Is convergent evolution evidence against common descent?

This came up on another thread, but was closed down, presumably for being off-topic. I am sure this has been studied and debated somewhere, but I have not seen it so I ask this question here.Convergent evolution, of course, is the view that some data suggests that traits and similarities, including behaviour of species, can develop independently of each other, and not from both inheriting those traits from a common ancestor.To my mind, this is strong evidence against common descent because it shows similarities, including morphology, traits, behaviour, etc,...can develop not from mutual common descent, but independently.It also seems to me that convergent evolution, which can occur due to similarities in environmental pressure, same physical laws, and other commonalities besides mutual ancestry poses a lot of problems with using fossils and DNA to try to link organisms and determine "relatedness."If the bone structures, behaviour, diet, etc,...developed in 2 different lines of creatures evolving, different branches if you would, independently of one another, and we discovered their fossils, we may incorrectly assume they shared a common ancestor that passed these traits on when that was not the case.This could especially happen if the fossils were found in the near vicinity. Take Marsupials. If they migrated over here to thousands of years ago, and we found them all mixed up with placental mammals, how might we think they had evolved?Let me use an illustration of something I think could happen as well. Keep in mind that I am going to try to express things in everyday language, or as best I can, to get at the process involved. I am not interested in debating terms and words since the process is the same regardless of how one describes it. If someone misunderstands what I am saying because I do not use or lack technical terminology in a post, please just ask me, and I will explain the process itself and try to get that across.Back to the illustration. Ford and Chevy SUVs are very similar and with some differences, and both the similarities and differences are driven by competition. Let's call them species for this illustration. If one species (or model) does not adapt to the other improvements, it may well lost marketshare and go extinct. Likewise, some differences must develop, due to environmental pressures (the consumer's tastes), or they will not gain an edge, and something else can come along and knock both out of the water. The key here is that changes are driven by marketplace "natural selection". So you could have 2 independent models in the same environment, not necessarily separated and isolated geographically, that nevertheless through convergent evolution due to a commonality in environmental pressures selecting for similar traits.If that occured, would we not come to the wrong conclusion starting out with the assumption that these traits preexisted in a common ancestor when in reality, they did not.For sake of brevity, I will hold off on some additional thoughts, and wait to see if this topic is adopted.This message has been edited by randman, 06-04-2005 03:35 AMThis message has been edited by randman, 06-04-2005 03:35 AM

I cannot comment in-depth at the moment, but thanks for the responses thus far.It is interesting though that if there appears to be internal differences that produce similar function and morphology, that the assumption is convergent evolution, but that nonetheless shows some similarities and traits can develop independently.What if other aspests did develop independently, but since there is more agreement and less differences, such as internal differences, the assumption is that there must be a common ancestor?It still seems to me that the general principle is that we are accepting the possibility of evolution producing similar traits, function, etc,...without a common ancestor passing those traits on.It may seem most logical to assume convergent evolution in comparing some species, and mutual ancestry passing traits along comparing for others, but that is more or less a guess, an inference. It's possible that we are assuming common descent as an explanation when other commonalities can explain shared traits and similarity, right?

I've got a few minutes, and will try to get some of these.My point is more on the reliability of how we view the evidence, namely the veracity of underlying principles in which we examine data, and by "we", I really mean the scientific community. I do not work or, nor have a degree in life sciences. Maybe that was clear...But be that as it may, if similarities, and I read WK as suggesting even the possibility of DNA sequences arising through convergent evolution, then we have very strong evidence that commonalities can arise in different species independently, right? That means that commonality is not necessarily evidence for mutual ancestry.Now, I realize the assumption is they all eventually had a common ancestor, but that's getting ahead of ourselves in the thinking. Tne belief in common descent is based in large part on how we view the data, and specifically in light of this principle.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. These traits could have emerged all independently, and so we are making false assumptions.That would seem, to me, to cast doubt on the entire process of examining data and assigning relatedness. Maybe all we are seeing are similarities that arose from something besides common descent.

But the inside has to had according to common descent have evolved as well, from creatures with a vastly different "inside" if you go all the way back, even to arguably no "inside" or it's all the same.So just because we see that convergent evolution had to have occurred for common descent to be true, that does not rule out the possibility of convergent evolution occurring for both the inside and outside to a degree, especially since it is not like we have full details between species all along the evolutionary chain.In fact, we have a great dearth of evidence often, and just have fossils, many of which do not show everything.So just because there are obvious cases pf convergent evolution does not rule out the chance that we are assigning mutual ancestry passing a trait along when that is incorrect, and more importantly, the principle of assuming similarities are the result of common descent is thus highly questionable.Mutual ancestry is just one possibility, not the only possibility for acquired traits, including the inside, outside, etc,.. in species to be similar.What if there was multiple origins for descent? We don't understand how or even if abiogenesis really occurred, and to consider that if it is a naturally occuring phenomenon, then who is to say it would not produce a somewhat similar life form each time?Or, let's take the idea of special creation at different times, or ID, and then those "kinds" evolve. Please suspend all the arguments on whether it's proper for science, and let's just think as human beings if the data we have said rules that out, in this one area, is correct.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.

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

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.

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.

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.

But my experience is that common descent is presented and believed most dogmatically, more than any other scientific theory, and is similar to religious zeal in the assertions of evolutionists. Sometimes, it's comedic such as some PBS show or something saying this species evolved at this time or some such. The truth is if you took a step back and just looked at how evolutionists present their claims to the public, in TV science shows, in articles (including some science journals), in textbooks, and when talking with them, you run into a dogmatism which is astonishing, and even hear claims of "proven beyond all reasonable doubt", etc,....and yet the truth is the evidence is very subjective, based on choosing to interpret the data only one way.In the case of convergent evolution, we see that the basic principle that shared traits indicates shared ancestry is wrong.Also, convergent evolution, nor any evolution, is not produced by chance, but is governed by the conditions of the environment. That means something that commonality which seems highly unlikely to emerge can indeed emerge since there are common forces acting, not chance, upon the different species.Lastly, I would like to address the dogmatism which states since we have no better explanation, this must be true. Most assert it as proven, even beyond all reasonable doubt.Let's take someone in ancient times that asserts that the sun is a god that comes by every day to help us, or some such, and another says, well, I don't think it's a god. The other one says, well, what is your explanation, and he rightly says, you know, I don't know what it is, but your explanations of all this stuff being gods is iffy. Sure, it works. You say that every year the death god comes up and destroys stuff and makes it cold, and that we have to make sacrifices, and then the spring god will come back and help the sun-god make things warm again, and yeah, I know, it always "works."So the sun-god advocate proclaims, well, there you have it. You have no better explanation, and this one works, so we must be right.Same sort of thinking, Ned, if you ask me.

LOL. Get real, buddy. So now evolution is compatible with all forms of origins.Is it compatible with aliens seeding life and intervening?Is it compatible with special creation, or multiple special creation events? How about Intelligent Design?How about multiple origins?Hogwash, buddy.TOE we are talking about is the theory of universal common descent from a single source, period.If you are just talking evolution in a general sense, YECers are evolutionists too!