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Topic: Lack of vestigial organs suggests design
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Zia H. Shah
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Member # 284
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posted 28. May 2002 13:04
There are hardly any or very few vestigial organs in human body. This suggests intelligent design (ID). To give an example, there are hundreds of skeletal muscles in human body and it is suggested in respect of only one or very few that they may not have a significant function.
If humans evolved as a result of unintelligent phenomena then it will hold to logic that there would be numerous vestigial organs in the body as long as they did not introduce a significant disadvantage to their recipients.
William Paley, the pioneer “secular” spokesperson for “Argument from design” observed the following about nails:
“The scarf-skin, which clothes all the rest of the body, gives way, at the extremities f the toes and fingers, to nails. ….. If the deviation were accidental, an error, an anomalism; were it anything else than settled by intention; we should meet with nails upon other parts of the body. They would be scattered over the surface, like warts and pimples.” Natural theology, Chapter XI
(I have added the adjective “secular” for William Paley as the religious prophets have been doing the same job over the centuries.)
It is claimed by the Human Genome Project that 90-95% of human genome is redundant. If that be true, then in that line of thinking, one would expect numerous vestigial organs, filling the major portion of abdomen, chest and skulls of humans.
It would be interesting to find out whether Neural Networks or other means of Artificial intelligence lead to extensive redundancy?
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James A. Barham
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posted 28. May 2002 18:55
Ziah:
You raise a very interesting point about vestiges. Many anatomical structures whose functions were initially unknown were labelled "vestiges," only to be relablled as functional when more was known about them (the thymus is a classic example).
Here is another fine example of the same phenomenon that I recently read about and that you might be interested to know about (if you don't already).
Horses have long tendons in their legs with very short muscles attached to them (digital flexors). It had been widely assumed that such short muscles must be vestigial, but a convincing case has now been made that they serve to damp vibrations in the tendons (see A.M. Wilson et al., Nature, 2001, 414: 895--899, as well as the "News and Views" commentray by the eminent expert on biomechanics, R. McNeill Alexander (pp. 855 & 857)).
Alexander ends his commentary piece by musing: "Their work makes us wonder whether other vestiges (such as the human appendix) are as useless as they seem."
What to make of this? I think that the traditional distinction between "functional" and "non-functional" based on hypothetical selection history is unsupportable, and should be replaced by some sort of teleological, engineering criterion. Obviously, not all functions are created equal (we can live without the colon, but not the liver), so I have argued that we should use a "central/peripheral" distinction, in relation to the dynamical stability of the organism as a whole, to classify functions, instead of such traditional concepts as "selection of vs. selection for," "selected vs. neutral," "exaptations," "spandrels," and all the rest of the increasingly scholastic jargon of Darwinian evolutionary biology.
It is in cases like so-called "Junk DNA" (which is almost certainly functional, even though it doesn't "code" for protein) that we see the best example of the harmfulness of Darwinian thinking for science. It is a form of intellectual laziness to assume that something we do not currently understand the function of, has no function. I think that it is demonstrable that the Darwinian style of thinking is actively blocking progress in such cases.
[ 28 May 2002, 18:56: Message edited by: James A. Barham ]
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Frances
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Member # 169
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posted 28. May 2002 19:42
quote:
It is in cases like so-called "Junk DNA" (which is almost certainly functional, even though it doesn't "code" for protein) that we see the best example of the harmfulness of Darwinian thinking for science. It is a form of intellectual laziness to assume that something we do not currently understand the function of, has no function. I think that it is demonstrable that the Darwinian style of thinking is actively blocking progress in such cases.
A good point but did such thinking block progress? Or did Darwinism take into consideration new findings about 'junk DNA'? New data increased our understanding which seems to show that a reliable design inference requires one to be omniscient, that is all relevant and yet to become relevant hypotheses need to be rejected before design can be infered. This is an inherent problem for an eliminative approach which also claims to be free from false positives.
But I find it fascinating to hear the accusation of 'Darwinian style of thinking is actively blocking progress' because it assumes that something whose function is not yet understood cannot be understood. Yet this seems to describe the ID inference which is eliminative and claims to have no false positives. Does this mean that we can extend the argument to suggest that ID's approach might block progress? In fact, is what happened with Junk DNA typical only for Darwinism or is it typical for any version of scientific inquiry? That is that we might find that our hypotheses were erroneous when more data is collected? Perhaps we should not single out Darwinism as being unique in this area?
As far as vestigial organs are concerned there are quite a few excellent examples to be found. Male nipples, hindlimbs in snakes or whales, wings on flightless birds, non functioning eyes in cave fish etc.
We even know of such rudimentary organs that arise during embryological development (pharyngeal pouches, teeth in whales). The question to ask if finding a function yet unknown for such rudimentary organs would be a challenge for Darwinism.
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LePlage
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posted 29. May 2002 07:45
The subject of vestigial organs is an interesting one. To make a discussion of the subject fruitful I believe that some distinctions must be made.
First we must define what a vestigial organ is.
Is it:
1) An organ with no present function that seems to be derived from an ancestral functional organ?
2) An organ that has function but presumably had a different original function in an ancestral organism?
The classical darwinian interpretation is the first one, and this kind of vestigiality is the one most contradictory to a design perspective. However, as mentioned by James and Zia, the number of organs that truly fit this description has steadily decreased. It seems reasonable to assume that in the end there will remain few vestigial organs. The case of blind cave fish is an example of where this definition of vestigiality will probably remain true.
Vestigial organs defined as in 2) is another question. I believe that several of the examples Frances mentioned fits into this description. The wings on flightless birds for example are used for balance, swimming and other purposes. The point I want to make regarding vestigial organs according to this definition is that they are less conclusive in a comparison between a teleological perspective and a darwinian one.
I do not believe that darwinian theory necessarily predicts vestigial organs in the sense of 1). Intuitively the darwinian theory fits rather well with both cases of vestigial organs, but I believe that morphological features in general are quite much under pressure from natural selection. Organisms that did not evolve co-option strategies for their useless organs (as the swimming-function of the penguin wing) should not have survived.
In the case of junk-dna I see no reason for natural selection not to tolerate a fair amount of functionless junk in the genetic code. If there in fact is function in it all, I believe that it would favor a teleological perspective.
I want to emphasize that I consider darwinism to be a quite flexible theory in this case and that neither a high degree of perfection nor a degree of suboptimality would be regarded as significant problems for darwinian theory.
To James:
I believe that you are partially right about darwinism being a stumble block in this area, simply because it really does not provide any guidance in this matter. But I think that accusing darwinian theory of blocking progress is a bit rough, it rather delayed the progress since it already fitted comfortably with the outcome of junk-dna.
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James A. Barham
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posted 29. May 2002 11:51
On junk DNA:
My remark presupposed that "junk DNA" is not junk at all. There is an increasing amount of evidence for its functionality, especially in regulation of the "editing" process (see many of the essays in L.H. Caporale (ed.), Molecular Strategies in Biological Evolution, NY Acad Sci, 1999). Of course, I could be wrong, and it might really be junk after all.
But just assume for a moment that I am right, and that there is no such thing as nonfunctional base pairs in the eukaryote genome---that every bit of the material in the chromosomes has its functional role to play somewhere or other. Assuming for a moment that that is indeed true, then wouldn't you agree that the opposite Darwinian assumption would have to be seen, in retrospect, as having slowed the investigation of the functional properties of non-coding regions of chromosomes?
I guess you could say, in that case, that "junk DNA" was just a false hypothesis, and every false hypothesis in science necessarily sends us down a wrong track, and so costs us time. But I feel that the default position in biology ought to be that things have functions. The overwhelming evidence seems to favor that position.
This is troubling for the Darwinian, because reductionist science does not know what to do with function. The theory of natural selection does not explain it, but merely presupposes it (because functions obviously must exist before they can be selected). So, the Darwinian impulse is to downplay embarrassing function wherever possible, and stress chance, "bricolage", "spandrels", "junk", anything to avoid addressing the big problem staring us in the face---the fact that the cell, along with all of life, is patently teleological in character. (It is true that one can read Darwinian paeans to adaptation, as well, but I think the more philosophically sophisticated the Darwinian, the more embarrassed he is by teleology and the more he wants to downplay it---witness Gould and Lewontin.)
So, perhaps you are right that in part the problem is a general one facing any scientific hypothesis. But I still think that in biology in particular, Darwinian assumptions are playing an extra deleterious role, because they constitute a systematic refusal to address the essential question at the heart of biology, which is the ultimate source of natural teleology.
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Zia H. Shah
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posted 29. May 2002 13:23
One of the key issues I need to stress on vestigial organs is that if random processes are going to create anything useful at all, they would certainly create more garbage than functional organs. After all it is a random process. How can it score a home run almost every time?
If Darwianian hypotheses do not propose any mechanisms as to how nature gets rid of all the vestigial organs or redundancy, that is not harmful to the organisms, then that can be a seroious criticism against "naturalism". The emphasis is on "not harmful to the organisms".
Where is all the noise and garbage produced by random processes, in the biological systems?
I do suggest that the issue of Junk DNA is a very important subject and we should have a new and separate thread for that.
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Johan de Boer
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posted 29. May 2002 14:51
There are certainly ways in which the cell can get rid of so-called "junk DNA" in genomes (the term junk is of course in the eye of the beholder, for much of it we simply have not yet found a function because that is much more difficult to do than for coding sequences):
1) Genome size may be under selection for smaller size because it reduces the energy requirements for replication.
2) In Rickettsia, deletions in pseudogenes are more common (and longer) than insertions (Andersson and Andersson papers). This tends to reduce the size of the genome by eliminating this DNA.
3) A deletional bias is a major contributor to making bacterial genomes smaller (Mira, Ochman and Moran papers)
4) The rate of DNA loss in Drosophila virilis is approximately 75 times faster than that estimated for mammalian pseudogenes (Petrov et al., 1996) (but only for deletions over 5 base pairs)
5) For differences between mammals and lower species we have to keep in mind that there are billions more individuals of e.g. fruitflies than e.g. humans, and this drives changes a lot faster there.
6) Differences in genome size between species can (sometimes at least) be caused by differences in deletion frequency (see Petrov et al. 2000 Science 287). Crickets have much larger genomes and a slower deletion frequency then the fruitfly.
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Zia H. Shah
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Member # 284
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posted 29. May 2002 15:28
The true test of the junk DNA will be only if human cloning is done. I am not advocating it.
If clones are made and it can be shown that clones without the Junk DNA are just as human and just as capable on several axes, then of course it was junk.
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Johan de Boer
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posted 29. May 2002 16:02
Zia, from a technical point of view that is very very simplistic reasoning. In addition, we don't know what is junk and what is not. The term junk was coined in the time when coding genes were identified and these have easily identifiable function: coding for a protein. The rest was not understood and therefore got the collective term junk. Much of it will end up having a function, and much of it will be real junk (see my previous post). Anyway, such an experiment as you propose might be doable with fruitflies or an amoebe too. There is no need to do it on humans.
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Zia H. Shah
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posted 29. May 2002 16:37
Johan
I did talk about cloning without junk DNA mostly in a facetious manner. I assumed that such experiments will never succeed in producing humans or even life, if the whole of so called junk DNA is deleted. I do share your bias that most if not all of the so called junk DNA will turn out to be functional.
Indeed, it will be better to do cloning experiments with the lower animals.
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charlie d.
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posted 29. May 2002 18:42
Zia:
the pufferfish has happily done away with 90% of its non-coding DNA. It has no signs of the classic repetitive sequences that make up the bulk of human "junk DNA" (Alu's and LINEs). Its genome is about 1/8th ours (400 Mb), with a comparable number of genes.
I say one can safely conclude that 90% of the vertebrate non-coding genome IS dispensable after all.
Further, as far as James's post, although the name "junk DNA" is indeed unfortunate, there has really been no sign of a lack of interest by scientists in its potential functions: hypotheses on its role in gene expression regulation, chromatin structure and chromosomal organization have been around since the beginning, and probably hundreds of papers have been published on the potential functions of repetitive elements, CG-rich islands and such. If "Darwinian censorship" was at play (and why should it anyway? Ultra-adaptationists have always been uncomfortable with "useless" features like repetitive DNA), it sure did not work very effectively.
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James A. Barham
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posted 30. May 2002 08:56
Charlie D.:
If there has been as much intensive investigation of the function of non-coding DNA all along, as you say, then I must stand corrected.
However, in the same breath, you cite empirical evidence that the non-coding DNA has no function after all, so I am a little unclear what you believe to actually be the case.
For me, the bottom line is that all organisms are teleologically organized through and through. The standard natural selection account is an effort to explain this fact away, rather than to give an actual explanation of it. I don't believe it works, for reasons I have already repeated here many times (but will be happy to repeat again, if you wish).
There is a sense in which many working biologists merely give lip service to Darwinism, and do not let it interfere with their day-to-day research, which is squarely based on the premise that all biological structures and processes are functional (i.e., teleological, not to put too fine a point on it). As the late Robert Rosen once remarked, Darwinism in the English-speaking world is a lot like Dialectical Materialism under Communism. "everyone avowed it: It was mandatory to do so. But no one really believed it." (Essays on Life Itself, Columbia UP, 2000, p. x).
But insofar as Darwinism (i.e., the belief that teleology is an illusion and everything is reducible to the random mutation, selective retention mechanism) is taken seriously, then I think it constitutes a kind of mental anaesthetic, and thus a roadblock in the path of science.
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charlie d.
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posted 30. May 2002 09:29
James:
as far as my "personal opinion" on non-coding DNA, I stand where the data are: it is pretty clear that some non coding DNA plays a role in gene expression and in determining chromatin structure. Some of it is involved in chromosomal organization (especially in the telomere and centromere regions). There is even some evidence that some repetitive elements are expressed into RNA, although what that may do is totally unclear.
However, it is also quite evident at this point that a) much (most, probably) of non-coding DNA is dispensable in at least some complex organisms, and b) that the amount of non-coding DNA in any genome is determined stochastically by the equilibrium of deletion/duplication mechanisms in different organisms. Thus, pufferfish and drosophila have a tendency to deletion and have lost most of their non-necessary sequences, while salamanders and crickets have a tendency to retain duplicated DNA, and as a result have comparably large genomes (salamanders have 30 times as much DNA as we do!). Of course, whether such changes in the deletion/duplication equilibrium may have some adaptive value in and of themselves is also open to debate and research.
Like most scientists, I think holding any (adaptationist or anti-adaptationist) a priori assumption about empirically verifiable facts, such as the function (or lack thereof) of "junk DNA", is generally not a good recipe for healthy scientific enquiry.
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James A. Barham
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posted 30. May 2002 19:24
Charlie D.:
Thanks for the clarification.
That all seems fair enough. I would only add that it seems reasonable to assume functionality as the default position, if only because otherwise we are sure never to find out what a thing's function is (if indeed it has one).
That is, we cannot discover something unless we first decide it is worth making an effort to do so.
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