Lianne wrote:And humans very obviously are not lobe-finned fish. By any definition.
Of course we are.Tetrapods evolved from a group of organisms that, if they were alive today, we would call fish. They were aquatic and had scales and fleshy fins. However, they also had lungs that they used to breathe oxygen. Between 390 and 360 million years ago, the descendents of these organisms began to live in shallower waters, and eventually moved to land. As they did, they experienced natural selection that shaped many adaptations for a terrestrial way of life. Like other terrestrial sarcopterygians, modern humans still carry the evidence of our aquatic past in the way our arms and legs attach to our bodies, as well as in the many other features that link us to our fishy origins.
Sarcopterygii = lobe finned fish.
See also
this page.
The palaeontological record makes clear that the terrestrial verterbates evolved from lobe-finned fishes nearly 400 million years ago during the Devonian, and are therefore members of the Sarcopterygii. The only terrestrial vertebrates still living today are the tetrapods, which originated around 350 million years ago and are defined as that group which comprises the common ancestor of the living amphibians and amniotes plus all its descendants.
'All of its descendants' includes us.
See also
this page.
Fishes, as we think of them, are actually a paraphyletic or "unnatural" group. When scientists say “fishes”, they are discussing a group of organisms that includes all the descendants from a common ancestor. So, the correct grouping of fishes includes us, the tetrapods (amphibians, turtles, crocodiles, birds, squamates, mammals, and countless extinct forms).
Yes, you are a fish. Now that your view of the world has been forever altered, let us explain. In general, there are three main groups of fishes still living today; the cartilaginous fishes (e.g., sharks, rays, skates, chimeras), the ray-finned fishes (e.g., goldfish, tuna, cichlids, clownfish, and our beloved anglerfish from the logo), and the lobe-finned fishes (e.g., coelacanths, lungfishes, frogs, birds, humans). While terrestrial (or land) vertebrates such as frogs, dogs, and humans are classified as tetrapods within the lobe-finned fishes evolutionary lineage, we owe our earliest vertebrate origins to an aquatic environment. In short, just as humans are mammals, mammals are tetrapods, and tetrapods are all fishes. Welcome to the club!
All of these websites are university affiliated. The first one is from Berkeley, the second is from University College London, the third is from the University of Kansas.
This is something well known among biologists. Maybe they haven't been popularising it enough for the public. Things in science tend to trickle down to the public in a slow manner. Most people know or now accept that homo sapiens are great apes, and over the last few decades more and more people have heard that birds are therapod dinosaurs. But I think cladistics and evolutionary biology is still relatively unknown among non-biologists.
I think this article called '
On Being a Fish' written by a biologist is a great read:
If you are troubled to discover that logic has made a monkey out of you, then you are likely to be scandalized by the discovery that you are a fish as well.
In the late Devonian period, members of the lobe-finned fish clade, Sarcopterygii (a clade within Osteichthyes, the bony fish) began to exploit shallow water habitat with increasing frequency. A clade of terrestrial amphibians, ancestral to the clade of all terrestrial vertebrates (Tetrapoda), resulted, ultimately giving rise to the approximately 6,000 partly terrestrial, and nearly 22,000 fully terrestrial, sarcopterygian fish species now living. Dozens of these terrestrial fish taxa have spawned partial (e.g. seals, sea turtles, penguins) or complete (e.g. whales, sea snakes, manatees) reversions to an aquatic habit, though every secondarily-aquatic tetrapod species continues to breathe air, and many continue to breed on land.
AMONG OTHER THINGS, you are a mammal. This is an assertion that no rational person is likely to dispute. Such a person might reasonably ask: “What makes people mammals?” This question would likely be answered as follows: “People have hair, make milk, have a single bone in their lower jaw, and so on.” But this answer is completely wrong. It is, in fact, the correct answer to the question, “What characteristics can be used to recognize a mammal?” The correct answer to the question above is: “People are mammals because they are descended from the most recent common ancestor of all mammals.”
We are a kind of terrestrial fish. And the same logic is used by linguists. Linguists
don't say that French is Latin because it has all of the characteristics of Latin. That simply wouldn't be true. French underwent
significant restructuring, lost many of the things that we understand as 'typical' of Latin at the epogee of the Roman Empire. Modern French would be unintelligble for a native Latin speaker from the Roman times and vice versa.
No, linguists say that French is Latin because it is
descended from Latin. At no point has French ever stopped being Latin, just like at no point have we ever stopped being eukaryotes (organisms whose cells have the nucleus encased within a nuclear membrane). Of course, humans are
modified eukaryotes with over-weening delusions of being masters of the Universe, but we're still eukaryotes and we'll never stop being eukaryotes. Let me just say that it's one of those scientific insights that brings me peace and comfort, like Carl Sagan when he says we're all made out of 'star stuff'. Well, we're distant relatives to a tree, a fungus, a bee, all of which are
also modified eukaryotes that went off in their own different branch on the evolutionary tree.