Transitional Fossils

[Jose]

Creationists seem to claim that no transitional fossils have been found, thus disproving the theory of evolution. Evolutionists claim to have found very many of them. What's going on?

1. What is a transitional fossil?
2. What would one look like?
3. What are your criteria for coming to these conclusions?

I've put in the last question as an afterthought. It might help us resolve differences in our definitions.

[Jose]

Well, it looks like we won't get anywhere. Pity.

I'll try again.

You don't like the theory of evolution. Well, the thing to do is test it. How do you test theories (or hypotheses in general)? You say "the hypothesis predicts XXX" and then you look at whatever data exist, to see if XXX is borne out, or if the data contradict XXX.

We seem to be stuck at this point.

We've looked at some original data--there's a whole bunch of fossils. We've stated a hypothesis that explains the pattern we see in the fossils: evolution, by means of occasional mutations occurring in various lineages, so that the morphological characteristics change with time. The hypothesis includes the notion that the critters are a continuous lineage, an extended family.

Therefore, the prediction is what you've said: if we had all possible fossils of all individual organisms that ever lived, we'd expect to see a continuous step-by-step series of changes. But, we don't have all possible fossils of all individuals that ever lived, so we have to make do with some fossils, rather than all. That's OK. There should still be characteristics of fossils that are in a series, by which we can recognize them as part of that series, even if we don't have some of the tiny steps in the series.

You were willing to accept that a fossil tree is probably not part of the fish-to-amphibian series, which indicates that you have a sense of what characteristics would be in the series, and what characteristics would not. Tree characteristics would not.

So, what do you think the intermediates would be like?

It's evasion to say that you challenge the idea that there is fossil evidence for evolution. To support your challenge, you'd have to demonstrate to us that transitional fossils don't exist. It's also evasion to say that fossils don't reproduce. Unless biology was very different in the past, ancestors have always lived before their descendents.

So, how about getting on with it, and saying what your idea is for what transitional fossils should be like? If you simply won't say, then we'll have to conclude that your decision to consider evolution to be false is based entirely on personal whim, with no consideration whatever of the physical facts that God placed here for us to evaluate.

[Grumpy]

rigadoon

Fossils don't reproduce so we can't observe who is who's parent etc. Someone needs to make a case that the fossil record can be interpreted in terms of "fossil X is a parent of fossil Y" etc.

How ridiculous can you get???

Once again you try to say that because we don't have the whole movie, but only snapshots of the events, that the EVENTS THEMSELVES did not happen. Don't try that logic in a court of law, by the way, you'll lose bigtime.

Archeopteryx is a representative transitional fossil between therapod dinosaurs(Due to it's skeletal structure, teeth,etc. IDENTICAL to other therapods) and birds(the only modern phyla to have feathers and that type of wing structure). That mix of morphologies in that one fossil validates the FACT that evolution occurred between those two "kinds" of creatures, what you demand is just detail not necessary to support that fact(though it would be nice to know, for sciences sake).

Grumpy 8)

[rigadoon]

We've looked at some original data--there's a whole bunch of fossils. We've stated a hypothesis that explains the pattern we see in the fossils: evolution, by means of occasional mutations occurring in various lineages, so that the morphological characteristics change with time. The hypothesis includes the notion that the critters are a continuous lineage, an extended family.

Therefore, the prediction is what you've said: if we had all possible fossils of all individual organisms that ever lived, we'd expect to see a continuous step-by-step series of changes. But, we don't have all possible fossils of all individuals that ever lived, so we have to make do with some fossils, rather than all. That's OK. There should still be characteristics of fossils that are in a series, by which we can recognize them as part of that series, even if we don't have some of the tiny steps in the series.

OK, we have a rough sketch of an hypothesis and its predictions. If we had all possible fossils, the hypothesis predicts we could put them into series of small differences, which would then be interpreted as step-by-step changes. We don't have all possible fossils but we do have lots of them so then what is the prediction?

There should still be characteristics of fossils that are in a series, by which we can recognize them as part of that series, even if we don't have some of the tiny steps in the series.

How can they be recognized as part of a series? Perhaps some of them form a sub-series of step-by-step changes. No problem there. What if they don't fall into such a sub-series or are at the ends of a sub-series? That means the differences between fossils are not minor. For the hypothesis to make a prediction, either the hypothesis must be enhanced with rules about how fossil series are formed or enough must be known about how fossil series are formed so that particular rules about fossil series could be stated. These rules would then be the basis for predictions about fossil series that include some fossils and some missing (hypothesized) fossils.

This is like interpolating a series of numbers. For example, to interpolate the series 3, 5, x, 9, 11, the rule that this is a series of odd integers must be hypothesized or known; then x can be predicted. Or if you are given 2, 8, 12, you could hypothesize that this is part of a series of even integers with 4, 6, and 10 missing or "intermediate" (so if you "found them" you'd know where to put them to complete the series).

So those who are promoting darwinism need to come up with sufficient rules about how to put fossils into series so that the missing or intermediate fossils can be predicted. Then all known fossils can be put into either (1) series of step-by-step changes or (2) series formed from fossils with large differences along with rules that predict what the intermediate fossils look like. Of course such rules must be specific -- like "form-type X is followed by form-type Y".

So, what do you think the intermediates would be like?

Tell me the rules for forming fossil series and I'll tell you what the intermediates would be like if the hypothesis is correct.

It's evasion to say that you challenge the idea that there is fossil evidence for evolution. To support your challenge, you'd have to demonstrate to us that transitional fossils don't exist.

No, I don't have to demonstrate to you that transitional fossils don't exist. Missing fossils are a problem for darwinism because using the fossil record to demonstrate evolution requires series of step-by-step changes. So fossils that can't be put into such a series need to be explained in a manner consistent with the hypothesis. That means the series can be reconstructed by using rules about how fossil series are formed. That's your responsibility. You have the burden of proof, not me.

It's also evasion to say that fossils don't reproduce. Unless biology was very different in the past, ancestors have always lived before their descendents.

I'm not making an hypothesis about how long currently observed biological processes can be extrapolated into the past. If you are making such an hypothesis, I ask that you present evidence for it ("always" is a long long time).

So, how about getting on with it, and saying what your idea is for what transitional fossils should be like? If you simply won't say, then we'll have to conclude that your decision to consider evolution to be false is based entirely on personal whim, with no consideration whatever of the physical facts that God placed here for us to evaluate.

I'm waiting for you to produce rules about how fossil series are formed, as I said above. This has nothing to do with personal whim. This is about using reason and evidence alone.

[Jose]

OK...let's see if I can phrase things differently.

Creationists like to claim that "there are no transitional fossils." There are numerous examples of this; let's not clutter the thread with quotes. The question is, "on what basis do they say this?"

The model that has been presented most often is that "there should be a step-by-step progression of small changes" in an evolutionary transition. This, then, is usually described as every characterisitic of the species changing a little bit, step by step, as the transition occurs.

By this model, Archeopterix is not viewed as a transitional fossil, because it has some characteristics that are fully bird-like, and other characteristics that are fully dinosaur-like. It does not fit the prediction of all characteristics changing a little bit with each step.

Of course, this model is extraordinarily silly, because it does not account for the biology. This model is not part of evolutionary theory. Evolutionary theory includes normal genetics. Therefore, different characteristics must change at different times, in accord with the random occurrence of mutations. Genetics also requires that some characteristics will not vary smoothly, because some mutations have bigger effects on morphology than do others.

Thus, Archy fits the expectation for an intermediate--it's total suite of characteristics is between "full-dinosaur" and "full-bird," but some characteristics are more bird-like than others, as a result of which genes had mutated and which had not.

Therefore, while creationists insist that there should be exactly predictable intermediates, with every characteristic changin in unison, genetics indicates that this is not possible. It also indicates that an exact prediction is not possible, because of the vagaries of mutation.

[I'll have to consider other topics you raised in a later post]

[rigadoon]

Creationists like to claim that "there are no transitional fossils."

Well, I'm not saying there are no transitional fossils.

The model that has been presented most often is that "there should be a step-by-step progression of small changes" in an evolutionary transition. This, then, is usually described as every characterisitic of the species changing a little bit, step by step, as the transition occurs.

While I agree that an evolutionary model would predict "a step-by-step progression of small changes", that progression could be over the whole organism at once or one part at a time or something else (as long as it's step-by-step).

By this model, Archeopterix is not viewed as a transitional fossil, because it has some characteristics that are fully bird-like, and other characteristics that are fully dinosaur-like. It does not fit the prediction of all characteristics changing a little bit with each step.

I have no problem with Archeopterix being a transitional fossil. But an evolutionary model would predict more that an "H" between a "B" and a "Q". It would predict the other letters (steps) as well. Or at least the existence of other letters (steps).

Evolutionary theory includes normal genetics. Therefore, different characteristics must change at different times, in accord with the random occurrence of mutations. Genetics also requires that some characteristics will not vary smoothly, because some mutations have bigger effects on morphology than do others.

So you're saying the morphological changes may be "jumpy" but they would still be step-by-step because the genetics would be step-by-step? Then what predictions does this evolutionary theory make about the fossil record (or at least those parts that are pretty complete)? It seems like the fossil record could show anything and you could say "genetics did it."

[Jose]

Well, I'm not saying there are no transitional fossils.
...
While I agree that an evolutionary model would predict "a step-by-step progression of small changes", that progression could be over the whole organism at once or one part at a time or something else (as long as it's step-by-step).

Great. I agree fully. It should, indeed, be step by step.

I have no problem with Archeopterix being a transitional fossil. But an evolutionary model would predict more that an "H" between a "B" and a "Q". It would predict the other letters (steps) as well. Or at least the existence of other letters (steps).

The classic creationist objection is that Archy is "not a transitional fossil" because it is a mosaic of dino-like and bird-like features. But, if different features can change at different times (in different generations), then "mosaic" intermediates are what we expect.

Agreed, that we should have more than just H between B and Q. The trick is finding them. Until we have all fossils, we won't know what's there. But then, we don't worry too much if we look at a map and see only St. Louis between New York and Denver. We are pretty confident that, if we look more closely, we'll find some things in-between. It's the same thing here--there really should be things between H and B, and between B and Q. We just have to find them (if they were even fossilized).

Evolutionary theory includes normal genetics. Therefore, different characteristics must change at different times, in accord with the random occurrence of mutations. Genetics also requires that some characteristics will not vary smoothly, because some mutations have bigger effects on morphology than do others.

So you're saying the morphological changes may be "jumpy" but they would still be step-by-step because the genetics would be step-by-step? Then what predictions does this evolutionary theory make about the fossil record (or at least those parts that are pretty complete)? It seems like the fossil record could show anything and you could say "genetics did it."

It seems like that, doesn't it? As it turns out (and as we would expect), there are constraints. First, mutations can only change what is present. If there are genes for forelegs, then mutations can eventually turn them into wings, but not into leaves...at least, the number of mutations required to create wings is rather few, while the number of mutations required to create leaves is vastly greater. This constraint is what makes us think "step-by-step" change is needed, rather than wholesale change all in one sudden transmogrification.

We also find additional constraints being added daily, in the form of devo-evo research. As the genes are discovered that determine the development of various structures, we can refine the models of "how mutations could cause a particular transition." Vertebrate arms and legs and wings use the same genes in much the same way. Leaves use different genes. So, leg-to-wing transitions require relatively minor tweaking of common genes; leg-to-leaf transitions would require losing a set of genes, and acquiring another set, and at the same time tweaking all of the other genes that affect the development of the rest of the organism so that it can work properly with the structures it has.

I think this means that in the vague, popular notion of "mutation," anything is possible; but, in the strict scientific meaning, and the genetic mechanisms involved, very few things are actually possible.

This does not say, however, that all changes must be gradual, bit-by-bit steps in a "morphing" from one form to another. The devo-evo genes can produce fairly dramatic changes (within the constraints of their physical activities, of course). The Hen's Teeth thread points out one of these: the loss of teeth in birds by virtue of a devo-evo mutation that prevents the "tooth pathway" from being initiated. The tooth genes are still there; they just don't get used.

I'll harp again, if you don't mind, on a theme I've raised before. This is an example of the importance of discussing specific examples. Overall, in the entire collection of living things, mutations have done a bazillion things--"mutations can do anything." But, in a particular instance, with any single gene, there are very limited numbers of things mutations can do.

In any event, you might think of it this way:

We have fossils from time B. We have a bunch from time Q. Now, we get one from time H. Could H be an intermediate in any of the lineages we see represented in collections B and Q? If it has characteristics of one kind of animals from B, and characteristics of a different kind of animal from Q, then it looks like a good candidate for a transitional form between those two animals. That's what Archy is--a good candidate for a transition between theropods and birds.

Are we satisfied, and sit down and conclude we're done? No. As you said, this isn't much of a transition; we need C,D,E,F, and G, as well as I,J,K,L,M,N,O, and P. So, people are out there collecting, and re-evaluating the interpretations with each new find.

[rigadoon]

Agreed, that we should have more than just H between B and Q. The trick is finding them. Until we have all fossils, we won't know what's there. But then, we don't worry too much if we look at a map and see only St. Louis between New York and Denver. We are pretty confident that, if we look more closely, we'll find some things in-between. It's the same thing here--there really should be things between H and B, and between B and Q. We just have to find them (if they were even fossilized).

...So, people are out there collecting, and re-evaluating the interpretations with each new find.

Interpolation must be justified as much as extrapolation. Until these fossils are found, that part of the theory should have an "under construction" sign on it. Why make claims beyond the evidence?

...It seems like the fossil record could show anything and you could say "genetics did it."

It seems like that, doesn't it? As it turns out (and as we would expect), there are constraints. First, mutations can only change what is present. If there are genes for forelegs, then mutations can eventually turn them into wings, but not into leaves...at least, the number of mutations required to create wings is rather few, while the number of mutations required to create leaves is vastly greater. This constraint is what makes us think "step-by-step" change is needed, rather than wholesale change all in one sudden transmogrification.

We also find additional constraints being added daily, in the form of devo-evo research. ...

I think this means that in the vague, popular notion of "mutation," anything is possible; but, in the strict scientific meaning, and the genetic mechanisms involved, very few things are actually possible.

Delineating the constraints is an absolute must in order to avoid merely taking an idea (evolution) to extremes. It seems to me that the debate between darwinism and its critics is really over these constraints.

[Jose]

Interpolation must be justified as much as extrapolation. Until these fossils are found, that part of the theory should have an "under construction" sign on it. Why make claims beyond the evidence?

Evolutionary biologists make the claim that the evidence supports the theory. That's all they claim. Scientists are not the ones saying "theory" is "presented as fact." That's the anti-evolutionists. Scientists say "it's a theory." This means "under construction." It also means "tested many, many times," which the anti-evolutionists conveniently forget.

Delineating the constraints is an absolute must in order to avoid merely taking an idea (evolution) to extremes. It seems to me that the debate between darwinism and its critics is really over these constraints.

It's not, really. This is evident in the fact that, some years ago, the Kansas school board, when the extremists were voted out, put evolution back into the state standards--and they started getting hate mail, with death threats, and calling them "babykillers." If it were merely an argument about constraints, they wouldn't equate "teaching evolution" with "killing babies." No, to them, it's a fight to the death over morality, and over the very existence of an Afterlife of Eternal Bliss. If they wanted to talk about "constraints," they'd say "what about the constraints?"

There is a popular game of pretending that mutations are something they aren't, precisely to make evolution sound impossibly stupid. Part of that game is the goofiness of claiming that "transitional forms" should represent a smooth transition of all characteristics simultaneously. Of course, this really reflects America's very poor understanding of science, and isn't really very surprising when put in this light.

Again, it is not the scientists who are "taking evolution to extremes." It's the rampageous imagination of the public, spurred on by the public anti-evolutionists.

[Grumpy]

rigadoon

Interpolation must be justified as much as extrapolation. Until these fossils are found, that part of the theory should have an "under construction" sign on it. Why make claims beyond the evidence?

I lived in Raleigh NC for 15 years. Raleigh has a Beltline going all the way around it, some 40 odd miles of mostly six lane highway. During the whole time I lived there there was ALWAYS one section or another that was "under construction", we used to joke about a band of gypsy road workers which constantly moved from one off ramp to another around the city!!!

The point is that even though it was never finished and parts were always being improved or repaired, the Beltline was still always usable to travel on. In some parts it was better than in others but usefull nonetheless.

Such is also the case with evolutionary evidence, it is constantly being improved but is useful as it is now. And, like all science, it will be "under construction" from now on, there is always more to learn!!!

Grumpy 8)