Is convergent evolution evidence against common descent?

Hrun, the problem is the word "relatedness" which can mean similarities or related via ancestry. Let's just start with similarities. We see animals, plants, organisms, that have similarities, and are trying to assess the degree of relatedness via ancestry. I think that's a better way to begin.

No, which is why I am asking you guys for those examples, and the implications of the general principle.But I will be looking as the thread goes along.Moreover, I am not as convinced by the inside/outside illustration, especially since I've seen a lot of stuff such as whale evolution scenarios based on fossils, which don't seem so different than what you are talking about. I could be wrong, but it seems as there is less evidence (more links missing in layman's terms), that pretty big differences are glossed over, and the assumption is not convergent evolution, which could just as easily explain the similarities, as otherwise, but like I said, I will start looking.Maybe someone here can point to an area that has been problematic?Surely there are examples out there like that. Well, I thought marsupials were mammals, and that they might be a good area to get into it for this discussion.Besides the placenta versus the pouch thing, what are the major internal differences in the seeming pairs of placenta mammals and marsupials?This message has been edited by randman, 06-04-2005 07:38 PM

randman writes:

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My point is more on the reliability of how we view the evidence, namely the veracity of underlying principles in which we examine data,

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And that is always a legitimate issue. That's why science undergoes peer review: It forces you to submit your work to other people who will do everything they can to try and show it to be false. You always question whether or not you've done it right because you might not have.That said, by what basis do you claim that we have got it wrong? The issue of convergent evolution and its relation to common descent has been studied by a great number of people and found not to be in conflict. In fact, their existence has been integrated into the theory.That doesn't mean they're right, but it does mean you need to come up with a reason why they're wrong beyond, "I don't see it."

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If we see some fossils, for example, in one strata and consider they are of a certain age, and then another set of fossils not so far with just some differences, and then a third with more differences at a later date, but they share similarities, we put them together in the tree of evolution, as you pointed out, but convergent evolution suggests that we could well be wrong.

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No, it doesn't. It says that the organisms in question must be evolutionary related and not distinct species who simply had "convergent evolution." Convergent evolution involves the sharing of a small number of traits that are similar only in final effect and not in fundamental structure. Your example, on the other hand, flips that around: The organisms share the vast majority of traits and those similarities are present all the way down to fundamental structure, not simply in superficial effect.Convergent evolution is why sharks and dolphins have flippers. Everything else about sharks and dolphins is pretty much different (they don't even swim the same way), but they share the large-scale shape of a flipper...which if you were to look at the internal structure you would see that they don't share anything in common other than the external shape.

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These traits could have emerged all independently

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No, they couldn't have. Everything else about the organisms tells us they didn't.By your logic, it is reasonable to think that because there are organisms that are 99% different but 1% the same and that the similarity is due to independent origin, this must mean that organisms that are 99% the same but 1% different, then the 99% similarity is also due to completely independent origins.If you have a series of independent events, what is the likelihood that they will all reproduce the same result? That is, suppose I have a coin, a die, a deck of cards, and a roulette wheel. What are the odds that if I flip the coin, roll the die, draw a card, and spin a number, I'll be able to reproduce that exact same sequence of events a second time?Well, there's a 1/2 probability of getting a coin to flip to a certain number, 1/6 for a die, 1/52 for a card, and 1/38 for a roulette wheel (assuming a 00 wheel). Each is independent, so you multiply them together: 1/2 * 1/6 * 1/52 * 1/38 = .00004 or four thousandths of one percent.If we find two organisms sharing so many of the same traits, we necessarily conclude that they are evolutionarily related, not the result of convergent evolution: They're too similar.

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Rrhain

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Thank you for your submission to Science. Your paper was reviewed by a jury of seventh graders so that they could look for balance and to allow them to make up their own minds. We are sorry to say that they found your paper "bogus," specifically describing the section on the laboratory work "boring." We regret that we will be unable to publish your work at this time.

No, I am suggesting the opposite. That just because there are obvious cases where similarities cannot be the result of mutual ancestry passing along those traits does not rule out less obvious examples.I other words, one could claim something is an obvious case of shared ancestry, but be wrong since convergent evolution could also be the answer.Furthermore, I am suggesting that convergent evolution casts doubt on the whole concept of univeral common descent because it shows that similar traits can arise through other commonly shared aspects, such as filling similar niches, than from common descent. The assumption is that if we see similar looking species, that they are related through a common ancestor, but that may not be the case.We think that because we choose to view the evidence through an assumption which we now know is not exclusive. We now know that the same data can be produced through other means.That's a powerful concept.Basically, the argument has been the only explanation for shared traits we see in biological life is due to a common ancestor.But now, we see traits can emerge independently, and thus prove that the earlier assumption is wrong. It is not the only explanation.Other shared factors such as the laws of physics, environmental factors, similar restraints in diet, etc,....can produce similarity as well.As far as presenting an alternative theory, imo, there is a bit of an error in that. Let me explain. Man has generally tried to put forth explanations for things when he did not have them. He has had to have an answer, and this has led to a lot myths being adopted.A perfectly reasonable alternative, which eschews what is sort of a religious motive to have to always have an alternative explanation, is just that we don't know.Understanding the difference in what we do know and what we don't know though can be very helpful. It can help one be more open-minded and rational.In fact, some here would celebrate the agnostic stance for faith in God, and yet seem averse to anyone have an agnostic attitude towards their belief system.All I am saying here is trying to discuss the narrow implications of how convergent evolution demonstrates "shared traits" can arise without mutual ancestry for those traits. That to me is a powerful concept and greatly undercuts the assumption that shares traits is evidence for univeral common descent.Once we look at the data without assuming common descent, we may get a clearer picture of what happened.Certainly, revising how data can emerge due to the fact that other common factors can produce commonality, I would think would be an interesting area of study for evolutionists and others.

randman writes:

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I don't want to divert this topic so maybe we should stay away from ID for now, but if there is an Intelligent Force introducing new species into the environment, it might well look just like the data we do have.

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If so, then why would this "intelligent force" use a method that looks exactly like an evolutionary process? And by what justification would we possibly claim that it wasn't?Suppose I were to take a handful of coins and toss them on the ground. Would you not agree that those coins land the way they do all on their own without any "intelligent force" deliberately, consciously, and purposefully making them land that way?If not, there is no point in continuing. But if you do agree that the coins land where they do all on their own, then suppose I were to then come in with an identical handful of change and were to place them in the identical positions.Would you be able to tell the difference? And by what criteria would you claim that the coins were deliberately placed rather than naturally occurring?If this "intelligent force" is going to use a process that is absolutely identical to a natural process, then how could we possibly be faulted for describing it as a natural process? It looks just like a natural process.And as the saying goes, a difference that makes no difference is no difference. An "intelligent force" that is indistinguishable from a natural process IS a natural process. Natural processes don't allow for willful adjustment of the results. Therefore, an "intelligent force" that produces natural results must also be incapable of allowing willful adjustment of the results...which does away with the "intelligent force" and thus the process is natural.

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Rrhain

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Thank you for your submission to Science. Your paper was reviewed by a jury of seventh graders so that they could look for balance and to allow them to make up their own minds. We are sorry to say that they found your paper "bogus," specifically describing the section on the laboratory work "boring." We regret that we will be unable to publish your work at this time.

Actually, we haven't really gotten into the genetics on this thread yet.Moreover, the inference of common ancestry came decades prior to the development of genetic research.Not trying to dodge the point, and do want to hear comparisions between say individual marsupial species and their counterparts that are placental mammals, and consider that evidence. If you have a link to something like that, I would be glad to peruse it.Can you provide such a study?

NosyNed, I am talking about the evidence and how we view it.We now accept convergent evolution can produce similar traits, but we only assign convergent evolution as the cause in obvious cases, and assume all the rest did not occur from convergent evolution, but:1. What if they did? How could we tell if convergent evolution produced more similarity? The answer is we could not. We dismiss it because we say one is more likely than the other, but that's not that strong. We can't say exactly if the truth be known. Lots of very unlikely things happen. We observe unlikely things happen all the time so the idea that, the one that appears to be more likely, well, that's how it had to be is wrong. The real answer is we don't know. We don't have enough evidence to say for certain, at least not from just examining the species similarities and differences.2. The other point is that the whole of common descent rests on the assumption that common traits have to be the result of common ancestry, but now we know that's not always the case. That's a wrong assumption in fact. We've been looking at the data with a wrong assumption.3. Lastly, an alternative view may be something you need to be able to doubt the current view, but that's not me. I would rather admit what I do know and don't know. I think that helps me keep an open mind. I think doing otherwise encourages overstating one's case, which is a feature I see within the evolutionist camp.

Why wouldn't it/He/whatever?Why did the sun look like a god coming up out of the sky everyday?Both questions are of the same "kind", if you ask me. Actually, I can point to intelligent forces. First, they would not have landed on the ground if you had not thrown them. Secondly, assuming someone did create the physical laws of the universe, those forces had a lot to do with the way those coins landed.But you might want to rethink your argument. If the coins could not land that way on their own, why should we assume the universe can, or that life can spontaneously generate on it's own?I think also you are woefully wrong on the natural processes point. Let's just assume all is natural process. What if we discover a different way of producing traits in species without using common ancestry to produce those traits, will that prove ID?Already, we have discovered one process that produces similar traits without the mechanism of a mutual ancestor passing those traits along, right?Edit to add the following: So when we use genetic engineering, there is no willful adjustment of the results? We are incapable of that, eh? Your post seems illogical to me. We already do have ID through humans manipulating natural processes. Are you claiming we are relying on non-natural means of doing this?This message has been edited by randman, 06-04-2005 08:16 PM

Exactly. So let's apply this principle to the presumed first life form. The idea among the common descent camp is abiogenesis. OK, it would seem to me highly likely that the conditions for that existed prior to and after this event, no?I realize this is a stretch because we have so little evidence for abiogenesis, but for sake of argument, let's assume it happened.Maybe it happened and happens a lot, and maube it produces a similar "solution" each time? We could well have thousands of separate sources for all of life evolving then.You can take this principle and apply it to other scenarios. I don't really want to do that because it diverts the thread.The main issue is common traits are not necessarily the product of common ancestry. They could be the result of common situations producing common solutions as you say, and once you admit that commonalities are not necessarily the result of common ancestry passing those traits along, you have undermined the basic tenent of common descent that common descent is merely the extrapolation of "microevolution" on the macro-level.

As someone has stated before, "what's to stop it?"What's to stop it from producing more than a small number of traits?If it can produce a small number of traits, why can it not produce more than that? Remember we are talking of a very, very long time.By the way, I find your argument, that hey, it's been studied already and they didn't see it that way, to be extremely weak.What's the point of this forum then, if we are going to say, hey, you need to publish in a peer-reviewed journal, which probably is controlled by men with a very strong disposition to avoid the topic of criticizing common descent.In fact, if you feel that way, why are you posting here?I am raising a logical point. Common descenters have insisted all along that similarity proves common descent, that there is no other explanation, ad nauseum, and lo and behold, there is another explanation.

For science we work with the best we have. We only know to the degree that we have evidence and a model which fits that as well as we can. If the patterns we see in fossils and life are due to chance then that odds against it are astronomically huge. No, it does not just rest on the common traits. It rests on what we can see in life today. It rests on the particular patterns we see.You pointed out the pattern in the fossil record. If living things reproduced from other living things through the time the fossil record was being formed then the later, slightly different ones (as you pointed out) came from the earlier ones (unless you have a better explanation). This is common descent. I have no problem with your view then. You may decide that you don't know. Biologists may simply say they don't know for absolutely sure. However, given that there is not better alternative explanation and given how well the explanation we have works the degree of surity is rather high indeed.In the sciences we work with the best explanation that we have. We teach that explanation and the underpinings for it. We will also doubt and test the current model even without having another one. That is normal in the sciences too. However, we work with the one that works in the meantime.You may prefer to say "don't know" but that is heavily based on the fact that you know very, very, very little about the biology, physics, geology and paleontology involved. I might say you know microscopically little and much of what you do "know" is wrong besides. Under such circumstances "don't know" isn't an unreasonable position to take.Most of the time, when I know very, very little about an area I would have to both say "I don't know" and "I will go along with the experts until shown otherwise". I don't see any other position as being resonable.This message has been edited by NosyNed, 06-04-2005 08:32 PM

If not common descent then what? A chance happening?

The odds of a lot of the evolutionary scenarios via common descent are not that great either, but the argument is given enough time, millions upon millions of years, these things can happen.Now, you seem to be trying to run from that argument, which is interesting and serves my point on how data may simply be viewed with preconceptions and not objectively. The argument that something is unlikely is not a strong argument that it "could not" have happened.

And this explanation is?This message has been edited by NosyNed, 06-04-2005 08:35 PM

So what? Now we're into it. So what? Now we have the genetic evidence. Why don't you start by looking up "wolf" and "Tazmanian wolf."