I’m not sure what the value is in considering the label “monkey” to apply to a paraphyletic taxon. If you get down into the technical details, then it’s simpler to deal with the clades, so it’d be preferable to consider the clade of (common ancestor of old-world and new-world monkeys and all of its descendants), rather than the taxon consisting of that clade less the great apes. And if you don’t get down to the technical details, the common usage is to consider apes to be monkeys. There’s only a narrow layer of pedantry, insufficiently technical to prefer the cladistic view but insufficiently common to accept the common view, that maintains that the term “monkey” should exclude apes.
I think the wikipedia article on paraphylymay help. Also the one on cladistics. I would try to summarize but I have not yet convinced myself that my understanding is sufficiently rigorous.
What Darwin actually said was this:
So, it’s not really the case that organisms over-reproduce, but rather if every individual grew to adulthood, the resulting population would be unsustainable. However, they do not all reach adulthood, because there is competition between the offspring and their siblings, conspecifics, or neighboring species (and even with “the physical conditions of life”) to actually obtain the resources necessary to do. So the “over-reproduction” is with respect to the finite resources available in a given place and time, rather than a raw number.
From a strict cladist viewpoint, humans are, indeed, fish (specifically, sarcopterygian fish). Birds are, too. Humans are primates < mammals < synapsids < amniotes < tetrapods < sarcopterygians < osteichthyes. Birds are theropods < saurischians < dinosaurs < archosaurs < reptiles < synapsids < amniotes < tetrapods < sarcopterygians < osteichthyes (with several other important branches omitted in both cases, of course). Basically, you can’t say anything about sarcopterygian fish (or the more general category of osteichthyes) that doesn’t also pertain to humans or birds, because we all share uniting characteristics (which, of course, is a product of our common ancestry).
Uh…birds are sauropsids, not synapsids. Sorry about that.
I look at it from the practical view point.
When penicillin first came out it was a wonder drug against all forms of disease. As the years have gone by, it has lost its effect on may of these diseases. Syphilis is one example of this. There are some syphilis infections that are resistant to penicillin.
The penicillin is the same, so the disease must have changed. How did it change if not for evolution?
Same applies for TB and a number of other diseases.
So you’re in favour of redefining “monkey” to be synonymous with the clade “simian” - it’s a valid point of view, I can respect it, even if I don’t agree that it should be so or that it is, in fact, the “common view” of sufficiently educated people - my 5 YO can easily tell you the difference between monkeys and apes (“only monkeys have tails, silly:rolleyes:”*). I’m OK with the existence of paraphyletic taxons for everyday descriptions - like the common use of “reptiles” which excludes “birds”, or the taxon “algae” which jumps whole kingdoms.
ETA: that would be her rolling her eyes at me, not me at you.
I’d take issue with this - from a strict view, humans *are *class Sarcopterygii (and superclass Osteichthyes), but they are *not *fish, because “fish” is not a clade, but a paraphyletic group.
I think you mean polyphyletic. “Fish” isn’t a clade, but “sarcopterygian fish” can definitely be considered a clade (indeed, Sarcopterygii is typically referred to as “fleshy-finned fishes”, vs. the “ray-finned fishes” which make up Actinopterygii). “Fish”, taken by itself, however, is polyphyletic, since it’s basically a haphazard grouping of all “swimmy things with fins”, which includes everything from early vertebrates to gnathostomes to chondrichthyes, and the more traditionally-fishy teleosts, while excluding several other related groups.
So sure, there’s no actual “fish” clade, but there are “fleshy-finned fish” and “ray-finned fish”, just as there’s no actual “monkey” clade, yet there are “new world monkeys” (Platyrrhini) and “old world monkeys” (Cercopithecidae).
And I’m surprised that you use both clades and Linnaean ranks, to be honest…
Nope, I mean paraphyletic, as I understand it viz. a group that contains all “fish” up to their last common ancestor also contains things that are not “fish” viz. all the tetrapods. But that last common ancestor was probably a fish, too (i.e. a swimmy finned thing).
For it to be polyphyletic, it’d have to *exclude *the ancestor and be a wholly artificial grouping (like grouping birds, pterosaurs and bats together as “flyers” when their last common ancestor was not a “flyer”).
I agree that “sarcopterygian fish” is a clade, actually.
These things happen when dragging non-cladistic systems like “fish” or the like into things. We use what works and gets the message across, don’t we? The Linnean stuff still has some meaning to impart, even if it’s not always the best way. Not by first choice, of course, I’d prefer a straight cladistic approach without ambiguity.
In general, a paraphyletic grouping can be expressed as “clade A - clade B”. E.g., “non-avian dinosaurs”, which is composed of all dinosaurs except for birds.
For fish, it depends on where the clade for fish “begins”. You could say, for example, that “fish = Craniata - Tetrapoda”, but there are a lot of pre-Craniata chordates that look pretty fishy. And you also have hagfish in there, looking all snakey and non-fishy. If you move it back to Chordata, then you also have the decidely-un-fishlike tunicates mucking up your definition (that is, fish = Chordata - Urichordata & - Tetrapoda).
If we go by Wikipedia’s defintion, “a fish is any aquatic vertebrate animal that is covered with scales, and equipped with two sets of paired fins and several unpaired fins.” then we are still leaving out a bunch of critters (basically, anything before placoderms [since placoderms were the first major group to have two sets of paired fins], despite their decidedly fish-like appearance).
So, to my mind, since “fish” cannot easily be expressed as “clade A - clade B”, they are more poly- than paraphyletic. That may or may not be strictly true, but that’s my take on it. It can potentially be made paraphyletic by stating “fish” = Gnathostomata - Tetrapoda, but that remains unsatisfying to me because of all the fishy stuff between Chordata and Gnathostomata. I’m not even sure it’s possible to define fish using a crown-based definition (“the common ancestor of Taxon A and Taxon B, plus all its descendants”), since no matter what you pick, you’re probably not going back far enough unless you make it so general that that it becomes synonymous with Vertebrata.
The traditional definition of fish, it seems to me, is more gradistic than cladistic.
Fish are Craniata - Tetrapoda, at least to me. And hagfish are “fish” just as much as lampreys are.
And I think it’s a bit disingeneous for you to take Wiki’s first, simplest definition when the next section goes on to say:[
](Fish - Wikipedia)Exactly what you say you don’t agree with. Note also where it says:
My emphases.
Just do a google search - there are no relevant results for “fish are a polyphyletic group”, whereas “fish are a paraphyletic group” returns 33 000 hits. If even 1% of those have relevance, that’s a lot more than think fish are polyphyletic.
I agree with this.
Disingenuous? Wha? I was just using that definition as another possibility. Geez, I thought this was just a friendly disagreement…
So long as you consider conodonts “fish” and critters like Pikaia as non-fish, then I agree that fish is paraphyletic.
I would also like to point out that Wikipedia [url="Diversity of fish - Wikipedia’]disagrees with itself](Fish - Wikipedia) on this definition:
So on the one hand, they are Craniates - Tetrapods, on the other they are Chordates - Tetrapods. And it uses the same source as the cite for both!
They go on to discuss whether the so-called “jawless fishes” are actually fish or not, despite the fact that many are basal gnathostomes, and those are quite definitely craniates. And that hagfish are “the only fish which aren’t vertebrates”, when they just said that “fish” goes all the way back to Chordata!
Not that I’m using this to discount what you said, just that Wikipedia itself seems a bit confused on the matter. It’s entirely possible that the Chordate reference is in error.
Since this thread is about what you know about evolution from just your own head, let me just say that classification is one of those things with which I am insuffficiently informed.
I’ll try reading the links.
Regarding terminology, just remember that sometimes scientists take existing terms and then mangle them to suit their own needs, such that the modern scientific use does not necessarily bear any relation to the common use. An example might be “planet” or “star”, for instance, and “dinosaur” also fits that category.
Was watching a science program on History Channel last night that mentioned the time when the “dinosaurs ruled the land and the sky”. It’s my understanding that most of the flying things at that time were not what is currently classified as dinosaurs, even though they were big, scaly, scary things.
It’s not so much an attempt to mangle the terms, but to standardize them. if everyone has their own personal definition of what a “monkey” or “ape” or “dinosaur” is, then it becomes difficult to discuss any of these groups without lengthy explanations as to which definition, exactly, you are using. And if folks don’t agree on definitions, then discussion effectively goes nowhere.
For the most part, scientists agree on their definitions. The problem, really, is that the public awareness of changes in terminology lags behind the “official” acceptance. So, while paleontologists can agree on what a dinosaur is (or is not), popular culture still lumps pterosaurs, Dimetrodon (which wasn’t even a Mesozoic animal!), plesiosaurs and mosasaurs as “dinosaurs”. The trick is getting all of this out to the general public (who, I think, seems to be coming around to the whole “birds are dinosaurs” thing finally, albeit slowly).
While there were certainly flying birds around during the Cretaceous, the Mesozoic fliers most folks are familiar with were pterosaurs. Which, while not currently considered dinosaurs, were certainly closely related to them.
I wasn’t trying to be unfriendly, honest. Sorry about that. I apologise completely, both for the word and the tone. I think I was just a little miffed that you quoted a Wiki article that says right there that fish are para.
Well, I do. Conodonts are definitely in, since the latest discoveries (South African, too! I’m quite chuffed) point to a lamprey/hagfish-like physiology, and Pikaia is definitely out, like lancets.
I agree that Wiki is confusing - perhaps because Craniata is such a new grouping? I’ve tried looking up the reference, but my nearest library doesn’t have the 2006 edition yet, damn it. Call themselves a University!
Proof of Martians ‘to come this year’
**Final proof that Mars has bred life will be confirmed this year, leading NASA experts believe. The historic discovery will come not on Mars itself but from chunks of the red planet here on Earth.
**David McKay, chief of astrobiology at NASA’s Johnson Space Centre in Houston, says powerful new microscopes and other instruments will establish whether features in martian meteorites are alien fossils.
He says evidence for life in the space rocks could have been claimed by the UK if British scientists had used readily-available electron microscopes. Instead, images of colonies of martian bacteria were collected by American scientists.
The NASA team is already convinced that colonies of micro-organisms are visible inside three martian rocks that landed on Earth. If so, this would have profound implications for our understanding of life in the universe.
http://www.scientificamerican.com/article.cfm?id=proof-of-martians-to-come-this-year-2010-01
Assuming they discover biological stuuf in these rocks, how will this affect the views of the people who don’t believe in evolution? Will this just be another test that god made to test the faith of true believers?
It is a miracle! God made life on other planets 6,000 years ago too!