Incredibly, I actually did learn this today because it was in the NYT crossword and I went down a very similar rabbit hole. I never made it to Freud, though, after I discovered and got sucked into the European Union Eel Regulation Framework[1].
If you, like me, are masochistically fascinated by this kind of “I can’t believe this is a real thing that the government actually does” documentation I recommend giving it a once-over.
They all breed in the Sargasso Sea, so... critical habitat risks.
adrian_b · 1h ago
The author does not appear to be aware of this but eels are not the most snake-like among fish.
Already the Ancient Greek and Roman authors had a classification of fish, where eels where less snake-like, because they have pectoral fins, while the most snake-like group of fishes consisted of morrays and lampreys, both of which have neither scales nor any kind of fins, being less similar to other fish than eels.
The loss of the legs and the elongation of the body, resulting in a snake-like form has happened not only in many groups of vertebrates, including eels and morrays, caecilian amphibians, snakes and several groups of legless lizards, but also in many worms, e.g. earthworms and leeches, which evolved from ancestors with legs. Even among mammals, weasels and their relatives have evolved towards a snake-like form, though they still have short legs.
ghkbrew · 2h ago
I regret to report that there is surely no such thing as a fish.[0]
It also reminds me of a bit in Unsong, a book where there's quite a bit of discussion about whether the whale is a fish or not.
bloak · 1h ago
There's a chapter in Moby-Dick with a similar discussion.
IAmBroom · 37m ago
Nope.
But geese are.
cl3misch · 2h ago
I read the blog post. Then I thought "surely the eels in my local southern German lakes can't be from the sea". But sure enough, the European eel hatches close to the Bahamas.
I audibly wtf'ed multiple times while going down this rabbit hole. Thanks!
I had the same thought. I always knew they were fish but always assumed they were local fresh water fish. I mean everyone talks about how Salmon does this incredible journey. If there was another species which did something equally incredible I should have heard about it.
Thanks for the link! A rabbit hole indeed.
maxglute · 36m ago
TFW random eel content popping up while i enjoy my unagi.
It goes from 410 to 389 in streetview. Gotta be in the middle of those.
rawling · 19m ago
I put in 399 and I got an apartment block.
boesboes · 2h ago
Apparently we are all fish. Or fish don't exist.
To explain: if you want to define a taxonomy in which all things that look like fish and swim are 'fish' then we are too. We are more closely related to most 'fish' than sharks are. I.e the last common ancestor of herring AND sharks is older than our & herring's LCA.
SAI_Peregrinus · 1h ago
Fish exist, and we're not fish. Fish just isn't a monophyletic taxonomic category. If you allow "fish" to be a list of all those animals that look like "fish" and swim like "fish", you'll end up with a bunch of animals who's most recent common ancestor is also the most recent common ancestor of all tertrapods (including humans), so "we are all fish". But if you don't demand a single common ancestor & instead just have a list of several different taxonomic classes you can define "fish" as anything in the list, thereby excluding humans.
It's like the difference between culinary berries (sweet parts of plants) and biological berries (parts of plants containing the seeds internally). Tomatoes are not a culinary berry, but are a biological berry. Strawberries are a culinary berry, but not a biological berry (the seeds are on the outside). It's confusion caused by mixing a jargon use of a word with the common use of that same word.
Looking at the Wikipedia article for fish, it looks like a reasonable definition would be:
* Everything in the subphylum vertebrata (i.e. vertibrates)
* Except tetrapoda (tetrapods: amphibians, reptiles, mammals and the like).
It's not perfect because tetrapoda does fit within vertebrata in a biological / genetic sense (as a sibling comment put it: fish is not a monophyletic group). But it's a precise enough definition that I don't think we need to claim that we're all fish or that there's no such thing as a fish (as the QI elves would say).
dillydogg · 1h ago
But what about our precious friends the coelacanths?
Edit: foolish me coelacanths are not tetrapods
But a better question may have been regarding the lungfishes
No comments yet
daedrdev · 1h ago
Mammals include orcas and whales
SideburnsOfDoom · 1h ago
And orcas and whales are not fish.
ralfd · 2h ago
At least you could exclude jawless, cartilaginous, and lobe-finned fish. That would leave you with 99% of what people call fish. But as said it would exclude sharks, they would need to be their own group.
More bothering me is that there are no trees. There are just many plants which have independently evolved a trunk and branches as a way to tower above other plants to compete for sunlight.
pavel_lishin · 2h ago
Yeah. Terms like "fish" and "tree" are more like "quadruped" than they are like "rodent".
IAmBroom · 50m ago
Except that "quadruped" is (AFAIK) phylogenetic: Tetrapoda.
ndsipa_pomu · 26m ago
Except that you can come up with a decent definition of "fish" and "quadruped", whereas there's no definition of "tree" that covers all the cases.
It's much more valid for trees. They've evolved many times and there is no common ancestor that is itself a tree.
Fish evolved once, and then a specific subgroup is excluded. That's fine.
handsclean · 2h ago
This is just a consequence of life beginning in the ocean. Land-based life is related to ocean-based life at the point of the fork, and there were prior forks which, by definition, remained in the ocean.
bryanlarsen · 1h ago
Not a surprising result given that complex sea life significantly predates complex land life. It's had much longer to genetically diversify.
Similarly either we are all black, or black as a genetic race doesn't exist. The genetic diversity within humans in Africa exceeds the diversity outside of it. You can find two "black" Africans that are more genetically different than an Australian aborigine compared to a red headed Irishman.
IAmBroom · 46m ago
Not sure of that last claim, as Australian natives are (AFAIK) considered one of the very oldest groups to separate from other Homo sapiens. IIRC, they're the only major group that has no Neanderthal DNA, because they migrated/were separated before H. sapiens met H. neanderthalis.
Dylan16807 · 1h ago
> Apparently we are all fish. Or fish don't exist.
I get very annoyed at this argument. It pretends that the only classification systems are strictly following a single ancestor or ignoring ancestry entirely.
The common definition of fish is neither of these. It's paraphyletic. Everything descended from A, except things descended from B and C.
sestep · 2h ago
For reference, this idea is becoming more popular recently due to the Green brothers: https://youtu.be/-C3lR3pczjo
topaz0 · 1h ago
Or the book "why fish don't exist", which got a lot of press last year if you consume media outside of youtube.
IAmBroom · 46m ago
That's a month old. I heard it over a year ago.
nixpulvis · 2h ago
I could be way off base here, and I don't honestly know much about biology... but just because two species don't have recent common ancestors, doesn't mean they couldn't have co-evolved and ended up very similarly, right? Wouldn't this be grounds for relating their classification?
jgwil2 · 51m ago
They could have a similar phenotype without being genetically similar.
philwelch · 2h ago
Convergent evolution happens all the time but taxonomy is nonetheless based on ancestry.
SAI_Peregrinus · 1h ago
Also "horizontal gene transfer" happens in bacteria, and even happens in multicellular sexually-reproducing organisms after viral infection in some cases. Taxonomy should be a directed acyclic graph, not a tree.
taeric · 1h ago
For a fun somewhat related topic, it was neat to see the hierarchy of strings and characters in Common Lisp the other day. Can be used to illustrate a bit of the shortcoming of using ancestry to answer if two things are related. https://lispcookbook.github.io/cl-cookbook/strings.html#stri...
IAmBroom · 54m ago
You should have used "phylogenetic taxonomy". A "taxonomy" is literally any way of grouping organisms, like "all red things" (mature salmon, some roses, red algae).
tgv · 2h ago
> things that look like fish
Well, apart from the circularity, we don't look like fish, do we? What we look like, we define, just like we define what 'fish' is. There's no need to go all Linnaeus about it.
taeric · 1h ago
My stance is somewhat similar, I think? Arguments that try and precisely define "fish" in some sort of "context free" space are doomed because people don't think of terms outside of context.
rikroots · 1h ago
Human embryogenesis would like to disagree with you.
Evolving from doesn't make you the thing, does it? It makes you something else. Fish in particular, since that's a group of animals named by us, based on physical appearance.
dragonwriter · 36m ago
> Evolving from doesn't make you the thing, does it?
Depends on the system of taxonomy; in phylogenetic taxonomy, that’t exactly how membership in a clade is determined.
IAmBroom · 39m ago
Ontogeny does NOT recapitulate phylogeny.
Exactly.
But I believe in weak Haeckel's principle.
madcaptenor · 2h ago
Does this hold even if we don't include whales and dolphins in "things that look like fish"?
LeifCarrotson · 1h ago
Those aren't the problem. The real issue is that the tetrapods which evolved into most land animals (amphibians, reptiles, birds, mammals) are further down the phylogenetic tree of bony fishes than coelacanths and lungfish, which are further down the tree than cartilaginous fishes like sharks and rays, which are further down the tree than jawless fishes like lampreys and hagfish.
In taxonomy, it's called a "Paraphyletic group" [1].
Yes, the issue is the ancestry between "fish" being very distant. It doesn't matter if you exclude marine mammals. Many fish in the ocean are still more closely related to beings on land than another fish. It's the equivalent of calling all flying animals birds. If we excluded bats from this new definition of "bird" then a bumblebee won't suddenly become more closely related to a Buzzard.
dillydogg · 1h ago
It surely does. This website is a good way to visualize the common ancestor of the bottlenosed dolphin and zebrafish. It's the same common ancestor as a human and a zebrafish, or a bird and a zebrafish. It's an ancient ancestor!
Apparently if you go even further back and apply the same logic, we are all fungi. In fact, we both can synthesize vitamin D from sunlight, although I'm not sure if we do it the same way or use it for the same purpose.
IAmBroom · 41m ago
Fungi and Animalia split from Eukarya. Fungi didn't exist before then.
I realize "we are all eukaryotes" doesn't have the same punch...
calibas · 1h ago
There's a certain species of ape that takes offense at this, and doesn't like to think of itself as a "fish".
IAmBroom · 44m ago
You know what I say to that? Go back to Sumatra, ya ginger galoot!
"I want to be like you-u!" Yeah, right.
littlestymaar · 2h ago
Yes, fish, like trees or reptiles, don't exist as a monophyletic group (or clade).
cybice · 2h ago
While reading an article, I went to check how an eel differs from a lamprey - and I found out that a lamprey isn’t actually a fish
Dylan16807 · 1h ago
"Lampreys /ˈlæmpreɪz/ (sometimes inaccurately called lamprey eels) are a group of jawless fish"
I'm not sure what you mean? Jawless fish are pretty far from most fish but that's not much of a reason to say they're not fish.
cybice · 27m ago
GPT-5 says that now its not.
So while lampreys are technically fish under traditional definitions, modern evolutionary science places them as one of the most primitive branches of vertebrates—not part of the “true” jawed fish group.
topaz0 · 1h ago
Suggest looking up the word "spat" and relatedly "spate"
m0llusk · 1h ago
Also interesting that eels, much like crabs, are a body form that has evolved many times in various ancestral lineages.
riffraff · 1h ago
usual reminder that European eels[0] are close to extinction, being critically endangered, and yet, for reasons, they are still being fished and eaten all over.
Wait until you figure out that cucumber is a fruit.
josefritzishere · 1h ago
Everything is a secret third thing.
pbd · 2h ago
I love these 'wait, what!' moments in biology. Thanks for sharing this - definitely going to be my fun fact for the week!
rideontime · 2h ago
I was curious to see what would happen if I clicked the "Unsubscribe" button at the bottom of this page, and sure enough, it told me that I unsubscribed. Neat.
netsharc · 2h ago
Huh, someone (OP?) will potentially miss the next edition of this newsletter.
I just noticed the URL has a lot of parameters, probably for their analytics to identify the subscriber.
pavel_lishin · 2h ago
It looks like the URL won't load without both the p (presumably page?) and s (presumably subscriber?) parameters, and there was no other way to share it.
I wonder what the point is of having a newsletter that doesn't have an indexed web version. It's just a blog, right? Just one that happens to arrive in your inbox as well. What's the downside of listing the entries on the author's homepage as well, making them available to everyone?
If you, like me, are masochistically fascinated by this kind of “I can’t believe this is a real thing that the government actually does” documentation I recommend giving it a once-over.
1. https://oceans-and-fisheries.ec.europa.eu/ocean/marine-biodi...
Already the Ancient Greek and Roman authors had a classification of fish, where eels where less snake-like, because they have pectoral fins, while the most snake-like group of fishes consisted of morrays and lampreys, both of which have neither scales nor any kind of fins, being less similar to other fish than eels.
The loss of the legs and the elongation of the body, resulting in a snake-like form has happened not only in many groups of vertebrates, including eels and morrays, caecilian amphibians, snakes and several groups of legless lizards, but also in many worms, e.g. earthworms and leeches, which evolved from ancestors with legs. Even among mammals, weasels and their relatives have evolved towards a snake-like form, though they still have short legs.
[0] https://quoteinvestigator.com/2024/12/04/no-fish/
But geese are.
I audibly wtf'ed multiple times while going down this rabbit hole. Thanks!
https://en.wikipedia.org/wiki/European_eel
Thanks for the link! A rabbit hole indeed.
"We don't know where eels come from" https://www.youtube.com/watch?v=y0UIJekwyPY
https://www.newyorker.com/magazine/2020/05/25/where-do-eels-... ("Where Do Eels Come From?" (2020))
https://news.ycombinator.com/item?id=23265000 (56 comments)
https://www.youtube.com/watch?v=On2V_L9jwS4
https://www.youtube.com/watch?v=-C3lR3pczjo
https://www.youtube.com/watch?v=ElpRJQ2FZiM
The address in the footer appears to be a cafe: https://www.google.com/maps/place/389+Court+St,+Brooklyn,+NY...
To explain: if you want to define a taxonomy in which all things that look like fish and swim are 'fish' then we are too. We are more closely related to most 'fish' than sharks are. I.e the last common ancestor of herring AND sharks is older than our & herring's LCA.
It's like the difference between culinary berries (sweet parts of plants) and biological berries (parts of plants containing the seeds internally). Tomatoes are not a culinary berry, but are a biological berry. Strawberries are a culinary berry, but not a biological berry (the seeds are on the outside). It's confusion caused by mixing a jargon use of a word with the common use of that same word.
https://www.loweringthebar.net/2022/06/court-says-bees-are-f...
* Everything in the subphylum vertebrata (i.e. vertibrates)
* Except tetrapoda (tetrapods: amphibians, reptiles, mammals and the like).
It's not perfect because tetrapoda does fit within vertebrata in a biological / genetic sense (as a sibling comment put it: fish is not a monophyletic group). But it's a precise enough definition that I don't think we need to claim that we're all fish or that there's no such thing as a fish (as the QI elves would say).
Edit: foolish me coelacanths are not tetrapods
But a better question may have been regarding the lungfishes
No comments yet
More bothering me is that there are no trees. There are just many plants which have independently evolved a trunk and branches as a way to tower above other plants to compete for sunlight.
https://www.theatlantic.com/science/archive/2018/04/how-do-y...
Fish evolved once, and then a specific subgroup is excluded. That's fine.
Similarly either we are all black, or black as a genetic race doesn't exist. The genetic diversity within humans in Africa exceeds the diversity outside of it. You can find two "black" Africans that are more genetically different than an Australian aborigine compared to a red headed Irishman.
I get very annoyed at this argument. It pretends that the only classification systems are strictly following a single ancestor or ignoring ancestry entirely.
The common definition of fish is neither of these. It's paraphyletic. Everything descended from A, except things descended from B and C.
Well, apart from the circularity, we don't look like fish, do we? What we look like, we define, just like we define what 'fish' is. There's no need to go all Linnaeus about it.
https://www.bbc.co.uk/news/health-13278255
Depends on the system of taxonomy; in phylogenetic taxonomy, that’t exactly how membership in a clade is determined.
Exactly.
But I believe in weak Haeckel's principle.
In taxonomy, it's called a "Paraphyletic group" [1].
[1]: https://en.wikipedia.org/wiki/Paraphyly#Examples
https://www.onezoom.org/life/@Gnathostomata=278114?otthome=%...
Apparently if you go even further back and apply the same logic, we are all fungi. In fact, we both can synthesize vitamin D from sunlight, although I'm not sure if we do it the same way or use it for the same purpose.
I realize "we are all eukaryotes" doesn't have the same punch...
"I want to be like you-u!" Yeah, right.
I'm not sure what you mean? Jawless fish are pretty far from most fish but that's not much of a reason to say they're not fish.
[0] https://en.wikipedia.org/wiki/European_eel
I just noticed the URL has a lot of parameters, probably for their analytics to identify the subscriber.
I wonder what the point is of having a newsletter that doesn't have an indexed web version. It's just a blog, right? Just one that happens to arrive in your inbox as well. What's the downside of listing the entries on the author's homepage as well, making them available to everyone?