# Change in species **URL:** \ **Category:** The BBQ Pit\ **Created:** [August 10, 2026, 9:16pm UTC](https://boards.straightdope.com/t/change-in-species/1032282 "2026-08-10T21:16:45Z")\ **Posts on this page:** 20\ **Page:** 7
**Author:** ![Irishman](https://avatars.discourse-cdn.com/v4/letter/i/b487fb/32.png) [@Irishman](https://boards.straightdope.com/u/Irishman)\ **Post date:** [August 13, 2026, 1:28pm UTC](https://boards.straightdope.com/t/change-in-species/1032282/121 "2026-08-13T13:28:37Z")
> [@cladking](#): > > AI thinks I should add the ideas like evidence is only meaningful when it fits the model of reality, not when it fits a category. Taxonomies are maps, not mechanisms. Evolution is procedural, not statistical. “AL” is pretty bright, but sometimes has his head up his ass. Oh, A I. That’s why we need _serifs_, dammit! Data is data. Evidence is in interpretation. Yes, biology has a lot of maps. That’s the thing with nature - it doesn’t want to fit into neat boxes. But it’s humans tend to like neat boxes to organize our “stuff”. Ideas are “stuff”. “Species” is a nice human box that nature tends to ignore. Concepts like “ring species” test the notion of interbreeding. Fertile hybrids like coyote-wolves and polar-grizzlies strain it the other way. And yes, “fish” is a pre-scientific label for anything from the water. It also is used for a basic shape of sea critter. Except we made scientific carve-outs like whales. None of that negates the comprehensive understanding that Evolutionary Theory provides to biology. ---
**Author:** ![Darwins\_Finch](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darwins_finch/32/20304_2.png) [@Darwins\_Finch](https://boards.straightdope.com/u/Darwins_Finch)\ **Post date:** [August 13, 2026, 2:26pm UTC](https://boards.straightdope.com/t/change-in-species/1032282/122 "2026-08-13T14:26:49Z")
> [@keeganst94](#): > > The fish thing has come up before on some science Youtube channels I watch, and the discussion is usually around how a term that is so basic about something so important to humans is basically meaningless. “Fish” is so broad and arbitrary that it’s basically impossible to make a proper definition of it, which is somewhat unusual even for paraphyletic (not evolutionary based) groups. Like, we’re more closely related to bony fishes than sharks are to bony fishes, and that’s also true for lobe-finned fish and lung-fish compared to ray-finned fish, but we group all of them together and not us. So it’s not evolutionary, but it’s also not about body-plan because of things like lampreys, starfish, or jellyfish. You can’t say a fish is “all mobile multicellular aquatic organisms” because most people wouldn’t consider lobster or clams fish. You can’t say it’s about swimming because of things like octopus, salps, or krill. It just comes down to the old porn thing: “I know it when I see it”. Some random ramblings on ‘fish’, because I’m bored: Traditionally, “fish” have been identified as belonging to one of three vertebrate Classes: 1. Agnatha (“jawless fishes”) 2. Chondrichthyes (“cartilaginous fishes”) 3. Osteichtyes (“bony fishes”) The problem there is that two of those three groups are paraphyletic - that is, they do not include all the descendants of a parent group. Agantha (mostly extinct critters, but with some extant clades such as hagfish and lampreys) is paraphyletic because all veterbrates evolved from aganathan ancestors. So, taxonomically, either Agnatha is paraphyletic (and thus not much use for inferring evolutionary history), or, if one wished to make it monophyletic and include all the descendants, it becomes synonymous with Vertebrata which is not particularly helpful. Chondrichthyes (sharks, rays, etc.) is a monophyletic clade, so we’re good here. Osteichthyes contains two main groups of “fish”: Actinopterygia (ray-finned fish) and Sarcopterygia (fleshy-finned fish). Actinopterygia is monophyletic (The vast majority of what people tend to associate with “fish” are probably Actinopterygians); Sarcopterygia…not so much. Since terrestrial vertebrates (aka Tetrapods) originate from this group, excluding them to only include aquatic members makes them paraphyletic. So, on the one hand, we can say that “fish” is simply taxonomically invalid because it is paraphyletic. On the other hand, we can add some qualifiers, sort of how “non-avian dinosaur” has become vogue when talking about the “traditional” dinosaurs once we started (properly) grouping birds as dinosaurs; thus, we can say that “fish” includes all non-Tetrapod vertebrates. Still not terribly useful scientifically, but it can be useful as “short-hand” taxonomy. And it then excludes invertebrates, such as molluscs, echinoderms, sea jellies, etc., and an assortment of other swimmy things (e.g., sea snakes, amphibians, cetaceans, etc.). Not that that valid taxonomy has ever stopped folks from referring to “shellfish” and “starfish” and “jellyfish”… ---
**Author:** ![Pleonast](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pleonast/32/1183_2.png) [@Pleonast](https://boards.straightdope.com/u/Pleonast)\ **Post date:** [August 13, 2026, 2:45pm UTC](https://boards.straightdope.com/t/change-in-species/1032282/123 "2026-08-13T14:45:04Z")
> [@DSeid](#): > > > [@Norse](#): > > > > Some of us posts replies because we hope that someone else that the OP might learn something. Even if the OP is a lost cause. > > Nah. Pretty much everyone else here at least understands the very basics of natural selection. You’re not teaching here. Don’t forget that not everyone reading this thread has posted in it. ---
**Author:** ![Pleonast](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pleonast/32/1183_2.png) [@Pleonast](https://boards.straightdope.com/u/Pleonast)\ **Post date:** [August 13, 2026, 3:21pm UTC](https://boards.straightdope.com/t/change-in-species/1032282/124 "2026-08-13T15:21:59Z")
> [@Darwins\_Finch](#): > > > [@keeganst94](#): > > > > The fish thing has come up before on some science Youtube channels I watch, and the discussion is usually around how a term that is so basic about something so important to humans is basically meaningless. “Fish” is so broad and arbitrary that it’s basically impossible to make a proper definition of it, which is somewhat unusual even for paraphyletic (not evolutionary based) groups. Like, we’re more closely related to bony fishes than sharks are to bony fishes, and that’s also true for lobe-finned fish and lung-fish compared to ray-finned fish, but we group all of them together and not us. So it’s not evolutionary, but it’s also not about body-plan because of things like lampreys, starfish, or jellyfish. You can’t say a fish is “all mobile multicellular aquatic organisms” because most people wouldn’t consider lobster or clams fish. You can’t say it’s about swimming because of things like octopus, salps, or krill. It just comes down to the old porn thing: “I know it when I see it”. > > Some random ramblings on ‘fish’, because I’m bored: > Traditionally, “fish” have been identified as belonging to one of three vertebrate Classes: > > 1. Agnatha (“jawless fishes”) > 2. Chondrichthyes (“cartilaginous fishes”) > 3. Osteichtyes (“bony fishes”) > > The problem there is that two of those three groups are paraphyletic - that is, they do not include all the descendants of a parent group. > > Agantha (mostly extinct critters, but with some extant clades such as hagfish and lampreys) is paraphyletic because all veterbrates evolved from aganathan ancestors. So, taxonomically, either Agnatha is paraphyletic (and thus not much use for inferring evolutionary history), or, if one wished to make it monophyletic and include all the descendants, it becomes synonymous with Vertebrata which is not particularly helpful. > > Chondrichthyes (sharks, rays, etc.) is a monophyletic clade, so we’re good here. > > Osteichthyes contains two main groups of “fish”: Actinopterygia (ray-finned fish) and Sarcopterygia (fleshy-finned fish). Actinopterygia is monophyletic (The vast majority of what people tend to associate with “fish” are probably Actinopterygians); Sarcopterygia…not so much. Since terrestrial vertebrates (aka Tetrapods) originate from this group, excluding them to only include aquatic members makes them paraphyletic. > > So, on the one hand, we can say that “fish” is simply taxonomically invalid because it is paraphyletic. On the other hand, we can add some qualifiers, sort of how “non-avian dinosaur” has become vogue when talking about the “traditional” dinosaurs once we started (properly) grouping birds as dinosaurs; thus, we can say that “fish” includes all non-Tetrapod vertebrates. Still not terribly useful scientifically, but it can be useful as “short-hand” taxonomy. And it then excludes invertebrates, such as molluscs, echinoderms, sea jellies, etc., and an assortment of other swimmy things (e.g., sea snakes, amphibians, cetaceans, etc.). Not that that valid taxonomy has ever stopped folks from referring to “shellfish” and “starfish” and “jellyfish”… Everything above is correct, and I’d like to make explicit a useful concept: grade. A “grade” is a fuzzy collection of features that describe what a species does and how. The stereotypical grade is “fish”, that is basically that any animal that moves about in the sea. Or, “tree”, which is any tall self-supporting plant. A grade is useful for communicating with other people. “I caught a fish while sitting under a tree” is a useful statement in some contexts even if “fish” could mean _Glyphis siamensis_ or _Henicorhynchus siamensis_ and “tree” could mean _Pinus palustris_ or _Quercus palustris_. We don’t often need scientific precision when describing our afternoon’s pasttime. In terms of utility in describing evolutionary history, the clade, a group of organisms descended from a common ancestor, is superior. Scientists use typically use clades because nature doesn’t make sense without taking into account evolution and using clades makes that easier. > **[Evolutionary grade](https://en.wikipedia.org/wiki/Evolutionary_grade)** > > A grade is a taxon united by a level of morphological or physiological complexity. The term was coined by British biologist Julian Huxley, to contrast with clade, a strictly phylogenetic unit. The concept of evolutionary grades arises in the context of phylogenetics: the study of the evolutionary history and relationships among or within groups of organisms. These relationships are determined by phylogenetic inference methods that focus on observed heritable traits, such as DNA sequences, protei... > **[Clade](https://en.wikipedia.org/wiki/Clade)** > > In biology, a clade (/kleɪd/) (from Ancient Greek κλάδος (kládos) 'branch'), also known as a monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach to taxonomy adopted by most biological fields. The common ancestor may be an individual, a population, or a species (extinct or extant). Clades are nested, one in another, as each branch in turn splits into smalle... ---
**Author:** ![puzzlegal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/puzzlegal/32/3827_2.png) [@puzzlegal](https://boards.straightdope.com/u/puzzlegal)\ **Post date:** [August 13, 2026, 3:40pm UTC](https://boards.straightdope.com/t/change-in-species/1032282/125 "2026-08-13T15:40:11Z")
Interesting post. > [@Darwins\_Finch](#): > > Sarcopterygia…not so much. Since terrestrial vertebrates (aka Tetrapods) originate from this group, excluding them to only include aquatic members makes them paraphyletic. Can you give an example or two of a sacoptergia fish? Also, “sea snakes” aren’t really tetrapods, so i think they are still “fish”. 😆 ---
**Author:** ![Alessan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/alessan/32/465_2.png) [@Alessan](https://boards.straightdope.com/u/Alessan)\ **Post date:** [August 13, 2026, 4:00pm UTC](https://boards.straightdope.com/t/change-in-species/1032282/126 "2026-08-13T16:00:01Z")
> [@puzzlegal](#): > > Can you give an example or two of a sacoptergia fish? Coelacanths and lungfish. ---
**Author:** ![Darwins\_Finch](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darwins_finch/32/20304_2.png) [@Darwins\_Finch](https://boards.straightdope.com/u/Darwins_Finch)\ **Post date:** [August 13, 2026, 4:00pm UTC](https://boards.straightdope.com/t/change-in-species/1032282/127 "2026-08-13T16:00:07Z")
> [@puzzlegal](#): > > Can you give an example or two of a sacoptergia fish? > > Also, “sea snakes” aren’t really tetrapods, so i think they are still “fish”. 😆 The most famous example of a sarcopterygian fish is the coelacanth (_Latimeria_ sp.). And, of course, while sea snakes aren’t, strictly speaking, tetrapods (in that they have no pods, much less tetra of them), they are members of Tetrapoda. ---
**Author:** ![its\_the\_daddy](https://avatars.discourse-cdn.com/v4/letter/i/bb73d2/32.png) [@its\_the\_daddy](https://boards.straightdope.com/u/its_the_daddy)\ **Post date:** [August 13, 2026, 4:06pm UTC](https://boards.straightdope.com/t/change-in-species/1032282/128 "2026-08-13T16:06:52Z")
> [@Pleonast](#): > > Don’t forget that not everyone reading this thread has posted in it. I should draw your attention to the correct spelling of ‘fish’, ie: ‘ghoti’. ---
**Author:** ![ParallelLines](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/parallellines/32/3575_2.png) [@ParallelLines](https://boards.straightdope.com/u/ParallelLines)\ **Post date:** [August 14, 2026, 12:01am UTC](https://boards.straightdope.com/t/change-in-species/1032282/129 "2026-08-14T00:01:05Z")
My pythons and boas have[pelvic spurs](https://en.wikipedia.org/wiki/Pelvic_spur), so vestigial pods! (speaking of evidence of evolution, and “fuzziness” of some common definitions) ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [August 14, 2026, 12:39am UTC](https://boards.straightdope.com/t/change-in-species/1032282/130 "2026-08-14T00:39:52Z")
Something in evolution I find interesting is that very few herd animals stick together in a fight. Wild pigs, cape buffalo, musk ox, and elephants are a few that I can think of. If they did stick together, they would quickly overpopulate and eat themselves out of existence. I wonder if there were periods during evolution where more animals stuck together to fight off predators. Not sure about the American bison but I know they will fight predators.. ---
**Author:** ![RitterSport](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rittersport/32/6326_2.png) [@RitterSport](https://boards.straightdope.com/u/RitterSport)\ **Post date:** [August 14, 2026, 11:32am UTC](https://boards.straightdope.com/t/change-in-species/1032282/131 "2026-08-14T11:32:23Z")
Before this thread, I hadn’t seen you post in a long, long time (maybe we just inhabit different parts of the Board). I just want to say, it’s great to see you back! Your posts on evolution are really fantastic. ---
**Author:** ![Left\_Hand\_of\_Dorkness](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/left_hand_of_dorkness/32/7156_2.png) [@Left\_Hand\_of\_Dorkness](https://boards.straightdope.com/u/Left_Hand_of_Dorkness)\ **Post date:** [August 14, 2026, 12:40pm UTC](https://boards.straightdope.com/t/change-in-species/1032282/132 "2026-08-14T12:40:55Z")
100% agreed. ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [August 14, 2026, 1:25pm UTC](https://boards.straightdope.com/t/change-in-species/1032282/133 "2026-08-14T13:25:20Z")
Yeah. If engaging with trolling even sometimes results in that, it’s worth it! ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [August 14, 2026, 1:25pm UTC](https://boards.straightdope.com/t/change-in-species/1032282/134 "2026-08-14T13:25:56Z")
> [@Spice\_Weasel](#): > > > [@cladking](#): > > > > The only arguments I’ve ever won is by wearing down my opponent to the point they agree to shut me up. > > I don’t know your posting history, but man, that is not the own you think it is. Indeed. This is a common tactic used by people who are wrong, but will not let evidence sway them. Their opponents try to explain the science, and then decide that the person who is wrong isn’t worth the effort. The person who is wrong proclaims victory. But they didn’t win the argument. They lost the argument by demonstrating that they will never see reality. ---
**Author:** ![Left\_Hand\_of\_Dorkness](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/left_hand_of_dorkness/32/7156_2.png) [@Left\_Hand\_of\_Dorkness](https://boards.straightdope.com/u/Left_Hand_of_Dorkness)\ **Post date:** [August 14, 2026, 1:29pm UTC](https://boards.straightdope.com/t/change-in-species/1032282/135 "2026-08-14T13:29:28Z")
An argument is won if at least one participant, and preferably all participants, involved in it come away with a deeper understanding of the matter. Any other definition of victory is Calvinball. ---
**Author:** ![Great\_Antibob](https://avatars.discourse-cdn.com/v4/letter/g/e47c2d/32.png) [@Great\_Antibob](https://boards.straightdope.com/u/Great_Antibob)\ **Post date:** [August 14, 2026, 1:38pm UTC](https://boards.straightdope.com/t/change-in-species/1032282/136 "2026-08-14T13:38:11Z")
I see Pigeon Chess is still quite popular 'round these parts! ---
**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\ **Post date:** [August 14, 2026, 1:43pm UTC](https://boards.straightdope.com/t/change-in-species/1032282/137 "2026-08-14T13:43:44Z")
Note that the OP hasn’t been seen (as listed on his profile page) for 3 days. So he isn’t even reading these responses. ---
**Author:** ![scudsucker](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/scudsucker/32/14101_2.png) [@scudsucker](https://boards.straightdope.com/u/scudsucker)\ **Post date:** [August 14, 2026, 2:05pm UTC](https://boards.straightdope.com/t/change-in-species/1032282/138 "2026-08-14T14:05:37Z")
> [@Darren\_Garrison](#): > > Note that the OP hasn’t been seen (as listed on his profile page) for 3 days This thread, and especially the OP’s username brought to my mind the Hans Christian Andersen story, “The Emperor’s New Clothes” for some reason. That Emperor was very much unclad, and also very much unwilling to observe the obvious. ---
**Author:** ![Darwins\_Finch](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darwins_finch/32/20304_2.png) [@Darwins\_Finch](https://boards.straightdope.com/u/Darwins_Finch)\ **Post date:** [August 14, 2026, 3:27pm UTC](https://boards.straightdope.com/t/change-in-species/1032282/139 "2026-08-14T15:27:17Z")
> [@RitterSport](#): > > Before this thread, I hadn’t seen you post in a long, long time (maybe we just inhabit different parts of the Board). I just want to say, it’s great to see you back! Your posts on evolution are really fantastic. Thanks! I took a break from the board back in 2016 for mental health reasons, but came back earlier this year. Still getting used to the new look and feel, but glad to be here! ---
**Author:** ![Euphonious\_Polemic](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/euphonious_polemic/32/3002_2.png) [@Euphonious\_Polemic](https://boards.straightdope.com/u/Euphonious_Polemic)\ **Post date:** [August 14, 2026, 3:57pm UTC](https://boards.straightdope.com/t/change-in-species/1032282/140 "2026-08-14T15:57:59Z")
> [@Der\_Trihs](#): > > > [@Spice\_Weasel](#): > > > > Is this performance art? > > No; it’s faith. Define the “truth” _first,_ and demand all evidence be twisted to fit it or be ignored. I agree with Spice Weasel. This is an act. [Previous page](https://boards.straightdope.com/t/change-in-species/1032282.md?page=6) [Next page](https://boards.straightdope.com/t/change-in-species/1032282.md?page=8)