|
Post by deanm on Feb 16, 2009 4:36:22 GMT
Tomhet signature has an interesting quote. I am curious as to where it is from/who set it etc.
"(...) the cladistic approach, since it is based on the principle of parsimony (economy), contradicts the essence of the evolutionary process in nature, because evolution is wasteful in every respect. Cladistists exclude stratigraphy, embryology, physiology, ecology and biogeography from consideration and take into account only formalized morphological characters, irrespective of space and time"
I'm not interested in starting a flame war or anything else over the merits of cladistics, phenetics, or any other taxonomic theory/practice.
|
|
|
Post by kuni on Feb 16, 2009 8:40:12 GMT
This is true, but only to a point.
This is the reason why scientists prefer to use DNA sequences to make phylogenetic trees as opposed to morphology, which can give you very shaky results, especially if the same trait evolves more than once in a lineage (which happens!)
However, with the fossil record, you're stuck with morphology as a "best guess". However, this doesn't mean you get to throw out phylogenetics/cladistics, because it's still better than the alternatives (as there are none, unless you like creationism...)
|
|
|
Post by kuni on Feb 16, 2009 8:50:43 GMT
Oh, and the quote's from an obscure journal article written by a Russian author in 2003. The article's been cited all of 3 times, and (I just read it to be sure) is basically crap. Many of the points it makes have been refuted in more current literature.
|
|
|
Post by tomhet on Feb 16, 2009 8:55:31 GMT
As far as I know It's not from 2003, it's from 2006. And that's from a very respected scientist. The information may be valid or not, but that view of cladistics is still shared by a lot of non-paleos And I think he's right when he says that paleos are wrong when they think that the fossil record is complete enough to establish clearly where birds came from It's actually funny how all people that don't share the same point of view are accused of being creationists.
|
|
|
Post by sid on Feb 16, 2009 11:20:01 GMT
As far as I know It's not from 2003, it's from 2006. And that's from a very respected scientist. The information may be valid or not, but that view of cladistics is still shared by a lot of non-paleos And I think he's right when he says that paleos are wrong when they think that the fossil record is complete enough to establish clearly where birds came from It's actually funny how all people that don't share the same point of view are accused of being creationists. Totally agree with you,Tom...And i also agree with your signature,obviously ;D
|
|
|
Post by deanm on Feb 16, 2009 14:05:47 GMT
Most of the cladists I know use all of the "apparently forbidden to them" pieces of information to build their trees.
I have no interest in flame wars but when it comes to DNA based trees they have a series of faults. First being sample size (one or two parts of a gene does not equal the whole organism). Second, gene evolutionary tree does not map out to the species evolutionary tree (several studies have found that when they look at more than 2 genes they get contradictory phylogenies).
Proper application of technique and scientific rigor (not saying rigor = parsimony) is required whatever dataset you use. The other thing is sometimes some common sense goes a long ways. I have read studies that have abused any and all techniques to get an answer that was "dubious at best". Some of my favorites include hamsters being more closely related to man than chimps are (a DNA study), hairs on the abdomen of blackflies defining species relationships (a morphological cladistic study).
By the way I am not a taxonomist so I don't have an axe to grind either way.
|
|
|
Post by kuni on Feb 16, 2009 18:04:24 GMT
The term at this point is really phylogenetics, palentology just happens to use the less-reliable method of morphology instead of genetics (necessarily). Even then, the abundance of characters and fossils available on birds and birdlike dinosaurs has swamped
The guy in question seems to be a pretty knowledgeable bird paleo, but not someone who understands phylogenetics. Also, some of the stuff he references (esp. the digits) have been refuted at this point.
Remember, to a degree, phylogenetics/cladistics is the only game in town, because all species are related on a larger tree of life (disputing THAT really does make you a creationist...), though phylogeny can still be hard to tease out. The real argument here is about which methods you use to build your tree. For example, a tree using only mtDNA(mitochondrial DNA) will not be usually taken as seriously as one with mtDNA sequencing plus several nuclear genes, and even then, you have to be careful with which nuclear genes you selected.
It's pretty complicated stuff, but it's one of the newest and fastest-growing fields of science.
|
|
|
Post by Dinotoyforum on Feb 16, 2009 18:29:20 GMT
What is the ref for this quote, exactly?
|
|
|
Post by kuni on Feb 16, 2009 18:53:05 GMT
EN Kurochkin Parallel evolution of theropod dinosaurs and birds Journal Entomological Review Issue Volume 86, Supplement 1 / January, 2006
|
|
|
Post by [][][]cordylus[][][] on Feb 16, 2009 18:54:27 GMT
As far as I know It's not from 2003, it's from 2006. And that's from a very respected scientist. The information may be valid or not, but that view of cladistics is still shared by a lot of non-paleos And I think he's right when he says that paleos are wrong when they think that the fossil record is complete enough to establish clearly where birds came from It's actually funny how all people that don't share the same point of view are accused of being creationists. Actually, nobody calls anybody else creationists, but rather they deal with evidence like creationists. I think it is relatively complete to say where birds came from--- Ok, no definite species--- But I'm sure we all know the big class of ruling reptiles from which they arose.
|
|
|
Post by tomhet on Feb 16, 2009 19:03:53 GMT
I think it is relatively complete to say where birds came from--- Ok, no definite species--- But I'm sure we all know the big class of ruling reptiles from which they arose. Not really
|
|
|
Post by [][][]cordylus[][][] on Feb 16, 2009 19:19:15 GMT
You think they evolved from those "thecodonts" like longisquama then?
|
|
|
Post by kuni on Feb 16, 2009 20:49:49 GMT
I think it is relatively complete to say where birds came from--- Ok, no definite species--- But I'm sure we all know the big class of ruling reptiles from which they arose. Not really Feel free to disagree, but realize that you're against the majority of paleontologists on this one.
|
|
|
Post by stoneage on Feb 16, 2009 22:12:19 GMT
Not really Feel free to disagree, but realize that you're against the majority of paleontologists on this one. Just remember the majority isn't neccessarily right. Remember when they thought dinosaurs were slow cold blooded reptiles. They thought Apatosaurus lived in swamps to support it's weight and it ate soft water plants because it had weak teeth. Remember when they thought Iguanodons spike was on its nose. Remember when dinosaurs dragged their tails. Remember when hadrosaurs looked like ducks. Remember when sauropods had swan necks. Remember when the majority of people thought the world was flat. Remember when the majority of the people supported George Bush. Paleontology isn't a democracy. Being in the majority doesn't make you right! ;D
|
|
|
Post by [][][]cordylus[][][] on Feb 16, 2009 22:21:18 GMT
Feel free to disagree, but realize that you're against the majority of paleontologists on this one. Just remember the majority isn't neccessarily right. Remember when they thought dinosaurs were slow cold blooded reptiles. They thought Apatosaurus lived in swamps to support it's weight and it ate soft water plants because it had weak teeth. Remember when they thought Iguanodons spike was on its nose. Remember when dinosaurs dragged their tails. Remember when hadrosaurs looked like ducks. Remember when sauropods had swan necks. Remember when the majority of people thought the world was flat. Remember when the majority of the people supported George Bush. Paleontology isn't a democracy. Being in the majority doesn't make you right! ;D Also, these days, common sense is used way more then back then. Back then they didn't bother to think of how a sauropod would be able to hold it's neck high, they didn't bother to look at the bones of plesiosaurs to determine whether they could come out of the water or not, etc.
|
|
|
Post by kuni on Feb 16, 2009 23:27:39 GMT
It's true -- ultimately, the evidence is the only thing that matters. It's also true that the majority of that evidence favors birds as dinosaurs at this point in time. That could change, but -I- certainly wouldn't put money on it at this point in time.
|
|
|
Post by stoneage on Feb 17, 2009 0:57:42 GMT
It's true -- ultimately, the evidence is the only thing that matters. It's also true that the majority of that evidence favors birds as dinosaurs at this point in time. That could change, but -I- certainly wouldn't put money on it at this point in time. ;D Your evidence is based on pure speculation and assumption! ;D
|
|
|
Post by kuni on Feb 17, 2009 1:42:35 GMT
;D Your evidence is based on pure speculation and assumption! ;D Nope, you're incorrect. (as usual? ;D)
|
|
|
Post by [][][]cordylus[][][] on Feb 17, 2009 1:43:35 GMT
Not really stoneage. There are plenty of bird-like dinosaurs and dinosaur-like birds. I'm pretty sure that is what he is using as evidence.
|
|
|
Post by stoneage on Feb 17, 2009 2:30:44 GMT
Not really stoneage. There are plenty of bird-like dinosaurs and dinosaur-like birds. I'm pretty sure that is what he is using as evidence. Well what about respiratory physiology. The lungs of bird are not similar in many important ways to the lungs of dinosaurs. John Ruben has compared the respiratory structures of modern birds, mammals, and crocodiles with fossils of early birds and theropods.Crocodiles have piston-style diaphragms . Theropod fossils show a similar separation in the visceral cavity and key skeletal characteristics similar to those of crocodiles. Birds have no diaphragms seperating the body cavity. They have a different type of lung which uses the movement of the pelvis and chest to breathe. It is difficult to imagine diaphragm-less birds evolving from dinosaurs with diaphragms. Such a condition would cause large scale breathing problems! ;D
|
|