Science and Reason: The Evolution Debate

Evolution is a huge subject which has been "debated" endlessly on the net. Most of the claims of anti-evolutionists that aren't purely bogus have been addressed time and time again, and you can find a lot just by Googling -- which newly-minted evolution skeptics rarely seem to bother doing. Anyway, here is my two cents.

Anti-evolutionists like to confuse matters right at the beginning by suggesting that evolution is a religion. But is it?

No, for two main reasons. The first is of lesser importance: Religion is usually concerned primarily with "supernatural" phenomena -- things that transcend the natural world, and especially entities that are never actually seen or touched, except (perhaps) in very unusual states of mind. Science, on the other hand, is concerned primarily with natural phenomena -- things that can be seen or touched. In explaining natural phenomena, science often goes beyond what can be seen or touched to explain natural phenomena, but it always remains connected to natural phenomena by a chain of logic and reasoning involving orderly principles.

The more important difference is that science relies on a process of rigorous skepticism to perform an intellectual triage on proposed explanations for any given natural phenomenon. Religion, on the other hand, relies on various beliefs which may not be questioned, because they were (usually) dictated long ago and must simply be accepted on faith. Faith means putting an end to skepticism.

The main failure of many anti-evolutionist arguments is the attempt to indict and convict Darwinian evolution of not following the rules of good skepticism. If the supporting arguments were correct, Darwinian evolution would indeed be a religion. However, there are many fallacies in the supporting claims.

One of the main fallacies involves the nature of skepticism itself. The problem is, if skepticism isn't employed correctly, it can be simply a lazy intellectual nihilism. (Dictionary definition: the denial of any basis for knowledge or truth.) "Postmodern" critiques of science fall into the same trap. The general pattern here is the contention that can be summarized as "There is no absolute truth; all knowledge is relative." If that were true, it would contradict itself, just as the statement "This assertion is false" does.

Such an attitude is really just a form of solipsism. It's not fully possible to prove the philosophy of solipsism is false, yet hardly anyone actually adheres to that philosophy. I'm sure that most evolution skeptics have many beliefs about such things as politics and ethics (for instance). They can't justify these beliefs absolutely, yet they nevertheless accept them as truth for all practical purposes.

Science is the same way. Practitioners of science recognize that there is no such thing as a theory that is complete and has been proven with absolute certainty, beyond any possible skepticism or doubt. Not even mathematicians make such claims about their subject (though they come fairly close). Instead, the attitude of science is "Let's develop the best theory we can about a given natural phenomenon. But if new data or a better theory comes along and better passes thorough skeptical examination, that's good, that's progress."

Not all questions that can be asked admit scientific treatment at the present time. Such questions belong to philosophy or religion rather than science. The "nature of consciousness" and the "mind-body" problem may be in this catetgory, though a few scientists think this is on the verge of changing. The status of questions as philosophy vs. science definitely does change over time. The question about the mechanics of the solar system changed in the time of Galileo and Copernicus. The question of the very early history of the universe made the transition only within the last 50 or 60 years. This doesn't mean that there is complete agreement yet on the answers to such questions. It just means that the questions can be addressed with legitimate methods of empirical science. (I've written about how this has developed in the science of cosmology.)

Most biologists think that this transition occurred in their field beginning with Darwin. That doesn't mean that all of the answers given by Darwin and his successors are conclusively proven. Only that they are clearly within the realm of empirical science.

Proponents of creationism in any of its forms, including "intelligent design theory" plainly disagree. Although they pretend to advocate things like "creation science" or "science of intelligent design", the claim that these are "science" is fallacious, as I will explain. What they offer is purely philosophy, not empirical science. At best, the only plausible claim they can make is that the subject matter addressed by the theory of evolution, namely the process through which life on Earth came to be the way it is, is not yet a proper scientific question. However, the evidence for even that claim is overwhelmingly against them. Most of modern biology verges on and entertwines with evolution in one way or another. It is by far the largest scientific enterprise ever undertaken.

Contrast this with "intelligent design science". There isn't actually any content to it at all. Just try to cajole one of its advocates to say what "intelligent design science" is. You will not get anywhere. All they can do is make the philosophical assertion that some unknown intelligent entity caused life as we know it to take the form it does. They cannot, or will not, specify what that entity might be (and that is how they differ from Biblical creationists). Their "science" consists of nothing but various criticisms of evolution. While it is legitimate to analyze evolution critically, that in itself does not constitute a scientific theory.

It's just as much a confusion tactic to call intelligent design a science as it is to call evolution a religion. Anti-evolutionists want to blur the distinction, but that is not intellectually honest.

"Intelligent design theory" does not even pretend to address the simplest questions. (And yet its proponents demand that evolution answer vastly more detailed questions.) For example, they would agree that there is no fossil evidence for what can be called "modern humans" that is more than about 200,000 years old. So modern humans must have appeared on Earth about that long ago. Exactly how did the first modern human arrive here? Was it brought here in a flying saucer? Did it shimmer into existence as if delivered by a Star Trek transporter? Did the Intelligent Designer fashion it our of clay then breathe life into it as Genesis says? Advocates of intelligent design cannot give physical details to answer such a question. In other words, they really have no theory at all.

The approximate date of 200,000 years doesn't really matter. Whenever or wherever the first "modern human" showed up, intelligent design theorists have no answer at all regarding the event's mechanism and what it physically consisted of. How could such a non-theory be "taught" in classrooms as "intelligent design" advocates demand? There isn't anything to teach! All they have to talk about is critiques of evolution. A collection of critiques is not a theory.

It's interesting to compare this with evolution. Critics of evolution often point out that evolution cannot explain how life began. They frequently make quite a big point of this. And they are correct. Science does not know how life began. However, there are various plausible theories that describe on a physical level how life could have begun. It is certainly a very difficult question to address, but at least it can be researched scientifically in various ways.

But evolution is about far more than the origins of life. In fact, it doesn't pretend to describe the origins of life, and really isn't about the origins, though it will almost certainly be involved if and when a scientfic theory of origins does come together. It is a rather devious debating trick to imply that evolution must describe the origins of life, when that is not what it's mainly about. What it's mainly about is describing how life evolved after it first appeared. And it does that in pretty good detail, with massive amounts of supporting evidence. "Creation science", or "intelligent design", on the other hand, have no physical description at all of either the origins of life, or any other stage of life's history. So evolutionary theory, though incomplete, fulfills the requirement of being a clearly superior explanation of events, given existing evidence. But then, it's not hard to best a "theory" that physically describes nothing at all.

What about the incompleteness and gaps in evolutionary theory? Our knowledge of the natural world has always been incomplete. But it is becoming more complete all the time, with increasingly fewer and smaller gaps. Religion has always attempted to fill any such gaps with the "explanation" that "God did it", no matter what the question is. This is known as the "God of the gaps" argument. Nowadays, in order to avoid the stigma of being religious, the argument has become "Intelligent-designer of the gaps" instead. No difference. It amounts to answering "Because" to every why question.

So, what exactly is the evidence for evolution? Paradoxically, the problem is that there is so much of it that one can't summarize it in a few paragraphs. Essentially, the evidence comprises most of modern biology. On a shelf within arms' reach I have a decent college biology textbook. It's over 1000 pages (two columns per page) and weighs 6 pounds. Almost all the information fits comfortably within the evolutionary framework. That is no trivial feat. The ability to make consistent sense out of so much information is pretty remarkable.

Just try to make up a theory from scratch that consistently and plausibly explains so much information. "Intelligent design theory" doesn't do this. It doesn't even try. The only answer it offers as to why organisms are the way that are is simply "That is what the Designer chose." Yet the more one learns about biology, the more it's obvious that living organisms, as remarkable as they are, consist of a huge collection of patches on top of patches, and simply not the consciously designed product of an intelligent designer, who must have had what seem to us to be supernatural powers. It looks much more like a vast sequence of temporary "solutions" to problems which followed upon each other by trial and error -- evolution in other words.

For instance, there are literally dozens of mechanisms that help check the integrity of an organism's DNA and take corrective action if errors are found -- either by fixing the DNA when it is copied during cell division, or halting the division process, or simply causing a cell to die if its DNA can't be fixed. Why would a designer use so many mechanisms, instead of one or two that work more reliably? Why not start with a chemical entity that's more robust against errors in the first place? Most computer programmers understand what's going on here: every time a problem is found, the software is simply patched in the most expedient way possible, rather than being rewritten better from scratch.

It is a problem in defending evolution that there is so much evidence for it. The cumulative weight of such a large amount of evidence is what makes it so convincing -- if you are familiar with the data. But this circumstance is also precisely what makes it so difficult to answer skeptics who are not familiar with most of the data. Skeptics of evolution, and the audience they generally appeal to, want simple, short answers. Explanations in a paragraph or two. Anything that needs much more detail quickly loses credibility.

Tell the average person that they need to read a college textbook to appreciate evolution, and their eyes glaze over. Even if such a person is favorably disposed, they just aren't all that interested. They have other things they'd rather do with their time than spend a couple weeks studying a technical book.

So the strategy of anti-evolutionists is fiendishly clever. Keep the teaching of evolution out of the schools, so that the average person is never exposed to even the rudiments of the subject. Or else demand "equal time" for the teaching of "intelligent design". But there is so little that can actually be said about the latter, that "equal time" means almost no time at all to present all the evidence in support of evolution. The less is taught about the facts of biology, the more likely people are to doubt evolution.

All that the anti-evolutionists have to offer is a selection of issues cherry-picked from all of biology which lack (or seem to lack) complete evolutionary explanations. Some of the example issues involve giraffe necks, caterpillars, peacock tails, human intelligence, and the origins of life itself. They mix up trivia (giraffe necks) with actual Big Issues like the origins of life and intelligence.

Most of the small issues actually have very satisfactory evolutionary answers, though the answers may be known only to specialists. Many biologists spend the bulk of their careers studying very narrow questions. Stephen Gould's specialty was the paleontology of snails. Alfred Kinsey (before he took up human sexuality) was an entomologist who specialized in gall wasps and collected over a million moths. Most of the work of science deals with incredibly picayune details that take years to assemble. Such details are what makes it possible to answer evolutionary hypotheses, postitively or negatively, for very specific issues.

Behind almost every sentence in that biology textbook I mentioned are dozens and perhaps hundreds of research papers. Each of those papers was "peer reviewed" by "referees" who are expert in the field. Referees are expected to skeptically examine every aspect of a paper, to poke any holes in it they can, with regard to methodology, logic, or information already in "the literature". Out of self defense, authors of papers themselves examine their work as skeptically as possible before submitting it for publication. It is precisely this process of organized, professional skepticism that makes modern science as reliable as it is.

And then along comes a "skeptic" with no training in the subject, who raises questions about something like giraffe necks and demands a quick, simple answer. The skeptic wants an airtight explanation in 25 words or less, yet he isn't even interested in investigating the question himself in a library or on the internet. And the skeptic becomes miffed and indignant, and he accuses scientists of being uncooperative and "dodging the question" and hostile, when he can't get as simple and quick an answer as he would like.

This is what I had in mind early on when I mentioned "rigorous skepticism". To be a rigorous skeptic, it's not enough just to ask a lot of tough questions. In science, at least, if not in everyday life, the skeptic has an obligation to frame questions in terms of the best accepted information that already exists and to justify any logical steps in his own arguments. That's why scientific papers are peer reviewed by other experts in the field, not by experts in other fields or intelligent non-experts (such as expeienced jurists). Ideally, the reviewer of a scientific paper should know at least as much about the overall field as the author, though that's not always possible. But you won't find a tougher legitimate skeptic anywhere than an experienced scientist who favors a different theory about whatever issue is involved in a given paper.

This is where most skeptical arguments against evolution fall apart. One of the favorite arguments of evolution skeptics is that evolutionary explanations of something or other are "implausible" if not "wildly improbable" because that something or other is "irreducibly complex". Often this involves the question of "morphological novelty" -- new biological features such as lungs, legs, feathers, eyes, etc.

But it's nowhere near enough to claim that a particular development is highly improbable just because it might appear to be so to a casual observer. The skeptic has an obligation to defend his argument by actually computing a probability. But you can't just compute probabilities in a vacuum. You must have a detailed model of all steps in the process in question, so that you can estimate the probability of each step in the process and then use an appropriate mathematical technique to compute the overall probability.

In such cases, evolutionists often do not have or claim to have a detailed model of the steps involved. This is indeed a weakness in evolutionary theory, because it requires a knowledge of events that took place without leaving much in the fossil record. For instance, there are good reasons for believing that birds evolved from dinosaurs, but this is not a settled issue, and there remains substantial professional disagreement. So of course, the precise steps that may have occurred between some sort of dinosaur and something more birdlike are not known. Likewise, the exact steps that led to real feathers from precursor features aren't known. It's like a historian trying to say what George Washington had for breakfast on April 1, 1775 (if he didn't happen to write about it in his diary).

But in order to prove that feathers could not have evolved, the skeptic would need to consider a particular model of the steps involved, and then calculate probabilities for each step. Worse, the skeptic would need to consider all conceivable models and do the same for each. Clearly, this is as impossible a task as requiring evolutionists to specify the exact steps that lead from dinosaurs to birds.

Responsible people on both sides recognize that such lines of argument don't lead anywhere. But that doesn't stop many anti-evolutionists. They often use probabalistic arguments -- such as regarding the origins of life out of chemical processes, for example. But without specifying the exact process (which skeptics don't do, and biologists don't claim to either), there is no way to calculate a probability. Skeptics talk about "point mutations" and how they may or may not lead to new features, without showing any comprehension about how morphology is actually determined in the process of embryonic devleopment. They resort to totally off-the-wall comparisons of of evolutionary development to scenarios of monkeys banging away on typewriters. What on Earth that has to do with a particular evolutionary process isn't explained.

In expressing skepticism over the possibility of random chemical processes leading to the origin and evolution of life, anti-evolutionists scoff at the "implausibility" of complex life developing from such processes. They should try to appreciate an interesting fact. Namely, a human, or other large animal, having on the order of 100 trillion cells in its body, develops in only a few months out of one single cell, a fertilized egg. Of this cell the biologist and essayist Lewis Thomas wrote (in The Medusa and the Snail):

For the real amazement, if you wish to be amazed, is this process. You start out as a single cell derived from the coupling of a sperm and egg; this divides in two, then four, then eight and so on, and at a certain stage there emerges a single cell which has as all its progeny the human brain. The mere existence of such a cell should be one of the great astonishments of the earth. People ought to be walking around all day, all through their waking hours calling to each other in endless wonderment, talking of nothing except that cell.
And yet, biologists understand fairly well, at least in broad details, how this works. It is entirely a chemical process. Genes in the fertilized egg direct the production of proteins. These drive the cycles of cell division. They also affect the behavior of other genes, which "turn on" at appropriate times to start producing new proteins which eventually lead to differentiation of cells into about 200 different types that make up the body. This is all a random process of chemical entities (like proteins) interacting with each other in a liquid medium.

And so, this random chemical process in only 9 months makes a baby out of a single cell. It isn't something hypothetical that happened billions of years ago in a warm pond somewhere. It happens every day in millions of bodies. We know it happens. Yet it seems wildly implausible doesn't it?

Some skeptics offer a "theory of implausibility" that says, "If something looks implausible, it probably is."

So much for the "theory of implausibility".

To repeat myself, without a detailed model of the process in question, calculating meaningful probabilities is impossible. All the models that anti-evolutionists offer when they employ this line of argument are ridiculously simplistic -- about as relevant as the monkeys and typewriters silliness. Certainly they are not any models that evolutionists themselves use.

In fact, evolutionary theorists make extensive use of computer models. Generally these deal with such things as the way novel genes spread through a population. (The field is called "population genetics".) There's also a lot of modeling done in "behavioral genetics", which looks at game-theoretic aspects of animal behavior and how it leads to "evolutionary stable strategies". At a lower level, models are being developed of cellular processes. Such models are used, for example, to test the effects of potential therapeutic drugs to treat a variety of diseases. This field is known as "computational biology" or "bioinformatics". (See here.)

Of course, just because a model gives correct answers when run on a computer doesn't mean that the model itself is correct. Just as with scientific theories in general, a particular model can't be proved to be absolutely correct. Models can only be proven incorrect -- but with a little more adjustment they become more correct. This is how they are developed. A computer model is a type of description of reality. The more one learns of reality, the more one adds to the description.

And the same is true of the scientific process itself.


[Home page]

Copyright © 2005 by Charles Daney, All Rights Reserved