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.

[gluadys]

Also, my definition would be the most basic definition of a transition. If this definition cannot be met, how can any other more subjective definitions be met? If we cannot establish that M is a transition between L and N, how can we show that M is a transition between A and Z?

That's silly. It's like saying that if you can't determine that 37 falls between 36 and 38, there is no possibility of determining if it falls between 25 and 45.

We make determinations like this all the time. Your kids watch Sesame Street? One of the exercises you will sometimes see on that program (and in any kindergarten class) is the sequencing of events. A set of pictures is displayed and using clues in the pictures the kids are asked to put them in chronological order.

If we applied your standard for transitional fossils to that exercise, it would be quite impossible to determine the chronological order unless we had a complete set of pictures taken at the rate of one per second (or a film rather than snapshots).

Fossils supply us with a set of snapshots. Interestingly, they also tell us what time frame they were taken in, so the chronology is known. All we still need to do is see if the morphology matches the predicted transition.

Since the morphology is an expression of the genetic changes, they are also accounted for indirectly.

[otseng]

Eventually i think your objections will come down to the methodology how to determine if something is a transitional - the difference between "it could be a transitional" and "we know it is a transitional".

Quite possibly. So, how do we "know" that it is a transitional?

How about endogenous retroviral sequences? They very conclusively demonstrate common descent.

I know nothing about endogenous retroviral sequences. Could you elaborate on it in the Common Descent thread?

So if we find a fossil that has some characteristics of dinosaurs and some characteritistics of birds, what is subjective about identifying it as a possible transitional?

It can be identified as a possible transition. No problem. But, it cannot then be shown that common descent is true based on such a fossil.

It's like saying that if you can't determine that 37 falls between 36 and 38, there is no possibility of determining if it falls between 25 and 45.

I'm not arguing that since we cannot demonstrate that the fossil record supports my definition, that any definition of a transitional fossil fails. (Well, at least not yet.) What I am saying is that my definition is a basic definition.

A one-dimensional number line is perhaps not the best analogy. But, a two-dimensional coordinate system would be better suited. If we take different species as whole number coordinates and one step of the evolution is to the next integer, then my definition would be akin to species A at (1000,1) and B at (1000,2) and C at (1000,3). Now, suppose we have a species D at (100,30000) and another E at (500000,100000). And we have another species F that has similar characteristics with D and E, where do we put it on the chart? It could be anywhere. With my definition, there is no ambiguity.

[gluadys]

A one-dimensional number line is perhaps not the best analogy. But, a two-dimensional coordinate system would be better suited. If we take different species as whole number coordinates and one step of the evolution is to the next integer, then my definition would be akin to species A at (1000,1) and B at (1000,2) and C at (1000,3). Now, suppose we have a species D at (100,30000) and another E at (500000,100000). And we have another species F that has similar characteristics with D and E, where do we put it on the chart? It could be anywhere. With my definition, there is no ambiguity.

That is where we would use a cladistic analysis to figure out the placement.

[The Happy Humanist]

I have a few questions on this subject. I am by no means a scientist, but I understand the scientific method. (Observe, hypothesize, test, revise, conclude...publish, get rejected, go home, get drunk, start over). I understand the basic concepts of Evolution, but this looks like a good place to get a little more education.

First, wasn't the concept of "transitional fossils" something the Creationist camp came up with? Because as was stated earlier, in a sense all fossils, indeed, all species, are transitional (according to Evolution). And as such, doesn't the challenge issued ("Show us a transitional fossil") necessitate the automatic presumption, for sake of argument, that Common Descent is true? If that is the case, then how is it "begging the question"?

OR...is the Creationist arguing that there are no examples of transitionals between two species closely related in terms of being almost right next to each other on the "tree of life"? (Such that there can only be one transitional between them). Perhaps you need a new term for this...say, an "atomic transitional." This way we can narrow the discussion down. Does the Evolutionist claim that such examples exist?

Second, what is wrong with the list of transitionals given at http://www.talkorigins.org/faqs/faq-transitional.html? Why are these not acceptable to the Creationist?

Third, to those of you with a Creationist bent...out of curiosity, what will you do if you become convinced by this thread that transitionals exist, and are indeed, unambiguously transitional? Will you abandon Creationism? Can you see that happening in the future if say, a true "atomic transitional" is discovered, a "missing link" as you call it?

==JJS==

[otseng]

That is where we would use a cladistic analysis to figure out the placement.

I'm afraid that cladistic analysis is simply adding another point in the self-supporting circle.

The assumptions that cladists make are:

1. Any group of organisms are related by descent from a common ancestor.
2. There is a bifurcating pattern of cladogenesis.
3. Change in characteristics occurs in lineages over time.

So, the circle becomes:
Cladistics assumes common descent is true.
Cladistics is used to determine a transitional.
The transitional is then used to show that common descent is true.

First, wasn't the concept of "transitional fossils" something the Creationist camp came up with?

I have no idea. But, for purposes of this discussion, it is something that we are simply trying to find a definition for.

Because as was stated earlier, in a sense all fossils, indeed, all species, are transitional (according to Evolution). And as such, doesn't the challenge issued ("Show us a transitional fossil") necessitate the automatic presumption, for sake of argument, that Common Descent is true? If that is the case, then how is it "begging the question"?

From my take on things, transitional fossils are used as primary evidence that common descent is true. If this is done, then it is begging the question.

Perhaps you need a new term for this...say, an "atomic transitional."

I can accept that terminology.

This way we can narrow the discussion down. Does the Evolutionist claim that such examples exist?

Good question. Any takers on that one?

Second, what is wrong with the list of transitionals given at http://www.talkorigins.org/faqs/faq-transitional.html? Why are these not acceptable to the Creationist?

To reiterate, the definitions in my opinion are too subjective. How can one objectively demonstrate that it is in fact a transitional based on those definitions? A satisfactory answer to this has yet to presented.

Third, to those of you with a Creationist bent...out of curiosity, what will you do if you become convinced by this thread that transitionals exist, and are indeed, unambiguously transitional? Will you abandon Creationism?

I do not think evolution and creationism are mutually exclusive. There are many points of evolution that I believe in. So, no, by demonstrating that some points of evolution are true would not cause me to abandon creationism. Much can be said about this, but I will leave at this for now.

Can you see that happening in the future if say, a true "atomic transitional" is discovered, a "missing link" as you call it?

If an atomic transitional is discovered, I would be able to wholeheartedly say that it is a transitional. Would it conclusively demonstrate that common descent is true? Not yet. But it would be a good step.

[The Happy Humanist]

To reiterate, the definitions in my opinion are too subjective. How can one objectively demonstrate that it is in fact a transitional based on those definitions? A satisfactory answer to this has yet to presented.

Something about this whole exercise strikes me as a bit...loaded. The Creationist claims there are no transitional fossils, meaning there are no fossils that indicate a line of descent by showing a smooth transition from older to younger fossils. The evolutionist points to examples, and then the creationist says "But you are assuming common descent in their definition." Isn't it just that we are saying, look how this one has characteristics of this older one, and characteristics of this newer one, showing a smooth transition? Common descent may not be proven, but it is easily inferred, is it not?

The Creationist explanation for this, I suppose, would be that God merely made his different "kinds" to appear to descend from a common ancestor. But something tells me that the debaters here are a little more sophisticated than that, knowing that that argument can be used to invalidate all human discovery.

I think it is up to the challengers to provide a starting point for what they will accept as a definition for transitionals that will satisfy their challenge.

[gluadys]

To reiterate, the definitions in my opinion are too subjective. How can one objectively demonstrate that it is in fact a transitional based on those definitions? A satisfactory answer to this has yet to presented.

Something about this whole exercise strikes me as a bit...loaded. The Creationist claims there are no transitional fossils, meaning there are no fossils that indicate a line of descent by showing a smooth transition from older to younger fossils. The evolutionist points to examples, and then the creationist says "But you are assuming common descent in their definition." Isn't it just that we are saying, look how this one has characteristics of this older one, and characteristics of this newer one, showing a smooth transition? Common descent may not be proven, but it is easily inferred, is it not?

To some extent what we are up against here is the problem of argument from induction. When looking for a transitional, we have to be specific. We have to have in mind something definite that is the origin point and something definite that is the final point. And we have to find something that shares the characters of both.

Now all kinds of living and fossil organisms meet these criteria. But each establishes one transition. None on its own establishes universal common descent. Nevertheless, IMO the many, many samples of transitions we have found considered collectively establish universal common descent well enough to consider it the default postion for science. The challenge now is really to creationists to come up with a species, living or fossil, that is not linked to the universal phylogeny.

That would falsify common descent.

I think it is up to the challengers to provide a starting point for what they will accept as a definition for transitionals that will satisfy their challenge.

That is the way this thread began. My difficulty with otseng's definition is that when working with fossils a genetic basis is impractical. So if one is looking for a transitional fossil (as opposed to living transitionals in ring species or observed speciation) the definition must be morphologically based.

So far, we have not been able to come up with a mutually agreeable definition based on morphological characteristics.

[The Happy Humanist]

To reiterate, the definitions in my opinion are too subjective. How can one objectively demonstrate that it is in fact a transitional based on those definitions? A satisfactory answer to this has yet to presented.

Something about this whole exercise strikes me as a bit...loaded. The Creationist claims there are no transitional fossils, meaning there are no fossils that indicate a line of descent by showing a smooth transition from older to younger fossils. The evolutionist points to examples, and then the creationist says "But you are assuming common descent in their definition." Isn't it just that we are saying, look how this one has characteristics of this older one, and characteristics of this newer one, showing a smooth transition? Common descent may not be proven, but it is easily inferred, is it not?

To some extent what we are up against here is the problem of argument from induction. When looking for a transitional, we have to be specific. We have to have in mind something definite that is the origin point and something definite that is the final point. And we have to find something that shares the characters of both.

Now all kinds of living and fossil organisms meet these criteria. But each establishes one transition. None on its own establishes universal common descent. Nevertheless, IMO the many, many samples of transitions we have found considered collectively establish universal common descent well enough to consider it the default postion for science. The challenge now is really to creationists to come up with a species, living or fossil, that is not linked to the universal phylogeny.

That would falsify common descent.

I understand and agree completely, and your thoughts echo my own. So then, why is evolution on the defensive? Why is there this ringing battle cry of "There Are No Transitionals" when the challenge should be "Give Us An Example of a Non-Transitional Species!" ?

I think it is up to the challengers to provide a starting point for what they will accept as a definition for transitionals that will satisfy their challenge.

So far, we have not been able to come up with a mutually agreeable definition based on morphological characteristics.

Then I submit a new approach is needed, since this approach is going to be a stalemate. The Creationist can insist on a genetic definition, and when none is provided, claim victory. They have no vested interest in compromise, as by and large, they are out to prove God did it, not explore other possibilities. Not saying that Otseng necessarily falls into this camp, but his approach does point up a potential "impasse" that could be exploited by less ingenuous Creationists.

How about something like, "Please provide an alternative rational explanation for the picture of common descent that is painted by every one of the thousands of fossils extant. If you choose to invoke God, that's fine, but you are now outside the realm of science, and hence, out of the running to have your curriculum included in public education."

In other words, treat the "No transitionals" challenge like the red herring it is, and then knock the ball into the Creationist court.

Just my two cents.

[gluadys]

That is where we would use a cladistic analysis to figure out the placement.

I'm afraid that cladistic analysis is simply adding another point in the self-supporting circle.

The assumptions that cladists make are:

1. Any group of organisms are related by descent from a common ancestor.
2. There is a bifurcating pattern of cladogenesis.
3. Change in characteristics occurs in lineages over time.

So, the circle becomes:
Cladistics assumes common descent is true.
Cladistics is used to determine a transitional.
The transitional is then used to show that common descent is true.

Not really. Assuming provisionally that common descent is true and therefore a relationship between two species exists, does not create a relationship where none exists. So the analysis can still show that the relationship is not established or is not what was expected.

Besides, in this case, we already have an intermediate, from your analogy.

Now, suppose we have a species D at (100,30000) and another E at (500000,100000). And we have another species F that has similar characteristics with D and E, where do we put it on the chart?

We put it in the place detemined by cladistic analysis. That might be somewhere between D & E--and it might be closer to D than to E or vice versa. Or it mght be outside of the space between D & E, in which case it would not be transitional from D to E or vice versa, but might be a common ancestor to them, or a species related to a common ancestor of D & E.

This way we can narrow the discussion down. Does the Evolutionist claim that such examples exist?

Good question. Any takers on that one?

The talkorigins FAQ on transitionals includes several species-to-species transitions in Part Two (mammalian evolution).

http://www.talkorigins.org/faqs/faq-transitional.html

These are all vertebrate lineages. Smooth gradations in invertebrates, especially those with shells, may be even more common. Though, ironically it is more difficult to get web info on them. But here are a few.

Consider the brachiopod Eocoelia from the Lower Silurian of Great Britain (Ziegler, 1966). We find two species both classified as Eocoelia based on the details of internal morphology. However, the shells of the older species are coarsely ribbed whereas the shells of the younger species are smooth (Ziegler, 1966). If we examine samples collected from geochronologically intermediate positions, we find a succession of Eocoelia that progressively reduced and ultimately lost the ribs (Ziegler, 1966). This morphologic progression can be illustrated both qualitatively with specimen illustrations and quantitatively by measuring rib strength and plotting the data as a series of histograms in stratigraphic order (Ziegler, 1966). http://www.gcssepm.org/special/fr_cuffey_00.htm

http://www.geo.ucalgary.ca/~macrae/talk ... ansitional

http://www.don-lindsay-archive.org/crea ... eries.html

[otseng]

Eureka, I think I've found it. Just when I thought we'd be going back and forth on this issue forever, I think I have a breakthrough.

What I'd like to propose is the mathematical phylogenetic tree (MPT) to resolve the issue. It goes along with what I stated earlier about using a coordinate system to map species.

We'll start with some base assumptions:
- Common descent is true.
- A phylogenetic tree can be constructed in which all life (extinct and extant/known and unknown) can be mapped onto the tree.
- The tree is mapped in which species reside on integer coordinates (for example, species A can be at location (100,100)).
- Directional lines are drawn to represent the direction of speciation from one species to another.

Now for some definitions given species A, B, and C:

Transitional:
B is a transitional if a line can be drawn between A, B, and C. The direction of the line must be from A to B to C.

Atomic transitional:
B is an atomic transitional if the distance between A and B and between B and C is one unit.

Multiple step transitional:
B is a multiple step transitional if the distance between A and B and/or between B and C is greater than one unit.

Common ancestor:
B is a common ancestor if the direction of the line is from B to A and from B to C.

Not relational:
B is considered not relational to A and B if no line can be drawn between the three.

This might need more clarification and refining, but I think this approach will give clearer definitions to transitionals.