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.

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.

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.

For reference, this idea is becoming more popular recently due to the Green brothers: https://youtu.be/-C3lR3pczjo

> Apparently we are all fish. Or fish don't exist

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 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?

Yes, fish, like trees or reptiles, don't exist as a monophyletic group (or clade).

> 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.

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.

Does this hold even if we don't include whales and dolphins in "things that look like fish"?

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).

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.

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.

There's a certain species of ape that takes offense at this, and doesn't like to think of itself as a "fish".

> 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.

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).

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.

"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.

That's 389