You are intentionally misrepresenting the analysis that goes into determining phylogenetic relationships. For years it has been based on more than simply looking at skeletons and saying “This looks similar.” It involves dating of the fossils (for which there are multiple, cross-check-able methods) and comparing genomes as well. Fossils that are contemporaries and whose genomes show they are the same species would not be accidentally mistaken as ancestors of one another.
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Whether or not something is or isn’t “predictive” has no particular philosophical bearing in whether or not it is or isn’t true. And some “predictive” value, depending on the hypothesis or particular factor involved, is limited to limiting or ruling out certain conclusions, rather than determining specific predictions. We just realize that some things are consistent.
If forensics determined that a crime was committed by a “male,” would this not have predictive value in your philosophy, since it didn’t determine a particular suspect?
Or, to turn it around, how specific must predictions be to have predictive value in your system? Does evolutionary theory provide professor Lenski, for instance, specific predictions for how his e coli are going to evolve? What specific proteins they will evolve? Can you predict which organism will be the next to evolve echolocation de novo? If we discovered echolocating bears, I would not object to your saying, “evolution predicted that this kind of thing could well have happened”, I would not object that scientists had not specifically predicted it would happen in bears instead of squirrels.
When the idea was suggested that nylonase evolved de novo from a frame shift mutation, the Darwinian theory, predicated as it is on the idea that these kinds of de novo proteins must be commonplace enough to explain all of present biology, had no issue with that. Design hypothesis suggests that to develop something so particularly functional was far more likely a small beneficial modification of a pre-existing protein that already had similar function. In this case, it seems that the design hypothesis proved of greater “predictive” value, even if its prediction entailed simply ruling out erroneous paths.
What is actually studied is the transitional forms that are recorded in the fossil record. Researchers don’t identify a fossil as transitional. For example the transition of the feet of horses from four toes to a single toe is done by examining the fossil record of the various horse genera that are found. What is found is a reduction in the number of toes. Features are never analyzed in isolation but are combined with others as seen in the work done in whale origins.
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I don’t believe I am, I thought I had been clear…
I thought I noted clearly enough, these kinds of relationships may well be established by various means and methods, and to conclude that a certain fossil is “transitional” between two other organisms is a perfectly legitimate pursuit, on the methods you mention. I’m objecting only to the idea that a transitional fossil alone can be used as an argument for a certain ancestral relationship, while also depending on the fact of that ancestral relationship for it to be established as a transitional fossil.
Once it has been established as transitional on other grounds, its consistencty with the pattern may also well corroborate the larger theory. But it simply cannot be used as evidence to prove a certain transitional relationship, while at the same time depending on the reality of that transitional relationship for it to be classified as “transitional.”
My dog illustration was simply to clarify the potential for circular reasoning involved, not to suggest this is in fact the means by which all other such methods are done.
And once you do this, why can’t you label the fossil a “transitional fossil” based on these legitimate conclusions? Then you use the transitional fossil as an argument.
In order for it to be designated a transitional fossil, certain evidence needs to have led to certain conclusions, so you are misrepresenting the process. Establishing the ancestral relationship is the conclusion, not the premise. That specific conclusion can be used in other, more general arguments.
It seems like you are arguing with the idea that scientists accept the premise “organisms are biologically descended from ancestor organisms” when arguing to their conclusions about transitional fossils. What is wrong with that premise? It is a fact.
Your dog illustration was not valid because you claimed that fossils from the same burial site could be interpreted as transitional fossils of each other, when in fact, no such conclusion could ever be made because they are all contemporaries and would have been found in the same layer of rock. The designation/conclusion of transitional fossil requires the fossil under consideration to be spaced between two other fossils with significant geologic time between the ancestor form, the transitional form, and the more modern form.
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The intelligent designer is beginning to look a lot like evolution. Human designers are often able to do a total redesign, as in the case of Visual C++. It was a total rewrite; no old Legacy C++ code was used. It would be a sloppy programmer who kept commenting out code, and not eventually removing it. Legacy software is eventually abandoned.
One can use the determination of evolutionary transition, made on the basis of other factors as discussed, to reach the conclusion that a particular organism (and/or its fossil) is “transitional.”
And one can then certainly use that conclusion (that said fossil is transitional) as a premise in a different argument. But not as a premise in the same argument.
One can’t use the conclusion that a certain organism/fossil is transitional as a premise in arguing that a certain transition happened in the first place. Consider:
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Premise 1: Organism A, B, and C are dated such that they reflect chronology consistent with ancestral/transitional relationship descending from A, through B, arriving at C.
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Premise 2: Morphology is consistent with ancestral/transitional relationship descending from A, through B, arriving at C.
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Premise 3: The genetic structure of these organisms is consistent with ancestral/transitional relationship descending from A, through B, arriving at C.
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Premise 4: Organism B is a transitional organism/fossil demonstrating the ancestral/transitional relationship descending from A, through B, arriving at C.
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Conclusion: there is an ancestral/transitional relationship between organism A, B, and C with organism B (fossil B) being a transitional organism/fossil between A and C.
Premises 1, 2, and 3 are legitimate empiric observations which inductively lead to the conclusion. But premise 4 is simply a restatement of the conclusion. If the conclusion of the argument involves organism B being transitionally/ancestrally related to organism C, then one can’t use the “fact” of B’s ancestral relation with C as a premise to reach the conclusion that B is ancestrally related to C.
That “premise” as you stated it isn’t simply a fact, I’d say it is logically necessary, self-evident, and axiomatic. No one could logically deny the general statement “offspring organisms are biologically descended from ancestor organisms.” This claim is self-evident and indisputable.
But I’m talking about arguing any particular case: Once someone wants to argue (conclude) that a particular organism is descended from a particular ancestor, then no, one can’t use that “fact” to argue to a conclusion about transitional fossils. In any particular case, the statement “organism Z is descended from Y, but Y is descended from X” is essentially equivalent to saying that “Fossil Y is a transitional fossil between X and Z.” There’s no argument involved at this point, it is simply restating the same information in different words. These statements are essentially synonymous and logically equivalent.
For instance, if someone says tells me that pakicetus was a transitional organism between land animals and whales, and they then tell me that a Pakicetus fossil is a transitional fossil reflecting the transition of land animals to whales, they have not given me any new information. This is the same information expressed in two different ways.
Hence you can’t have a situation wherein the same information serves as both a premise, and the conclusion, of an argument.
Exactly! And we also note that living horses have vestigial splint bones in place of the missing toes. More evidence.
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This doesn’t make sense. If it is a fact that B has a ancestral relation with C why do you need to make a conclusion that states the same thing?
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It seems to me that once you have established that B is a transitional fossil between species A and C, “therefore a transition happened” is entailed. You don’t need a separate argument. If I establish conclusively that A killed B, I don’t need to use that as a premise for a new argument “B is dead.” It is entailed.
In principle, yes, but how, exactly, would one establish that B is a transitional fossil without, in the process, previously establishing the reality of the transition on other grounds?
I am not seeing a scenario wherein a scientist can look at fossil B in isolation and determine it to be transitional before already having other reasons to believe that species A , B, and C are related?
Perhaps it would help if you looked at an actual paper on this subject instead of just chatting about it around the water cooler.
No, not quite.
“Transitional fossils” are better described as fossils having transitional features. In other words, stem group species branching off of the lineage leading to the crown group. With this understanding, Pakicetus has transitional features - it is a stem-group whale - but it was likely not directly ancestral to any living species. It may have been, but unless we have preserved DNA, there is no way to be absolutely sure.
If you’d like a primer on stem group/crown group thinking, and its relevance to “transitional” features, here’s a piece I wrote some years ago:
I am so confused. What do you mean “look at a fossil in isolation?” The whole exercise
when determining if a fossil is a transitional form is a process of comparison with reference to other fossils and predictions made by existing hypotheses, so how could you look at the fossil “in isolation.”
That’s like saying you need to catch the killer by looking at his DNA “in isolation,” not in reference to DNA from the crime scene, and without reference to whatever facts of the case have made him or her a suspect. That doesn’t make any sense.
The fossils are what “establish the reality of the transition.” The transitional morphology, explainable DNA changes, the fact that the transitional form occurs in the right era and geographical area–are what validates the hypothesis of the transition. And you don’t come up with hypotheses in a vacuum, you base them on educated probabilities, so you would have reasons for suspecting fossil B fits the bill because your hypothesis would make predictions.
Just like the DNA on the murder weapon, the motive, the means, and the opportunity are what support the hypothesis that it was Professor Plum in the study with the candlestick. The police wouldn’t pull that out of thin air, but they don’t have to establish the “reality on other grounds” before they interrogate Prof. Plum and test his DNA. You follow the evidence to validate or invalidate the hypothesis.
Why do you want to see this scenario? That isn’t how science works.
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Hi Daniel,
I appreciate reading the lively exchange. Thanks for piping in.
Is there not a difference between predictions of interpolation and extrapolation? You are suggesting that predictions ought to be extrapolative, suggesting what directions evolution will take in future. I am a layman in such matters but from what I’ve seen, I think most of the most powerful predictions of evolutionary theory have been interpolative, e.g., if creature Z at time t(3) is proposed to be in the same lineage as creature X at time t(1), then we ought to expect to find a creature Y around time t(2). And voilà, that is what we find…
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Sir, appreciate the thoughts. You are essentially correct, there is predictive value there, however I would observe that “not finding” what is expected not to exist may be essentially as predictive as the alternative, though there are still philosophical differences (absence of evidence does not necessarily entail evidence of absence, e.g.).
Additionally, though, it is important to note that the evidence you are referring to here is evidence only of common descent. while this is certainly related to evolutionary theory, they remain two distinct questions. One could absolutely prove common descent of all life beyond any shadow of doubt and this does not in any way speak to the particular means by which those new animals arose, or in any way affirm the sufficiency ofmthe natural selection/variation method to produce those new forms of life.
Christy,
Don’t want to keep discussing this, I think we’ll have to acknowledge we’re at an impasse. I’ll try to explain a different way but if you don’t see what I am getting at then we’ll have to leave it there.
A fossil is essentially the remains of a dead organism. From the fossil we can derive:
- the morphology of the organism,
- the rough timeframe the organism lived
- occasionally, if soft tissue remains, we may also derive genetic information of the organism.
From those particular data (as derived from the fossil) we can conclude that the organism in question is transitional between others.
Therefore, as a corollary, the extant remains of that animal, commonly called a “fossil”, are thus recognized as the remains of a transitional organism. For shorthand, we call it a “transitional fossil”. But this remains within the conclusion of the investigation. In other words, we have:
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Premise 1: Organism X has a transitional morphology (as derived from the fossil).
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Premise 2: Organism X lived during a timeframe consistent with it being transitional (as derived from the fossil).
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Premise 3: Organism X’s genome (as derived from the fossil’s soft tissue) is consistent with it being transitional.
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Conclusion: Organism X is transitional.
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Corollary: X’s fossil, being the remains of a transitional animal, is therefore called a “transitional fossil.”
So again, “This is a transitional fossil” is clearly within the conclusion of the investigation into transitional relationships between organisms. It therefore simply can’t be one of the premises.
From a fossil we can directly derive lots of particular information (shape, date, genetics), and those particular data most certainly can and should legitimately function as premises in order to determine transitional relationships or common descent. But we simply can’t put “this is a transitional fossil” as one of the premises. This is the conclusion.
I don’t think that is a premise used by any researcher. When reading articles written for the public or articles written by YEC/ID folks it is often stated in such a way as to make it seem to be a conclusion.
Also the genome of currently living species can also help to establish the transitional feature under study.
If Christy concurs with you, then I think we have all come to agreement!
Agreed. But I think the problem is that scientists have a hypothesis based on observations that makes predictions, and then they look for corroborating evidence. They don’t list a bunch of premises and a logical conclusion. It seems like you are reacting to “This is a transitional fossil” being part of the hypothesis and “This is indeed a transitional fossil.” being the conclusion. Hypotheses are not premises.
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