You’re forgetting our first land ancestor, the fish that decided to come up on land. By certain definitions, all land animals that descended from that ancestor are fish.
It’s an obscure biology joke. Doesn’t play into day-to-day conversations. It is the same logic that causes biologists to say that birds are dinosaurs though—because they descended from dinosaurs. But by the same logic, birds also evolved from lizards, and before that amphibians, and from before that fish, etc. This definition is more like putting all of life into nested boxes. Or perhaps it’s more like the saying “all tigers are felines, but not all felines are tigers”.
This definition is helpful for evolutionary biologists to talk about evolution at grand scale and how we might share certain genes with fish. But it’s admittedly not very helpful for day-to-day conversations that say humans are pretty distant from fish and don’t resemble them much at all now. (Though I admittedly love little biology facts like how our middle ear bones evolved from gills.)
Anyway. I get silly excited about this stuff. Random nerdy rant done.
Catoblepas@lemmy.blahaj.zone 5 weeks ago
Every tetrapod evolved from fish, including humans and pterosaurs.
crazycraw@crazypeople.online 5 weeks ago
ok well yeah I don’t disagree all terapoda evolved from ancestors we call fish but then… they and we were also single cell life forms? OP is trying to say they ‘are fish’ and that’s just a random pull from history instead of direct lineage.
KTJ_microbes@mander.xyz 5 weeks ago
I mean, all eukaryotes are Asgardarchaeota ¯\(ツ)/¯
Single-celled is physiological description, though. But I like OPs point. We have a lot of “some group except” categories. Algae (photosynthesizers except land plants), fish (vertebrates except tetrapods), some definitions of protists (eukaryotes except animals, land plants, and fungi). Practically, we use dinosaurs for the long (>65mya) extinct lineages of the clade that also includes birds. But we don’t have another name for the clade, so the point is lost.
KTJ_microbes@mander.xyz 5 weeks ago
Okay, I don’t think people would call purple bacteria algae, it is a bit more complex, algae are basically cyanobacteria and eukaryotes with plastids except land plants.