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| Acmlm's Board - I2 Archive - World Affairs / Debate - Bird Origins |
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Which of these do you think are where the true origin of birds lies?| Birds are descended from dinosaurs |
100.0%, 16 votes | Birds are descended from animals related to both crocodiles and dinosaurs (i.e. "thecodonts" like Megalancosaurus and Longisquama) |
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0.0%, 0 vote | Birds are descended from crocodile related animals (i.e. pseudosuchians) |
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0.0%, 0 vote | Birds are descended from mammal ancestors |
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0.0%, 0 vote | Multi-voting is disabled.
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Thayer Fuzz Ball Level: 38  Posts: 705/988 EXP: 349428 For next: 21019 Since: 06-28-05 Since last post: 1 day Last activity: 1 day |
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I don't need third party sources if I've read the original works which are widely available.  If you want, I can send you the original sources of information for all. Just pester me on AIM some time, and I'd be happy to send you as much as you want and discuss at length there or in this thread.  |
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Skytroopa Red Paratroopa Level: 19  Posts: 124/175 EXP: 34773 For next: 1004 Since: 03-21-05 From: If you want know it , PM me. Since last post: 5 days Last activity: 1 day |
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| I vote first choice. I'm sure birds are from dinosaurs because some dinosaurs are similar as big birds. |
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Slay Level: 25 Posts: 317/339 EXP: 85592 For next: 4028 Since: 04-28-05 From: Threshold Between Heaven and Hell Since last post: 1 day Last activity: 1 day |
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The Thayer says... We tend to think of "dinosaurs" as a single thing, but I reckon that they were as varied as modern animals -- some with soft skin and feathers or fur, some with scales like modern reptiles. The Thayer says... Why do I suddenly feel six years old again? But seriously, paleontology has a certain romatic appeal to it. Traveling the world, scrounging around at ancient ruins for relics of ages past, recording extensive journals of your research and findings. I almost became an archeologist, for these reasons. The Thayer says... The Ziff says... Oh yes, let's all argue about how smart Slay is, that'll get us somewhere. The Zer0wned says... I never said it was unlikely, just yet to be proven. I simply don't subscribe due to the lack of direct proof. If you'll check my most recent post in the afterlife topic, I reckon it's probably the correct assumption, but for now it's just that -- an assumption. I specifically disbelieve Darwin's Origin of the Species, however, the theory that suggests all modern life stems from a single lifeform that branched out widely. I find it much more plausible that life sprang up all across the globe, in independant instances. In general, like creatures today stem from like ancestors, in that most if all reptiles descend from one or a few instances, most if all mammals descend from one or a few instances, and so on. I don't necessarily think that we had to go from fish to reptile to bird to mammal. The Zer0wned says... Ahh, an interesting reference, but who is to say that the moths turned dark specifically in response to their environment? I find it more plausible that there were various colors, and white simply fell out of favor for the afforementioned reasons. So, it was all there to begin with, and certain traits simply survived in greater numbers to future generations, not there was one trait that turned into another trait in future generations. I hope that makes sense. The Zer0wned says... I think you're confused -- dogbreeding is microevolution. We may have altered them significantly, but it's all superficial, just appearance. They're all still dogs by species, they all have the same inner anatomy, be it at different strengths and sizes. The Thayer says... For clarification, microevolution is changes within a species (dogbreeding) while macroevolution is change of species (fish to reptile). As for your question, probably yes. If there were certain species of dinosaur that were warm-blooded and feathered, it's completely likely in my mind that they could have microevolved into the birds we see today. I don't necessarily think that reptilian dinosaurs of the past would have turned into mammalian birds of the present. See, another problem arises that our classification system is simply constructed to organize our thoughts, and it may not be fully accurate. For example, let's say we have feathered, warm-blooded dinosaur X and modern bird Y. We have seperately classified them under completely different Phylum, Class, Order, Family, Genus and Species, but the fact may indeed be that Y is a descendant of X -- we currently have no missing link thus no way of knowing. That throws our entire organization system into chaos, if we suddenly had to merge the categories of birds and certain dinosaurs. It's nice and clean and neat to organize our scientific classification so that each animal we come across has it's own classifications, but nature and life itself is anything but neat and clear-cut. Another macro/microevolution problem also arises from our scientific classification structure; what could be inferred as a jump from one species to another (macroevolution) may in fact be evolution within a species (microevolution), which is what I was trying to illustrate with the XY example. We classify, for example, most mushrooms and most ferns as belonging to utterly seperate Kingdoms, when in fact we really don't know if they came from a single organism long ago. So I think my hesitation towards macroevolution stems mostly from a disagreement with the scientific classification system, not from disbelief that Fido was once Dino. The beneficii says... This, again, involves my disagreement with the scientific classification system. Let me start from the very begining of how I think life came to be in it's modern form, so we're clear on how I see things differently than they are presented in the scientific classification system. From my understanding, there was once no life on Earth. Then, at some point, life came to be on this planet. If I remember correctly (from a Discovery Channel program), it's been shown that simple chemicals, given the right conditions, can spawn life where there once was none. So that's how it started; chemicals in ancient Earth formed simple proteins and bacteria and unicellular orginisms. Now, this process of the creation of life didn't occur at one single spot, it happened all over this vast world, under different conditions, with different chemicals present and at different stages in Earth's history -- some when the planet had just recently formed, and some after an atmosphere had been established. These different instances of life, due to their environment and the energy sources available to them, evolved in completely different ways. In general, unicellular organisms would become multicellular organisms. In the oceans, some instances became fish, some became mollusks, some became cepholopods. On land, primitive versions of reptiles, mammals, insects and such would grow differently depending on the plant life that had formed around it and other factors. Now, here's where my views differ from conventionally accepted science. I don't believe that all life started in the ocean as fish, then fish became amphibians which moved on to land and became reptiles which adapted to become birds which further adapted to become mammals, and so on. That theory, I imagine as this... • - - - • - - - • - - - • - - - • - - - • - - - • - - - • - - - • - - - • - - - • - - - • - - - • - - - • - - - • - - - • One line. One central ancestor for all life - be it plant or animal, microscopic or normally visible - that exists today. My belief is that it was more like this... • - - - • - - - • • - - - • - - - • - - - • - - - • • - - - • - - - • - - - • - - - • - - - • • - - - • • - - - • - - - • - - - • - - - • Many various lines with many various ancestors. The lines don't crisscross or jump from one to another, even though a dot early on might represent a creature that is vastly different from a later dot that represents it's ancestor. Due to the sporadic and unpredictable nature of life, I don't think these lines can be successfully plotted out in two dimensions, as in A1 to A2 to A3, B1 to B2, C1 to C2 to C3 to C4, etc. under the scientific classification system, as per my XY example above. I realize the value and importance that comes from having scientific classification, I simply don't believe it's a reliable or even useful method to use when examining the origins of life. Repeated for emphasis, I don't think that scientific classification should be considered when pondering the origin of life, if only because our scope of understanding is so limited. If we could somehow instantly know exactly how life came to be today, then I believe a reliable taxonomic classification of creatures could be established. Since we're far from that, I don't see scientific classification as useful in this regard. And since "species" is a term of scientific classification, it is useless to debate as well. My use of the term "species" when referring to micro and macroevolution in this post was for the sake of simplicity, to illustrate that I don't believe dogs were once reptillian or humans were once aviary. I hope this makes my viewpoint a bit clearer. I just came up with an analogy. Scientific classification is a deck of cards thrown forward; each individual card may have landed in a different place, but you can trace them all back to a common point. My view is that there were multiple decks of cards to begin with, not just one. But, then again, I could be wrong. As for the original topic material; my view is that reptilian dinosaurs begat modern reptiles, birdlike dinosaurs begat modern birds, i.e. that dinosaurs were not all reptiles, but they weren't all birds -- they were highly varied, biologically. |
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Thayer Fuzz Ball Level: 38 Posts: 876/988 EXP: 349428 For next: 21019 Since: 06-28-05 Since last post: 1 day Last activity: 1 day |
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Originally posted by Slay Variation within a group isn't evidence of polyphyly, especially when the variation is the presence of derived characters (i.e. feathers and featherlike integument). Please provide support for suggesting that Dinosauria does not represent a monophyly.
I had nothing to say against you, just that Ziff seems to take your posts as being some kind of omfg pwnd, whereas I just don't see it, I'm afraid. 
Given what I've read, I've not seen anyone propose that mammals are descendants from birds. Try fish are a paraphyletic grouping, where mammals and reptiles share a common ancestor somewhere within that arrangement, and then birds are reptiles.
"Fish" is not a species. "Reptile" is not a species. Those are groupings of species, the difference between the two is that "fish" is a paraphyletic grouping of chondrichthyians (sharks, rays, skates and their sister taxa closer to them than they are to other "fish" and tetrapods) and osteoichthyians (other "fish" and tetrapods), whereas "reptiles" are a monophyletic grouping (Reptilia).
You just defined "microevolution" above as being within a species. Doesn't that defeat what you are saying here given that you're proposing "microevolution" is occuring from species to species? Incidentally, why are you saying birds are mammals?
Linnean System died decades ago. Where have you been?
You're not really making sense here, no one's proposed that dinosaurs gave rise to mammals, as far as I know. What are you talking about?
Again, what are you talking about? Birds to mammals? wtf 
No, try more like a giant tree.
No one has proposed that dogs were reptiles or that humans were once avians (I assume that is what you meant, an "aviary" is where birds are kept).
So you're proposing that modern (I assume non-"bird") reptiles descended from dinosaurs? Got character support for it? Anyway, your overall views seem to be a murky mix of a lot of creationist works I've read, very Sarafti-like, a lot of misinterpretations of what's been proposed in regards to paleontology and evolution, and just in general, a lot of outdated information. |
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