Today on
Total Drek we're going to respond to Mr. Tim Therrien's
remarks on the subject of evolution. His remarks are, in turn, part of an ongoing debate and my previous contribution can be found
here. Sooner or later I suspect I'll organize and index all this correspondence, but for the time being this is an active discussion and we'll just see where it goes. As we start, I'd like to mention that many of the points I make below have been made elsewhere. A good summary of several is available
here from
CSICOP. While not as complete as my own response, it is a much shorter (and quite possibly more engagingly written) piece on evolution that discusses many worthwhile issues.
To begin with, I want to thank Mr. Therrien for moving beyond his admittedly poorly worded questions. He rightly comments that sometimes a poor question has great value but, in this case, I would also observe that his
initial questions were not merely poorly worded, but also somewhat combative. I would also like to commend everyone in this ongoing debate who has tried to move this debate onto a more civil level, regardless of their position.
I am also pleased that Mr. Therrien has chosen to elucidate his intent more clearly- namely to demonstrate that evolutionary theory is not scientific. As he is not claiming scientific status for creationism or intelligent design, this should simplify matters considerably. As I have no objections to Mr. Therrien's religious faith, and have no intention to convert him to a pro-evolution position, it only remains for me to make a case in support of evolutionary theory as a scientific theory.
As we begin, allow me to make a few comments about the definitions Tim (I apologize if this seems forward, but I daresay I'll go mad if I must type Mr. Therrien throughout this post) uses.
First, the definition of theory. Tim refers to a theory as:
"An assumption based on limited information or knowledge..." and further remarks that:
"For the scientist, what the non-scientists means by 'theory' is actually an 'hypothesis'. I.e. - an assumption." This is, in a word, incorrect. In the present context an
assumption is something that is taken to be true without evidence. A
hypothesis by contrast is a proposed explanation or prediction that is subject to testing. Hypotheses are often derived from theories that are supported by evidence, so they are not believed to be true without any support. To equate hypotheses and assumptions is a mistake. True assumptions in science are more akin, though not identical, to "scope conditions," or limitations placed on the applicability of a theory or hypothesis. As we will see later, understanding the role of scope conditions is often critical to understanding the meaning of scientific work.
Tim next goes on to remark:
Since the non-scientist sees a theory as an assumption, they like to have evidence establishing the truth of an idea. We want proof. The scientist finds this anathema because they reject the idea that this is possible (which I will discuss shortly). Proof for the scientist is simply the validation of a part of any concept, which can later be shown to be false. Therefore, to request proof of evolution is to ask for an impossibility.
I think this does not fully reflect the scientific process. Scientists, like non-scientists, like to have supporting
evidence for their claims. The problem is that scientists regard it as impossible to
prove something to be universally true because our senses, and resources, are limited. In other words, because I cannot exist in all places in the universe at all points in time I cannot show with evidence that anything is necessarily true in all places and at all times. So, it is impossible to conclusively prove any universal statement correct. At the same time it is far from impossible to show considerable support for an assertion and an absence of successful falsification attempts.
It is also important at this juncture to comment on the difference between proving something to be true, and proving something to be
universally true. I might make an assertion to the effect that, "If I lift up my keyboard right now and let go, it will fall to the floor." In order to prove this assertion correct I need only lift up my keyboard and release it. If it falls to the floor, my assertion has been proven correct. (This, of course, supposes that we do not live in a universe managed by
Rene Descartes' famous
deceitful god.) It is, therefore, a relatively simple matter for me to prove any particular instance of a thing to be true. On the other hand, were I to make the assertion, "Any time I lift up my keyboard and let it go, it will fall to the floor," I am in a quite different position. There are any number of additional factors which might intervene to prevent my keyboard from falling to the floor- a strong gust of wind, a sudden reversal of gravity, the intervention of my quick-thinking girlfriend, and so on. Therefore, I cannot simply and conclusively demonstrate that a universal statement is always true, even if specific instances are provable. On the other hand, I
can potentially show that my universal statement is in error if, on certain occasions, when I lift up my keyboard and let it go it does
not fall to the floor. This logic does, indeed, seem a little odd to most people but this is simply because we are accustomed to proving things true in specific instances (e.g. the capital of Germany is Berlin, or that individual A killed individual B) and are not used to the problems inherent in proving that some things are always true. The doubt that individuals feel about the utility of showing what is
not true in order to discover what
is true (Tim's included: "Build up enough of these 'what it’s not' examples and (supposedly) you come closer to what it is.") can be largely dispelled, I think, by thinking about the game of "Twenty Questions." An answer of "no" is often as informative as an answer of "yes" if the question is properly phrased.
This takes us critically into the discussion of falsifiability. Tim does sum up the concept of falsification nicely, but then proceeds to remark that:
So, one of the foundations of the Scientific Method is - by no means - accepted by all scientists. Indeed, numerous articles indicate that there are many scientists who disagree with this requirement outside the non-evolutionary scientific circle.
I think this may overstate the issue somewhat. Popper's falsification criterion is widely accepted, but that isn't to say that we don't have debates on the specific way it should be applied.
Thomas Kuhn, for example, argued that falsification does not immediately cause a theory or hypothesis to be rejected for the simple reason that scientists may doubt the falsification. This doubt is no more remarkable than the doubt that results when two individuals use the same tape measure to determine the length of the same table. If they end up with different measurements, it doesn't necessarily mean that the table has changed but rather that their measurements may be in error. In Kuhn's view, we retain theories that are in the process of being falsified until something better becomes available, and then switch over. This is, more simply put, like waiting to get off of one horse until you have another one to ride instead. The seeming contradiction between a Kuhnian world in which we retain potentially flawed hypotheses, and a Popperian world in which we always reject that which has been falsified, has largely been resolved by
Imre Lakatos who focusses on the competition between various approaches to solving a problem. Over time as more falsification accumulates for some approaches, but not others, those falsified theories lose adherents. As a result, falsification isn't the sudden and final event proposed by Popper but, instead, is a lengthy and cumulative process.
The real relevance of all this, however, is that while the precise functioning of the falsification criterion is somewhat in dispute, its value to the scientific enterprise is solidly established.
Along those lines, I must take up Tim's remark about the mortality of humans:
However, since Popper is considered by many to be the authority, one would have to accept that you cannot scientifically establish that mankind is not immortal. To do so you would have to demonstrate that all men, everywhere, throughout all time - die. It is not observable, testable, repeatable or refutable. You can only say that there are numerous cases where men have died. So you can say that some men are not immortal, but not all men.
This is a very sloppily phrased assertion. Science indeed cannot demonstrate that all humans are mortal. It is possible that there exists some individual somewhere who is immortal, or that at some time in the future an individual human will exist who is immortal. However, science can establish that all men are not immortal. Any single man dying would serve to falsify the assertion that all men are immortal. Further, while we can't "prove" that all men are mortal, we
can point out that there is a definite lack of contrary evidence.
On the other hand, science could hypothetically demonstrate that no humans currently living are immortal. Doing so would require only attempting to kill every living human and seeing whether or not they die. I think it unlikely for both ethical and logistical reasons that such an experiment would be conducted, but the assertion is provable when phrased in a specific sense (i.e. 'currently living').
Having dealt with certain misunderstandings of the scientific method and definitions, we may now turn to the meat of the evolution discussion. We begin with the issue of speciation. Tim remarks that:
The scientific concept that seems to enjoy the most popularity is the Biological Species Concept (BSC). BSC separates “species” into very fine groupings. I.e. - “Bluegill Sunfish” and “Pumpkinseed Sunfish”. Yet both are capable of interbreeding. Although, some scientists seem to base speciation on the ability to interbreed. They point to strains of yeast, or varieties of flies that have manipulated in the laboratory and are incapable of interbreeding. BSC is not useful in discussing evolution because some questions are unresolvable. Such as “Do Homo Erectus and Homo Sapiens represent the same or different species?” We cannot know because they did not, apparently, exist at the same time or in proximity to one another in order to attempt interbreeding. Regardless, using BSC, what is often referred to as evolution is commonly held to be adaptation. Changes in species are merely adaptations to their environment. Two groups get separated for long enough and they may not be able to interbreed. But it does not change the nature of what
they are.
He is correct in commenting that the precise definition of species is in dispute, at least in part because it doesn't always match up with common perceptions and, in the case of the BSC, because not all species
reproduce sexually. Therefore, a definition that is based on ability to interbreed is of little use for these creatures. However, the BSC, according to the
link I sent Tim, "...defines a species as a reproductive community." Thus, creatures that CAN interbreed, but do not for a variety of reasons (provided in the link) may not be considered the same species. This is, however, a relatively minor issue.
Of greater concern in Tim's remark that:
BSC is not useful in discussing evolution because some questions are unresolvable. Such as “Do Homo Erectus and Homo Sapiens represent the same or different species?” We cannot know because they did not, apparently, exist at the same time or in proximity to one another in order to attempt interbreeding.
This is not a correct statement. To say that a given criterion is not useful in
all circumstances is not to say that is entirely useless. A similar argument would be that because all cars are not Chevys and Fords, the terms Chevy and Ford are useless. The BSC remains a useful criterion in a number of circumstances, regardless of its definitional failues in others.
Finally, Tim dismisses the BSC with the following:
Regardless, using BSC, what is often referred to as evolution is commonly held to be adaptation. Changes in species are merely adaptations to their environment. Two groups get separated for long enough and they may not be able to interbreed. But it does not change the nature of what they are.
I would appreciate some links here as to what difference Tim perceives between adaptation and evolution. Evolution is
regarded as an accumulation of adaptations that results in the generation of new species. Put more fully:
"In the broadest sense, evolution is merely change, and so is all-pervasive; galaxies, languages, and political systems all evolve. Biological evolution ... is change in the properties of populations of organisms that transcend the lifetime of a single individual. The ontogeny of an individual is not considered evolution; individual organisms do not evolve. The changes in populations that are considered evolutionary are those that are inheritable via the genetic material from one generation to the next. Biological evolution may be slight or substantial; it embraces everything from slight changes in the proportion of different alleles within a population (such as those determining blood types) to the successive alterations that led from the earliest protoorganism to snails, bees, giraffes, and dandelions."
As such, I see no distinction between "adaptation" and "evolution" that could make Tim's remark meaningful. As the
bard remarked, "A rose by any other name would smell as sweet." In this case, evolution by any other name remains evolution.
Tim continues to attack the issue of speciation with the following:
“The literature on observed speciation events is not well organized.” Four factors relating to this include: A. Lack of scientific interest. Few researchers and grad students look beyond their assumption that the literature exists. B. The assumption is that “speciation” takes a long time, so few events would be observable. C. “The literature contains many instances where a speciation
event has been inferred . (Not documented or substantiated, simply inferred.). D. “Most of the current interest ... concerns theoretical issues.
So, as regards speciation, the literature is not well organized. The researchers are basing their research on the assumption that supporting literature exists. And the process may be too long to document so they go on information that has been inferred (rather than substantiated.) This is apparently deemed sufficient because they are more interested in theoretical issues than in establishing, for certain, that speciation actually occurs.
This passage contains a very serious misrepresentation of the
link I provided to Tim. The author of the documents on the far end of my link does, indeed, indicate that the literature on speciation is poorly organized, but this does
not mean that it is nonexistent. In point of fact, this one link provides over two dozen references to observed speciation events. A further
source of references for speciation events is provided from the original link. In total, the issue is not that a literature on speciation does not exist, but rather that it is somewhat difficult to navigate. That many researchers assume that this literature exists (as it, in fact, does) is not unexpected given the immense utility of evolutionary theory to modern biology. One might as easily argue that gravity does not exist because most physicists are incapable of naming scientific articles that demonstrate that fact.
I must also take issue with Tim's remarks about
inference. He claims, "...they [the scientists] go on information that has been inferred (rather than substantiated.)" However, what the author actually said was, "Third, the literature contains many instances where a speciation event has been inferred. The number and quality of these cases may be evidence enough to convince most workers that speciation does occur." In other words, the author is saying that we have such an abundance of inferential evidence for speciation, that most biologists are convinced. Since a literature demonstrating speciation also exists, this is not unreasonable. It's worth pointing out as well that "inference" is not the same thing as "guesswork." When a polieman stops a reckless driver and discovers that the individual in question can't walk a straight line, has slurred speech, and reeks of alcohol, the officer likely
infers that the individual is drunk. Yet, however reasonable this assessment, the officer did not see the individual drinking alcohol. Would most people, then, say that the officer's conclusion is unsubstantiated? I think not. Inference is vastly more common, and respectable, than Tim's remarks might lead us to believe.
Moving on, we come to Tim's first objection to evolution:
For the purposes of the rest of this article I will use the term “species” with the Folk (or common)definition (again, from one of Dreks’ links). A. “reproductive compatibility and continuity. Dogs beget dogs, cats beget cats.” B. “You can tell species apart by looking at them.”
So, what is my problem with evolution? First of all, it does not fit with what we KNOW about species currently in existence. There are no “Dats”, “Cogs”, “Higs” or “Porses”. There are no feathered lizards, no scaly birds. There are not even wolves or cows with fins seeking to return to the water, or whales with feet or fingers sunning on the beach. In fact, a whale on the beach is considered so “unnatural” that we mount huge rescue efforts to get them back in the water. Are we actually hindering evolution?
First of all, Tim is employing a definition that combines two elements: reproductive continuity, and
phenotypic distinction. I don't think this is an ideal definition but I'm willing to work with it for the time being, without conceding that it is the proper definition for the present situation.
Based on this definition, Tim then objects that we do not, at present, see combinations of species. In his words, "There are no 'Dats,' 'Cogs,' 'Higs,' or 'Porses.'" It seems to me that there are actually two objections embedded in this paragraph, which I will phrase as questions. The first is, "Why don't we constantly see new animals that are combinations of new traits?" The second question is, "Where are the transitional or intermediate forms between species?" I will deal with both questions now.
In the first place, the fact that animals do not routinely and suddenly alter their form is not a problem for evolution because evolution does not predict that they would. Certainly some evolutionary theorists talk about
punctuated equilibrium in which change occurs
relatively quickly but "relatively" in this case still means "tens of thousands of years." It is quick only by comparison to
geologic time which is vastly longer than the span enjoyed by even the longest lived Human
civilizations. In more depth, evolution isn't just random, uncontrolled variation. It is, instead, often expressed as
selection acting on the natural variation within a species, as well as on
mutation, to produce new forms. Variation, in this case, refers to the diversity normal within a species- so if it is suddenly advantageous for a species to have a long neck, those individuals with long necks will survive more easily and reproduce more reliabily, passing on long necks to their progeny. Eventually, if long necks continue to be favored, we may see very long necks
indeed. Mutation is, essentially, random change in the genetic code. As such, it introduces additional variation into the organism, and that variation is then acted upon by natural selection. An understanding of variation and selection is critical because the presence of selection pressures will tend to curtail the development of change that degrades an organism's
fitness. As such, there are pressures both towards altered forms (when those forms enhance fitness) and away from altered forms (when those forms degrade fitness.)
Finally, it's important to keep in mind that organisms inhabit particular
ecological niches. A niche is the role in an ecosphere that a particular animal exploits. Thus, two species can share the same land area if they exploit different food and shelter resoures- different niches. The concept of a niche also helps to explain why we don't see constant change. Let's imagine for a moment that it's the deep past and all animal life lives in the ocean. Plants have colonized the land but are, as yet, unmollested by predators. The oceans are home to many animal species and fierce competition for resources. Now imagine we have a browsing species that lives in the area right at the shoreline. This is helpful- the shallow water makes it more difficult for predators to reach this species- and so feeding is good. At the same time, members of this species compete with each other for food and mates, and enjoy some natural variation. Now let's imagine that some of these individuals are a little better at existing out of water than their counterparts. They can browse a little further up the beach, a little more out of water, taking advantage of the foliage on land. (This folliage might be as simple as algae, moss, or ferns.) These individuals are able to exploit a new food resource in a new area (essentially a new, or expanded, niche) that their fellows cannot. They will, similarly, do better and reproduce more successfully.
Over time these traits grow more common and this species begins to browse futher and further up the beach. This movement both removes the species from the water, where they are vulnerable to predators, and grants them access to new food resources. Gradually ungainly fins are replaced with structures that more and more resemble feet and legs. Evolution is occurring as a new species colonizes a niche. So far, however, we've only considered browsers, but what about predators? The browsers on the beach are a potential food source, so a predator that can get a little further up the beach has new sources of prey to feed on. So, those predators that have more endurance out of the water begin to breed more successfully, just as their counterparts among the browsers did. Eventually, we end up with both predators and prey that can spend most, if not all, of their time out of water.
Now, imagine what happens to another species of browsing fish that has members capable of spending more time on land- those members confront not just competition from the earlier-evolved species of browsers, but also may be eaten by the largely terrestrial predators. Unlike the earlier waves of colonizers there is little advantage to moving ashore because the available niches are already filled. What this boils down to is simple: speciation may happen readily when there are new niches to exploit, but may happen slowly, or not at all, when competition in a niche is already heavy. Moreover, the availability of niches depends in part of which other niches are exploited- there were no niches for predators on land until niches for prey had been filled. So, the absence of rapidly-evolving species (keeping in mind that "rapid" in evolutionary terms generally translates to "less than 100,000 years") is not particularly surprising in a world where most available niches are already occupied.
More fundamentally the issue here is not that I need to defend evolution, but that we should actually deal with what the theory of evolution predicts. Claiming that evolutuon is wrong because we don't see things that evolution wouldn't predict in the first place is to attack a
straw man rather than the theory. This may be rhetorically impressive, but is logically nonsensical.
The second question, "Why don't we see transitional or intermediate forms?" is much simpler to answer. This is because we see many, many intermediate forms. We just don't usually recognize them as such. There is, for example, the
lungfish which is a fish that can breathe and function for short periods on land. The lungfish, therefore, fits quite nicely into the category of an intermediate form, and nicely resembles the creatures in my above example. Lungfish are uncommon, but that's what we'd expect given the presence of other animals better adapted to the land, or the ocean, that can compete with them. For another example, consider the entire class of
amphibians which are imperfectly adapted to life on land, even if they are far better adapted than the lungfish. You could consider amphibians as a class to be derived from a set of intermediate forms bridging between fish and
reptiles. Then, of course, there is the
flying squirrel which resembles rather nicely an intermediate form between more or less normal rodents and
bats. It, additionally, takes little imagination to see that
seals and sea lions resemble very much what modern day
whales must have looked like in the past. And, of course, while Tim's comment may have been a joke, we
have seen whales with
vestigial, poorly-formed limbs and digits. Moreover we have examples of extinct whale species whose previous life on land is apparent from their
skeletons and the continuing signs of that terrestrial life remain
apparent in modern whale
skeletons. (As a side note: the movement of some mammals back into the ocean doesn't contradict the earlier discussion of niches. A large number of semi-aquatic mammals like
otters have learned to exploit particular niches and marine mammals did the same.)
If we further open ourselves to fossil evidence, we find still more transitional forms. Modern
birds appear to be derived from dinosaurs, and we have fossils ranging from the mostly bird-like
Archaeopteryx to the much more reptilian
Sinornithosaurus and the other
feathered dinosaurs as support. Beyond this simple example, there are many additional
examples of transitional or intermediate species in the fossil record.
Finally, if we want to consider artificial selection, I can think of at least two examples of speciation, one involving intermediate forms, that have been produced by humans. One example derives from a link I provided to Tim in my previous response. A speciation event was described as follows:
The Russian cytologist Karpchenko (1927, 1928) crossed the radish, Raphanus sativus, with the cabbage, Brassica oleracea. Despite the fact that the plants were in different genera, he got a sterile hybrid. Some unreduced gametes were formed in the hybrids. This allowed for the production of seed. Plants grown from the seeds were interfertile with each other. They were not interfertile with either parental species. Unfortunately the new plant (genus Raphanobrassica) had the foliage of a radish and the root of a cabbage.
A plant with the foliage of a radish and the root of a cabbage appears phenotypically distinct from both parent plants. Further, while it cannot breed with either parent plant, it can breed with others of its own type (Raphanobrassica). This meets both of Tim's requirements for a species and, so, we have a demonstrated speciation event that results in a blending of the features of two original parent species. This is not, however, an intermediate form.
For intermediate forms, I ask that you consider the
Chihuahua and the
wolfhound. Both are phenotypically distinct (speaking personally, I think they resemble each other less than an otter resembles a
ferret.) and both are reproductively incompatible (if only mechanically) under all but the most unusual of conditions. Yet, both share a common intermediate or transitional form: the
wolf. Certainly both dogs are genetically compatible, and can be exposed to each other's genomes via more closely related intermediates like
terriers, but they meet Tim's criteria to be distinct species (Even if the BSC would consider them to be the same species), and have a living intermediary.
The point of all this is that intermediate and transitional forms are far from absent. These forms are, instead, abundant both in living and extinct species. The problem is that we don't usually think of an amphibian as an intermediate step between fish and reptiles- we just think of it as an amphibian. Yet, for all our failure to see them as such, these are examples to a greater or lesser degree of intermediate forms.
As for Tim's comment about the "unnaturalness" of whales on land, I will remind the reader that a century or two ago in the United States the idea of a woman wearing trousers was considered unnatural. Common judgments about such things are of dubious value. Additionally, I would say we certainly are interfering with evolution by helping these beached whales back into the water- but not because we're preventing them from growing legs. Rather, I suspect we're making beaching events more likely by saving the lives, and genes, of animals that are so inclined.
Having dealt with that objection, we come finally to Tim's stated attempt to demonstrate that evolution is not scientific. He makes this claim using four specific points, which I will address in order.
1. It is not Observable. Outside of the lab, no one has yet cited anything to me beyond “It’s all around us” or “It’s happening all the time”. Which tells me that most of you cannot think of one instance (that you can observe) of evolution in progress. We have been keeping records of descriptions of animals for at least a thousand years. No one can point to a significant difference between what they were then and what they are now. The only differences are adaptational (color, size, habitat, diet, etc.).
The problem here is determining what is meant by "observable." Tim seems to think that "observable" means we must see the thing itself in action. This would be one way to observe evolution, but not the only way. In fact, there are many elements of science that are not directly "observable." Atoms, for example, cannot be seen and, so, must be detected by their effects on other things. We know what these effects are because scientific theories make
predicitions which can then be tested. If the prediction holds, then the theory is supported. On the other hand if the prediction fails, then the theory loses support and may be partially or fully falsified. By way of example, physicists and astronomers are confident that
stars derive their power from
nuclear fusion despite the fact that we have never "built" a star. Moreover, we can't directly observe the inner core of a star. The confidence of astronomers and physicists stems from a series of predictions made from theory that are substantiated by observational evidence- stars behave precisely as we would expect if they are powered by nuclear fusion. Additionally, while we can demonstrate nuclear fusion on Earth at a small scale, we cannot reproduce the scale of activity present in a star. Yet, despite our inability to directly observe something, we retain the ability to formulate and test theories about it. Given all this, to determine if evolution is observable, we must ask, "Does it make observable predictions about the world?" As it happens, the theory of evolution makes numerous observable predictions about the world. These predictions are described in vastly more detail than I can provide
here. The document I provide a link to also includes a more detailed explanation of my above points:
Scientific theories are validated by empirical testing against physical observations. Theories are not judged simply by their logical compatibility with the available data. Independent empirical testability is the hallmark of science—in science, an explanation must not only be compatible with the observed data, it must also be testable. By "testable" we mean that the hypothesis makes predictions about what observable evidence would be consistent and what would be incompatible with the hypothesis. Simple compatibility, in itself, is insufficient as scientific evidence, because all physical observations are consistent with an infinite number of unscientific conjectures. Furthermore, a scientific explanation must make risky predictions— the predictions should be necessary if the theory is correct, and few other theories should make the same necessary predictions.
As a clear example of an untestable, unscientific, hypothesis that is perfectly consistent with empirical observations, consider solipsism. The so-called hypothesis of solipsism holds that all of reality is the product of your mind. What experiments could be performed, what observations could be made, that could demonstrate that solipsism is wrong? Even though it is logically consistent with the data, solipsism cannot be tested by independent researchers. Any and all evidence is consistent with solipsism. Solipsism is unscientific precisely because no possible evidence could stand in contradiction to its predictions. For those interested, a brief explication of the scientific method and scientific philosophy has been included, such as what is meant by "scientific evidence", "falsification", and "testability".
In the following list of evidences, 30 major predictions of the hypothesis of common descent are enumerated and discussed. Under each point is a demonstration of how the prediction fares against actual biological testing. Each point lists a few examples of evolutionary confirmations followed by potential falsifications. Since one fundamental concept generates all of these predictions, most of them are interrelated. So that the logic will be easy to follow, related predictions are grouped into five separate subdivisions. Each subdivision has a paragraph or two introducing the main idea that unites the various predictions in that section. There are many in-text references given for each point. As will be seen, universal common descent makes many specific predictions about what should and what should not be observed in the biological world, and it has fared very well against empirically-obtained observations from the past 140+ years of intense scientific investigation.
It must be stressed that this approach to demonstrating the scientific support for macroevolution is not a circular argument: the truth of macroevolution is not assumed a priori in this discussion. Simply put, the theory of universal common descent, combined with modern biological knowledge, is used to deduce predictions. These predictions are then compared to the real world in order see how the theory fares in light of the observable evidence. In every example, it is quite possible that the predictions could be contradicted by the empirical evidence. In fact, if universal common descent were not accurrate, it is highly probable that these predictions would fail. These empirically validated predictions present such strong evidence for common descent for precisely this reason. The few examples given for each prediction are meant to represent general trends. By no means do I purport to state all predictions or potential falsifications; there are many more out there for the inquiring soul to uncover.
The remainder of the first objection simply re-introduces the
specious distinction between "adaptation" and "evolution," and complains that we haven't witnesses significant natural evolution in 1,000 years of record keeping. Given that, as discussed previously, the entire length of human civilization is not thought to be sufficient for us to witness extensive natural change, this is not a reasonable objection.
The second objection is as follows:
2. It is not Testable. Efforts have been made with yeast and flies. But neither has resulted in yeast or flies becoming something else. Yeast at the start, yeast at the end. Any differences seem to be only in compatibility with one another. Even after millions of evolutions. To truly test evolution, as stated by the staunch supporters of evolution, would require millions of years. By definition it is impossible for man to do so. (Quite convenient for the evolutionists, though. You can’t argue with something that so outdistances your own lifetime, eh?).
As indicated above, evolutionary theory makes numerous predictions that
are susceptible to testing. Intermediate and transitional forms should exist, and they do. Traces of previous forms should exist in modern species, and
they do. The testable, confirmable evidence of evolution is all readily available (and, as a side note, much of it is linked to in this post).
If there is a problem here, it is that there is too much emphasis on "seeing" the thing happen. Imagine for a moment that you are sitting on a jury for a murder trial. There are no witnesses to the murder, but witnesses did hear the defendant declare his intent to harm the victim. The victim was then found dead from a stab wound. When the defendant's home was searched, a knife with the victim's blood on the blade, and the defendant's fingerprints on the handle, was discovered. Moreover, the defendant lives alone and has no alibi for the time of death. Finally, spittle from the defendant was found in the victim's wounds. Now, nobody
saw the murder take place, but the case that the defendant did, in fact, kill the victim is pretty strong. We have motive/intent, means, and opportunity, as well as supporting physical evidence. The situation is similar with evolution: we have motive (competition), intent (survival/reproduction), means (variation, selection, mutation), opportunity (geologic time), and ample physical evidence (genetics, fossil evidence). To say that the defendant can't have killed the victim simply because the police didn't arrive in time to see it happen is no more wise that claiming that evolution can't have happened because human scientists haven't been around watching for the past several million years.
Finally, the timespan over which evolution occurs does not make it untestable. As stated in my last response to Tim, we
have tested evolution in the lab and have been able to cause speciation in fruit flys, plants, and bacteria. These creatures reproduce very rapidly and, so, can accumulate and express evolutionary change more rapidly. Longer-lived species cannot be tested in this way but, as stated, we have plentiful evidence for their change over time. Moreover, the fact that something takes place very quickly or very slowly doesn't make it untestable. The sciences of
astronomy and
geology both deal with processes that occur over extremely long periods of time, and both have enjoyed considerable success in predicting things. Moreover, we can't watch
quantum mechanical processes occurring in real time, but we can still derive an understanding of them. Without such an understanding, modern microelectronics would be considerably less advanced.
The third objection is:
3. It is not Repeatable. In spite of their best efforts, scientists cannot make what they say happened happen again.
Absolutely incorrect. As stated above, evolutionary theory makes numerous predictions that have been supported over, and over again. We have found repeated indications of evolution, and have generated evolutionary change in the lab on multiple occasions. It's possible that what this objection means is, "scientists have not reproduced an entire planet full of advanced life forms identical to those on Earth," but this is a ludicrous condition. We haven't had the time or resources to try and, in any case, evolution would never predict the same species would emerge in the exact same way. Given the role of random mutation in evolution, even the same starting conditions could produce significantly different outcomes while using the same mechanisms. To demand we reproduce the Earth is akin to demanding that we reproduce the exact number and pattern of raindrops in a thunderstorm in order to claim that we understand weather. Just like astronomers and physicists have been able to show success in explaining star formation while being unable to "repeat" it, it is not necessary for us to "repeat" all of evolutionary history in order for observations to be repeatable.
Finally, the fourth objection:
4. It is not Falsifiable. If you can’t test it, you can’t repeat it. If you cannot do those things, you cannot set up an experiment to subject it to verification or refutation. By Poppers’ standard, you cannot prove that evolution is right, only that it may not be wrong. Which is a far cry from proof by anyone’s definition.
As explained above, evolution is observable, testable, and repeatable. Further, it makes predictions about the world that, if they are not true, call the theory into question. As such, it is most assuredly falsifiable.
In totality, the above indicates that evolutionary theory is, indeed, scientific.
There are several remaining objections that I will try to deal with quickly. The first is this:
Evolution suffers from another contradiction with science, in that it violates the 2nd Law of Thermodynamics. This, basically, observes that the universe is breaking down. Things go from order to disorder. A new car rusts. A rusty car does not become more solid, no matter what environment you place it in. However, evolution is defined as “A gradual process in which something changes into a different and usually more complex or better form.” Evolution is supposed to be a process through which single celled organisms became mutli-celled (more complex). It assumes that the stronger organisms survive (they are a better form). Yet we see that nature lends itself to a process whereby things break down, decay and die. Once dead, they revert to elemental forms (molecules, atoms, etc.). They do not get better, they get worse. Evolution is the scientific belief that the development of life is, as a whole, capable of defying the 2nd Law of Thermodynamics.
This objection, that evolution violates thermodynamic principles, is one of the most common from the anti-evolution camp, but it does nothing but demonstrate a profound lack of understanding of physics. The
second law states that all work tends towards the production of greater entropy over time. This is often taken to mean, as Tim takes it to mean, that a system cannot increase in complexity. This interpretation is simply not correct. The expenditure of energy to do work always includes some amount of friction or inefficiency. This is why no human has ever succeeded in producing a perpetual-motion machine; since some of the energy added to the system is lost to inefficiency (entropy) the machine must, eventually, stop unless it receives additional energy from outside the system. This, however, brings us to an important scope condition: the second law applies to
closed systems, but not to
open systems. Thus, a system that is receiving new energy from outside can behave anti-entropically over time in a local sense (i.e. within the system) even though it's still part of a global increase in entropy. Without this scope condition not only would evolution be impossible, but life itself as well. Your body is an open system, deriving energy from food to continue operating and make repairs. If the second law prevented this from happening (i.e. if there was no distinction between open and closed systems), there would be no way for your body to continue powering itself. Your body heat would simply disperse your metabolic energy with no way to recover it, resulting in death. Just as a human being derives energy from food, the biosphere of the Earth- essentially our evolutionary "system"- derives energy from the sun. As that energy is added from an external source, the existence of life and the operation of evolution do
not violate the second law of thermodynamics. A brief, but perhaps more lucid, response to the thermodynamics argument is also available
here. Finally, as a side note, as I am not a physicist, I humbly invite any physicists in the audience to correct any mistakes in my explanation, or elaborate on any points.
Last, but not least, we come to a final objection:
But consider this, please. If I am wrong, I lose nothing. When I die I will return to my elemental form and feed worms. If you are wrong, you risk rejecting the Creator of all things. The price of that rejection is terrible. Not that He will send you to Hell. But that you send yourself there.
This objection more or less amounts to, "Disagree with me and you'll spend eternity in suffering." As threats have no place in a civilized debate, I don't think there's a great deal of value in this point. So long as we're discussing
Pascal's Wager, however, I suppose we may as well do a good job. First, this argument is flawed simply on the face of it. If I were to do everything someone told me to do because of the unsubstantiated negative consequences of not doing so, I think I would be wearing a
tin-foil hat right now. Second, even were I to accept your argument, I would be faced with the problem of determining which hypothetical deity to believe in. As there are a multitude of deities, many of which (we are told) will punish us for not believing, I'm in quite a fix. The only alternative to evolution is hardly belief in a Christian god. Finally, I think you are constructing a
false dichotomy between religious belief and evolution. Quite a number of Christians, as well as people of other faiths, have no problem accepting evolution within the framework of a loving but inscrutable god. If the Lord does, indeed, work in mysterious ways, I see no reason to exclude evolutionary mechanisms from His mystery. Which takes us to my final point.
So long as we're throwing around quotes that don't really bear on the discussion, allow me to provide you with one from
former President Jimmy Carter:"...there can be no incompatibility between Christian faith and proven facts concerning geology, biology, and astronomy. There is no need to teach that stars can fall out of the sky and land on a flat earth in order to defend our religious faith." In conclusion, while debate exists in science over the precise application of falsifiability, it is a well-established principle. The use of scientific theory and hypotheses is clear, and their distinction from assumptions is obvious. The observability, testabiliy, repeatability, and falisifiability of evolutionary theory have been established and, therefore, so has its status as a scientific theory. Arguments contradicting evolution on the basis of thermodynamics have been shown to rely on an inaccurate understanding of physics. Finally, the presence of abundant evidence for evolution is apparent, both in modern organisms and in the fossil record. In my view, the challenges offered to evolution have been answered, and I welcome any additional questions.
As a parting note, I wish to say two things. First, I have no interest in "converting" Tim to an evolutionary viewpoint. I respect his right to his religious beliefs and see no worthy purpose in attempting to force my perspective on him. I do, however, have every interest in countering misconceptions of evolution wherever they arise. Disagreement is fine, but disagree with the real theory, and argue against the real evidence- do not call a different theory by the name of evolution or ignore the evidence. Second, I have gone to considerable trouble to include a substantial number of links to information that supports, illustrates, or expands my points. In the event that Tim, or anyone else, chooses to respond, I ask that you do likewise. Unsupported rhetoric may be fun to read, but is ultimately of little value.
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