In order to be a valid scientific theory, you have to not only provide the theory, but show how you can be proved wrong. For instance, when Einstein proposed relativity, he also proposed three different tests that could be run to see if he was right or not. These were subsequently done (for example, gravitational lenses, etc). Even in biological circles, genetics has theories which are easily falsifiable, eg. about dominant and recessive genes. But is there an experiment that can be done to prove that evolution is wrong? Has one even been suggested?
This story is courtesy of a University of Sydney lecturer. He puts up a slide of a beautiful fish found in the Great Barrier Reef ... all tropical colours and flowing fins. And says, "This is an angelfish. It evolved to suit its environment. " He then shows a picture of an eel that is ugly as sin; brown skin, big teeth, a menace. "This is an eel that is found in the same area. Can someone see a problem here? We're using the same theory to explain two completely inconsistent phenomena. This theory has no predictive value". Good scientific theories, e.g. relativity, give you predictiveness. You can ask, "according to the theory, what if I do this?" Similarly, with genetics. You can ask: if I breed a yellow rose and a red rose, what colours and in what proportions will they come out? But evolution, on the other hand, can't be used in that way. Of course, you can retrofit an evolutionary explanation onto things, but that's not science, and it's not the scientific method.
These seem to be obvious points to me; points that any good scientist should have noticed. It just reinforces in my mind the feeling that evolution is accepted religiously and without question today, because some people misguidedly believe it absolves the need for God, and they don't want God around; it creates a problem for materialistic philosophy. If you even begin to suggest that there's something wrong with it as a theory, you are labelled as a philistine or a heretic. It has become sacrilege to question it, making those who hold onto it unquestioningly as dogmatic as the very people they condemn for being creationists. I just view it as scientific hypocrisy.
As an aside; I do agree with natural selection in the sense that a given species adapts to a given situation (e.g. moths changing colour for new environments), but I don't think it explains the diversity of species; nor does it explain the speed of evolution. There is something else going on.
However, my argument would be that the fault is not with the theory - it's with the people. Fanaticism is a basic human condition, and in the absence of religion many turn to fanatical atheism, fanatical rationality or fanatical politics.
This neither disproves the existance of God nor undermines the validity of the theory evolution. It's just the way people are.
You seem to be assuming that the ultimate form of evolution, if it exists, is camoflauge; that is, the best thing is to hide in the Reefs, thus, the eel is a failure, disproving evolution. The eel is not an angelfish, thus evolution is a crock.
Unfortunately, you ignore the possibility that evolution can take numerous paths. You could easily attempt that same logic with an antelope and a lion; they are not the same creature, thus, evolution is a fraud. In the wild, however, there ARE distinctions between predator and prey. The antelope evolved as prey; it developed the ability to live off the plants it encounters in daily life. The lion, on the other hand, evolved to be a predator; it relies on eating the antelope.
Relating it to your example, the angelfish is not a predator, and the eel is. The theory of evolution, if I recall it, does NOT state that all creatures will evolve into the same being.
And your first argument can be shot down soon as someone develops a test...
However, I'm not big on this stuff, but I do seem to know that they are able to carbon date fossils that they find in the ground... It seems as though they can use this to prove evolution, whether there's some sort of test or not. I would like to point out that since evolution is such a slow process, it's impossible to just say "BAM!" and make a test that a high school student can do in one class period.
And since you brought up genes... Isn't it partially the dominant genes that control evolution? For instance, way into the future, I predict that white people will just disappear because their skin color is recessive. We will evolve into a colored race because, as time goes by and people continue to intermix, the black and asian (and indian, etc.) traits will dominate.
We can already see this beginning to happen, and... well... I don't know if that's sufficient proof for you, but it is for me.
ymelup isn't saying evolution doesn't happen---e's saying that it is not that scientific a theory---which may well be true.
As for ymelup's first argument, just try to construct an experiment that will demonstrate to a reasonable degree of certainty that long-scale Darwinian evolution actually occurs. Chances are, you can't. It's certainly a useful model, though---much more so than scientific creationism. If you're an instrumentalist or a positivist, that's all that matters, anyway.
Now then, I dont want to take an official stand that the theory of evolution is not "true" or that it is not a theory. Quite the contrary, I have great faith in the general logic in it. However, I do want to suggest that it might be falsifiable, but we have not devised ways to falsify it ( And of course, it is at least possible that it is not falsifiable at all because empirical reality is such that no counter examples occur. If this is the case, then evolution is not discarded for lack of "theory-ness", rather it becomes a scientific law... but time will (tell.)
That the theory of evolution is not predictive is nonsense to assert and silliness to believe. There are predictions that can be made about the overall development of life on Earth using the theory of evolution as a guide. The problem, it seems to me, is that being able to generate the empirical data that would confirm or disconfirm those predictions is something beyond the likely time-line of most people. Thus, it becomes a bit tought to engage in prediction of events. However, what we can in fact do is examine empirical evidence to see if the data match the predictions we might have made previously: post-dicting. The contention that this IS NOT the SCIENTIFIC METHOD is wholly unsustainable. That is in fact what the scientific method is about.
Finally, I refer the kind reader to the book FULL HOUSE by Stephen Jay Gould. Here he takes an interesting tack on the theory of evolution where he suggests that contrary to the normal thinking that evolution tends towards specialization and complexity, evolution mostly tends to generate simplicity. That nutshell review of the argument is in itself simplicity, so please, if you are curious, pcik up the book.
Respectfully,
Dogboy
Some have said that a theory must be falsifiable. This isn't a good way to put it, since any theory that's falsifiable (able to be proven false) is by definition an invalid theory. It might be better to say that a valid theory withstands the rigors of opposing tests. Regardless, we have another theory, the theory of gravity, that also has no tests to disprove it. What experiment would you perform that could possibly disprove the existence of gravity? We should keep in mind when bringing this up that scientists still don't know what gravity is, how it works, or how it fits into the simplified model of the universe we're trying to build. We know how it operates, but not what makes it work. It's interesting to note that we accept gravity, though, as quite obvious, but there's more hard evidence to support the existence of the process we call evolution than there is to support the existence of the force we call gravity.
A theory is not necessarily predictive. The theory of chaos, for instance, is inherently not predictive. The theory of chaos holds that things cannot be predicted, and chaos plays a major part in evolution, gene pooling, and natural selection.
To hold up an angelfish and an eel and say that their taking different forms denies the theory of evolution simply isn't good thinking. It overlooks the fact that both the angelfish and the eel are perfectly suited for their environment, and each has a design and set of strategies that make their existence sustainable, meaning that given a stable environment and set of circumstances, they could exist in their present form in perpetuity. This situation complies perfectly with the theory of evolution.
It's very ironic that man has taken a species we now call wolf, and over centuries of breeding have developed numerous breeds of domesticated dogs. All your boxers, bloodhounds, and poodles, were first bred down from wolves. We have, in short, used the principles of evolution to our own ends, by forcing evolutionary pressures on these animals and developing entirely new species (for the domesticated dog is no longer of the same species as the wolf), but still some deny that evolution exists, even while we make it our own tool.
And if you ask anyone familiar with the clothing industry, they're gearing up for making clothes for taller people. This is because the height of the average person in our part of the world has increased in the last few years by about an inch and a half. This is the very process of evolution in play within our lifetimes, with evident effects. As a group, we're growing taller because of our diet, lifestyle, etc. A biological population reacting to its environment. Evolution.
The evidence for evolution comes to us at least 65 million years in the making, but it's not just in the field of biology. Evidence comes from the fields of geology, archaeology, anthropology, zoology, chemistry, and most other disciplines. In short, the theory of evolution is supported by the facts we have at our disposal from all branches of knowledge, each of which forms a part of the complete picture.
***Update (10-19-00): After submitting the above w/u, someone contacted me directly to point out an error. His contention was that wolves and domesticated dogs are indeed the same species. This led to a bit of discussion back and forth with him politely pointing out that dogs and wolves interbreed quite easily...me retorting with the point that their species are very closely related, enough that interbreeding isn't really a problem...he stating that inhibited interbreeding is part of the basic defining quality that differentiates species...my replying that yes, but it's not the only one and that canis lupus and canis familiaris are two similar but different species in the canis family, etc.
I was, of course, relying on my independent research in this area and my studies with a zoologist who once assured me that wolves and domesticated dogs are indeed different species according to our most widely used taxonomical standard.
Every time I replied to my new friend, I always double-checked my facts (I simply hate embarrassing myself). Lo and behold, as I was getting ready to write my latest to him, I found some new information at http://www.kc.net/~wolf2dog/annd2.htm, where it's pointed out that in 1993, with no formal announcements or fanfare of any kind, scientists quietly reclassified the dog family. Both domesticated dogs and wolves are now considered canis lupus. Wolves are now canis lupus X, and crossbred individuals are canis lupus familiaris.
So, my hats off and sincere apologies to my kind correspondent, ShadowNode, with much gratitude for his helping to complete my understanding here. He was right, after all, and I'm glad to have learned something new.
First, it should be noted that while Popper's view that scientific theories are judged on their falsifiability, it is by no means universally accepted. The 20th century did have other philosophers of science, and they weren't all students of Popper!
But the question of falsifiability is still an interesting one, even if one doesn't accept it as the sole determinant of being a scientific theory. And at its most abstract, natural selection is indeed unfalsifiable. It describes the (quasi-) stable state of a system (the ecology), when that system is so large as to be a singleton, and is already known to be in its quasi-stable state. In plainer English, this means that you're looking at a system shaped by Evolution, and that this is the only system available for you to examine. Thus, you cannot see Evolution in action, for the simple reason that you cannot see the ecology's adaption to environmental changes over "reasonable" timescales.
Note, however, that this rejection does not apply to the existence of intra-species variation, but only to natural selection on that variation. The existence of variation is easily established empirically; this is much less than ymelup's claim above about genetics.
But we still don't have to reject natural selection. First of all, it is the only possible theory which makes sense in the presence of random natural variation: If there is such variation, and environmental changes occur, wouldn't you expect to see "survival of the fittest" types of variation? It's the only logical possibility! So naturally, it is unfalsifiable -- one might as well try to falsify statements like "1+1=2".
And on smaller scales, we don't have to wait so long, so we can observe natural selection. The best examples are of course bacteria. Bacteria can exchange genetic material directly (with plasmids), which is a lot faster than sex. And their life cycle is anyway much faster than ours. And their environment changes drastically. Guess what? Hospitals are manufacturing antibiotic-resistant strains of bacteria! How do they do it? My guess is this: Some strains of bacteria are resistant to some antibiotics. Normally, whenever a gene conferring such resistance transfers to another bacterium, it is almost certain to confer no advantage to that organism (since this antibiotic is rare, especially in the environment of a bacterium of another strain). So the incidence of that gene remains low. But in a hospital environment the antibiotic is extremely common, so having resistance confers a spectacular advantage. Sure enough, pathogenic bacteria are incorporating these genes. Of course, it's not clear that the original variation was random in origin (how do you prove something is random, anyway?). But all "neutral" variations (i.e. those not conferring any advantage) appear random. And natural selection explains why "positive" variations (i.e. those conferring some advantage) concentrate so much. And while random variation has been observed, directed variation has never been.
To sum up: The existence of random genetic variation is the only part evolution that might be open to the "argument by unfalsifiability". It is falsifiable, of course, but only in the presence of large amounts of directed variation; but it's not open to direct proof. We've never seen directed mutation (even if it exists, you'd expect it to be very rare; unfalsifiability, anyone?). And in the presence of random genetic variation, natural selection is inevitable, and a clear logical consequence. All scientific theories contain such a logical "kernel" (for physics, e.g., it is mathematics), which is unfalsifiable in and of itself.
As a theory, Evolution is safe.
It seems to me that evolution as a process has never had a clearly-stated general theory, but rather is the portmanteau term we tend to use to refer to the byproducts of several theories related to natural processes that are more clearly defined, which are falsifiable and are very often predictive, at least within the limits of our ability to design and execute experiments to test these theories.
One further "twist" on the question of empirical proof: Is a theory invalid if all the experiments that might serve to prove or disprove it happen to be considered unethical in the present social climate? If we accept this as a premise, then would it follow that scientific validity is somehow contingent on the vagaries of social change?
Experimental methods and empiricism in general were (or so I was taught) simply "unfashionable" during the era of Aristotle, Plato and Socrates. While Aristotle especially managed to intuit many principles that seem to have largely held their ground to this day, it is shaky at best to describe his approach as scientific. Yet it was perhaps, with the exception of a handful of his maverick and outsider contemporaries, the closest the Ancient Greeks came to what we now describe as Scientific Method.
As such, "evolutionary process" is something that is actively being revised, challenged and redefined on a daily basis by those who work in the fields that tend to require constant improvement and challenges to existing theories and hypotheses. Since there is no unified evolutionary theory in the first place (at least that I am aware of) it seems to be a species of straw man argument to challenge the "theory" on the terms ymelup has done.
This, perhaps, is where God comes in. What is to say that the various observed processes we have managed to infer from what surrounds us are, taken collectively, not in fact something like such an experiment?
This is not to imply that I think life as we know it is merely some deity's lab bench. While uncertain of the existence of any particular deity, I also feel it is presumtuous of humans to imagine we might be able to understand a (presumed) deity's motives for its actions.
Still, nothing I'm aware of in the theories that get lumped into the ill-defined category of evolutionary thought claims to disallow the existence or involvement of a divine entity or entities. If evolution challenges religion in any way, it is merely challenging forms of religious understanding that presume to describe and define the intent and ways of creation that the Deity might employ, should such a Deity in fact exist. I personally have a hard time accepting any justification humans may present for engaging in such hubris as telling God how He/She/It did or does its Divine Works.
There is some confusion of terms in these recurring evolution debates. Evolution is used both for the idea that different species gradually develop from a common ancestor, and for the "mixing and mutations + natural selection" theory of how this development come about. If you, like the author of the first writeup, do not belive that the latter is primarily responsible for the former, you can certainly demonstrate it: just show the true cause.
Here I argue that the theory of natural selection is a valid one. The first argument in the original writeup seems to imply the second: A theory that makes predictions is falsifiable. It is true that we cannot use evolution to predict what kinds of animals will develop in a coral reef, but that is understandable because it is such a complex system. We cannot predict the weather a month from now either, but that's not because the Navier-Stokes equations are faulty.
In simpler contexts, evolutionary theory makes several predictions that are possible to verify:
At this point comes the counter-argument "but you are not really testing predictions, you are just supplying explanations after the fact. That's not science, and it's not the scientific method". To this I say that the scientific method of "hypothesize; derive predictions; test; repeat" is strongly idealised. In practise I do not think it is all uncommon that a theory is derived by "peeking" at the desired predictions.
The standard theory of natural selection has made predictions, some of which have only been possible to test with modern gene technology, and they have been confirmed. Competing theories like Lamarckianism also made predictions, and were falsified. If we are running out of ideas for new trials, and the burden of proof is starting to shift towards those who reject it, it might indeed make sense to stop calling Evolution a "theory". Thomas Kuhn used the term paradigm for such a theory.
Someone more bold might call it a fact.
There is also a pretty simple way to observe evolution in action, i.e. in simulation. Thousands of geeks around the world have independently knocked-up evolutionary simulations, based on Darwin's abstract principles of Heredity, Variation and Selection and watched their creations adapt and converge.
Finally, something I don't think many people appreciate, is that a rich and complex environment encourages the development of complex systems which in turn become the backdrop for other systems, reflecting the richness back. This feedback effect drives the explosive complexity that we see happening everywhere; nature, society, computers..
ymelu is incorrect across the board.
To begin with, the Theory of Evolution is certainly falsifiable. (OK, first understand I am not a biologist.) Logically, if you took an organism with a rapid generational period (a fruit fly for example) and placed different populations in separate and measurably different controlled environmental conditions, according to the theory you should note differences between the populations over generational time. Under repeated experiments, if the theory were false, the organisms would never change. (Someone tell me if there is a problem with this logic.)
Not predictable? Hog-wash. Remember that classic study with the moths in England? I can certainly predict the evolutionary change of moth generations based upon a firm understanding of the environmental conditions and a strong understanding of the existing biological function of the organism in question. I can predict the evolution of the species set given a solid foundation. The fact that we often lack that cannot be held against the complex issues of evolutionary change.
From the religious aspect - since it was brought up - I have no problems accepting both the existance of God and the Theory of Evolution. I believe that God, in the understanding of his infinite wisdom and power, is certainly capable of creating and manipulating through a manner as sublime as evolution. To believe otherwise - to my mind - belittles the almighty.
Here I was trying to type up a response in my Crystal Reports class, and find a half-dozen people beat me to my thoughts. :(
e-troon: I accept your observation re: the moths. It is a nice catch, and just the kind of thing I would let slip 15 years removed from any meaningful biology studies. :) Adaptation it is.
However, I would contend that my items regarding the flies still holds. Your question "But will they develop completely new features as a new species?" is valid. The trick would be to maintain the experiment long enough and under conditions sufficient to measure the differences between resulting adaptions and actual species differentiation. Which would be exactly the point to a determined effort to falsify the theory, holding to the origin of this nodeshell.
Falsifiable Theories What is evolution? The standard definition in science is:
Speed of evolution It is hard to judge the relative speed of something without knowing the entire process. Claiming changes over 1000 years has a very different view if one believes the Earth is 6000 something years old vs. 4,000,000,000 years old. The radioactive dating of rocks is an accepted practice. Given a known rate of decay from one element to another it is possible to make estimations of the age. These estimations have been proven to be accurate.
So how fast is evolution occurring? There are evolutionary processes that take millions of years. Others take less time. Corn has been bread from its original grass over a few thousand. Evolution happens with speed according to how fast the environment is changing - as does extinction. The mass extinctions of the past have caused great spurts of evolutionary change because many species went extinct and lots of ecological niches were opened up. Humans have been changing the environment of the planet for a few thousand years, and rather quickly at times - is it any surprise that species are changing quickly along with that?
Diversity of Species And why shouldn't there be a great diversity of species? There are a great diversity of different ecologies. In the Santa Cruz mountain range there are species that can't survive on the sunny side of the valley, and others that have adapted to it, yet can't survive in the shaded side. There are different thousands if not millions of variables for a particular micro-ecology and different species will be best suited to each one of those. A polar bear couldn't survive in the same places that a grizzly bear does. Different combinations of plants surviving means different animals surviving. Even though a species of plants may be able to live in a climate does not necessarily mean that it can survive there - if its form of pollination and seed dispersion does not work. Likewise, even if an animal can survive in a climate, its food source may not be able to.
One good example of this is the humming bird, bees, and the flowers. Two species of flowers - identical in all aspects other than color. One is red, the other is blue. Hummingbirds are attracted to the red flower, bees attracted to the blue. While the flowers can grow in either climate, only the red ones grow where humming birds and no bees are and only the blue ones grow where bees are with no humming birds.
Diversity needs no explanation other than this. It has predictable consequences too. Left to nature, if you plant the red species where there no humming birds, after a generation of flowers goes by, they won't reproduce and flourish.
Summary The above gives adequate explanation for what is happening. What else could be happening?
Evolution suggests that when faced with selective pressure, the frequency of alleles in the population will change. Over time, pressure for the maintenance of these frequencies or simply divergence due to isolation will lead to speciation. Both these claims can be challenged, but both can be demonstrated to occur. The example of the peppered moth demonstrates that selection pressure alters allele frequencies. The transposable P element in drosophila demonstrates that speciation can occur, and has done in our lifetimes.
Demonstrating that either of these was uncommon would allow evolution to be discredited. This wouldn't be difficult, but it hasn't happened.
Evolution makes one powerful prediction - over time, organisms will become more suited to their environment. It does not make any predictions about the manner in which this will occur, hence the wide range of different solutions to the same problem.
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