questioner121 wrote:theropod wrote:Tempted to comment at length regarding the fossil record and Questioner 121's assertion(s), but meh.
One question though. How did modern birds arise? The fossil record shows that they evolved from non flying theropod dinosaurs and constitute a clear example of macro evolution. Got anything to overturn this, Questioner121?
RS
The fossil records seem to show a gradual change in the bone structure of animals.
Correction, they DO show the relevant changes. Here's a relevant paper covering this:
Theropod Forelimb Design & Evolution by Kevin M. Middleton & Stephen M. Gatesy,
Zoological Journal of the Linnaean Society,
128(2): 149-187 (February 2000)
Middleton & Gatesy, 2000 wrote:We examined the relationship between forelimb design and function across the 230-million-year history of theropod evolution. Forelimb disparity was assessed by plotting the relative contributions of the three main limb elements on a ternary diagram. Theropods were divided into five functional groups: predatory, reduced, flying, wing-propelled diving, and flightless. Forelimbs which maintained their primitive function, predation, are similarly proportioned, but non-avian theropods with highly reduced forelimbs have relatively longer humeri. Despite the dramatically different forces imparted by the evolution of flight, forelimb proportions of basal birds are only slightly different from those of their non-avian relatives. An increase in disparity accompanied the subsequent radiation of birds. Each transition to flightlessness has been accompanied by an increase in relative humeral length, which results from relatively short distal limb elements. We introduce theoretical predictions based on five biomechanical and developmental factors that may have influenced the evolution of theropod limb proportions.
Then there's this paper:
The Evolutionary Continuum Of Limb Function From Early Theropods To Birds by John R. Hutchinson & Vivian Allen,
Naturwissenschaft,
96(4): 423-448 (April 2009) [Full paper downloadable from
hereHutchinson & Allen, 2009 wrote:AbstractThe bipedal stance and gait of theropod dinosaurs evolved gradually along the lineage leading to birds and at some point(s), flight evolved. How and when did these changes occur? We review the evidence from neontology and palaeontology, including pectoral and pelvic limb functional morphology, fossil footprints/trackways and biomechanical models and simulations. We
emphasise that many false dichotomies or categories have been applied to theropod form and function, and sometimes, these impede research progress. For example, dichotomisation of locomotor function into ‘non-avian’ and ‘avian’ modes is only a conceptual crutch; the evidence supports a continuous transition. Simplification of pelvic limb function into cursorial/non-cursorial morphologies or flexed/columnar poses has outlived its utility. For the pectoral limbs, even the classic predatory strike vs. flight wing-stroke distinction and separation of theropods into non-flying and flying—or terrestrial and arboreal—categories
may be missing important subtleties. Distinguishing locomotor function between taxa, even with quantitative approaches, will always be fraught with ambiguity, making it difficult to find real differences if that ambiguity is properly acknowledged. There must be an ‘interpretive asymptote’ for reconstructing dinosaur limb function that available methods and evidence cannot overcome. We may be close to that limit, but how far can it be stretched with improved methods and evidence, if at all? The way forward is a combination of techniques that emphasises integration of neontological and palaeontological evidence and quantitative assessment of limb function cautiously applied with validated techniques and sensitivity analysis of unknown variables.
In more detail, we have:
Hutchinson & Allen, 2009 wrote:IntroductionNineteenth-century scientists were quickly struck by the similarities between the pectoral (fore) and especially pelvic (hind) limbs of theropod dinosaurs such as
Compsognathus and
Megalosaurus on one hand and living birds on the other (Gegenbaur 1864; Huxley 1868). This similarity to them, as it still does us today, implied similar limb function and even stance, gait or locomotor dynamics. It also indicated either a remarkably detailed convergence due to the constraints of bipedalism or an ancestor-descendant relationship, the latter being the modern consensus (Gauthier 1986; Chatterjee 1997; Sereno 1999; Xu et al.2000, 2003, 2007; Prum 2002; Zhou 2004; Mayr et al. 2005; Chiappe 2007; Senter 2007). But how similar would the terrestrial locomotion of, for example, the deinonychosaur
Velociraptor and an emu (
Dromaius) of comparable size be? Or how differently would the first bird Archaeopteryx and a magpie (
Pica) fly? These are interesting questions of how form and function are linked (or decoupled) during evolution and how one can interpret locomotion from fossil remains. These are also less well understood or even explored research avenues, but a recent burgeoning of inquiries into locomotor and limb function in
theropods (including extant birds) prompts us to review progress in this field. We will show how the study of theropod locomotor function and evolution has evolved and has great scientific potential as long as its limitations are kept in mind.
In this review, we focus on studies of theropod locomotor function (including perspectives from functional morphology and biomechanics) by covering terrestrial and aerial locomotion and then related aspects of limb function (e.g. prehension, climbing, swimming). General aspects of dinosaur and more basal archosaur locomotor function or general biomechanics were reviewed elsewhere recently (Christiansen 2000; Padian 2001; Paul 2002; Zhou 2004; Alexander 2006; Hutchinson and Gatesy 2006; Hutchinson 2006; Chiappe 2007). In particular, Farlow et al. (2000) and Gatesy (2002) gave thorough reviews of theropod locomotion, so we centre our treatment on theropod locomotion studies since ∼2000. To exemplify the value of and high
methodological standards for empirical studies of locomotion in extant theropods, we have integrated some of the more significant recent studies of extant bird locomotion into our review as a step towards improved synthesis of neontological and palaeontological perspectives in evolutionary biomechanics and morphology.
Oh wait, not only have scientists compared anatomy, but they've compared
how those anatomical features affect motion. Looks like biomechanics is another subject you're going to have to spend a decade studying. Here, for example, is the page covering the pelvic bone articulations in different theropods:
- Theropod Limb Transitions.jpg (323.07 KiB) Viewed 1475 times
And here is an illustration of the models used to perform relevant biomechanical analyses:
- Theropod Locomotor Analysis.jpg (291.97 KiB) Viewed 1475 times
And of course, they're able to do this because, wait for it,
they've studied the processes at work in living organisms with similar bone and muscle articulations. Such as ostriches.
questioner121 wrote:This in no way proves that these animals were able to reproduce with each other over time to evolve into the animals we see today.
Are you serious? The mere fact that
descendants exist with similar anatomical features should be telling you that the animals in question were capable of reproducing. But then, evolutionary theory
doesn't postulate that
members of different species do this. What evolutionary theory
actually postulates, if you bother to pick up an actual biology textbook, is that
since species are populations, changes in those populations may, over multiple generations, give rise to sufficient differences between subsets thereof, that those subsets cease to be capable of reproducing with each other, at which point we have new species.
questioner121 wrote:It's an assumption
No it isn't. The mere fact that those organisms produced descendants
forming a continuum through the fossil record up to the present tells us this.
questioner121 wrote:based on the likeness of the structures
The words you're looking for are "comparative anatomy".
questioner121 wrote:which scientist use to make a claim that the animals were able to reproduce with one another through the generations.
Never watched animals shagging? Biologists do this all the time. Indeed, I've shot footage of
insects mating before today with my own camera.
questioner121 wrote:I'd like to see a dog evolve into a cat or vice versa over any length of time that can observed by successive generations of humans.
Oh for fuck's sake, not
this retarded piece of creationist drivel.
Once again,
evolutionary theory doesn't postulate farcical caricatures such as the one you've just erected. What it
actually postulates, if you pay attention to actual biology textbooks instead of lying scum like Harun Yahya, is that
the population changes. Tell me, is the human population today identical to the human population of 100 years ago? No it isn't. The individuals making up today's population, whilst having inherited their characteristics from those past humans, are
not genetically identical to those past humans. The population has
changed.All it takes, is for a given population to be split into two, and those two new populations to be prevented from mixing with each other by some suitable barrier, and eventually, those populations will
diverge from each other. As was observed taking place in just 30 generations in a founder population of lizards on a Croatian island, which diverged from their mainland ancestors by changing their diet, and acquiring new intestinal features to accompany that dietary shift.
questioner121 wrote:I don't know what stellar evolution is.
There's a lot you manifestly don't know, as your posts keep telling us.
questioner121 wrote:But again we are simply making interpretations of our observations.
Oh look, it's the "interpretations" creationist bullshit once more. Time for this:
The "assumptions" canard (with "interpretation" side salad).This is a frequent favourite with creationists, and usually erected for the purpose of attempting to hand-wave away valid science when it happens not to genuflect before their ideological presuppositions. As I have stated in [2] above, science is in the business of
testing assumptions and presuppositions to destruction. As an example of destroying creationist apologetics with respect to this canard, I point interested readers to
this post, where I destroyed the lies of the laughably named "Answers in Genesis" with respect to their assertion that
14C dating was based upon "assumptions". I've also trashed this canard in detail with respect to radionuclide dating as a whole, so don't even try to go down that road. Likewise, if you try to erect this canard with respect to other valid scientific theories, you will be regarded as dishonest.
Another favourite piece of creationist mendacity is the "interpretation" assertion, which creationist erect for the purpose of suggesting that scientists force-fit data to presuppositions. Apart from the fact that this is manifestly false, it is also defamatory, and a direct slur on the integrity of thousands of honest, hard working scientists, who strive conscientiously and assiduously to ensure that conclusions drawn from real world observational data are robust conclusions to draw. This slur, of course, is yet another example of blatant projection on the part of creationists, who
manifestly operate on the basis of presupposition themselves, and appear to be incapable of imagining the very
existence of a means of determining substantive knowledge about the world that does
not rely upon presupposition. Well, I have news for you. Science does NOT rely upon "presupposition". Indeed, scientists have
expended considerable intellectual effort in the direction of ensuring that the conclusions they arrive at are
rigorously supported by the data that they present in their published papers. There exists much discourse in the scientific literature on the subject of avoiding fallacious or weak arguments, including much sterling work by people such as Ronald Fisher, who sought during their careers to bring rigour to the use of statistical inference in the physical and life sciences. Indeed, Fisher was responsible for
inventing the technique of analysis of variance, which is one of the prime tools used in empirical science with respect to experimental data, and Fisher expended much effort ensuring that inferences drawn using that technique were
proper inferences to draw.
Basically, there is only one "interpretation" of the data that matters to scientists, and that is
whatever interpretation is supported by reality. Learn this lesson quickly, unless you wish to be regarded as discoursively dishonest on a grand scale.
In short, drop this "interpretations" bullshit once and for all, because it IS bullshit.
questioner121 wrote:It's not going to be possible to experiment with it to prove it's true.
Bullshit. Those lizards I mentioned above? They were
deliberately introduced to that island specifically to test the relevant hypotheses. Here's the paper in question:
Rapid Large-Scale Evolutionary Divergence In Morphology And Performance Associated With Exploitation Of A Different Dietary Resource by Anthony Herrel, Katleen Huyghe, Bieke Vanhooydonck, Thierry Backeljau, Karin Breugelmans, Irena Grbac, Raoul Van Damme, and Duncan J. Irschick,
Proceedings of the National Academy of Sciences of the USA,
105(12): 4792-4795 (25th March 2008) [Full paper available in HTML format on the PNAS website
here, also available as a PDF download from the same website via
this link]
From the abstract:
Herrel et al, 2008 wrote:Although rapid adaptive changes in morphology on ecological time scales are now well documented in natural populations, the effects of such changes on whole-organism performance capacity and the consequences on ecological dynamics at the population level are often unclear.
Here we show how lizards have rapidly evolved differences in head morphology, bite strength, and digestive tract structure after experimental introduction into a novel environment. Despite the short time scale (≅36 years) since this introduction, these changes in morphology and performance parallel those typically documented among species and even families of lizards in both the type and extent of their specialization.
Moreover, these changes have occurred side-by-side with dramatic changes in population density and social structure, providing a compelling example of how the invasion of a novel habitat can evolutionarily drive multiple aspects of the phenotype.
The experiments have been done. It's Game Over for mythology.
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