Is convergent evolution evidence against common descent?

Hi randman, this might appear to be slightly off-topic, but Ned thought this might be the best place for it. I'm not entirely sure of that, but I trust his judgement so I'm going with it.The reason why its not entirely on topic is due to the fact that it doesn't really discuss convergent evolution. I would like to discuss with you (and heh - the last time we discussed it it was fairly off topic anyway )Analogy timeLet's imagine we need to convey a secret message to Mr Bush. The message is "Lookout! The terrorists are coming". To do this we use a code book that Mr Bush has a copy of. The number '6' would refer Mr Bush to the message "Lookout! The terrorists are coming". In order to arrive at this number we use a collection of three digits and find the sum of them. For example:
213: 2+1+3 = 6
222: 2+2+2 = 6
312: 3+1+2 = 6
114: 6And so on. We can see clearly here that there are many ways of arriving at the same message.Why is the analogy applicableOK, replace 'message' with protien. So instead of saying "Lookout! The terrorists are coming", we are now saying "Cytochrome c". Instead of using digits, we use A,G,C or T (or rather the chemicals they represent), in three-long 'codons'. Instead of only needing one codon we need 104.Each of the 104 codons refers to an amino acid. Different codons can code for the same amino acid (1+1+4 gives the same result as 2+2+2), and so there are many many different ways of coding for any given protien.Some figuresThere are twenty amino acids that go towards making protiens. There are 4³, 64, different combinations for the codons. The upshot of all this is between one through six different ways of making any given amino acid...which means there are an awful lot of different ways of making a 104 amino acid long protien.A picture is worth a thousand wordsLook at this diagram. It shows the entire DNA string for cytochrome c in humans, and cytochrome c in mice. There are 78 codons which are identical. Is this a strange occurance?How many different ways can these 78 codons have been? Look at the diagram there - 1.3 x 10³³.MorphologyThe way that Cytochrome C is made has no bearing on morphology. Indeed - human cytochrome c can be genetically engineered into yeast cells and they will function identically. Indeed, how the amino acids are put together to form the protien is made is irrelevant to the morphology of the creature. I can say this because it has no relevance to the morphology of the protien.The pointThere is no reason a Creator would code Cytochrome C in Chimpanzees in an identical manner to humans, and code it slightly differently in Rhesus monkeys (one amino acid difference). The fossil record shows us that the general order that life evolved through was fish->amphibian->reptile->mammal (a simplification of course). There is no reason whatsoever for a Creator to code Cytochrome C in similar ways for mammals, less similar for reptiles, less similar again for amphibians and less similar again to fish.In conclusion
The cytochrome c protien could be coded the same way in humans as it is in herring, and dramatically different in Chimpanzees. For some reason, this is not the case. Whilst a Creator might have set this up (for no known reason), it seems more parsomonius to assume this is the result of heriditary and divergance from common ancestry.And this is just considering one protien. We haven't considered this study which looks at over 500 genes, and arrives at the same conclusions. We haven't considered broken genes such as the broken vitamin C gene in primates.Creationists like to use statistics to prove that evolution is so unlikely as to be impossible. The chances of mice and men having the same 78 codons for one protien are approaching astronomical levels. The chances that almost all creatures have the appropriate (for evolutionary predictions) codons is approaching incredulity unless common ancestory is the cause. And this is just ONE protien...this relationship can be found in hundreds of these things.Convergence
I'll add this bit in just to make it a bit more relevant. A diagram is useful here More cytochrome goodnessLook at the bottom two. Lamprey and tunafish. According to evolutionary models, the tunafish is closer related to us than the lamprey, yet the picture shows a different story right? Since we are dealing with random mutations, we have convergence here. When we start to examine other genes, this appearance vanishes.This message has been edited by Modulous, Sun, 05-June-2005 09:05 PM

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Eternity is in love with the productions of time.
The busy bee has no time for sorrow.
The hours of folly are measur'd by the clock; but of wisdom, no clock can measure.

Thanks randman, I hope your OP gets the answers you are looking for. Well - given the odds of it being a coincidence in just the man and mouse scenario I think we can discount it. Especially as the odds get multiplied up when other creatures are examined. So yes, I think it is safe to assume there are common factors involved. I don't see what impact this would have. Can you explain it for me? Agreed, from the mouse evidence we can only conclude that maybe they have had a common ancestor. If we look at more and more organisms we can extend this to find more and more things with a common ancestor. An interesting hypothesis, but there is really no evidence, that I have seen at least, that ACG confers any significant advantage over CCA in the genome (if we assume that both of those sequences bind on the ribosome for the same amino acid). Once again a possibility, but without some kind of mathematical backing, it has the danger of becoming scientific mumbo-jumbo the likes of which Star Trek use. Another possibility, but unfortunately a philosophical one at this time until some evidence for the possibility surface. Agreed. Number 5 was the leading reason for all things until relatively recently, and we know that wasn't lightly dismissed. The others remain hypothesis which need more evidence. Only number 2 has any significant amount of corroborating evidence. Not science, but logic. The only kind of Creator that would follow this pattern, that agrees with cladistics and stratigraphy so well, would seemingly be a Creator that wanted to convince us that evolution happened. Granted. But amazing design and imperfection is exactly what evolution would expect, evolution can also explain why protiens are coded for in related ways in related organisms (to the appropriate degree), explain why the major properties of organisms (warm blooded, wings, gills, lungs) coincides with the protien encodement relatedness, and why the fossil record is in the order that it is. Evolution clearly explains more, explains it better, and explains it more parsomoniously. Of course, we should avoid circular logic. Which is why I clearly said "the fossil record shows us that the general order that life evolved through...". What I was saying was, as above, the protien encodement method of assesing relatedness coincides with the order that life appears in the fossil record. Using the method we can see that primates are closely related, other mammals are less related, reptiles less related still, amphibians even less related and fish even less related. Where related means shared a common ancestor.I even showed you a paper, which you should really look at. It is using a more involved method than the one above, to actually predict where common ancestry should be (which just happens to agree with the fossil record (where fossils exist)). In other words, this is a genetic method of being able to predict the fossil record. If the genes weren't related to the fossil record in the manner described by the ToE how would this be possible? Here is an excerpt from the paper:

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Molecular times for the origin of the major lineages of vertebrates
in the Palaeozoic and early Mesozoic eras are similar to those that are based on the fossil record14 (Fig. 3). The molecular time estimate for the marsupial—placental split, 173Myr ago, corresponds well with the fossil-based estimate (178—143Myr ago)16. The bird—crocodilian divergence is slightly younger than the earliest fossils suggest10, at 240Myr ago, but this difference is less than one standard error. The molecular estimate of the lissamphibian—amniote divergence at 360Myr ago also agrees with the fossil based estimate10,14. Fewer genes are available to time the earliest divergences among vertebrates, but molecular times (of 564 and 528Myr ago) are consistent with the Late Cambrian fossil record for the first appearance of vertebrates (at 514Myr ago)14.

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Another coincidence to go on top of all the other coincidences? You might say that it is not proof, and nothing is certain and that there are other possibilities. Of course there, there as many other possibilities as the human imagination can conjur, but you cannot deny this is strong evidence in favour of evolution.This message has been edited by Modulous, Mon, 06-June-2005 12:26 PMThis message has been edited by Modulous, Mon, 06-June-2005 12:30 PM

Perhaps you should look at Message 78 which will show you a link to a study that uses genetics to calculate common ancestry. Whilst there are, as always, a few anomolies, the technique managed to calculate other things to an astonishing degree, when compared with what we know from the fossil record.It puts marsupials waaaay back in time. The rodents, present the aformentioned anomoly, but are still a lot more recent than marsupials, thus mice are closer to us than they are kangaroos. The more genes and protiens that are studied, the less error is likely to creep in.Ooops - Thanks WK, my mistake. It wasn't message 78, it was my reply to message 78, Message 92 I meant.This message has been edited by Modulous, Tue, 07-June-2005 04:35 PMThis message has been edited by Modulous, Tue, 07-June-2005 05:29 PM

I'd be interested to hear your thoughts on the paper I have presented to you three times. It is a genetic study that shows the split of marsupials happened a long time ago. Since it is based on genetic differences I think this shows that placental mammals are more similar genetically than they are to marsupial mammals.

Actually they assume common ancestry in a couple of cases (for calibration), then they use their calibrated testing device to test what age it would put the divergence of marsupials (for example), and the result they get matches with the physical evidence (fossils). Maybe their callibrating assumptions were wrong, but they produce astonishingly accurate results.This is the equivalent of not knowing the weights of any object, so using what little information you have, you assume the blue object is 1kg...if you then use that assumption and weigh the green object as being 10kg, which closely resembles some information you found in a book (8-11kg), then you might assume your initial assumption (the weight of the blue object) was possibly accurate. Especially when you weigh other objects and they agree to.In short, using this method it shows that marsupials are a long way away from us, and mice, genetically speaking. I know this isn't the direct comparison between morphologically similar placental/marsupillian organisms, but I don't think the general trend can be easily ignored.

Seems to me more like it has a hypothesis, and it tests the hypothesis. Frankly I'd be surprised if other studies haven't been performed in the last seven years. The study already mentions known anomolies...so I'd not be surprised. I'd continue looking at the trend for accurate prediction. I'm totally sure when I entered this thread I said that very thing, and apologised for it. Indeed, in my last post I alluded to that very thing.

Yet both studies agree closely with fossil estimates of 178-143 MYa.

I am aware that 130Mya is out the range, but it is not a significant amount. All measuring devices have error in them. We are looking a three different measuring systems, all with some degree of error. The 1998 study gets the date for bird/crocodillian split as 240Mya (too early according to fossils) and they say "but this difference is less than one standard error".Given the nature of the method, these things are never going to give us times, dates or years. All they do is give us ball parks (much like the fossil records do). If the ball parks are generally in agreement, things would appear to be going swimingly.If the genetic methods consistently gave us 50mya for the split of marsupials and 750mya for split of primates, then we would be in trouble. As it turns out, each method gets the relative splits with a good degree of accuracy, and the dates are not usually far out.

173-130=43 million years.Divide that by two and you get 21.5 million years. If the actual split happened 150 million years ago, both are out by about 21.5 million years. Quite an amount I agree, but not necessarily massively significant.I actually read through the paper (rather than just the abstract) of the 130 million year figure. It actually gives two figures for the age of the split. One is 130 million years (+ or - 9.7 million years), the other is 143 million years (+ or - 16.8 my). Things don't look so problematic now. And given they callibrated their dating to a different point and were looking at mtDNA rather than 600 genes, they were bound to get different figures at the end of it. Amazingly, the more you look at it, the less problematic it appears. Here is the paper

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Eternity is in love with the productions of time.
The busy bee has no time for sorrow.
The hours of folly are measur'd by the clock; but of wisdom, no clock can measure.

Yes, it *could* be convergent evolution...but the fossil record seems to tell a different story. Mammals could not converge to reptilian features, until mammals existed...where did they seem to come from? They arrived on the scene when reptillian creatures dominated the land. Thus it is theorized they evolved from the reptillian creatures, rather than converged to them (that is to say, there is no evidence of convergence and there is evidence of common ancestry). The 'some' you are referring to must be in the minority. Everyone I have seen writing here seems to be discussing the anomolies quite straightforwardly. Its not really a logical inference. We don't know the statistic likelihood of eyes evolving from seperate sources without an arch-designer. Evolution is happy that nature would do this, since vision is a massive advantage to an organism. That eyes end up with similar function is entirely to be expected.The logical inference then, is that nature reinvents things because it is a blind process, but is working from largely the same parameters (pretty much the same things are being selected for and against in the evolution of an eye).

Agreed, I'm saying pretty much the same thing:

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...but the fossil record seems to tell a different story.

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True, but dolphins didn't converge until after dolphin-like creatures existed to do the converging. Which is what I was saying:

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Mammals could not converge to reptilian features, until mammals existed

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When I brought up a 1998 genetic study you called it outdated. Now you are bringing up a 20 year old genetic study and 19th century anatomists? All that the study suggests is that marsupial moles appear to have diverged from other marsupials about 50million years ago.That still places them closer to other marupials than other placental moles, doesn't it? I'd actually be interested to see what anatomists were saying just prior to the molecular data, rather than 100 years before it.

Wow - you kind of missed my point, and concentrated on a jolt of humour. Perhaps I should restate my actual point, which was on topic:

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That still places them closer to other marupials than other placental moles, doesn't it?

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If I'm following the thread rightly here, placental and marsupial moles, was what we were talking about.I'll say another thing again:

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I'd actually be interested to see what anatomists were saying just prior to the molecular data, rather than 100 years before it.

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That is to say, a modern anatomist who didn't have the benefit of genetic comparisons. I would be interested to see if they thought that "it had it closest affinities with the (placental) golden moles".Let's imagine our modern anatomist examines the marsupial mole and finds (to paraphrase from Message 239)The braincase is small and narrow. It houses a relatively small and simple brain compared to that of similar-sized placentals.
The jugal is large, extending posteriorally so that it actually contacts and forms part of the glenoid fossa.
The lacrimal canal is slightly anterior to the orbit so that it opens on the surface of the face rather than inside the orbital space.
The bullae are sometimes not ossified, and when they are, they are formed largely by extensions from the alisphenoid.Would they consider that more closely related to a placental mole or a wombat?Your counter to this is that over a century ago an anotomist initially couldn't find the epipubic bone (I assume then, that he eventually found it, and speculation wasn't so rife?). Whereas my one sentence and one question were mildly off topic - this entire rant is totally off topic. We are talking convergent evolution, currently revolving around marsupial and placental mammals. Is it me or is going off topic with wild generalisations about the debating tactics of your opponents, the comparisons it has to politics, dogma and exagerating about exageration, a tad ironic? Don't answer of course, it would be off topic (unless you want to be really ironic...haha)

You showed me the opinion of an anatomist who couldn't find a bone. Had he found the bone, what would his opinion on the marsupial mole have been? Did he find the bone? When was the bone discovered? What happened when it was discovered? All you are really showing here, is that without full data, an anatomist might find it difficult to classify a creature. I made no such claim. I actually asked a question, and even if you rephrase my question into a claim, I didn't make the claim. Let's look at what I said: You're right, nobody is denying that marsupial moles diverged from other marsupials 50 million years ago. I'm quite happy to accept that fact for the time being. Now - does that make it closer to the wombat or to the placental mole? We've already agreed that the marsupial/placental split (if it happened, which of course is what we're debating) was probably somewhere in the region of 150 million years ago , so I think the conclusion is fairly apparent.This message has been edited by Modulous, Fri, 10-June-2005 07:25 PMThis message has been edited by Modulous, Fri, 10-June-2005 07:27 PM

I read the dang article.So what was the 100 year part meant to illustrate? Are you saying that because they had more data in the 80s (before the genetic test), they already knew that marsupial moles were more closely related to wombats than placental moles?So what else does the article say? It says that an anatomist couldn't classify an animal because he couldn't find a bone (Having looked around, I think he found it the following year, but I could be wrong).
It also says that

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On the basis that marsupial moles have some characteristics in common with almost all other marsupials, they were eventually classified as an entirely separate order

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It then says the 1980s genetic test said that the marsupial mole branched off from other marsupials about 50million years ago, so the anatomists who thought the mole should be in a seperate order were right, according to the 1980s genetic study. Did you intend to show me how the anatomists and the genetic classification correlated?Let's go through this once again.

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For many years their place within the Marsupials was hotly debated, some workers regarding it as an offshoot of the Diprotodontia (the order to which most living marsupials belong)

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On the basis that marsupial moles have some characteristics in common with almost all other marsupials, they were eventually classified as an entirely separate order: the Notoryctemorphia

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It was decided that they were a seperate order to the order Diprotodontia. Based on the characteristics they share with almost all other marsupials, they put them in a seperate order. Later a genetic test revealed they were indeed a seperate order from most other marsupials, having diverged from them 50 million years ago. I know you aren't trying to tell me that taxonomy agreed with the genetic test, so one of us is missing something. That's fine, you can take it as rhetorical if you want. I'll transform this question into a claim:"An anatomist, who has not seen the genetic data, would, after examining the necessary bones, consider the marsupial mole closer related to the wombat than it is to a placental mole"This still sounds nothing like the claim you said I was making. Huh? Are you even paying attention to what I am saying? I just accepted what was said in the article:

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I'm quite happy to accept that fact for the time being.

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Flat out wrong about what? What is your claim? I thought your claim was that convergent evolution is evidence against common descent. That claim is debated...Of course, by the 80s they had specimens to study, which allowed them classify the marsupial mole more accurately. What has this got to do with people who didn't have the necessary data over a 100 years ago? What am I attempting to do here? I'll tell you, I'm trying to figure out where you are going with this article. Is this bogus?This message has been edited by Modulous, Fri, 10-June-2005 08:38 PM