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In spite of its revolutionary philosophic impact, Darwin’s concept of natural selection is quite easy to understand (and to misunderstand). It was based on observations of artificial selection, the results of selective breeding by farmers and animal fanciers. Darwin, for example, referred to all the different breeds of pigeons that had been produced by artificial selection. The ordinary one in Fig. 11 is the wild rock pigeon, the one you often find around city statues and country barns. But all the other birds pictured are just pigeons, too: the fan tail, the one with the neck pouch, etc. All these birds can be bred from the wild rock pigeon, and crossing among the different varieties can lead right back to the wild rock pigeon. Everyone knows, of course, about the results of selective breeding with dogs, cats, cattle, roses, and so on.
“So,” Darwin said, in effect, “we see what artificial selection by man can do. I believe selection can also happen in nature. After all, there is a constant ‘struggle for survival’ because of population growth and limited resources, and certainly each kind can produce many varieties. Therefore, there will be ‘survival of the fittest,’ or natural selection, of those varieties of a population that fit best into their environments. Given enough generations [time] and the right trait combinations [chance], organisms that seem designed for their environment will simply result from natural selection [natural processes].” Apparent design in nature was not the result of creation, Darwin was saying, but of time, chance, and natural processes.
Darwin’s argument certainly seems logical. Is there any evidence that Darwin was right? Can nature select as well as man? Answer: there is considerable evidence that Darwin was indeed correct about natural selection.
Perhaps the best example of Darwinian selection is the one that’s in all the biology textbooks: the peppered moths. Take a look first at the top photo in Fig. 12, which represents a camera close-up of tree bark with some moths on it. How many moths do you see? One is easy to see, and most people see two. (Some claim to see three, but I’ve never found the third!) At least we can agree that one moth stands out and one is camouflaged. Presumably that’s the way birds saw it, too, back in the 1850’s. The darker moth stood out, but the lighter one was camouflaged against the mottled gray lichen that encrusted the trees back then. As a result, birds ate mostly dark moths and light moths made up over 98% of the population.
But then pollution killed the lichen on the trees, revealing the dark color of the bark. As a result, the dark moths were more camouflaged than the light ones. The moths themselves didn’t change; there were always dark moths and always light moths from the earliest observations. But the environment changed, and so the dark ones were better camouflaged. Thus, the dark ones had a better chance of surviving and leaving more offspring to grow into dark moths in succeeding generations. Sure enough, just as Darwin would have predicted, the population shifted. The “dark environment” just naturally selected the dark moths as more likely to survive and reproduce. By the 1950’s the population was over 98% dark, proof positive of “evolution going on today.” At least, that’s the way it’s stated in many biology books, and that’s what I used to tell my biology students.
When I was an evolutionist, sometimes an unsuspecting student (often a “religious type”!) would approach me and say, “Look, if evolution is true, why don’t we see it going on today?” And I would say, “Evolution going on today? Glad you brought that up! It just so happens that we have a perfect example of evolution in action.” Then I would launch into the peppered-moth story. Those moths are the showcase for evolution. Over twenty years after they first became famous, they were chosen, for example, as the frontispiece for Lewontin’s article on adaptation in the Scientific American book Evolution.
Well, the peppered moths do seem to provide strong evidence of natural selection. But is that evidence of evolution? Notice, I’ve changed the question. That’s a key point. First, I asked if there was any evidence that Darwin was correct about natural selection. The answer quite simply is, “Yes, there is.” But now I’m asking a radically different question, “Is there any evidence for evolution?” Many people say, “Isn’t that the same question? Aren’t natural selection and evolution the same thing?” Answer: no, absolutely not!
When someone asks if I believe in evolution, I’ll often say, “Why, yes, no, no, yes, no.” The answer really depends on what the person means by evolution. In one sense, evolution means “change.” Do I believe in change? Yes, indeed—I’ve got some in my pocket! But change isn’t the real question, of course. Change is just as much a part of the creation model as the evolution model. The question is, what kind of change do we see: change only within kind (creation), or change also from one kind to others (evolution)?
Take a look again at the peppered-moth example (Fig. 12). What did we start with? Dark and light varieties of the peppered moth, species Biston betularia. After 100 years of natural selection, what did we end up with? Dark and light varieties of the peppered moth, species Biston betularia. All that changed was the percentage of moths in the two categories: that is, just variation within kind. (For details, see the master’s thesis by one of my students, Chris Osborne.3)
According to the Biblical framework of history, struggle and death began when man’s rebellion ruined God’s perfect creation. Natural selection is just one of the processes that operates in our present corrupted world to insure that the created kinds can indeed spread throughout the earth in all its ecologic and geographic variety (often, nowadays, in spite of human pollution).
As a matter of fact, 24 years before Darwin’s Origin, a scientist named Edward Blyth published the concept of natural selection in the Biblical context of corrupted creation. He saw it as a process that adapted varieties of the created kinds to changing environments after sin brought death into God’s world. A book reviewer once asked, rather naively, if creationists could accept the concept of natural selection. The answer is, “Of course. We thought of it first.”
But if natural selection is such a profound idea, and Blyth published it before Darwin, then why isn’t Blyth’s name a household word? Perhaps because he was a creationist. It was not the scientific applications of natural selection that attracted attention in 1859; it was its presumed philosophic and religious implications.
Evolutionists were not content to treat natural selection as simply an observable ecological process. Darwin himself was a cautious scientist, painstaking in his work. But others, especially T. H. Huxley and Herbert Spencer, insisted on making natural selection the touchstone of a new religion, a “religion without revelation,” as Julian Huxley later called it. For them, as for many others, the real significance of the Darwinian revolution was religious and philosophic, not scientific. These early evolutionists were basically anti-creationists who wanted to explain design without a Designer.
But in spite of what might be claimed, natural selection has been observed to produce only variation within kind, merely shifts in populations, for example, of moths to greater percentages of darker moths, of flies resistant to DDT, or of bacteria resistant to antibiotics. But evolution means more than change from moth to moth, fly to fly, or bacterium to bacterium. Any real evolution, “mega- or macro-” evolution, means change from one kind to another: “Fish to Philosopher,” as the title of Homer Smith’s book puts it, or “Molecules to Man,” the subtitle of the government-funded BSCS “blue-version” high-school biology textbook.
Still, I must admit that there is a potential connection between observed natural selection within kind and hypothetical evolution from one kind to another. That connection is called “extrapolation,” following a trend to its logical conclusion. Scientists extrapolate from population records, for example, to predict changes in the world population. If world population growth continues at the rate observed in the ’60’s, statisticians said, then the world population by 2000 A.D. would be over 6 billion. Similarly, if natural selection continues over very long periods of time, evolutionists say, the same process that changes moths from mostly light to mostly dark forms will gradually change fish to philosophers or molecules to man.
Now there’s nothing wrong with extrapolation in principle. But there are things to watch for in practice. For example, simple extrapolation would suggest a population of a “zillion” by 3000 A.D. But, of course, there will come a point when the earth is simply not big enough to support any more people. In other words, there are limits, or boundary conditions, to logical extrapolation.
Consider my jogging (or should I say “slogging”) times. Starting years ago at an embarrassing 12 minutes per mile, I knocked a minute off each week: a mile in 11 minutes, then 10, 9, 8, 7, 6, 5, 4, 3, 2, 1. Wait a minute! As you well know, I reached my limit long before the one-minute mile! (Just where, I’ll keep secret!) This is an embarrassing example, but it makes an important point: no scientist would consider extrapolation without also considering the logical limits or boundary conditions of that extrapolation.
Evolutionists are aware of the problem. In their classic textbook, Evolution, the late Theodosius Dobzhansky4 and three other famous evolutionists distinguish between SUBspeciation and TRANSspeciation. “Sub” is essentially variation within species, and “trans” is change from one species to another. The authors state their belief that one can “extrapolate” from variation within species to evolution between species. But they also admit that some of their fellow evolutionists believe that such extrapolation goes beyond all logical limits, like my running a one-minute mile.
Can evolution from “molecules to man” be extrapolated from selection among dark and light moths?What does the evidence suggest? Can evolution from “molecules to man” be extrapolated from selection among dark and light moths? Or are there boundary conditions and logical limits to the amount of change that time, chance, and natural selection can produce?
The answer seems to be: “Natural selection, yes. Evolution, no.” As it turns out, there are several factors that sharply limit the amount of change that can be produced by time, chance, and Darwinian natural selection. (For exquisite detail on The Natural Limits to Biological Change, see Lester and Bohlin.5)
Perhaps the biggest problem for evolutionists is “the marvelous fit of organisms to their environment.” As I mentioned in the first chapter, many adaptations involve whole groups of traits working together, and none of the individual pieces has any survival value (“Darwinian fitness”) until the whole set is functioning together. Remember the woodpecker? Let’s look at another example.
Since death entered the world, there are many large, predatory fish that roam the oceans. But as they feed on smaller fish and shrimp, their mouths begin to accumulate food debris and parasites. Lacking recourse to a toothbrush, how is such a fish going to clean its teeth?
For several kinds of fish, the answer is a visit to the local cleaning station. These are special areas usually marked by the presence of certain shrimp and small, brightly colored fish, such as wrasses and gobis. Often, fresh from chasing and eating other small fish and shrimp, a predatory fish may swim over to take its place in line (literally!) at the nearest cleaning station. When its turn comes, it opens its mouth wide, baring the vicious-looking teeth.
You might suspect, of course, that such a sight would frighten off the little cleaner fish and shrimp. But no, into the jaws of death swim the little cleaners. Now even a friendly dog will sometimes snap at you if you try to pick off a tick, and it probably irritates the big fish to have a shrimp crawling around on its tongue and little fish picking parasites off the soft tissues of the mouth. (Try to imagine shrimp crawling around on your tongue!) But the big fish just hovers there, allowing the cleaners to do their work. It even holds its gill chambers open so that the shrimp can crawl around on the gill filaments picking off parasites!
At the end of all this cleaning, the second “miracle” occurs. You might think the fish would respond, “Ah, clean teeth; SNAP, free meal!” But, no. When the cleaning is done, the big fish lets the little cleaner fish and shrimp back out. Then the big fish swims off—and begins hunting again for little fish and shrimp to eat!
The fantastic relationship just described is called cleaning symbiosis. Perhaps you have seen cleaner fish in a major public aquarium, or seen pictures of their behavior in television footage or nature magazines. Cleaning symbiosis is a well-known example of mutualism, an intimate relationship of benefit to both types of species involved, in this case, the “cleaner and the cleanee.”
Obviously, cleaning symbiosis has survival value for both types of species involved. But does survival value explain the origin of this special relationship? Of course not. It makes sense to talk about survival value only after a trait or relationship is already in existence. Question: did the survival value of this cleaning relationship result from time, chance and struggle, or from plan, purpose, and special acts of creation?
The major problem is using Darwinian fitness to explain traits with many interdependent parts when none of the separate parts has any survival value. There’s certainly no survival value in a small fish swimming into a large fish’s mouth on the hope that the big fish has somehow evolved the desire to let it back out! Sea creatures don’t provide the only examples of cleaning symbiosis, either. A bird, the Egyptian plover, can walk right into the open mouth of a Nile crocodile—and walk back out again, after cleaning the croc’s mouth!
The situation is even more dangerous for the famous “bombardier beetle.” The bombardier is an ordinary-looking beetle, but it has an ingenious chemical defense mechanism. Imagine: here comes a mean ol’ beetle-eater, a toad, creeping up behind the seemingly unsuspecting beetle. Just as he gets ready to flash out that long, sticky tongue, the beetle swings its cannon around, and “boom!” It blasts the toad in the face with hot noxious gases at the boiling point of water, and coats the toad’s tongue with a foul-tasting residue. Now that doesn’t actually kill the toad, but it surely kills its taste for beetles! Pictures show the toad dragging its tongue across the sand trying to get rid of the foul taste.
Successful firing of the bombardier beetle’s cannon requires two chemicals (hydrogen peroxide and hydroquinones), enzymes, pressure tanks, and a whole series of nerve and muscle attachments for aim and control. Try to imagine all those parts accumulating by time, chance, and natural selection. One crucial mistake, of course, and “boom!” the would-be bombardier beetle blows itself up, and there’s surely no evolutionary future in that! Trial and error can lead to improvement only if you survive the error!
Creationists and evolutionists agree that adaptations such as the woodpecker’s skull, cleaning symbiosis, and the bombardier beetle’s cannon all have survival value. The question is, how did they get that way: by time, chance, and the struggle for survival, or by plan, purpose, and special acts of creation? When it comes to adaptations that require several traits all depending on one another, the more logical inference from the evidence seems to be creation.
Darwin himself was acutely aware of this evidence of creation and the problem it posed for his theory. His chapter in Origin of Species on adaptations was not titled “Evidence for the Theory” but “Difficulties With the Theory.” In it, he discussed traits that depend on separately meaningless parts. Consider the human eye with the different features required to focus at different distances, to accommodate different amounts of light, and to correct for the “rainbow effect.” Regarding the origin of the eye, Darwin wrote these words:
To suppose that the eye, [with so many parts all working together] … could have been formed by natural selection, seems, I freely confess, absurd in the highest degree.
“Absurd in the highest degree.” That’s Darwin’s own opinion of using natural selection to explain the origin of traits that depend on many parts working together.
Modern evolutionists continue to recognize these “difficulties with the theory” of evolution. Harvard’s Stephen Gould6 writes, for example, “What good is half a jaw or half a wing?” Gould also recognizes that many people (especially artists employed by museums and textbook publishers) have tried to present a hypothetical series of gradual changes from one kind to others. So he adds, “These tales, in the ‘Just-So Stories’ tradition of evolutionary natural history, do not prove anything. … Concepts salvaged only by facile speculation do not appeal much to me.” Even though Gould is an evolutionist, he recognizes that the classic textbook concept of gradual evolution rests on made-up stories and “facile speculation,” and not on facts.
In another article, Gould7 points out that the perfection of complex structures has always been one of the strongest evidences of creation. After all, he says, “perfection need not have a history,” no trial-and-error development over time from chance trait combinations and selection. So, Gould continues, evidence for evolution must be sought in “oddities and imperfections” that clearly show the effects of time and chance.
But creationists recognize imperfection, too. The Bible clearly indicates that “time and chance and struggle” have indeed corrupted what God originally had created in perfection. Imperfection, then, is not the issue; perfection is. And evolutionists from Darwin to Lewontin and Gould admit that “perfection of structure” has always been “the chief evidence of a Supreme Designer.”
Darwin’s theory also points us back to creative acts when it comes to the origin of traits. In spite of the title of his book, Origin of Species, the one thing Darwin never really dealt with was the origin of species. That is, he never explained the origin of the truly new traits needed to produce a truly new kind of organism, something more than just a variation of some existing kind. There are many other logical limits to extrapolation from natural selection to evolution, but the simplest is this: natural selection cannot explain the origin of traits.
Take the famous example of “Darwin’s finches” (Fig. 14). On the Galapagos Islands about 600 miles (nearly 1000 km) west of Ecuador, Darwin observed a variety of finches, some with small beaks for catching insects, others with large beaks for crushing seeds, and one with the ability to use spines to pry insects from their tunnels. How did Darwin explain the “origin” of these various finches? Exactly the same way a creationist would. He saw finches with variation in beak type on the South American mainland and presumed these finches might have reached the islands on a vegetation mat or something similar. The ones with seed-crushing beaks survived where seeds were the major food source, and those with insect-catching beaks out-reproduced others where insects were the major source of food. Given finches with a variety of beak types, then, natural selection helps us to explain how and where different varieties survived as they multiplied and filled the earth. That, of course, is just what a creationist would say—except, that a Biblical creationist would add that the “struggle and death” part of migration did not begin until man’s rebellion ruined the world God had created without death. (Contrast Genesis 1–2 with the Fall in Genesis 3.)
Natural selection works well: it helps us explain how and where traits survive—if we have adapted or adaptable traits to start with. In his article on “Adaptation” in the Scientific American book Evolution, Lewontin8 emphasizes this point over and over again:
… evolution cannot be described as a process of adaptation because all organisms are already adapted …
… adaptation leads to natural selection, natural selection does not necessarily lead to greater adaptation… .
That is, adaptation has to come first, before natural selection can act. Natural selection obviously cannot explain the origin of traits or adaptations if the traits have to be there first.
Lewontin recognizes that this simple (but crucial) point is often overlooked, so he gives an example. As a region becomes drier, he says, plants can respond by developing a deeper root system or a thicker cuticle (waxy coating) on the leaves, but “only if their gene pool contains genetic variation for root length or cuticle thickness.” (Emphasis added.) Here again, the genes for deep roots and thick, waxy coats must be present among the genes of a kind before natural selection can select them. And if the genes are already there, we are talking only about variation within kind: i.e., creation, not evolution. As creationists were saying even before Darwin’s time, natural selection does not explain the origin of species or traits, but only their preservation.
Lewontin is an evolutionist and outspoken anti-creationist, but he honestly recognizes the same limitations of natural selection that creation scientists do:
… natural selection operates essentially to enable the organisms to maintain their state of adaptation rather than to improve it. (Emphasis added.)
Natural selection does not lead to continual improvement (evolution); it only helps to maintain features that organisms already have (creation). Lewontin also notes that extinct species seem to have been just as fit to survive as modern ones, so he adds:
… natural selection over the long run does not seem to improve a species’ chances of survival, but simply enables it to ‘track,’or keep up with, the constantly changing environment. (added.)
It seems to me that natural selection works only because each kind was created with sufficient variety to multiply and fill the earth in all its ecologic and geographic variety. Without realizing it at the time, Darwin actually discovered important evidence pointing both to God’s creation (the variation) and to the corruption of creation (struggle and death).