Uncovering the Truth: The Power of Predictions in Evolutionary Evidence

[daniel_i_l]

I'm currently reading a book that presents the different kinds of evidence for evolution. Throughout the book, the author claims that evolution can make certain testable predictions. For example, he writes about biologists who examined birds and reptiles and predicted that they'd find a common ancestor in a certain level of rock. When they looked for fossils in that level they actually found the common ancestor.

Now, since the fossil record is rather sparse (less than 0.1 percent of living animals are fossilized), there are many common ancestors that we can't find. So even when biologists don't find the proposed ancestor, they can always say that this doesn't disprove the theory because the fossil record is missing so many evolutionary steps anyway. With this in mind, why are the fulfilled predictions of evolution more impressive that the predictions of a false prophet? If only a small percentage of evolution's predictions come true, and there's a ready explanation for all the times that they don't (which is most of the time), then how can the true predictions be proof of anything?

 

[Evo]

then how can the true predictions be proof of anything?

How can finding the fossils of a common ancester prove anything? They prove that the scientist's guess about the common ancestor was correct. Sometimes they find a common ancestor that surprises them. We're finding more and more fossil information all of the time.

You can't seriously be trying to compare scientists who are studying the past to cranks predicting the future? One is factual science, the other is not.

 

[Borek]

I don't think Daniel compares scientists and cranks, basically he is asking about testifiable predictions of evolution theory.

 

[daniel_i_l]

I don't think Daniel compares scientists and cranks, basically he is asking about testifiable predictions of evolution theory.

Exactly.

You can't seriously be trying to compare scientists who are studying the past to cranks predicting the future? One is factual science, the other is not.

Obviously, I'm not fully comparing the them, there's a lot of evidence for evolution regardless of the predictions I mentioned. I'm only comparing one aspect of the two.

Don't you agree that in order for predictions to prove anything, they have to come true consistently? You say that the fulfilled predictions prove that the biologist's guess was correct and I agree. But the author of the book was trying to say that the fulfilled predictions add proof to the theory of evolution in general, not just to one particular common ancestor. In that sense, how is it different from the cranks
that try to prove the fact that they have superpowers by making many predictions and highlighting the ones that happen to come true?

If for example the crank says that the winning lottery number tomorrow will be 1111 and it turns out that he was right then that proves that his particular guess was correct. But it doesn't prove that he has supernatural powers, especially if he also makes many mistakes. Similarly, if the biologist uses evolutionary theory to predict where a certain fossil will be found, then finding the fossil shows that his "guess" was correct. But that alone doesn't show that his theory is correct, especially if not all of his predictions work out.

I'm not debating the truth of evolution itself, but merely questioning one particular method of proof. To sum it up, I'm aware of the vast quantities of evidence in favor of evolution, but I fail to see how the fulfilled predictions add proof for anything other than the specific ancestor that was found.

 

[Evo]

What book are you reading?

 

[daniel_i_l]

What book are you reading?

"[URL
Why Evolution is True[/URL] by Jerry Coyne

 

[Ken Natton]

Your claim, daniel _i_l, is that you accept the evidence for evolution and that your question is genuine. Your problem is that your argument bears a strong resemblance to that commonly used by deniers of evolution. It is an old joke that whenever such people have been scornfully pointing out absence of a particular fossil to provide the evolutionary link between two known species, and palaeontologists then find that ‘missing link’ fossil, the naysayers then immediately point out that there are now two missing links.

But taking your claims at face value, the truth is that your statement about how sparse the fossil record is, is not accurate. The rate of palaeontological finds has been growing steadily, and there is now a substantial body of evidence from palaeontology alone. But even more significantly, palaeontology has started to improve its work with other areas of evolutionary study. Once was the time, not so long ago, when university palaeontology departments and microbiology departments were at best oblivious to each other and at worst in open conflict. These days they work together and regularly uncover evidence that corroborates each other’s work. I know all this from a couple of books I have read, which I have already mentioned elsewhere on this forum. They are ‘Endless Forms Most Beautiful’ and ‘The Making of the Fittest’ by Sean B. Carroll. He talks very tellingly about this ‘modern synthesis’ is evolutionary biology. I think you would find his books very interesting and very stimulating. I certainly did.

 

[madcat8000]

Id also recommend this book and author in general: Life Ascending: The Ten Great Inventions of Evolution by Nick Lane. As for predictions a person must be very careful about that. People can proclaimate all kinds of predictions but it doesn't mean they are on the right path. Scientist's can be as full of themselves as any proper fool. And there is no fossil that holds some place in the record that will make it the perfect piece of evidence or proof. Its just one indicator that among many will let you know that your on the right or wrong path.

Anyways I do hope you will continue ask questions in this thread so that it can be discussed!

 

[epenguin]

It has been said that the only thing that has ever been rigorously proved is that nothing can be rigorously proved.

I think one has to take with salt the simplistic model of a mill of theory -> prediction -> experiment or observation -> falsification or not.

It is quite difficult for the many sciences where experiment is not possible. Although certain experiments will be useful to them. Fieldwork sciences. Astronomy, Earth science, bioevolution, even ordinary history. They are an eclectic combination of detective work, modelling, deduction etc. Although we cannot do experiments we are to an extent saved by the great number of "natural experiments" there have been - that we are not dependent on studying our one sun but can see myriad other suns in various stages of their lives (biology has more stories, fewer examples of most stories).

It is fairly obvious that e.g. mammals all have rather related body plans, then vertebrates a bit more distantly related. Then if you start to discover fossils which look also related, if also you can extrapolate known geological processes to get estimates of their ages, then if you are without prejudices you begin to frame certain ideas... Anyone with prejudices can object you haven't "rigorously" satisfied a criterion of scientificity (which they have invented).

Links fill in - not always. Reasonable people will believe the fact of evolution. This does not easily prove the Darwinian mechanism of evolution, whose epistemological status has been much debated. It was to an extent almost a theorem deduced from the facts of heredity known to Darwin, now much better understood. Why one animal was less well adapted than another descended from might be difficult to say, but with greater understanding of climate and geological change and seeing the evolution together of e.g. predators and prey, a greater understanding of physiology, biomechanics etc. one can make increasing sense in terms of fitness.

A far finer trace of evolution is contained in DNA sequences, now massively analysed. This has confirmed and much refined many of the previous conclusions, e.g. all the primates related, dogs foxes and wolves closely related, etc. but has changed some of the previously thought routes of evolution and relations of groups. It will take longer to relate DNA sequence to function, but in bits this has already been done.

We now have this incomplete but huge body of an understanding called modern science. Belief in most of it is less risky maybe than for earlier pioneers. But anyway this existing mass is a product of an evolution. Sometimes, I think, it is more instructive to look at how it has evolved than do what you seem to accuse the evolutionists of doing, fitting it into a preconceived plan of what ought to be?

 

[daniel_i_l]

Sometimes, I think, it is more instructive to look at how it has evolved than do what you seem to accuse the evolutionists of doing, fitting it into a preconceived plan of what ought to be?

I'm not "accusing" the evolutionists of anything. As I mentioned above, I wasn't trying to start a debate regarding the veracity of evolution. Because of the many types of evidence, I'm convinced that evolution happened. I'm just trying to ask a question about one fine point of the theory. For some reason some posters in this thread got all worked up about the fact that I might be casting evolutionary evidence in doubt, while in fact, I just want to have an objective and scientific discussion.

Anyway, I probably didn't explain myself properly either so I'll reformulate my question.

In physics, one major way to support a theory is to use it to devise an experiment that has two possible outcomes, one that's predicted by the theory and one that's not. For example, using Newtons laws of motion we can predict the time it will take for a ball to roll down a ramp up to a certain degree of measuring error. So we can measure the time and check if it falls within the error margin predicted by the theory. If the prediction was wrong then we'd know that there was a problem with the theory.

My question is, is there an analogous experiment for the theory of evolution? In other words, is it possible to come up with some experiment such that one set of outcomes are predicted by the theory and the other ones are not? The point I was trying to make before is that the prediction "If we dig in place X then we should find fossil Y" isn't enough because neither finding the fossil nor not finding it would go against the theory.

From what I understand, epenguin basically said that the type of experiment I asked about only exists in certain kinds of sciences and may not be applicable to evolution. Is that correct?

Thanks

 

[DaveC426913]

From what I understand, epenguin basically said that the type of experiment I asked about only exists in certain kinds of sciences and may not be applicable to evolution. Is that correct?

Thanks

It has been noted by many, yes, that evolution is not easily falsifiable. Falsifiability is a requirement for a good theory.

 

[JDStupi]

Haha, damn man that was harsh, I don't think he is questioning evolution, if anything it is simply an interesting debate for the Philosophy of Science and the methods of human inquiry. Simply that within Physics and similar sciences we have ideas about the nature of reality that are most times pitched within the language of mathematics, thus allowing it to have a level of quantitative predictivity that can be falsified and used in a somewhat more straightforward way. The question is simply about the methodology of science as practiced in evolution theory, not so much comparing Physics and Biology and saying that Biology doesn't predict in the same way and as a result is inferior, rather pointing out that Biology has a different methodology yet it still retains a degree of effectiveness and illuminates our understanding quite a bit. In light of this, how can we discuss Evolutionary methodology? Kind of like accepting a Humean critique of Newtonian Mechanics, but simply seeing that Newtonian Mechanics "works" as knowledge and what does this say about knowledge as a whole?...then we can discuss more specific aspects of Evolutionary inquiry, how it has proceeded, and how it should proceed.

 

[Ken Natton]

The suggestion that evolutionary biology cannot work by experimentation is not accurate. Neither would it be fair to say that non of its assertions are verifiable. That man I’ve mentioned already, Sean B. Carroll is an experimental microbiologist, and he gives some pretty vivid accounts of some of the experiments he has been involved in. The very reason that Drosophila melanogaster (the humble fruit fly) has become such a closely studies species is because of the experimental opportunities it offers to evolutionary biologists, because of its short breeding cycle and great fecundity in favourable conditions. And much of the history of evolution is written into DNA. The accurate dating of exactly when we became the naked ape, and when we started to wear clothes, for example, is written into the DNA of lice.

 

[unusualname]

Haha, damn man that was harsh, I don't think he is questioning evolution, if anything it is simply an interesting debate for the Philosophy of Science and the methods of human inquiry. ...

Ok, my "harsh" reply got deleted, so maybe I'll put it more gently...

The OP asked us to compare evidence for evolution with the predictions of a "false prophet" in post #1, then in a later post says "I'm not accusing the evolutionists of anything"

These are not the words of someone looking for a rational debate, at least not on a science forum. The term "evolutionists" sounds like something out of 19th century theological crusades against Darwin.

There is obviously no experiment which will help "prove" evolution since evolution occurred over a few billion years. The best you can do in that respect is examine the historical evidence, fossil records and dna comparisons. But you can show that genetic mutation and selection works in fruit fly breeding experiments for example, or with plants subjected to varying environments.

But that's pretty trivial, and hardly sounds worthy of debate.

Ultimately we will probably discover other planets with life in various stages of evolution, which would be nice evidence but still probably wouldn't convince those who don't want to be convinced.

 

[DaveC426913]

A point of order: it is not merely naysayers of evolution who are asking this question. It is a valid and concerning question for any scientist.

Your attempts at refutation are ad hominems. Refute the argument, not the arguer.

There is obviously no experiment which will help "prove" evolution since evolution occurred over a few billion years.

The same rhing could be said about the Big Bang. That event too happened long in the past.

Yet we have models that we can test, they can fail the tests, the models are falsifiable.


What predictions does evolution make that we can test for falsifiability?

 

[unusualname]

A point of order: it is not merely naysayers of evolution who are asking this question. It is a valid and concerning question for any scientist.

Your attempts at refutation are ad hominems. Refute the argument, not the arguer.What predictions does evolution make that we can test for falsifiability?

Evolution predicts that complex and varied life can evolve on a planet from simpler origins.

That happened.

 

[bobze]

A point of order: it is not merely naysayers of evolution who are asking this question. It is a valid and concerning question for any scientist.

Your attempts at refutation are ad hominems. Refute the argument, not the arguer.


The same rhing could be said about the Big Bang. That event too happened long in the past.

Yet we have models that we can test, they can fail the tests, the models are falsifiable.


What predictions does evolution make that we can test for falsifiability?

"Evolutionary theory" really is a unifying theory, as such its huge! There are literally hundreds of avenues one could explore on it's falsifiability.

To name a few; homology and phylogenetics, homology in cladistics, modes of speciation, fossil record complexity, etc

(Basically the advent of all of molecular biology has been one giant test of evolutionary biology, where time and again it could have been toppled by molecular biology).

 

[daniel_i_l]

... where time and again it could have been toppled by molecular biology.

I think that this is the difference between most evidence for evolution and evidence for physical theories. Of course it's possible to come up with ways that evolution could have been falsified [the famous rabbit in the Cambrian for example], but that isn't as powerful as an experiment designed such that one of two possible outcomes is incongruous with evolutionary theory. Has such an experiment ever been done?

 

[madcat8000]

Yeah it seems that evolution can only be studied in the rear view mirror. Setting up an expiriment with one right outcome doesn't take into account the way evolution takes the easiest path possible. Rewind the story of Earth a hundred times and youll get one hundred different movies. But mostly youll get movies that are 4.5 billion years long and involve bacteria munching minerals in a planet wide desert. You can prove it takes place but you can't predict by what pathway it will arrive at an end point. And it might not ever reach your end point.

This is as close as I've ever seen and its merely an observational experiment. http://myxo.css.msu.edu/ecoli/

 

[cesiumfrog]

Of course it's possible to come up with ways that evolution could have been falsified [the famous rabbit in the Cambrian for example], but that isn't as powerful as an experiment designed such that one of two possible outcomes is incongruous with evolutionary theory. Has such an experiment ever been done?

In the spirit of "know thy enemy", I read http://books.google.com.au/books?id=BG9EAAAAYAAJ" (beware, most of the authors just fail to understand statistical physics, and half consciously fore-go reason). An example therein was a test of the hemoglobin of some related (I think semi-aquatic) animals. One hypothesis is that the precise details of the molecule should correlate to how closely related the different species were overall (phylogeny). The competing hypothesis was that the precise details of the molecule should correlate with how similar the habits of the animals (as though designed for the purpose). This was presented as your binary test, in which the evolutionists made one prediction and the creationists made the other. Except that in this case the outcome favoured the latter. In hindsight we of course say that neither prediction would be inconsistent with evolution. As already said, the theory isn't terribly conducive to making simple hard predictions, and really a lot of evidence needs to be weighed.

 

[DaveC426913]

Evolution predicts that complex and varied life can evolve on a planet from simpler origins.

That happened.

It's not quite as simple as that. Evolution doesn't uniquely predict that outcome.


(I'm playing Devil's Advocate here, so my heart isn't really into criticizing its weaknesses. )

 

[Pythagorean]

I believe the OP's questions are in good faith. I don't think evolution is as concretely defined as most phenomena in physics is, so it has some ambiguity to it.

Equally, daniel_i_|, I believe the scientific study of evolution is in good faith and it's framework that has proven successful. It does require more scrutiny, but I think that's pretty well acknowledged and we're waiting on technology and theory to develop it more and give more concrete predictions of the particular mechanical events and their emergent behavior, as we perceive it. A paradigm shift is always possible, but I can't see how it wouldn't be congruent with a lot of the themes in evolution.

 

[Ken Natton]

The basic point that evolutionary theory cannot be tested by experiment in the same way that physical theories can, may have some basis in fact – I am not convinced that it is entirely correct – I’ll try to address that in a moment. But, whatever the genuine nature of the question posed in the original post, there is an implication that hangs over it that evolutionary science is somehow not proper science, or is at least not as good science as physical science. It is an implication I reject. My problem is, as I have said, I am as much the layman in biology as I am in physics, and I lack the ability to provide the rigorous riposte that this question really requires, certainly for a mind as acute as yours, DaveC426913. This is not the first time I have been involved in a thread that cried out for a contribution from an embryologist that you had to recognise, just wasn’t going to happen. In any case, a very strong feeling that I have developed from what I have read, and from my interactions with forums on this subject, is that embryology is really where it is at. Many of the real, cold, hard, scientific answers lie in the study of embryonic development. There are many echoes of our evolutionary history that are perfectly observable today in developing embryos. Another notion that seems to run through this thread, even from the contributors who ostensibly support my view, is the scarcity of knowledge about these things. Again I have to say that this is just not an accurate picture of the reality. The body of data that exists and the degree of understanding that accompanies it is far more extensive and much more detailed than any of the contributors to this thread seem to understand.

Famously, Darwin knew nothing of DNA or of genes. Certainly, he understood the fact of heredity very well, but then so did many a breeder of domesticated plants and animals of his time. In On The Origin of Species then, Darwin builds his evidence from nothing more then observable morphology and behaviour. Nonetheless, the book is a slow and steady building of ultimately overwhelming and unanswerable evidence. Modern evolutionary biology then, has a wealth of powerful evidence entirely unavailable to Darwin, and it has investigated and analysed that data in great detail.

The best example I can give you of the kind of scientific experiment conducted by microbiologists, is the best, off the top of my head summary I can give you of the account of an experiment done by that man who could really knock this particular ball clean out of the ball park – Sean B. Carroll. He gives an account of an experiment he was involved in, under extreme pressure from those funding his work, when, very much in last chance saloon, they finally produced the results they had been attempting to achieve. It all involved the use of certain chemical dyes on fruit fly embryos that at a particular point in time gave the embryo a very stripy appearance. What the dyes were indicating was the effects of the segmentation of the embryo by the Hox genes. Hox genes are a class of genes that operate very early in the embryonic developmental process. Their effects are observable in the segmented nature of the body of the adult fruit fly. Their effect is also observable in adult humans in the segmentation of our spines.

Another excellent example I can give of detailed knowledge centres a round the Pax6 gene. When a particular allele (mutation) of that gene is present in a fruit fly, the adult fruit fly has no eyes. Of course, it has never been done by experimentation on humans, but it is an extremely rare condition for human beings to be born with that same allele of the Pax6 gene. When they are, they do not have no eyes, but their eyes have no pupil. That kind of knowledge has been built with exactly the same kind of dispassionate scientific methodology as that employed by physicists.

 

[Pythagorean]

I didn't mean to imply any kind of inferiority. All I really mean is that biology is a much more complicated subject and still developing. Core physics is the low-hanging fruit and much of it has been picked by now. The physics of biological systems, however, is still a frontier.

 

[unusualname]

Evolution predicts that complex and varied life can evolve on a planet from simpler origins.

That happened.

It's not quite as simple as that. Evolution doesn't uniquely predict that outcome.(I'm playing Devil's Advocate here, so my heart isn't really into criticizing its weaknesses. )

No, but since we only have one Earth and one history to look at that's what we have to work with.

As I mentioned previously, it is probable that we will discover other planets with life at some time in the future which will give us other data to work with.

In the meantime, we have a well confirmed timeline via carbon-dating and geological evidence that simple lifeforms existed 2-3 billion years ago and more complex lifeforms emerged in the last billion years.

I can't see how any alternative theory can explain that, the interesting questions are about the exact mechanism of mutation and selection in varying environments, which seems to have many subtle and complex open problems.

But evolution could easily be falsified by showing that complex lifeforms came into existence over a short timescale, the evidence to dismiss that is so incredibly huge that only an unscientific person would still believe it.

Obviously there remain questions about the exact mechanisms that cause evolution, and it is probable that widely differing types of life could have emerged, but the basic idea of evolution is obviously sound. To claim otherwise is not rational.

We can't do evolution experiments over billions of years, so until we find life on other planets we can only speculate as to what types of life might evolve. We do at least have proof of the existence of the dinosaurs, which at least shows how spectacularly varied the outcome of evolution could be.

 

[Borek]

we have a well confirmed timeline via carbon-dating and geological evidence that simple lifeforms existed 2-3 billion years ago

We have a well confirmed dateline, that for sure, but carbon dating has nothing to do with it, it doesn't work reliably for objects older than about 50-60 ky.

 

[unusualname]

We have a well confirmed dateline, that for sure, but carbon dating has nothing to do with it, it doesn't work reliably for objects older than about 50-60 ky.

Yes sorry, I meant (more generally) Radioactive dating

 

[Borek]

Yes sorry, I meant (more generally) Radioactive dating

And now we speak the same language

 

[daniel_i_l]

First of all, thank you for the interesting and well informed posts. I think that they helped me answer my original question.
Basically, I think that the answer is that even though it's theoretically possible to devise a decisive experiment for evolution, similar to what can be done in physics, it's orders of magnitudes harder. The reason for this is the shear complexity of biological systems. So for any given experiment it's difficult to quantitavely predict the outcome. And even after the experiment is done, the results can be tricky to interpret. Because of this situation, biologists have rely on other, equally valid, methods of evidence such as geology, archeology, embryology and microbiology.
Is my conclusion accurate, or have experiments of the kind I talked about actually been carried out? (And yes, I read Ken Natton's and unusualname's posts, and while the evidence you describe falls into the "equally valid methods" category, it isn't exactly what I'm looking for)

 

[Ahmed Abdullah]

It has been noted by many, yes, that evolution is not easily falsifiable. Falsifiability is a requirement for a good theory.

Evolution can be easily falsified by fossil evidence.
Findings like - say a human fossil in Jurrasic (199.6± 0.6 Million years from now) period will just do fine.

 

[bobze]

I think that this is the difference between most evidence for evolution and evidence for physical theories. Of course it's possible to come up with ways that evolution could have been falsified [the famous rabbit in the Cambrian for example], but that isn't as powerful as an experiment designed such that one of two possible outcomes is incongruous with evolutionary theory. Has such an experiment ever been done?

Sure you can design experiments to test individual parts of evolutionary theory (remember evolutionary theory is a big unifying theory, as such it incorporates many parts).

Suppose we wanted to test speciation, using evolutionary theory we predict that for a population, in which subsets become divide off each individual subset will continue to undergo selective pressures exerted by the environment until such a time that the populations no longer interbreed even if brought back together eventually.

Just such a famous experiment was carried out byhttp://evolution.berkeley.edu/evolibrary/article/_0_0/evo_45". What she found was that when a population is isolated to two different environments, even after they're brought back together, reproductive isolation starts.Another good example would be if we wanted to test the idea of selection itself. We could predict with evolutionary theory that allele frequencies in a population may not change randomly, but rather as a result of selection. How could we test this?

Suppose we wanted to look at how predation affected allele frequencies, after all evolution says that population under selective pressure should show adaptive changes due to the differential survival and reproduction of those changes. We could for instance, take a population of animals in the lab, let them live without selective pressure from predation for a time. Then introduce to the population, a predator which would provide a selective pressure. If evolutionary theory is right, we should see a change in allele frequencies over time (generations). We could even test this in the wild by introducing a new predator to a population which had not seen said predator before. That is to say, we have experimental (both dependent and independent) variables we can go in and manipulate.

Again, such a thing has happened in both the lab and in a "natural lab".http://evolution.berkeley.edu/evosite/evo101/IVB1bInthelab.shtml" Suppose we wanted to test the foundation of evolutionary theory; descent with modification. Evolutionary theory says that some clades of organisms should share common features because of shared ancestry and this should be to the exclusion to other clades. Here we can even get maths involved!

We could then use homology (evolutionary derived shared features) as a null hypothesis; "Such and such structure is not homologous in these two organisms".

We could then go out into the world and gather data, say the gene sequence (molecular genetics), the embryonic development (Evodevo) of said feature, the protein structure (proteomoics) etc.

We could then array these features in a matrix (lots of them!) and apply statistical tests to our observations and based on those tests accept or reject the null hypothesis.

If we were unable to reject the null hypothesis ever (that structures aren't homologous), you would certainly falsify evolutionary theory. There must be homologies shared between clades if evolution were true. Low and behold we do find homologies throughout clades of varying sizes (the continuity of the mammalian arm, the development of the notochord in vertebrates, etc).

We can then use everything we know about evolutionary theory to predict or make models of lineages and of course, some of those models are falsified from time to time. Say for example the common derived characteristic of the mammalian and mollusk eye, which was falsified on the basis of homology. There are literally thousands of examples of these different tests of evolutionary. So many, that I'm not even sure you could find a collective source for them all. I'd suggest, barring taking a upper level evolutionary biology course, you start with authors like Sean B. Carrol, Jerry Coyne, Steven Pinker, Richard Dawkins (at least his stuff involving evolution, not religion), Stephen Gould, Matt Riddley, etc

Honestly, I can't think of (with the exception of quantum physics) a scientific theory that has been more tested and scrutinized than evolutionary theory (And we don't even understand quantum physics in the way we understand evolutionary theory!)

 

[DaveC426913]

It occurs to me that evolution is not what we should be talking about. Evolution is fact. We see it happen all the time.

The thing that is in question is natural selection - what drives the evolution of critters.

eg. We know that there are finches on Galapagos that have evolved specialized beaks. The question is not whether they have evolved them over time, the question is what forces led to the variation.

Is it, indeed, that for example, ones who ate certain types of berries and who had longer beaks were able to take advantage of a food source and thus proliferate, eventually out-breeding other, more general types?

The mechanism by which an entire population changes, and the mechanism by which new species diverge from old ones - these are the things hotly contested.

 

[daniel_i_l]

bobze:
Thanks for those links, John Endler's guppy experiment is fascinating.

Now I take back what I said before. I think that my mistake was that I failed to recognize a distinction similar but not identical to the one that DaveC426913 pointed out. I was looking at evolution as more of an historical question, i.e are all the organisms we see today byproducts of natural selection as explained by evolution. And while this is also possible to prove, it's much harder to experiment with than sciences like physics because we're pretty much limited to natural experiments where we're not in control or even aware of all the factors. But the theory "organisms evolve through natural selection and that could conceivably account for life on Earth" can be tested with definitive experiments.
In addition, I think that I was a little fixated on evidence from fossils and, as I said before, nothing guarantees that we find what we're looking for. On the other hand, homology might be a better approach to this kind of experiment.

Even though this is a minor issue in comparison, I think that part of the problem was that in the book I was reading [in one of the first posts I said which one] the author repeatedly said things like "evolution predicts that fossil A will be found and we really found it" which in my opinion isn't entirely honest. Because like I said, sometimes biologists search for certain fossils without actually find them and this poses no problem for evolution. So I think that if the author wanted to give examples of fulfilled predictions he should have chosen examples similar to the ones posted in this thread.

 

[gerben]

I do not know the book, but I guess when the author says "evolution predicts that fossil A will be found and we really found it", he means "evolutionary theory predicts that species A existed and we found a matching fossil".

 

[bobze]

It occurs to me that evolution is not what we should be talking about. Evolution is fact. We see it happen all the time.

The thing that is in question is natural selection - what drives the evolution of critters.

eg. We know that there are finches on Galapagos that have evolved specialized beaks. The question is not whether they have evolved them over time, the question is what forces led to the variation.

Is it, indeed, that for example, ones who ate certain types of berries and who had longer beaks were able to take advantage of a food source and thus proliferate, eventually out-breeding other, more general types?

The mechanism by which an entire population changes, and the mechanism by which new species diverge from old ones - these are the things hotly contested.

Dave,


That's a great point, One I tried to make at the beginning of my post, but you certainly put it more clearly here.

Evolution has the misfortune of sharing that name of the theory, with the natural phenomena it explains. Evolutionary theory is really a catch-all for all the smaller, no less important, theories and hypotheses which explain the phenomena (fact, if you will) of evolution.

This I suspect, causes a great deal of confusion amongst lay-folk or anyone not particularly educated in biology. When biologists are "arguing about evolutionary theory" they aren't arguing something so exciting as, whether or not it occurred --Normally something much more mundane like, which selective pressure influenced such-and-such structure's evolutionary development more.


To this end then, one can easily see that "evolutionary theory" is falsifiable, at least the different theories and hypotheses referred to under "evolutionary theory" (sometimes retermed the "modern synthesis", which avoids some of the name commonality confusion).

The real chance to "falsify" evolution (the idea or phenomena) came from Watson and Crick's great discovery back in the 50s, that of the structure of DNA (arguably the most pertinent to human kind scientific discovery thus far).

Had it played out differently (with DNA, genes, mutations etc), Darwin's idea (descent with modification) may have went the way of the dodo. Rather than that, the molecular biology revolution cemented in fact, evolution.

It again plays to the old Englishman's genius. For in Darwin's day when he postulated Natural selection (a theory), the fact that theory explained, was not yet even a "fact". He really was one of the most perceptive or lucky scientists in history.

Anyway (sorry for the tangent ) where I was going with this is; You are exactly right.

Evolution is a fact and we use different theories to explain it; Natural selection, sexual selection, artificial selection, cladogenesis, sympatric speciation, etc. And those are all falsifiable.