken" is not at all "incompatible with the theory of evolution," is the point. The taxonomic layer is pasted on top.
That said, if we had perfect knowledge of the speciation process over the years, would our taxonomy not be extremely close to a perfect tree, where every node has 2+ branches, and branches don't converge to being species-compatible for breeding?
I get convergent evolution, but among large (let's say 10g+) organisms, I'm not aware of convergent evolution resulting in compatible species that would not otherwise have been compatible?
I'm super rusty on this topic, but if there is theory that large organism actual DNA-level speciation (resulting in individuals who cannot reproduce together) has eventuated to convergence back to a new species (who can reproduce together), I'd love a source. I definitely could have very rusty knowledge on this but it seems intuitive to me?
It's very much not. The thing is that every model is a lie, but they can often be very useful lies. The reason we use taxonomic trees is because they're "good enough" but there are tons of places where this really breaks down.
For example, horizontal gene transfer is a huge problem in microorganisms. If you take a soil fungi from one environment and put it in a completely new one it'll become so stressed out that it somehow increases it's rate of HGT and can borrow genes from completely different clades of life like bacteria or algae. HGT actually happens at more macro scales as well. Many of our GMOs take genes from bacteria and put them into plants. Parasitic plants like dodders are known for taking (and spreading) genes from the wide variety of plants it can parasitize (though this might be the wrong word to use given that we now know it plays a host of beneficial ecological roles to its hosts like acting as an above-ground myccorhizal network allowing plants to "talk" to each other). We also know that HGT is quite common across completely unrelated fish and sometimes we even have certain animals, like the hoatzin (Opisthocomus hoazin), that push scientists to completely reevaluate their "tree of life" assumptions[0] (aside: this one's particularly bizarre because it even looks like a medieval depiction of a hybrid beast that took different parts of different animals and mashed them together).
Another more obvious problem is just simple hybridization. It can happen across species with regularity (especially in some plant families), but over the deep history of time much larger jumps seem less "rare". On the micro scale it happens so often that "species" is rarely a useful category. Both botany and microbiology often refer to "species complex" instead
Additionally, it's not really clear what an "organism" often is. For example, lichen are actually a partnership between algae and fungi but are given their own species name. Neither of the two can live without each other. And actually we're finding that it's basically a whole ecosystem of many different algae and a fungi. That might not seem as complex but consider that millions of years ago a germ ate another germ and that eaten germ continued to live and reproduce inside it and eventually came to be known as "mitochondria" and form the basis of basically all animals and plants. To this day they have their own DNA but their reproduction is completely tied to us. Also consider the fact that a human is actually mostly germs. Germs outnumber the number of cells in your body (well this can vary based on antibiotic treatments or how long since your last shit). These complex ecosystems that play critical roles in our skin, eyes, guts, and even brains are necessary to our survival. We wouldn't be able to EAT without them! Lastly, take the example of the man o' war. Similar to lichen, it seems at some point ~13 or so different animals came together and worked together so strongly that they essentially merged and became a single organism. Some of the parts of a man o war can even survive without the rest of the "colony" for a short while (imagine if your kidney could just do it's own thing). But, like lichen, it gets its own species name
As you can see there's a number of flaws in the "tree" view of evolution. It works well enough for most cases and that's why we still use it. But try looking up the debates around a taxonomy of human languages. In theory the same approaches should be able to be applied and the same problems (cultural equivalents of "HGT", "hybridization", and blurry lines between "symbiosis and dependency") can apply.
Edit: oh hole #4: ring species!
[0] https://www.newyorker.com/science/elements/the-bizarre-bird-...
I'm super rusty on this topic, but if there is theory that large organism actual DNA-level speciation (resulting in individuals who cannot reproduce together) has eventuated to convergence back to a new species (who can reproduce together with fertile offspring), I'd love a source. I definitely could have very rusty knowledge on this but it seems intuitive to me?
Taxonomies are a human construction.