If birds are dinosaurs doesn't that also mean that whales really are fish after all?

[Bohandas]

Ok, so the argument with the birds and dinosaurs goes that since that birds are descended from dinosaurs that makes birds dinosaurs as well.

SO, if we extend that logic, we can note that the tetrapod lineage (which includes the mammals, as well as the birds, reptiles, and amphibians) is descended from the bony fishes. And therefore, by the same logic under which birds are dinosaurs, all mammals, including whales, are technically fish.

(And the birds and dinosaurs are also fish, as are the amphibians, reptiles, etc.)

[Berserk Mecha]

Yeah, you have the gist of it. That's how biological taxonomy works. But keep in mind that words like 'fish,' 'reptile,' 'insect,' and whatnot all have more 'mundane' definitions in regular speech. Just keep in mind that words have different meanings depending on the context.

[Mechalich]

In a strict cladistic taxonomy (which is the currently dominant paradigm and has sound reasons for being chosen but is, like all forms of taxonomy, ultimately arbitrary), only monophyletic groups are accepted. A monophyletic group includes all organisms and taxa sharing a common ancestor.

The problem is that strict adherent to monophyly can be extremely cumbersome linguistically.

Consider, for example, the birds and the dinosaurs. Birds are wholly nested within the Dinosauria - therefore birds are dinosaurs - however very few forms of birds were contemporaneous with dinosaurs and even fewer of those possessed much physiological or ecology similarity to other Dinosaurs during the Mesozoic. Therefore it remains useful and valuable to speak of the 'non-avian dinosaurs' and to exclude modern birds, and essentially all fossil forms, from the discussion. And in fact most modern dinosaur texts do this, having little disclaimers near the front where the author(s) explain that for the purposes of their book when they say 'Dinosaurs' they mean the 'Non-Avian Dinosaurs.'

The same thing unfolds with Fishes. Fishes, as current defined, are a paraphyletic group meaning 'Non-Tetrapod Vertebrates,' since Fishes+Tetrapods is all Vertebrates. Non-Tetrapod Vertebrates is a very useful category for discussions and retains a great deal of use in biology and paleontology (as Fishes). This is particularly true in the distant evolutionary past when diverse assemblages of multiple groups of not closely related fishes were active at the same time, as opposed to today when there are basically only two: Chondrichthyes and Actinopterygii.

[Eldan]

Ok, so the argument with the birds and dinosaurs goes that since that birds are descended from dinosaurs that makes birds dinosaurs as well.

SO, if we extend that logic, we can note that the tetrapod lineage (which includes the mammals, as well as the birds, reptiles, and amphibians) is descended from the bony fishes. And therefore, by the same logic under which birds are dinosaurs, all mammals, including whales, are technically fish.

(And the birds and dinosaurs are also fish, as are the amphibians, reptiles, etc.)

This gets pretty deeply into the weeds of taxonomy, but basically: "fish" is not a systematic term anymore. You may have heard "there's no such thing as fish". There's still animals that biologists will call fish, but fish is no longer a clade (a branch of the tree of life). It's now more a descriptor of morphology.

Side fact: "Reptile" also isn't used anymore by a lot of biologists.

[Willie the Duck]

SO, if we extend that logic...

I mean, I think this gets to the heart of the issue. Taxonomy was never meant to serve the master of someone making this statement. It was meant to be able to have a meaningful discussion about different types of life. Applying formal logic to it ignores that it is a linguistic convention. Linguistics have their own logic (and where they deviate from a logic, they work less well for things like science). However, 'this thing (birds) which can be seen as a subset of another thing (dinosaurs) isn't actually part of the other thing, since we're usually going to want to talk about one or the other, and the rare time we need to talk about them both (discussing that whole evolutionary branch) can have its' own name' would fit perfectly into linguistic logic.

The whole 'birds are dinosaurs' thing has always seemed to me to be an epic moment of pedantry in disservice of actual communication. Reminds me of a person I remember who was a historic bicycle enthusiast. They insisted on calling the bikes in their penny farthing collection their 'ordinary' bikes, while the Schwinn he rode to work in the morning his 'safety' bike. All technically true, but did nothing but confuse every conversation with any non-historic-bike peoples.

Yeah, you have the gist of it. That's how biological taxonomy works. But keep in mind that words like 'fish,' 'reptile,' 'insect,' and whatnot all have more 'mundane' definitions in regular speech. Just keep in mind that words have different meanings depending on the context.

Really, if we are going down the logical conclusion rabbit(fish) hole, whales and other mammals and other tetrapods shouldn't all be 'fish.' They, plus fish, all have a common ancestor, which just happens to also most resemble the fish, so we call it fish (but again it is the common ancestor to all). Whales, people, badgers, lizards, and fish ought really all be 'phish,' or 'ghoti,' or some such other word that signifies the totality of the group (and we do have such a word, vertebrates, but my point is they still shouldn't all be 'fish').

Side note: late-winter/early-spring Friday dining habits of religions can't be discussed here, but suffice to say, I find it amusing that beaver tail really is 'fish' meat after all.

[hamishspence]

Given how many "classic dinosaurs" are turning out to be feathered, and are turning out to have small wings - "birds are dinosaurs" can be quite a useful way of emphasising the relationship.

It's no different from "Humans are apes".

[Aedilred]

Fundamentally it's a difference in approach between biological taxonomics and linguistics. Some time ago, biologists got together and decided it would be useful to classify living things based on their genetic relationship to each other. However, prior to that, everybody had collectively decided to classify things based on extrinsic characteristics that were obvious to an observer, because that's more use to more people day-to-day. The biologists then started from that same system of classification, but over the years have found that the linguistic classification doesn't always match up with the genetic one.

So you end up with situations where the classification under each scheme doesn't match up. That doesn't make either scheme wrong, except by the standards of the other. Of course, to avoid confusion, biologists (who are the later, and better-organised, of the two groups) are adjusting their definitions to avoid confusion.

Statements like "whales aren't fish", "birds are dinosaurs", "humans are apes" should generally be read in the sense of seeking to correct a previous misunderstanding or false assumption, i.e. that while the full truth is generally more complicated than the statement suggests, they are more accurate than their opposite, as generally understood, which in a context where the opposite was previously the general belief, is still useful for the purposes of general knowledge.

[DavidSh]

It seems to me the options are either:
1) Include tetrapods, including humans and whales, as fish, or
2) Further refining the term "fish" to only include ray-finned fish, so excluding lungfish and sharks, or
3) Just deal with "fish" as a paraphyletic group.

[Mechalich]

It seems to me the options are either:
1) Include tetrapods, including humans and whales, as fish, or
2) Further refining the term "fish" to only include ray-finned fish, so excluding lungfish and sharks, or
3) Just deal with "fish" as a paraphyletic group.

#3 is really where things ultimately fall out. Paraphyletic groups are not without utility, especially in cases where the paraphyletic group forms a fairly clear grade group spread across a series of developments below a much more successful crown group (such grades are often referred to as 'Basal ____'). This is particularly important when all members of a grade shared some key trait that separates them from the crown group that is of profound ecological or biomechanical importance. For example 'Jawless Fish' is a paraphyletic group, since it technically includes all the gnathostomes and ultimately all tetrapods, but the lack of jaws still unites these organisms in terms of how they were able to function and that's useful to know.

It's important to recognize that Cladistics values only relatedness. That's important in terms of elucidating evolutionary relationships and is essential for the ability of cladistics to make formal testable evolutionary hypotheses - which it does and which is absolutely essential for the progression of taxonomic knowledge (the old method of evolutionary taxonomy allowed basically any suitably eminent scientist to grandstand on a point until they died). However, relatedness is hardly the be all and end all when describing species. For example, in ecological studies it's often more important to consider feeding method or metabolic rate, and paraphyletic groups like 'jawless fish' or 'parasitoid wasps' which are organized based upon similarities in such traits remain quite valuable in such fields.

xkcd, as usual, hits it right on the money.

[veti]

I mean, I think this gets to the heart of the issue. Taxonomy was never meant to serve the master of someone making this statement. It was meant to be able to have a meaningful discussion about different types of life. Applying formal logic to it ignores that it is a linguistic convention. Linguistics have their own logic (and where they deviate from a logic, they work less well for things like science). However, 'this thing (birds) which can be seen as a subset of another thing (dinosaurs) isn't actually part of the other thing, since we're usually going to want to talk about one or the other, and the rare time we need to talk about them both (discussing that whole evolutionary branch) can have its' own name' would fit perfectly into linguistic logic.

This. See also "tomatoes are fruit", "cereal is soup" and "hamburgers are sandwiches". At some point you're just arguing about the definitions of words, and then you realise you're not actually furthering anyone's knowledge of either birds or dinosaurs and the whole debate is just silly.

[Eldan]

Eh. The point of "tomatoes are fruit" is that words have different definitions depending on context. Botanically, a tomato is a fruit. Legally, ketchup is a vegetable.

Or in other words: colloquially, a fish has fins and swims. Taxonomically, they are a paraphyletic group. Legally, bees are fish in California. None of those definitions are exactly wrong.

[Mechalich]

Eh. The point of "tomatoes are fruit" is that words have different definitions depending on context. Botanically, a tomato is a fruit. Legally, ketchup is a vegetable.

Or in other words: colloquially, a fish has fins and swims. Taxonomically, they are a paraphyletic group. Legally, bees are fish in California. None of those definitions are exactly wrong.

One of the things here is that a lot of people have taken the fact that fish are paraphyletic and processed this through a strict cladistic lens that they don't entirely understand to make claims like 'there's no such thing as fish!' (this includes some cladistic systematists themselves, who played up the shock value of the new methodology fairly heavily during its period of popularization, mostly in the 90s). For example, a quasi-biography/quasi-memoir by Lulu Miller titled Why Fish Don't Exist managed to get itself named a 'Best Book of 2020' by a number of notable outlets despite completely failing to understand or even be about ichthyology at all (lots of interesting stuff about the history of Stanford though).

[LibraryOgre]

Fun related thing: Trees are not a group. They are just something some plants, only very distantly related, "decided" to do, more or less independently.

[Vahnavoi]

Yes, yes, convergent evolution makes fools of us all.

[snowblizz]

Fun related thing: Trees are not a group. They are just something some plants, only very distantly related, "decided" to do, more or less independently.

I refuse to believe this was not a decision taken at the entmoot.

[LibraryOgre]

I refuse to believe this was not a decision taken at the entmoot.

Counterpoint: How can there be an entmoot if there are no trees?

[Bohandas]

It's important to recognize that Cladistics values only relatedness.

Technically shouldn;t that he that cladistics only values descent?

Like hypothetically say there is a species that has a very long generation time, and a population of this species becomes isolated and eventually becomes a distinct species, while retaining the loh=ng generation time. Then sometime later a population of this second species cleaves off and becomes a third species which has, as one of its traits, generations that are much shorter than those of its ancestors. After sufficient time passes a point will be reached where species 3 will be less related to species 2 than species 2 is to species 1 due to the fact that so many more of species 3's generations have passed compared to the other two, yet despite this species 2 and 3 will still constitute a clade by themselves and while species 1 and 2 will not

[Mechalich]

Technically shouldn;t that he that cladistics only values descent?

Like hypothetically say there is a species that has a very long generation time, and a population of this species becomes isolated and eventually becomes a distinct species, while retaining the loh=ng generation time. Then sometime later a population of this second species cleaves off and becomes a third species which has, as one of its traits, generations that are much shorter than those of its ancestors. After sufficient time passes a point will be reached where species 3 will be less related to species 2 than species 2 is to species 1 due to the fact that so many more of species 3's generations have passed compared to the other two, yet despite this species 2 and 3 will still constitute a clade by themselves and while species 1 and 2 will not

That's not how the terms are used. In cladistics relatedness means how closely two species share a common ancestor. That's relatedness in terms of genealogy - ie. you're more closely related to a sibling than to a cousin. What cladistics does not value is similarity. You're quite right that because of variance in selective pressures, population sizes, and so on, evolution does not proceed at constant or equal rates and two closely related species could be considerably more dissimilar than much more distant relatives. A good example here is the Ratites - the group of flightless birds including the ostrich. If you look at a cladogram of that group you'll see that the gigantic elephant birds have as their closest relatives nit the highly similar ostrich or moas, but instead the comparatively tiny kiwis.

And in fact this is one of the key functions of cladistics - teasing out actual evolutionary relationships among groups where there's been a lot of convergent evolution by using math and statistics to evaluate characters rather than intuition. This admittedly works best with genetic data, which is effectively pre-primed for this kind of examination. When there is no genetic data, as in paleontology, researchers have to develop vast matrices of character states for statistical analysis which obviously involves a huge number of judgment calls, especially with regard to higher taxa (meaning large groups above the species level).

[Bohandas]

That's not how the terms are used. In cladistics relatedness means how closely two species share a common ancestor. That's relatedness in terms of genealogy - ie. you're more closely related to a sibling than to a cousin.

Wait, are you saying that cladistics is like genealogy, or that what I said is like genealogy?

Because I know that what I said is definitely like genealogy. My statement is basically equivalent to saying that you're more closely related to your first cousin than you are to your great-grandnephew*, even though the great-grandnephew can trace descent to your parents and the cousin cannot

*(or perhaps more fittingly, that you are more closely related to your fourth cousin than you are to your great-great-great-great-great-great-great-grandnephew, even though, again, the greatx7 grandnephew can claim descent from your parents and the fourth cousin can't even claim descent from your great-great grandparents)

EDIT:
I think I've done the math there correctly.

EDIT:
https://en.wikipedia.org/wiki/Coeffi...f_relationship

[Dame_Mechanus]

What I'm taking from this thread is that if you really think about it, we're all actually just single-celled organisms.

(Yes, I am aware that at certain levels of biology that's not so much wrong as it is imprecise.)

[tomandtish]

It seems to me the options are either:
1) Include tetrapods, including humans and whales, as fish, or....

That gives "So Long and Thanks for all the Fish" a rather horrific new meaning.

[Yora]

This. See also "tomatoes are fruit", "cereal is soup" and "hamburgers are sandwiches". At some point you're just arguing about the definitions of words, and then you realise you're not actually furthering anyone's knowledge of either birds or dinosaurs and the whole debate is just silly.

The really important thing here is that this are not arguments about the definitions of words, but the definitions of technical terms. In hindsight, any biological classifications should not have used any commonly used words at all and only made up new words.

As a professional gardener, I could explain to everyone the difference between the technical terms "thorn" and "barb". But I can also tell you that there really is no point in any of you knowing that, unless you have to pass biology exams.

When two words have been used for the same thing for centuries and suddenly some people in a dusty library decide that they could use those two terms to differentiate between two slightly different manifestations of that thing that matter only to them, that doesn't make the way normal people are using the term wrong.
I couldn't care less that some botanists have decided to create new categories for strawberries and raspberries, but decided to still call blueberries just "berries". (And also call bananas berries as well.)

[Aedilred]

There is of course a fundamental problem with the "birds are dinosaurs" thing, from a general-knowledge perspective anyway. When someone asks you to imagine a dinosaur, you probably think first of a carnosaur or a large sauropod. If asked to imagine multiple dinosaurs you probably bring in ceratopsids and maybe dromaeosaurids, and after that something like a hadrosaur or iguanodon or a stegosaurid. If you are a terrible person, you might picture a dimetrodon, in which case you can gtfo.

These dinosaurs are either very large, or have exotic features (or both), and are very extinct. They are pretty much automatically impressive, especially to children, and are therefore kind of cool. Dinosaurs in general are cool principally because our "type dinosaurs" are cool.

Birds, on the other hand, are just kind of there. (What are birds? We don't know. Birds are impossible to describe.) There are cool birds, of course, but birds in general are not particuarly cool. The "type bird" is probably something like a pigeon or a sparrow.

"Birds are dinosaurs" therefore only has impact because the underlying assumption is that birds are kind of mundane and dinosaurs are cool, so it invites us to look at birds in a different, more impressed way. But the more that understanding spreads the less impact it has, because we start to feel that dinosaurs are really just extinct types of bird and modern birds sink back to the status of being kind of lame relative to dinosaurs, while also potentially damaging the cool status of dinosaurs. And for dinosaurs to become less cool would be possibly the greatest disaster in the entirety of human history.

The point is: taxonomic pedantry is a dangerous tool and therefore should be deployed sparingly outside contained areas (like academia).

[Dame_Mechanus]

There are cool birds, of course, but birds in general are not particuarly cool.

Speak for yourself, I think birds in general are very cool. Especially corvids.

[veti]

The really important thing here is that this are not arguments about the definitions of words, but the definitions of technical terms. In hindsight, any biological classifications should not have used any commonly used words at all and only made up new words.

I don't disagree, but this wouldn't have helped. There are many instances of technical terms being appropriated and slipped into colloquial usage, and rapidly losing their precision in the process. See, for instance, practically all words associated with mental disorders, including "disorder".

All it takes is some scriptwriter to slip them into some popular drama, and that's pretty much it. I suspect this happens eventually to every technical term that's not just too darn' hard to remember or pronounce. (Which is why Latin still has a useful role to play in science.)

[Mechalich]

The really important thing here is that this are not arguments about the definitions of words, but the definitions of technical terms. In hindsight, any biological classifications should not have used any commonly used words at all and only made up new words.

Officially biological classifications are entirely in Latin anyway. 'Fish' is general language, the actual term of art would be Pisces or Ichthyes, just as 'Birds' would actually be Class Aves or Crown Group Aves.

[Eldan]

Doesn't always help either. Dinosaur started as a technical term. Greek, even. Now everyone knows it and it's not the only case.

It can also go the other way: Up until fairly modern times, "Reptile" meant "creeping or crawling animal" (Latin repere, to crawl). Including amphibians and sometimes worms. Then people applied that to a specific group, and it's the commonly understood meaning today.

[Chronos]

Quoth Yora:

I couldn't care less that some botanists have decided to create new categories for strawberries and raspberries, but decided to still call blueberries just "berries". (And also call bananas berries as well.)

In this particular case, I think the botanists just chose lousy terminology. There are so many things that are "berries" in common parlance but not in botanical parlance, and vice-versa, that even if that biological category is interesting and relevant, they should have chosen some better word for it. I mean, it's OK if the terms don't exactly correspond (strawberries were going to occupy a weird spot in any technical classification scheme no matter what you do, for instance), but they should be at least highly correlated.

[Eldan]

Yeah, I think "nut" and "berry" are two words we should justchave avoided in botany. There's no way to make those categories make anatomical sense.

[Mechalich]

In this particular case, I think the botanists just chose lousy terminology. There are so many things that are "berries" in common parlance but not in botanical parlance, and vice-versa, that even if that biological category is interesting and relevant, they should have chosen some better word for it. I mean, it's OK if the terms don't exactly correspond (strawberries were going to occupy a weird spot in any technical classification scheme no matter what you do, for instance), but they should be at least highly correlated.

Some of this is involves deference to the classics. The various European men responsible for generating what eventually became modern botanical and zoological terminology in the 17th through 19th centuries were classically educated and drew upon the works of antiquity, reusing, where they could get away with it terms that appear in Aristotle, Pliny, and similar sources. For example, the terms used in science for birds (Ornith-) and fish (Ichthy-) are both terms used in Aristotle's system of classification.