Thanks for the detailed answer, it's cool to get some new education in this stuff. I had to do more research and procure some fermented grains before responding, hence the delay. Sorry again for any amateurish jargon. I like to think my concepts are good even if the details are wonky.
True cladists do not accept any paraphyletic groups. Period. Cladistics is very cult-like, they like hard rules and paraphyly (or polyphyly) sends you straight to hell. Do not pass go, do not collect $200. Sometimes old non-monophyletic names get used as shorthand among like-minded people (every language has slang, right?) but when pressed, no cladist would actually say these were acceptable groupings. I think most scientists would be pretty offended at the citation of a wikipedia article as evidence of the prevailing opinions in their profession. Actually, I think any professional would be pretty offended. But it's particularly true in this case because primatologists hardly count as real scientists by folks who study other groups, since they are more interested in themselves and where they come from than the world around them (tongue in cheek here, no one get offended) so wikiApe is perhaps even less representative of modern cladistic opinion than say wikiFish.
Evolutionary taxonomists (not really the same as cladists, any more than Christianity is just a flavor of Judiasm) on the other hand might accept a paraphyletic grouping as "okay", since they tend to be mostly cladistically minded but with a bit of old phenetic/gradal flavor. Not a bad thing necessarily, as long as everyone is on the same page about what is meant. It is useful to say (for example) "in fishes, ions are exchanged through the gills". Sure, "fishes" is not a good cladistic group in this sense (as in a cladistic sense we are fishes as well, and we clearly do not use gills for ion exchange) but as long as everyone is clear that fishes is "slang" for aquatic non-mammalian vertebrate, it's a useful word. The problem is that because cladistics has such strong rules about what can be named and what can't, that folks apply cladistic rules to non-cladistic names and assume that because a word is applied to a group it must tell you something about the history of that group.
Thanks for sorting that out. When I used "cladistics" previously I guess I meant evolutionary taxonomists... first time I've heard that term.
What I mean to refer to is the conventional view, a "loose cladistics" that respects some taxonomic tradition, as presented in science articles in the New York Times, Scientific American, Nat Geo, Science, Nature, etc.
My view is that cladistics (strictly) will be slowly pushing aside the traditional taxonomic groups and for good reason -- the genetics will demand it. This is not to say we should start calling all tetrapods as a kind of "fish" (your example, a good one) but the relationship is definitely there, and it's possible that we'll see more similarities at the cellular and genetic level between salmon and humans than either of us to sharks. The ideal solution to cases like this IMO is to have some other technical term that is monophyletic and non-misleading that can take the place of the traditional polyphyletic term -- in this case, something like "ossovertiformes" (my invention) instead of "bony fish", just so we don't have to say that tetrapods are fish. The same applies to mammals and birds being subgroups of reptiles -- we don't want to call them reptiles since that conflicts with our prejudices, so we say instead that they are all amniotes, a nice solution, and that reptiles are now a polyphyletic, human-friendly (and genetics-hostile) group.
Getting back to monkeys, I think this is again a problem with colloquial slang. I will not pretend to be an expert on this particular group (far from my specialty, as is obvious by my biases!) but my understanding is that when modern biologists talk about monkeys, they mean the EXTANT tail-retaining primates (and this is slang for the proper names of these lineages--hence the constant specificity of old-world vs new-world). The ancestral primate that gave rise to the lineages that produced monkeys and apes was not a monkey per say. Extant monkeys have many derived characters that were not present in that ancestral group, and because "monkey" is slang for these extant lineages, the ancestor was not a monkey. It was a stem primate, lacking many of the derived characters that define extant monkey lineages. Because people are not particular about their definition of terms--and this is where that cladistic fanaticism is helpful--it is easy to use the slang definition of monkey (tailed primate) for this ancestor, when actually there is a much more precise definition of the cladistic groups to which extant monkeys belong which excludes this ape/monkey ancestor. Interesting that you think that genetics will solve all of this, as primatologists are obsessed with fossils, transitional forms, the where and when, and we will never get any DNA from most of these taxa so you'll probably never pin down using molecular data where any of these intermediates fell on the tree (ancient DNA technology is hot, but boy is it hard to extract and once you're a true fossil--that is a rock--there's nothing left to even try on).
This part of your argument I don't quite buy... to me it seems that we're calling creatures such as howler monkeys, white-faced capuchins, and squirrel monkeys, "monkeys", and these are all in the New World Monkeys group. Similarly we say rhesus macaques (my favorite), mona monkeys, blue monkeys, baboons, and everything else in the Old World Monkeys group are also "monkeys". And yet their common ancestor was
not a monkey? I don't see how the two disparate lineages can achieve
monkeyhood independently unless we admit the progenitor was a monkey. And it seems to me that we're just hand-waving a bit here in an effort to avoid saying that the whole ape tree, a spin-off from the old world monkeys, came from a monkey.
Another problem is the timing. The dates seem to shift a bit depending on the source you use, the age of the research, etc, but the approximate departure of the simians from the "haplorhini" (which includes tarsiers) was about 58 MYA. The split between Old and New World Monkeys was quite a bit later, 40 MYA, when the Atlantic Ocean was narrower but still a tough barrier and it must've been some incredibly lucky giant storm-wrenched tree full of monkeys that made it to the new world to seed it. Then, much later, at 25 MYA we see the apes split off from the Old World Monkeys. This is a huge gap, 15 million years, most certainly chock-full of new (Old World "new" that is) monkey radiations. To me this feels like we (apes) were firmly entrenched within the old world monkey tree before we generated our unique characteristics, so we're monkeys. Also I stand by my previous statement that rhesus macaques (a kind of "monkey") are more closely related to humans than they are to spider monkeys, another detail that should bug anyone thinking we aren't monkeys.
Finally, isn't the avoidance of ape-as-monkey pretty much the same issue that we see with avoidance of human-as-ape? And of course we science-literate types know exactly where these arguments are coming from, the religious dogma, anti-science, I've-got-my-facts-already-don't-need-to-investigate-anything crowd that are trying to wreck science teaching in the schools (which will be just fine if we're also allowed to teach evolution and big bang theory as alternatives to scripture in every church, mosque, synagogue, and temple). To put it more plainly, if we assert that humans are a kind of ape, then we also have to say apes are a kind of monkey -- it's the same logic.
In case I made my arguments badly, here's a guy who agrees with me.
Nice diagrams, even.
http://paolov.wordpress.com/2011/04/21/apes-are-monkeys-deal-with-it/