Saturday, August 21, 2010

The Law of Compensation

Are there constraints to how species can vary? A generation before Darwin the German polymath Johann Goethe and French naturalist Etienne Geoffroy Saint-Hilaire formulated their teleological law of compensation in which biological variation occurred according to functional needs. Darwin argued that the law did not apply to organisms in their natural environments. “With species in a state of nature,” Darwin argued that the law of compensation was true to a certain extent for domestic productions, “it can hardly be maintained that the law [of compensation] is of universal application,” even though “many good observers” believed it to be true.

Darwin then cited two particular species which he claimed supported his position. Most readers were probably impressed with the wealth of biological details that Darwin presented in his argument, but his logic was circular.

Darwin argued that the unique features of these two species show that the law of compensation does not hold in the wild because, after all, such unique features must have evolved. Darwin presupposed the truth of evolution in order to find evidence for evolution.

Let’s have a look at Darwin’s argument. Cirripedia, a class in the crustacea phylum, are sessile and highly unique barnacles upon which Darwin had completed a major systematic study. Over against Goethe and Geoffroy, Darwin argued that natural selection, rather than any internal law of biology, could bring about changes he argued were evident in two species named Ibla and Proteolepas:

If under changed conditions of life a structure, before useful, becomes less useful, its diminution will be favoured, for it will profit the individual not to have its nutriment wasted in building up a useless structure. I can thus only understand a fact with which I was much struck when examining cirripedes, and of which many analogous instances could be given: namely, that when a cirripede is parasitic within another cirripede and is thus protected, it loses more or less completely its own shell or carapace. This is the case with the male Ibla, and in a truly extraordinary manner with the Proteolepas: for the carapace in all other cirripedes consists of the three highly-important anterior segments of the head enormously developed, and furnished with great nerves and muscles; but in the parasitic and protected Proteolepas, the whole anterior part of the head is reduced to the merest rudiment attached to the bases of the prehensile antennae. Now the saving of a large and complex structure, when rendered superfluous, would be a decided advantage to each successive individual of the species; for in the struggle for life to which every animal is exposed, each would have a better chance of supporting itself, by less nutriment being wasted.

Thus, I believe, natural selection will tend in the long run to reduce any part of the organisation, as soon as it becomes, through changed habits, superfluous, without by any means causing some other part to be largely developed in a corresponding degree. And, conversely, that natural selection may perfectly well succeed in largely developing an organ without requiring as a necessary compensation the reduction of some adjoining part. [Origins, 6th Ed]

Darwin was not simply applying his theory to a set of observations. He was not illustrating how evolution might have formed these species. Rather, Darwin was building an argument for natural selection. But in constructing his argument, he presupposed that the species had evolved.

Darwin was unquestionably an expert on barnacles, and he could present a detailed example of highly-modified species that most people have never even heard of. But Darwin begs the question when he says that the unique structures of the Ibla and Proteolepas evolved and therefore natural selection can effect such changes.

12 comments:

  1. Dr Hunter:

    Darwin was not simply applying his theory to a set of observations. He was not illustrating how evolution might have formed these species. Rather, Darwin was building an argument for evolution. He was trying to show how species are not limited in how much they can change. But in constructing his argument, he presupposed that the species had evolved.

    To conditionally suppose the truth of a hypothesis is a step in normal inductive reasoning. There’s nothing illegitimate in Darwin’s approach here.

    For example, I’m making toast and the lights go out. I “presuppose” that there’s a causal connection between the two events, and I further “presuppose” that a surge of current in the toaster blew a fuse. So I check the fuse box. Lo and behold, I find a blown fuse. I have tested my presuppositions (hypotheses). Scientists following Darwin have been testing his hypotheses rigorously since his day.


    Darwin was unquestionably an expert on barnacles, and he could present a detailed example of highly-modified species that most people have never even heard of. But Darwin begs the question when he says that the unique structures of the Ibla and Proteolepas evolved and therefore variation is not limited in the wild.

    Again, Darwin is logically and legitimately exploring the implications of his hypothesis, begging no question.

    Anyway, thanks for bringing up Goethe and Geoffroy and the Loi de balancement. Landmarks in the history of science

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  2. David:

    Follow up the implications, i.e. at most we have provisional empirical support from a case study for a particular hypothesis, not demonstrative proof of an overall claim.

    Second, we --STILL -- do not have a credible chance and necessity account of the origin of the relevant regulatory information or of the genetic information that provides the complex functional structures, starting with the very first life form. Instead, the implicit assumption is that variation is sufficiently unlimited that it provides what is needed, AND that it somehow escapes the problem of compensating losses in functionality. Which was an empirically supported observation.

    So, a hypothesis on a different matter, was used to dismiss an empirically well-warranted law. (Last I looked, antibiotic resistant super-bugs have compensating losses in general capacity.)

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  3. GEM of The Kairos Initiative wrote:

    Follow up the implications, i.e. at most we have provisional empirical support from a case study for a particular hypothesis, not demonstrative proof of an overall claim.

    That is correct. Science can do no more.

    So, a hypothesis on a different matter, was used to dismiss an empirically well-warranted law.

    Darwin did not dismiss the so-called "Law of compensation", he evaluated it in light of his hypothesis of natural selection.

    The so-called "Law of compensation" is, of course, not a law, but another hypothesis.

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  5. GEM of The Kairos Initiative wrote:(Last I looked, antibiotic resistant super-bugs have compensating losses in general capacity.)

    We see compensation loss throughout evolution. Multicellular life yields increased time between generations compared to single-celled life, time in which the organism can be consumed. Eubacteria have an efficient genome with few introns and little junk, yielding fewer possibilities for morphologic change, though not hurting their status as the planet's master chemists one iota.

    Macrostomatan snakes (essentially all the snakes the nonscientist would be familiar with) have demolished their capacity to pick up airborne sounds as a result of increasing their gape. There is no logical reason from a design standpoint as to why hearing should be so tightly related to the working of the jaw, but with an understanding of evolutionary history, we see it as yet another quirk arising from exaptation (of the fish hyomandibular bone to serve as a stapes in tetrapods) rather than creation ex nihilo.

    Humans, of course are not immune from these types of problems, having a large, productive brain but dangerous childbirth as a wide pelvic opening inhibits balance in bipedal walking.

    Evolution has great flexibility (not fully taken advantage of by early breeders working with small populations that are not genetically diverse to begin with and that offer fewer mutations) but definitely works under the constraint of history.

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  6. Another post attacking Darwin. Science has come a long way since then. It might be more interesting to discuss the evolution of the "G-matrix" (Google turned up this paper), a more modern incarnation of trade-offs underlying multiple traits.

    In honor of a new contributor to this blog, Gordon E. Mullings, one might even call such attacks on Darwin strawmen soaked in the oil of ad hominem and ignited to poison the atmosphere, or something like that.

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  7. "Darwin was not simply applying his theory to a set of observations. He was not illustrating how evolution might have formed these species. Rather, Darwin was building an argument for evolution. He was trying to show how species are not limited in how much they can change. But in constructing his argument, he presupposed that the species had evolved."

    Of course he did. Darwin had already made the original observations that reinforced his changing views of nature. By the time he wrote this, he was convinced that evolution was a viable hypothesis. When he began his scientific adventures on board the Beagle, he was an ardent believer in fixity of species. His work, that of Lamarck (who was a brilliant naturalist, by the way), Alfred Russel Wallace and Charles Lyell, slowly led to him changing his views. It is not circular to say that Darwin was building a case for evolution, if that theory explained his other observations. All of our observations of black holes are based on our understanding of gravitational theory. It isn't circular to say that "black holes exist because they fit our understanding of gravitational theory" anymore than it is circular to say that Darwin's observations fit his understanding of evolutionary theory. Gravitational theory predicts black holes, and we have evidence that they exist. Evolutionary theory predicted what Darwin found.

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  8. Cornelius,

    You like evolutionist-Darwinists seem to have a problem with the idea of law in the sciences. Laws are not out there to be discovered, and not put out there by [placeholder]. A law is merely a mathematical relationship describing a phenomenon. Geoffroy's law isn't scientific, and as one of my scietists on this board says, it is a very rough hypothesis. The terms such as "form", "fixed" etc., have no rigorous operational definition to be tested or put through experiment.

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  9. Wasn't Geoffrey's law based on Empirical evidence? It was an attempt to explain why artificial selection and selective breeding only goes so far.

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  10. Nat,

    Geoffrey wasn't quite there even by the standards of the day, and definitely not by today's standards of evidence. But he was certainly way ahead than today's ideology/religion/metaphysical oriented evolutionist-Darwinists who spend a lot of time trying to discredit evolutionary biology. Geoffrey was a great naturalist - no doubt. Better methods lead to better theories, so we have moved far past Geoffrey.

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  11. I think that even today's breeders are way beyond this law. My wife is a Chicken/Flower breeder and while most breeding is just selecting from the existing gene pool, mutations do pop-up and most breeding manuals will list when these mutations occurred.

    Over time, there will be more mutations and the plant or animal will look less like it's wild ancestor. This is particularly true of some of the food plants that we have been using for thousands of years. The current varieties look nothing like their ancestors and to even consider that all of the genes for the current varieties existed in the originals is ridiculous. Dawkin's "The Greatest Show on Earth" has some great photos of these original wild plants.

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  12. Dr. Hunter you are misrepresenting what Darwin is saying in the paragraph which is clear form the sentence you omitted before your citation:

    "I suspect, also, that some of the cases of compensation which have been advanced, and likewise some other facts, may be merged under a more general principle, namely, that natural selection is continually trying to economise in every part of the organisation."

    The only thing Darwin wants to demonstrate is that under the assumption that the ToE is true The Law of Compensation can be explained by natural selection. And he provides examples for that. Neither are these or the paragraph meant to prove the ToE in general nor natural selection in particular are true.

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