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Member (Idle past 1666 days) Posts: 20714 From: the other end of the sidewalk Joined: |
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Author | Topic: Dogs will be Dogs will be ??? | |||||||||||||||||||||||||||||||||||||||||
crashfrog Member (Idle past 1727 days) Posts: 19762 From: Silver Spring, MD Joined:
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How can you tell if they are of the same reproductive population? What do you mean? Well, that's a good question. We can, of course, only reach that conclusion to a certain degree of certainty - we can't take every rabbit in the forest and try to mate it once with every other rabbit in the forest. If we want to know if the rabbits in East Forest are in the same reproductive community as the rabbits in the West Forest, there are some genetic tests we can do - we can take samples from individuals all over the forest, and see if the rabbits from East Forest are more similar to each other, genetically, than they are to the rabbits from West Forest. If a given allele is as likely to be found in the rabbits in East as in West, then we conclude that's the result of "gene flow" between those two groups, and the way that genes flow is by reproduction. So, we would say they're in the same species. Like I say, it's a hard problem because animals and plants don't come labeled with their species. That's a classification we impose on the natural world for our own human convenience.
Ok. So winged species in this corner, winged with tail over here, winged with tail beak over here? Yeah, that's basically it. By the time you get to the species level, it's like "Striate areas on the 9th abdominal segment? Melanotus cribulosus. No striate areas? Melanotus depressus." It seems nit-picky, but these tiny morphological differences really do reflect reproductive isolation between species in the same genera. It's reflected in the genetics.
What do you mean there is no such thing as a "reproductive community"? Well, are you part of the "human reproductive community" in any real sense? Are your children? (I imagine you hope that they are not.) Even if you have reproduced, would you say that it was with a community? Wasn't it just with a single person for whom you are the only person they reproduced with? The whole notion of "reproductive community" is a matter of theory, it's about who you could hypothetically reproduce with given the right conditions. You could, most likely, father children on any human woman assuming she was of age and fertile, and that you are, as well. But does that mean that your grandparents aren't human beings anymore, since their fertile days are behind them? No, of course not. It's about what could theoretically happen, who you could theoretically reproduce with, not who you actually do reproduce with. That's why it's not at all trivial to determine the scope of a reproductive community - it doesn't really exist. It's a model about what is possible, not what is real. Does that make any sense? Obviously it's not ideal but it's the only thing we've got.
So I could actually say that a we are all of the same kind, different species, subspecies all the way down the line? Well, it depends. What do you mean by that? Creationists use the word "kinds" to refer to the fact that they believe that the Earth is inhabited by multiple groups of organisms, all with their own separate origin. But in the natural world, it's all but impossible to draw those kinds of sharp distinctions between organisms. Whenever you say that one organism is of one kind, and a second is of another, I can go out into nature and find some organism that very neatly splits that difference right down the middle.
Like the sugar glider and flying squirrel...Do you think they should be in the same classification? Well, they are. They're both mammals, so they're in the same classification "mammal." But within Mammalia, it's hard to imagine how they could be any more different - one is placental and the other is marsupial. That's the most fundamental difference that exists within the class Mammalia. Actually, strike that - there's the monotremes, the egg-laying mammals. (Did I earlier refer to the platypus as a marsupial? That was a mistake on my part.)
Plants, animals, trees, anything alive is catagorized? Indeed. It's the obligation and privilege of the one who discovers, describes, and classifies a new, undescribed and unclassified organism to name it.
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crashfrog Member (Idle past 1727 days) Posts: 19762 From: Silver Spring, MD Joined:
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Yet they look almost exactly the same. How? It's likely the case that this is "convergent evolution", where two species that live in the same kind of environment are independently pressured to develop the same traits. It's not common, but we do see it. Of course, simply by being mammals, these two organisms have upwards of 90% identical genetics (just as you share 90% of the genes of a mouse) so despite starting from "different kinds", they're already pretty similar to begin with.
Well this is going to hard to define what a kind is then, it seems. To say the least. This problem - how do you define "kind" in terms of something physical that can be observed or tested for - is where creationism has always run aground. Creationists know what they want it to mean - "one group of organisms specifically created by God" - but it's impossible to reconcile that with the natural world.
Yeah interesting. I get it but at the same time I don't, but I do. A good friend of mine was once challenged, during his PhD defense in zoology, if he knew what a species was. His reply was "I don't, but every day I go to work as though I do." It's not an act of scientific fraud to talk about species as though we know for certain when two organisms are in the same species, or aren't. Like everything else in science, our knowledge about species is provisional, subject to revision in the light of better evidence, and frequently is revised due to new evidence. My wife is an entomologist, and her whole field was scandalized by the results of an enormous new genetic study that determined evolutionary relationships by sequence similarity on the 16S ribosomal subunit (it's one of the few cellular organelles that all living things have, because it's required for life.) The scandal was that the entire class Insecta was found to have descended from Crustacea, which means that they are crustaceans. It was a big upset; everybody used to believe that Insecta and Crustacea were both classes within the phylum Arthropoda. The TL;DR version of all this is that figuring out what is what, in the natural world, is not very simple at all.
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Taq Member Posts: 10304 Joined: Member Rating: 7.3 |
Creationists do not do themselves any favors by trying to hitch their idea of "kind" to Linnaean taxonomy (LT). The problem is that LT can be just as arbitrary as kind above the level of species. If any creationist hopes to develop a solid working definition of kind then they need to move away from LT entirely. Cladistics is a much better system.
What is stopping taxonomists from putting chimps and humans in the same genera? Nothing. They are free to do so, and even Linnaeus himself considered it. What is stopping taxonomists from putting orangutans in their own family and gorillas, chimps, and humans in another? Nothing. As long as the relationships between the families is correct then LT allows for tons of different possible organizations of those species. If the creationist model has any hope of working they need to describe kind in terms of physical and genetic comparisons. Pointing to the LT Family level and saying "somewhere around there" is not going to cut it.
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Chuck77 Inactive Member
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Hi RAZD, Crashfrog, Percy, Huntard and others. I need to do some reading before moving forward here I think.
I wanted to let you know i'm still looking to participate here and will respond to your posts soon. Also, Taq, I think you're right. As RAZD has said: Message 288 RAZD writes: Biology does not use "kind" as a classification, even though the taxonomic classification system was developed by Linneaus long before Darwin. Instead a number of levels are defined that show (or attempt to show) the levels of a nested hierarchy of descent from ancestors. This system is becoming increasingly unwieldy and many biologists are turning to cladistics. quote:-------------------------------------------------------------------------------- Cladistics Cladistics (Ancient Greek: , klados, "branch") is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants (and nothing else). ... Cladistics can be distinguished from other taxonomic systems, such as morphology-based phenetics, by its focus on shared derived characters (synapomorphies). Systems developed earlier usually employed overall morphological similarity to group species into genera, families and other higher level groups (taxa); cladistic classifications (usually in the form of trees called cladograms) are intended to reflect the relative recency of common ancestry or the sharing of homologous features. Cladistics is also distinguished by an emphasis on parsimony and hypothesis testing (particularly falsificationism), leading to a claim that cladistics is more objective than systems which rely on subjective judgements of relationship based on similarity.[2] and, in the same message:
RAZD writes: Now I would think that you, and other creationists, would agree that their view of a "kind" would constitute a "clade" as used by cladistics, I think were all on the same page, so far. Although crashfrogs posts about defining what a species is (and caffeine's) are duly noted. It doesn't seem like the easiest thing to do. Admittingly tho, i'm not too familiar with Linnaean taxonomy as compared to Cladistics, (or with Linnaean taxonimy at all) but from what has been talked about concerning Cladistics, it seems a good route to go. Edited by Chuck77, : No reason given. Edited by Chuck77, : No reason given.
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RAZD Member (Idle past 1666 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Hi Chuck77,
... I need to do some reading before moving forward here I think. ... Good plan. If you have any questions you can bring them here.
I wanted to let you know i'm still looking to participate here and will respond to your posts soon. Take your time, we will await your return. Enjoy.by our ability to understand Rebel American Zen Deist ... to learn ... to think ... to live ... to laugh ... to share. Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click)
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Taq Member Posts: 10304 Joined: Member Rating: 7.3 |
Admittingly tho, i'm not too familiar with Linnaean taxonomy as compared to Cladistics, (or with Linnaean taxonimy at all) but from what has been talked about concerning Cladistics, it seems a good route to go. Cladistics is based on shared and derived features. The root of a clade is the synapomorphy which is the list of shared characteristics. Each branch from that node is defined by their derived characteristics, features that are not shared with the rest of the clade. It is an elegant system at its most basic. However, shared and derived features can be hard to determine at times due to convergent evolution and loss of ancestral traits. You will also find that designed things do not easily fall into a nested hierarchy when using cladistics. We could use playing cards as an example. What are the shared features in playing cards? First off, all of the cards share the same rectangular shape, so the synapomorphy of the entire playing card clade is the rectangular shape (the characteristics shared by the entire clade). We have two colors so we have a red clade and a black clade which are derived traits. In the red clade we have two suits, and also two suits in the black clade. The synapomorphy in the red clade is the red color of the suit. The derived traits are diamonds and hearts. In the black clade, black is the synapomorphy while spades and clubs are the derived traits. How do we divide each clade further? The only thing left is the rank of the cards. This is where we hit a problem. We find the same rank (i.e. Kings, Aces) at the ends of SOME of the clades. At this point, the nested hierarchy fails. There are features shared by some cards in the diamond clade and the club clade that are not shared by all of the cards in the heart and spade clades. Does this help in understanding how cladistics works? Do you understand how a nested hierarchy is falsifiable?
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Tangle Member Posts: 9583 From: UK Joined: Member Rating: 6.7 |
Chuck writes: It doesn't seem like the easiest thing to do. it's not, that's why tens of thousands of taxonomists over hundreds of years have dedicated their lives to it; often just to focus one group of animals. It's also, terribly, terribly tedious unless you're turned on by counting the number segments in worms or have a mind like a librarian with a compulsive, obsessive disorder. (You can learn from this that taxonomy wasn't my favourite subject.) I think the point to note here Chuck, is that all this work has already been done and re-classifying all known animals and plants isn't something that an individual can ever hope to do no matter how driven. It's great to see you taking a real interest in the natural world though.Life, don't talk to me about life - Marvin the Paranoid Android
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Chuck77 Inactive Member |
I would like to try and keep up here I just don't think it's possible.
I think I should focus on one thing at a time. The thing that jumps out the most is Cladistics and how that works. If species hasn't really been defined to a tee then it seems there is room to work. Although I would really like to see if it's possible to catagorize "kinds". Inevitably tho, the Human - ape connection is going to come up and that is where the problem lies, I think. So if someone wants to take the lead here that's fine. There is a lot of reading to do on all of this and maybe we can go as we go here without me reading 150 years of the TOE. Keep it simple maybe? If possible. Micro-Macro, species, kinds, and where the line is for the seperations of each species, sub-species whether land or water.
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Chuck77 Inactive Member |
Taq writes: Cladistics is based on shared and derived features. Ok, but to what extent?
The root of a clade is the synapomorphy which is the list of shared characteristics. Each branch from that node is defined by their derived characteristics, features that are not shared with the rest of the clade. So for example hoofs, wings, feet, webbed feet etc? Genetics too or no?
It is an elegant system at its most basic. However, shared and derived features can be hard to determine at times due to convergent evolution and loss of ancestral traits. Convergent evolution and ancestral traits? For sake of argument here, could each clade have their own common ancestor? This may seem like a stupid question but what I mean is, could there be a Canine ancestor, felidae ancestor etc etc?
You will also find that designed things do not easily fall into a nested hierarchy when using cladistics. I don't understand what nested hierarchy is.
We could use playing cards as an example. What are the shared features in playing cards? First off, all of the cards share the same rectangular shape, so the synapomorphy of the entire playing card clade is the rectangular shape (the characteristics shared by the entire clade). We have two colors so we have a red clade and a black clade which are derived traits. In the red clade we have two suits, and also two suits in the black clade. The synapomorphy in the red clade is the red color of the suit. The derived traits are diamonds and hearts. In the black clade, black is the synapomorphy while spades and clubs are the derived traits. How do we divide each clade further? The only thing left is the rank of the cards. This is where we hit a problem. Yeah, the cards can't really be broken down anymore...what's left? I might say ask the person who made the cards to find out what they were thinking. Tho, the cards should say something themselves, but seems all the cards are the same, with slight to more modification. Where does that leave us...
We find the same rank (i.e. Kings, Aces) at the ends of SOME of the clades. At this point, the nested hierarchy fails. There are features shared by some cards in the diamond clade and the club clade that are not shared by all of the cards in the heart and spade clades. I wonder why it's so difficult. There should be something that either seperates the species or brings them together...why is the line so blurred? Or is it not blurred at all and they are very similiar yer very different?
Does this help in understanding how cladistics works? Do you understand how a nested hierarchy is falsifiable? A little yes, but I don't know how a nested hierarchy is falsifiable. After I understand what it is maybe then i'll see.
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Tangle Member Posts: 9583 From: UK Joined: Member Rating: 6.7 |
Chuck77 writes: A little yes, but I don't know how a nested hierarchy is falsifiable It's not really falsifiable in the way we talk about the way a theory or hypothesis is falsifiable Nested hierarchies aren't theories - they're observations of how the natural world is organised. If nested hierarchies didn't exist though, or if we found a animal like a horse but with - to be ludicrous - wheels where feet should be, or wings, or an exoskeleton, it would totally disprove common descent which IS a prediction of the ToE.Life, don't talk to me about life - Marvin the Paranoid Android
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Chuck77 Inactive Member |
From EvoWiki:
"Nested hierarchy" refers to the way taxonomic groups fit neatly and completely inside other taxonomic groups. For instance, all bats (order Chiroptera) are mammals. All mammals are vertebrates. Likewise, all whales (order Cetacea) are also mammals, and thus also vertebrates. While it might seem that this arrangement is obvious and unavoidable, it is not. Taxonomic groups are defined by traits and it should be possible to mix traits from multiple defined groups. An example from classical mythology is the Pegasus, a creature with features defined as both mammal (produces milk like a horse) and bird (has feathers). Mammals and birds are both orders, so, if Pegasus existed, it would be a violation of the nested hierarchy, a creature that belonged to two separate groups. Likewise for satyrs (human torso, goats legs), jackalopes (rabbit body with an antelope head) and crocoducks (crocodile head, body of a duck). It is not always possible to define a nested hierarchy for any arbitrarily selected set of items, though many creationists have used this as an outCamp, Ashby (2001) A Critique of Douglas Theobald’s "29 Evidences for Macroevolution", Part 1: “One True Phylogenetic Tree” [1]. For instance, motor vehicles do not show conservation of traits to single taxonomic groups, no matter how you choose to define your taxonomy. Whether a car has air-conditioning is completely independent of whether it has power-steering, for example. Life, however, shows a clear nested hierarchy, at least with regards to multicellular organisms. An animal that produces milk (Mammals), will also have hair, have four limbs, be endothermic (warmblooded) plus possess many other characteristics. Why should this be? Why do no other animals or plants produce milk? Why do no mammals have four limbs plus a pair of wings, like the Pegasus or angels? This fits easily with the idea of common descent, but is not what would be expected from special creation (although it isn't completely at odds with creation either, as the creator(s) could create life in any configuration imaginable). Page not found - Evolution Wiki Geez, i'm not confused at all (sarcasm). Ok, so this seems like what you are saying. If a horse had wheels as legs, this hierarchy would be falsified - so to speak. What's the big deal? Why is this at odds with special creation? What would special creation predict, wheels? I think I understand that similiar features are put in similiar groups but they are all still one group...broken down the best possible way to explain life in catagories. What I don't understand is when it's said "why would God try to trick us?" What does this mean? What is it about the common ancestor that shows if it's not a common ancestor God is tricking us? Is there something that is so distinct that it does show common decent? If so what is it The genetic code? A sort of universal genectic code? I think genetics is a big subject in all of this. Maybe if i'm trying to find a workable definition of "kinds" that would fit in a scientific theory it's best to look at the differences in a species rather than similarities. Edited by Chuck77, : No reason given. Edited by Chuck77, : No reason given. Edited by Chuck77, : No reason given.
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Chuck77 Inactive Member |
From EvoWiki:
ConclusionsCladistics is a robust method for deciphering phylogeny, and like any such method, it has its strengths, and weaknesses. Opponents of cladistics, who categorically dismiss this procedure, are as wrong as those who elevate cladistics to the level of phylogenetic panaceareality lies somewhere in the middle. In an imperfect science, attempting to piece together a riddle wrapped inside an enigma, cladistics will continue to serve us well. Page not found - Evolution Wiki Reality lies somewhere in the middle. Do we know where the middle is?
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Tangle Member Posts: 9583 From: UK Joined: Member Rating: 6.7
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Chuck77 writes: Ok, so this seems like what you are saying. If a horse had wheels as legs, this hierarchy would be falsified - so to speak. Nested hierarchies wouldn't be falsified, they just wouldn't exist :-) Nested hierarchies are simply the demonstration that one thing evolved from another - like in a family tree. Finding a horse with wheels or wings or that layer eggs, would be like finding a three legged martian as your great grandfather - it doesn't fit in the tree; doesn't belong. If all of life couldn't be categorised into families with similar features BUT WITH NO FEATURES FOUND IN NON-RELATED GROUPS (the nested hierarchy) then common descent could not possibly be true.
What's the big deal? Why is this at odds with special creation? What would special creation predict, wheels? The big deal is that nested hierarchies prove common descent. And, incidentally, they show that a designer is not necessary to produce the variety of life that we find on our planet. It also shows that if a designer was involved, then he made his design look like it happened via a process of evolution - not by design as a human designer would do it. (A human designer might well put wings on a horse or wheels on a pig - he'd take the best designs he had for say, an eye, and use that in every animal needing an eye - he wouldn't use sub-optimised parts if he had a better model; which is what we find in nature.)Life, don't talk to me about life - Marvin the Paranoid Android
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Chuck77 Inactive Member |
It also shows that if a designer was involved, then he made his design look like it happened via a process of evolution - not by design as a human designer would do it. (A human designer might well put wings on a horse or wheels on a pig - he'd take the best designs he had for say, an eye, and use that in every animal needing an eye - he wouldn't use sub-optimised parts if he had a better model; which is what we find in nature.) I still dont understand this. What do you mean "sub-optimsed" parts? You mean something like "generic" parts? How is it made to lool like via the process of evolution and not design? I'm not trying to get at anything here, I really just don't know. What do you mean "best designs"? Are you saying things are designed badly? I really still dont understand the argument for common decent. Are all features evolved sub-par? And a designer would do what different? Edited by Chuck77, : No reason given.
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Chuck77 Inactive Member |
chuck77 writes: Can we call the family Canidae a "kind"?RAZD writes: We could, but that could be interpreted as claiming that "kind" is defined by "family" taxon, and I would rather not be side-tracked by that issue. We can instead call it the Canidae clade, and avoid that issue. Sorry RAZD, it's been a while. What exactly is a clade compared to a family again? Down below where would clade go? Kingdom: AnimaliaPhylum: Chordata Class: Mammalia Order: Carnivora Suborder: Feliformia Family: Felidae I forgot how we got the where we are. Lots of information. I'm not sure I understand cladistics like i thought I was learning it to be. What is a clade compared to a family?
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