I draw on this publication
https://iopscience.iop.org/article/10.1088/1748-3190/ad66a3/pdf
So theyâre basically saying that a limb that was originally used for propulsion through fluid is versatile enough to be used for ⌠propulsion through fluid.
I donât think that has the impact intended.
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Whatâs missing from the above is any evidence that it actually is âthe bestâ, compared to other possible architectures that exist (such as the jointed exoskeletal limbs of arthropods which are also used in a wide variety of environments), and those that could exist but donât.
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There are no actual tests done in that paper, to compare different possible architectures. Itâs all basically just qualitative arguments that some thing is optimal.
There is not a single simulation or experiment done to try to change any of the attributes (of anything from muscle, ligament, tendon, bone structure, shape, number, joint angles or whatever tissue) of the limbs of any vertebrates to try to compare their performance on any of innumerable possible factors that could affect limb performance on anything from efficiency of body mechanics, to actual fitness and survival.
Where are the measurements? Where are the tests that show this really is the optimal structure, better than any conceivable alternative?
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The Burgess paper does not discuss Tiktaalik or any common ancestral tetrapod. Burgess would not subscribe to your suggestion of foresight. He is a card carrying ex nihilo YEC with full AiG approval.
Could you clarify your understanding of that paperâs criteria for determining optimality of limb anatomy?
Having read the paper, it strikes me a bit strange they utilize comparisons to human manufactured objects, while at the same time hedging such a comparison by stating:
It is also important to be aware that animal limbs are highly multifunctional and it may not be desirable to copy all of the animal functions in a bioinspired robot. Therefore, an optimal limb (e.g. leg) for an animal may not always be the same as an optimal limb (e.g. leg) for a robot.
And:
In this paper, the term âoptimalityâ generally refers to optimal design in the animal limb for the animal environment. When carrying out bioinspired design, the designer must take into account differences in objectives and constraints between the animal and the robot.
Itâs also strange to me they donât determine optimality based on biological comparisons, especially regarding the above statement, âthe animal limb for the animal environmentâ.
How would something like a whale flipper compare to a cartilaginous fish fin, or a bird wing compared to a bat wing? This paper was wholly unsatisfying when it comes to addressing those types of questions.
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Yes, if theyâre all optimal designs, why are bird, bat, and pterosaur wings so different? How were they all judged to be optimal, and just how big is the optimal region of morphospace, if it encompasses all these as well as, presumably, various unrealized forms?
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Is it me, or is the argument that limb anatomy is so optimal that it can be adapted to a wide range of forms of locomotion in stark contradiction to the original thesis that vertebrate limbs face such ârugged fitness landscapesâ that any adaption is impossible without the intervention of a 'âdesignerâ? So, as you canât have it both ways, which is it?
It is also worth repeating that we seem to have no more actual evidence (ânot a single simulation or experiment doneâ) supporting âoptimality therefore designerâ than we did for ârugged fitness landscapes therefore adaptions impossible without designerâ. We are simply left with empty apologetic rhetoric on both sides of this âheads I win, tails you loseâ argument.
Speaking for myself, I am no more impressed by âaccording to Burgessâ or âas Miller saidâ than I was by âaccording to Dembskiâ in Gilâs previous foray.
Gil misattributed the following words of Galileo to Einstein:
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual.
May I suggest a corollary:
In questions of science, the dubious âauthorityâ of all the evidence-free (and evidence-misrepresenting) pontifications of every mountebank in the Discovery Institute, and of every one of its Intelligent Design Movement fellow-travelers, is not worth the humble contents of any single paper that presents, and accurately represents, evidence.
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I donât see why the fact that bird, bat and pterosaur wings are different invalidates the thesis that the basic vertebrate limb layout, characterized by a) the three main joints, b) the two parallel bones in the lower limb, c) a network of small bones in the wrist or ankle, and d) multiple multi-joined digits, allows for all these various forms you are referring to to work optimally. Again, what is remarkable here, what need to be explained, is the versatility of the vertebrate limb pattern that allows for fine-tuned optimal design solutions in so many different contexts.
What needs to be explained is how optimality is being determined in the first place. The Burgess paper you cited doesnât really do this, since their determination of optimality is based on singular mechanical to biological comparisons, as opposed to a range of comparisons of both biological and non-biological structures. And as I pointed out in my prior post, they even hedge such a comparison by stating what is optimal for biological structures may not be optimal for robotics.
Reading the paper, they also have a very narrow view of vertebrate limb anatomy. For example, under wings they state:
The main design objectives for bird wings are to act as an aerofoil and control surface for flight. The wing shape must be adjustable in terms of angle of attack, degree of retraction and wing morphing such as bending of wing tips. Bird wings also need to be capable of retraction when the bird is not flying. Some birds also use their wings to fight or climb. Design constraints include developmental constraints and the requirement for very high stiffness-to-weight ratio to enable flying. Other constraints include the need for replacement of feathers whilst maintaining the ability to fly.
The emphasis of the design of bird wings is placed on flight, however, there are numerous species of flightless birds. Should we consider the wing design of the ostrich, emu, or other flightless species to be sub-optimal?
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Before we even attempt to explain that (natural selection btw) letâs first have it actually demonstrated that the limb pattern is optimal. This has merely been asserted. No comparison has been made anywhere that shows this particular layout outperforms all others.
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Even if the arrangement is merely advantageous, it would be selectable.
The heavier femur allows for load bearing and strength near the body, the radius and ulna allows for rotation, and the wrist and fingers allow for dexterity and manipulation, so yes a workable setup. I do not see, however, why this basic skeletal pattern would be beyond the reach of usual evolutionary mechanisms.
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Texas sharpshooter. There could have been another arrangement that produced even better limbs. In addition, there are many arrangements that are quite far from optimal for how things eventually ended up. An appendix that does nothing much more than sit there waiting to kill you is one example. A spine that is unsuited to upright locomotion without causing chronic back pain is another. Moreover, there is no telling how many possible âoptimalâ arrangements never happened at all because evolution is a random rather than foresightful process.
IOW, âTexas sharpshooter.â
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âfine-tuned optimal design solutionsâ
What does âfine-tunedâ even mean when there are so many solutions? How can all of them be optimal? You arenât addressing the point. What makes you think that some other basic arrangement couldnât also be âoptimalâ?
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The data gathered by the authors come from in vitro studies. This is a huge limitation, for enzymes might appear suboptimal in vitro, under laboratory conditions, but be well-optimized to their natural cellular environments which are not replicated accurately in experimental setups.
Moreover, the authors base their analysis exclusively on kinetic parameters. But optimality should be judged by considering that enzymes must balance multiple often competing needs, such as stability, substrate specificity, or adaptability to different environments.
Bottom line: the article you mentioned doesnât demonstrate that enzymes are suboptimal.
But as the optimality has been largely assumed rather than demonstrated, it is not clear that there is anything âremarkableâ that âneed [sic] to be explainedâ.
Putting it another way, the simplest explanation for this assumed optimality is that the assumption is simply wrong.
Bird inhabit a very wide constellation of niches. Bats on the other hand inhabit a far smaller and more constrained set of niches â mostly nocturnal (or crepuscular), and mostly insectivores, frugivores or nectarivores. This highly restricted set of niches, and the fact that the niches either involve stationary food-sources (fruit and nectar) or the added advantage of echo-location (nocturnal insectivores) suggests that bat-flight may not allow bats to compete on equal footing with avian flight. One obvious disadvantage (and thus suboptimality) is that most (but not all) bats cannot take off from the ground. This vulnerability would tend to both preclude ground-foraging niches, and make them more vulnerable to predators.
I cannot see how bat (or for that matter pterosaur) wings can be claimed to be âoptimalâ without some detailed exploration of such issues. Are bat wings truly optimal, or simply âgood enoughâ to get by where either an immobile food source, or the extra advantage of echo-location blunts the disadvantage due to their sub-optimal wings?
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They compare the performance of enzymes from primary and secondary metabolism, where the kinetic parameters from primary metabolism are superior to those of secondary metabolism. Which makes sense because the enzymes of primary metabolism are usually rate-limiting for growth, where those of secondary usually arenât.
Your list of possible excuses for why the study should fail to show suboptimality for enzymes would the require some exceptionally odd and ad-hoc hypothesis that enzymes from primary and secondary metabolism should be subject to differences in selection for and constraints on stability, substrate specificity etc. Or worse, that the kinetics of enzymes of primary metabolism would be better suited for in vitro environments than those of secondary metabolism. Why would they? Or why enzymes that act on larger substrates that diffuse more slowly should have worse kinetic parameters on average in vitro but not in vivo. Why should enzymes that act on larger substrates or function in secondary metabolism systematically require less substrate specificity, or higher conformational flexibility (or even stability) at the cost of kinetic parameters, than those of primary metabolism? None of that makes sense.
Really what the study show is that as expected, enzymes with activities less visible to selection (such as those of secondary metabolism), or that act on larger and more slowly diffusing substrates (which the substrates would do both in vivo and in vitro) naturally havenât been able to to be adapted to the maximum catalytic rate. Which only makes sense as the product of the enzymesâ kinetic parameters being limited by their visibility to selection over geological time, not as a product of some weird and ad-hoc idea that other entirely hypothetical design-parameters still somehow make them optimal.
So this study does in fact show that the average enzyme is sub-optimal, and that their parameters reflect the competing forces of drift and selection. That they are the products of evolution in populations of limited size and geological time, not of intelligent design.
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This threadâs title inspired me to produce the following:
The original version was not sufficiently âpeacefulâ for Peaceful Science, so I kept editing the list of classic Sharpshooter Fallacy offenders. And that is why I finally decided to provide a fill-in-the-blank so that you can all supply your favorite ending to the punchline and then post it on your office door.
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I donât think you understand what is meant by the term âoptimized.â If a particular arrangement is well suited to a number of different situations, that is the opposite of âoptimizedâ
Whereas, the observation that many different arrangements well-suited for multiple situations can be traced back to an arrangement that is less specifically suited to any one of those situations is exactly what evolution would predict. It certainly argues against the common ID claims that biological systems have to be âdesignedâ for a given purpose.
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