Why Humans are Fish [If that word refers to anything 'real' at all]

[Nesslig20]

@Rumraket

Thanks for the lengthy reply but I couldn’t find anywhere that you explain in what sense a group of organisms is real. But you’ve used the world real many times in your reply, but only in sentences where you merely assert the group, clade, fish is real. What is it about the clade that makes it real?

Of course, I said a lot more prior to that where I laid down the argument for why cladistics is objective (unlike phenetic and evolutionary taxonomy) to support that ‘fish’ - as a clade - is a real group. See here (emphasis mine):

@Nesslig20

There was a fierce debate between these schools [of taxonomy] regarding which is the best one and on what criteria. There was one criteria that phenetics used to argue for their own favor, but one advocate of cladistics actually showed that - even according that criteria of the advocates of phenetics - cladistics is better. Another criteria, one that is more relevant to the question that was asked to me, is objectivity; i.e. which classification system produces groups that represents a real and unambiguous property of nature. In order for phenetics to be objective, the identified taxa must represent some sort of natural phenetic hierarchy; and members of each taxon defining an ‘overall similarity’ which represents an ‘idealism’ of form for each taxon. However, there is no such thing as a real phenetic hierarchy in nature. Phenetic taxonomy is fundamentally subjective. This was one major critique aimed at phenetics from the evolutionary taxonomy side. This is ironic, since the same argument could be used against the paraphyletic taxa that evolutionary taxonomy considers to be valid. Evolutionary taxonomy may exclude certain descendant groups based on whether they have evolved to the point of being ‘different enough’ from their ancestors. However, how do we determine whether any descendants should left out? And if so, how do we determine which should be left out and which should stay? How ‘different’ is ‘different enough’? That is arbitrary. Thus, paraphyletic taxa are not objective (they don’t represent real properties of nature).

What about the phylogenetics based cladistics, with its monophyletic taxa (clades)? Well, unlike with phenetics, there actually is a natural phylogenetic hierarchy. It’s is a plain fact that organisms are more closely related to some than they are to others. Phylogenetic relationships are REAL, independent on what we think about them. Thus cladistics, specifically monophyletic taxa, are objective as they are representative of something that is real.

To summarise: There is a REAL natural phylogenetic hierarchy. Cladistic taxonomy represents this hierarchy as monophyletic taxa. i.e. clades. Hence why cladistics is objective. Ergo, clades are ‘real’ groups, unlike those that are paraphyletic or polyphyletic.

@Rumraket

I think you’re actually contradicting yourself without having realized it. Particularly where in the previous thread you responded to me like this:

@Nesslig20

You’ve just explained why the perceived distinction is an illusion, which only proves my point even further.

So the clade fish is only recognizable to us now as a distinct clade because a long line of it’s ancestors have gone extinct, leaving us with this illusion that only this particular set of characters seemingly sufficiently different from members outside of the clade, now exist only among members of the clade. Had those ancestors still existed, it would much easier to see how arbitrary it is where you put the line and say “that population right there, that’s objectively the common ancestor of fishes, all it’s decendants belong to the fishes, and all it’s ancestors do not”.

You misunderstood what I was saying there. Using your words, but making a few edits, what I meant by that statement is the following:

So the common paraphyletic sense of fish is only recognizable to us now as a distinct group because a long line of ancestors have gone extinct, leaving us with this illusion that the particular set of characters of some descendants (tetrapods) makes them seemingly sufficiently different from members of the fish group. Had those ancestors still existed, it would much easier to see how arbitrary it is where you put the line and say “these descendants right there, that’s objectively a new group distinct from - and not part of - the fish group. All it’s decendants don’t belong to the fishes, even while all it’s ancestors do”.

But to address the point that you were making here; about the fact that we couldn’t pint out the very first member of a group by looking at them. Not even theoretically, because at every point the direct ancestors / descendants would still look pretty much the same. But this has little to do with. cladistics. A clade is not defined by looks (phenotype), but in terms of phylgenetic relationships, i.e. a common ancestor + all descendants. That group is real. It exists independent of what we think about it. It exists regardless whether we are theoretically able to identify that specific ancestor (or ancestral population) among all the ancestors or not. Your point here (It’s impossible to point out the ‘first’ of a group based on phenotype) is actually a point against phenetics, NOT cladistics.

@Rumraket

Clades, too, are arbitrary distinctions. There isn’t anything that compels us to the clade fish in particular, other than quirks of fossilization and paleontological discovery. That is one of the problems with the old concept of taxonomic rankings into “domains”, “kingdoms”, “phyla” etc.

As explained previously, clades are not arbitrary. But seeing how you are referring to Linnaean ranks as an example of something that has the same problem, I think I can see the issue you are referring to. It’s true that assigning ‘ranks’ to groups, even if the groups are clades, is arbitrary. It is similarly arbitrary as to what name we assign to each clade. But the issue of picking a name for a clade is something I have already addressed preemptively in the very last paragraph of the top comment. Regardless what name (or rank) we give to the clade, it doesn’t affect the realness of the clade.

@Rumraket

And I think this is relevant to the previous discussion because it raises the issue of whether we can say that a group of entities sharing certain characters is “real” or not. You have implicitly admitted that we can group things by certain characters and that those groups really do refer to something physically real, even if that realness doesn’t exist at a fundamental physical level.

I’d think if the grouping represents something objectively real, then yes. Although, I don’t think I have admitted that we can group things specifically by “certain characteristics”. At least not here, as I have specifically argued against phenetics. Sure, a clade is inferred by identifying the synapomorphies, but that is how we infer the group, it’s not how the group is defined.

EDIT: This part below, I will copy paste it back to the previous thread since that is relevant to the original topic.

When it comes to the previous discussion, we have agreed (unless I am mistaken) that sex is a spectrum, with male and female representing the opposite ends of the spectrum, and intersex or DSD representing the middle. In this sense, male and female are real. However, if you treat ‘male’ and ‘female’ as ‘distinct (binary) groups’, I would say that they are not real. In this case, these are subjective constructs, similar to what portions of the spectrum of visible light constitutes the color ‘red’ or ‘blue’.