Kodiac Bears and Polar Bears

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There are plausible evolutionary explanations either way, it’s true, but that doesn’t stop the finding of Tiktaalik being a successful fulfillment of a specific prediction that served to provide further evidence of common ancestry and our ideas about tetrapod evolution.

This is a good philosophy paper by Elliot Sober on the subject that you might be interested in:

https://827166e3-a-bf4ca052-s-sites.googlegroups.com/a/wisc.edu/sober/selected-papers/PS-2009-Absense_of_Evidence.pdf?attachauth=ANoY7coPCQ67uwKb42Dj3JX2_Fal8qEtW6YavuSFnsiUJruXKfWxfxLQwiM6XAdMmw2NHGfdKrUymVCL4cupevpa3Ssafz4fwqHJHUoCnQLcOLnOge0oXiiGEL390TlOh2TgwhHHVwzYZYVrMa_UQHTtm9fcz0w2xapDh5AqiaKrSNcDW1HONZIcq8gaLTvP7sxX85Xu5NhgVwjyMfsHz-hOk3yeFdLyS-glc1U1vSkUA8vm_2EKxNKNtpRd8qlfdnP84YE0iIFl&attredirects=0

The abstract:

‘‘Absence of evidence isn’t evidence of absence’’ is a slogan that is popular among scientists and nonscientists alike. This article assesses its truth by using a probabilistic tool, the Law of Likelihood. Qualitative questions (‘‘Is E evidence about H?’’) and quantitative questions (‘‘How much evidence does E provide about H?’’) are both considered. The article discusses the example of fossil intermediates. If finding a fossil that is phenotypically intermediate between two extant species provides evidence that those species have a common ancestor, does failing to find such a fossil constitute evidence that there was no common ancestor? Or should the failure merely be chalked up to the imperfection of the fossil record? The transitivity of the evidence relation in simple causal chains provides a broader context, which leads to discussion of the fine-tuning argument, the anthropic principle, and observation selection effects.

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Just to be clear, I have no problem in general with common descent, and would of course expect that tetrapods evolved from sea-going vertebrates, so whether or not Tiktaalik had ever been found would make no difference to me.

All my criticisms of evolutionary theory have revolved around the questions of mechanism: I find significant disagreement among the real experts, and I find that the non-experts (sometimes biologists who have zero publications or research in evolutionary theory, sometimes people who aren’t even biologists, but merely self-styled champions of “science”) who fill the internet with their opinions about evolutionary mechanism only cloud the issue.

I have always found neo-Darwinism unconvincing as a mechanical explanation, and even when supplemented by “neutral theory”, I don’t find the typical narrative very convincing. I see too much apparent teleology in organic nature to believe that variation, mutation, drift, selection, the occasional lateral gene transfer, etc., even all taken together, can adequately explain what we see. This has nothing to do with creationism (I’m not a creationist); I simply find the typical evolutionary explanations unconvincing. But again, this all has to do with mechanism, not evolution as a process, which I’m quite willing to accept. So most of the “creation vs. evolution” debate is a waste of time for me. I’m really interested in questions of teleology, design, etc, not in disproving common descent.

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You sound much like an ID advocate :smile:

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You commented on the ability of evolution to explain “everything”:

I addressed that point, and directed you to a paper that specifically explains the value of such predictions.

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My criticism was not against evolution (which I define as a process of descent with modification), but against “selectionist” explanation which is so loose that it is compatible with any outcome. If natural selection can explain any outcome at all, if it can never be falsified no matter what the evolutionary process produces, then it is just as guilty of being unfalsifiable as the hypothesis of an omnipotent designer. I don’t think you were here at the beginning of this conversation, but it was that charge I was responding to, when another commenter here attacked the hypothesis of an intelligent designer.

My criticism of the elasticity of “just so stories” was not new, as it can be found in Lewontin and Gould, who are surely not “anti-evolution.”

I’ll take a look at the paper when I get time. Thanks for the reference.

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You said:

What does any of that have to do with selectionist explanations?

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Credit where credit is due. @Eddie did not say Darwinist or Darwinian. That is progress!

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48

You’re right; I have confused the argument here – I’ve been debating with about six different people here at once, and they are jumping in at different times, sometimes referring to the others, and sometimes not. Let me rephrase, to clarify:

  1. My original point to an objector was that the flexibility of “just so stories” regarding natural selection (the neck of the giraffe, etc.) made natural selection into a mechanism that could explain any result – and its opposite, therefore nullifying the explanatory value of natural selection. The person I was objecting to said that an omnipotent designer could explain any situation at all, and therefore was of no explanatory value. I was pointing out that often natural selection explanations were so speculative and loose that they fell under the same criticism.

  2. I then made the point that I don’t have any dog in the fight over common descent – common descent is fine with me. So I don’t really care whether or not fossils like Tiktaalik are found; I’m willing to grant that many transitional forms (or cousins of transitional forms, if one wants to be picky) are lost, so I wouldn’t say that the fish-reptile transition didn’t happen merely because we hadn’t found Tiktaalik. Absence of evidence is not evidence of absence, as they say.

  3. Then I confused the issue with the paragraph you quoted. So set that paragraph aside, and let me restate:

I’m perfectly willing to allow flexibility regarding dates. If we find a fossil elephant that is two million years older than the earliest previous specimen, I don’t think that in itself is a threat either to common descent or to particular evolutionary mechanisms. On the other hand, if evolutionary theorists find themselves frequently surprised by fossils that turn up significantly too early, then that suggests that they don’t have as firm a hold on evolutionary causality as they pretend to.

So, for example: Say an evolutionary theorist lectures a creationist on evolution, explaining that it proceeds by random mutations filtered by natural selection, and that the rate of mutations has been determined by experimental biology, and then goes on to inform the creationist that it would need 10 million years at that rate to turn a shrewlike mammal into a bat, and that the fossil record provides that 10 million years for the transition. All is well. But now, say the evolutionary theorist finds himself faced with a new fossil that shows only 5 million years between the shrew and the bat, what does he do? If he says, “Well, the mutation rate must have been much greater than we supposed” – then he is providing an ad hoc patch to rescue the model (i.e., that evolution proceeds by filtering mutations by natural selection). But why not, instead of deciding that the mutation rate was double, decide that the model itself (random mutations filtered by natural selection) is the problem? Why try to rescue the model by inventing ad hoc facts? Why not use the facts to cast doubt on the model?

If the issue were only common descent, this would be less of a problem, but since promoters of evolution are often also concerned with pushing a particular mechanism (varying according to the theorist), it often looks as if the defense of the model is more important than anything else. Of course, this is not new in science; it has been going on since the beginning. The complicated systems of epicycles etc. envisioned by astronomers were designed to preserve the belief that the planets moved only on circular paths, in the face of empirical evidence that they did not do so. The ability to add epicycles at will (not to mention eccentrics and equants) enabled the person determined to hold onto circular motion to do so regardless of what observation showed. Scientific people dearly love their theoretical explanations, and are loath to let them go, until they are absolutely forced to. This sort of infinite flexibility is usually ridiculed when we look back on the history of astronomy, as a desperate form of special pleading to save a favored hypothesis; but the same skepticism about elastic explanations should apply to evolutionary models (I’m speaking of causal models, not common descent simply) as well. And of course, not just to evolutionary models, but to analogues in any area of science.

P.S. I found the Sober article. Its argument concerns common descent, and I see now why you cited it in response to my remarks. I don’t have time to read it in detail at the moment, but I doubt I would disagree with his point about common descent and fossils. But I’m really more interested in proposed evolutionary mechanisms than in proving common descent. I’m interested in why evolutionary biologists are so confident that their mechanisms can explain all the integrated complex systems we observe in organic nature. And this concerns much more than common descent, and much more than population genetics; it take the discussion into the theory of biological form, the facts of developmental biology, evo-devo, etc. I’m convinced that the really interesting stuff about evolutionary mechanism lies somewhere in there. The genetics, the spreading of genes through populations, is of course important, and needs to be learned, but it doesn’t really tell us how and why organisms are built. Other areas of biology need to be called in. My understanding is that people like Newman, Wagner and others are working in this vein. I think that’s great.

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We can’t ask the Ptolemaics about this, but I’m inclined to doubt your assessment.

According to Kuhn, the system of cycles and epicycles made better predictions than the Copernican system. It seems unlikely that you would have accurate predictions from a system that gives infinite flexibility.

To do astronomy at all, you need a coordinate system. My assumption is that a system based on circles looked like a useful coordinate system. And then the epicycles were added as a way of tweaking the system to give better predictions.

The reason that scientists hold onto old theories, is that they have a proven record of working. Scientists are pragmatists. They are reluctant to throw out a theory that is working well, and replace it with a new fangled theory that has not yet proven itself.

Incidentally, this is why there is so much criticism of ID. It is a new-fangled theory that has not even made the effort to prove itself. Science isn’t about nice sounding explanations; it is about the ability to make useful predictions.

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I taught a course on the rise of modern science just a year ago, and in the course of it read voluminously on Ptolemy, Copernicus, epicycles, etc., and also made use of a number of really good animated simulations of ancient and medieval systems of planetary movement, so the material is reasonably fresh in my mind.

Yes, it is true that up to about 50 years after Copernicus, the Ptolemaic system produced better predictions. But my point was about the motivation behind the system. All historians of science and historians of ideas know that the motivation came from Greek notions of circle as the perfect figure and circular motion as the most perfect motion. This religious/aesthetic preference governed ancient Greek astronomy, and through it, European astronomy, up to the time of Kepler. In fact, Copernicus himself still insisted on circular motion of the planets; he kept that assumption, while making the earth move. It was only after Kepler that Europeans gave up the Greek demand for circular motion, and accepted (ugh!) elliptical motion for the planets.

The epicycles (themselves more circles!) were introduced in order to preserve the notion that celestial motion was always circular. The empirical evidence was quite against this: the planets exhibit retrograde motion which could not be explained by normal circular paths. The introduction of epicycles and other geometrical devices were made to “save the appearances”, i.e., to square observed motions of the planets across the sky with the demands of circular theory. On the face of it, the observed motions destroyed the hypothesis of circular motion, so there had to be a rescue by an ancillary hypothesis, e.g., that of epicycles. By having the planets move on circles which themselves had their centers on the path of larger circle, one could obtain a combined motion that matched the path of the planets across the sky. If that wasn’t quite accurate enough, one could add second-level epicycles (epicycles revolving around epicycles), or could resort to off-center circles (eccentrics) or to “equants”. (No point in explaining that one without a diagram.) The point is that the whole system was motivated by a prior metaphysical/religious/aesthetic commitment to the divine perfection of the circles. Nature was battered into shape, a circular shape, to please the holders of the theory, and observations that contradicted the theory were explained away.

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Looking at it from a modern viewpoint, the Ptolemaics were not wrong about epicycles as purely a descriptive model. After all, epicycles form a complete basis that can be used to describe any trajectory. The Ptolemaics were just very mathematically inefficient due to their dogmatism. And the first Copernican model was just as bad as it assumed that the heliocentric orbits were circles, so it also required epicycles. The real breakthrough came when Kepler changed from circles to ellipses, no longer requiring complicated epicycles.

So from this rough historical picture (which is probably wrong in some details), we see that the real shift was a shift of aesthetics, not predictions. Were using circles more important than simplicity and mathematical effectiveness? Nowadays people’s definition of elegance in theoretical physics is closer to mathematical effectiveness. But perhaps for the Platonics and Ptolemaics using circles was more elegant for different reasons.

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52

It can make some predictions about future events… Some is better than none. Evolutionary theory can make none. If you want to argue that evolutionary theory has no responsibility to do so, then fine. But the implication of that is that evolution is not a lawlike process, because if it were lawlike some prediction would be possible, as is the case in sciences which study lawlike processes.

But if you are willing to concede that evolution isn’t a lawlike process, I’m not sure I would disagree; evolution as usually conceived by evolutionary biologists – dependent on variation, mutation, drift, fortuitous endosymbiosis events, etc. – isn’t a lawlike process. So it’s not surprising that most evolutionary biologists would deny any obligation to predict future events.

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You are displaying your ignorance. Evolutionary theory makes many predictions about the future. Much of it is law like.

How much deeper do you want to dig?

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You’ve just contradicted yourself, Joshua. You told me above that evolutionary theory didn’t do so, that by “prediction” it meant something entirely different.

Give me an example of a prediction that any evolutionary theorist since Darwin has made about the evolution of future species, which has since come true. Did Gaylord Simpson predict the extinction of some bird in the Amazon? Did Dobzhansky predict that the coyote would be outcompeted in the American Southwest by the wolf? Did Ayala predict new varieties of fruit that would evolve in the Indonesian rainforest?

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How is this a fair requirement when evolutionary progress can take millions of years to come true?

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I did not contradict my self. I said that it makes predictions, just not the ones you are asking of it.

Thank you for providing great examples of predictions that it does not make. Just like there are many things that chemistry does not predict. This is all Brownian motion.

There are other things that evolutionary science does predict.

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I had my flu shots last week.

Are you asserting that having flu shots was a waste of time?

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Some would; not all would. Rabbits reproduce pretty fast. You can get a lot of generations in 50 years. Enough for an invading rabbit population to steal enough food from some other small mammal population to – at least in principle – make a visible difference in populations to forest rangers, government ecologists, etc. who keep track of such things. So a prediction might be possible. Sure, the 30-year-old evolutionary theorist might not see the results until he was 80, but science is supposed to be an activity of the race, that transcends generations. I’m not saying all predictions could be tested in our lifetimes. But they could be tested over longer periods, if biological records are kept.

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I’m waiting for an example of a future evolutionary outcome predicted by an evolutionary theorist.

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It predicts that usually divergence is the product of divergence time and mutation rate.

T = M R

From that, we predicted the rate of mutation in humans, by looking at the amount of differences between humans and chimps, before we could even measure it. That fundamental formula ends up predicting just an immense amount of biology.

That is just one example. Let’s start there to make sure we are on the same page.