Counter-argument: All you really need to do to disprove evolution is produce a genuine example of a centaur, griffin, faun, satyr, hippogriff, mermaid, or any of a variety of other creatures from mythology. All are impossible under current evolutionary theory. A centaur, for example, would be a) a hybrid of two widely separated animals, human and horse, and b) a vertebrate with three pairs of limbs, where no known land vertebrate, either living or fossil, has ever had more than two pairs of limbs. And genetics indicates pretty strongly that no naturally-evolved land vertebrate could have more than two pairs of limbs.

Or if you found a lifeform that used a different genetic code from all known Earth life, that also couldn't be explained by evolutionary theory. The only answer would be that this unique lifeform had been somehow specially created and/or planted here.

Counter-argument: Evolutionary theory can and has been used to make testable predictions. Both in the study of past life and the study of present life. For example:

• In the early 1970s, Don Johanson looked at the then-known fossil hominids, and based on them he predicted when their ancestor probably lived and what it probably looked like. He then found rocks of the right age in the Afar, went there, did some digging, and came up with Australopithecus afarensis, the oldest and most primitive, apelike hominid then known.
• In the late 1980s, Paul Sereno went looking for the oldest true dinosaur, the first animal that was unquestionably a dinosaur and not a pre-dinosaurian thecodont. He looked at the known dinosaur sites, and concluded that the most likely place to find what he wanted was Argentina, which had already yielded very primitive Mid Triassic dinosaurs. In the Ischigualasto Valley, Sereno found primitive dinosaurs in one set of strata, and advanced thecodonts in a somewhat older set of strata. He looked in unexplored strata in between, and came up with Eoraptor, the oldest and most primitive dinosaur ever found.

For a modern-day example, consider this. Evolutionary theory predicts that if you change a species' environment in such a way as to apply a selective pressure, the species will evolve to fit the selective pressure. With that in mind, look at the way insects have changed and become resistant to insecticides over the past half-century.

Or one more, from my own experience. In January 1996, on CompuServe's Dinosaurs Forum, I was discussing the evolution of birds with a gentleman who happens to be a rarity among creationists: knowledgeable, not particularly evangelical, genuinely interested in understanding evolutionary theory even though he didn't accept it, and generally an all-round nice guy. He'd asked "What ARE the 'ancestral' or 'transitional' forms that lead from Theropod to Bird???"

My response was:

In October 1996, a fossil from China called Sinosauropteryx prima made headlines in the world of paleontology as the first known dinosaur with feathers. Strictly speaking it didn't quite have feathers; it had a sort of downy protofeathers all over its body. Sinosauropteryx clearly met my prediction for the third stage in the dino-to-bird series.

Then in spring 1998, two more feathered dinosaurs were found in China. Named Caudipteryx zoui and Protarchaeopteryx, they clearly had long feathers on the head and forearms, but those feathers weren't shaped like flight feathers. They met my prediction for the fourth stage in the dino-to-bird series.

It's true that my predictions were very rough and could have been met by any of a wide variety of fossil finds. It's also true that while Sinosauropteryx, Caudipteryx, and Protarchaeopteryx are good morphological ancestors for the first bird Archaeopteryx, they aren't good chronological intermediates because their fossils all come from rocks younger than the known Archaeopteryx fossils. Still, the similarities between my predictions and these three fossils seem far too neat to be coincidence. If I, a self-educated amateur, can use evolutionary theory to make such successful predictions, then what can professional, trained scientists do with it?

Counter-argument: On the contrary, 'fitness' can be empirically determined, often by direct measurement. I have a couple of books that bear on this claim, such as LIFE'S DEVICES: THE PHYSICAL WORLD OF ANIMALS AND PLANTS, by Steven Vogel. This book is a collection of data and ideas on how the laws of physics apply to living things. These data and rules and equations produce a very simple, empirical way to measure 'fitness' of certain traits: organisms are more or less fit depending on how closely they approach the ideal as defined by the relevant equations.

For example, take a fish. The typical fish has a distinctive shape -- not by choice, but because that shape is forced on it by the fluid dynamics of the water in which it swims. The standard fish-shape tends to minimize drag and maximize countering forces, so the fish can swim with less energy expenditure. As the fish moves through the water, the pressure against its body changes in a predictable way: the highest pressure is at the mouth, while the lowest is back around the gill area, and so on. And this pressure flow changes depending on how fast the fish is moving. On many fish, the eye is located at almost exactly the point where this pressure differential is zero -- that is, the pressure flow at that point doesn't change no matter how fast or slow the fish is swimming. Since the pressure flow distorts light and and would therefore affect what the fish's eye sees, obviously it's a good thing if the eye is located so that the pressure flow, and therefore what the eye sees, doesn't change with the fish's speed. So 'fitness' for eye placement in a fish can be defined as how close the eye is to the zero pressure point. The closer the eye is to the optimum position, the more fit the individual fish is for that particular trait.

Likewise, fitness in birds' wings may be defined as how closely the wing-shape approaches an ideal airfoil. The fitness of a leg structure may be defined as how closely it approaches the ideal balance of strength, mass, and flexibility. For very large animals, overall fitness might be defined in part as how well it protects itself against accidental injury due to falls and such. One of the more interesting passages in Vogel's book is about how falling affects different size animals. Insects don't "fall" at all in the normal meaning of the word. Mice and other small mammals need to fall many times their own length to suffer serious injury. Cats and dogs need to be more careful -- a fall of ten or twenty feet can seriously hurt them. Cows can be hurt falling their own height, by tripping and such. And something as big as an elephant can be lethally injured just by tripping and falling. The wide carriage and slow, deliberate pace of an elephant are thus not a matter of choice; they're defensive reactions developed over millennia to minimize the chances of self-injury by tripping. Clearly, a fall-prone elephant is not what we would call highly fit!

Counter-argument: Macro-evolution is nothing but accumulated micro-evolution.

By direct observation, we know that variation and selection can modify a species to better fit its environment. Examples of this abound in today's world: insects becoming resistant to insecticide, birds changing nesting or feeding behavior, etc. Further, the variations occur within limits set by the existing gene pool. There is always a well-defined pathway linking ancestor to descendant. So, evolution can explain the observed patterns of changes within a species, the smallest generally recognized taxon, or grouping of organisms.

The next larger taxon is the genus. Evolution can explain changes within a genus (also called speciation). Examples of this also abound: "ring species" like the Herring/Lesser Black-backed Gull, many other birds, fruit flies, many types of plants. In particular, if you look at any single genus of animals (genus Felis within the cats, for example), you can see that the differences between species are little more than extrapolations of variations within a species. The evolutionary process can easily explain the derivation of Felis bengalensis (Asian leopard cat or Bengal cat) from Felis silvestris (European wild cat, including the domestic cat), or both from a single ancestral species. The long-eared, bobtailed bobcat is a little more extreme in form, but anyone who has seen a Maine Coon Cat and a Japanese bobtail cat knows that even the lynx's main features occur within domestic cats. Among all the traits that distinguish species of Felis, there is not one that can't be explained as a simple genetic variation of the same type that we know occurs within a species.

The next step up is to look at separate genera within a family. Continuing with the cats, we might compare a domestic cat (F. silvestris domesticus) to a lion (Panthera leo). The pattern repeats itself here: of all the differences between lion and housecat, two different genera, none reach beyond what can be explained by extrapolating from what we already know evolution can do within a genus. Further, if at this point we add fossil cats to the picture, no modern cat differs from recently-extinct cats in any way that cannot be explained by evolution. The same is true for many other families of mammals: horses, dogs, elephants, rhinoceroses, titanotheres just to name a few. Any species in any of these families can be connected to an older species within the same family by a longer accumulation of small-scale changes. The entire sixty-million-year sweep of the horse family can be explained by the evolutionary process.

Up another level, we get to the question of origin of new Families within an Order. Many families both living and fossil appear to lack a direct connection to any ancestral line, but in a few cases -- horses, for example, or ceratopsid dinosaurs -- we find reasonable links that explain how new families could have evolved. The well-known horned dinosaur Triceratops (family Ceratopsidae) can be traced back through a series of similar forms to Protoceratops (family Protoceratopsidae). Each step is easily deriveable from the previous one by evolutionary changes of the sort already known to exist within a family, which are themselves extrapolated from changes within a genus, thence from changes within a species.

Back another step: the origin of separate Orders within a Class. Again, the pattern repeats: most orders can't yet be directly connected to any ancestral form, but in a few cases we have a nice chain of forms that connects an ancestor clearly of one Order with a descendant that is clearly of another Order. Such a chain of known forms connects all modern cats, dogs, and bears (order Carnivora) with an ancestor in the Order Creodonta. The direct line of descent is unclear, but each step in the chain can be derived from the previous one by the sort of changes known to occur within an Order -- which are, as already shown, simply extrapolations of changes known to take place within families, genera, and species.

One more step: separate Classes within a Phylum. Again, the same pattern: most classes are unconnected to any ancestral line, but in a few cases we have a series of fossil forms that illustrate the development of a new Class from an old one. The best-documented example of this is the origin of the Class Mammalia from the therapsids, or mammal-like reptiles. In fact, a chain of forms can be followed from modern mammals all the way back to the first egg-laying (amniote) animals almost three hundred million years ago. Each form in the chain is derivable from one in the previous groups by the same types of changes which we already know can take place between Orders within a Class.

Finally, we reach the issue of origin of separate Phyla. Tremendous differences exist between organisms of different phyla, yet even here we have a few examples of chains of forms that connect two or more phyla. The best currently known example is a series of bizarre fossil creatures including Wiwaxia and Halkieria, which together connect no fewer than three phyla: molluscs, annelids, and brachiopods. The differences between these forms are certainly no more than those between two Classes, which (as was already shown) can be explained by the evolutionary process.

Over and over, the same pattern is repeated: at any taxonomic level throughout the entire animal kingdom, we can find at least one series of forms that illustrates a way for that taxon to have originated by the evolutionary process. Evidence for this is found all through my library -- FOSSIL HORSES by MacFadden covers the matter of evolution within a family; evidence of evolution at all levels can be found in the textbook VERTEBRATE PALEONTOLOGY AND EVOLUTION; Simon Conway Morris's book THE CRUCIBLE OF CREATION describes the chain of evidence that connects Wiwaxia and Halkieria to each other and to the phyla Mollusca, Annelida, and Brachiopoda.

Counter-argument: How much time is "enough?" There's a reason geologic time is also known as "Deep Time." The human mind can't conceive of just how long this planet has been around. We can't even really grasp "thousands of years." To us today, ancient Egypt and the Roman Empire seem equally long ago -- but in reality, by the time Rome was founded, the Kingdom of Egypt had already been around for over 2000 years. Few people living today were alive a mere 100 years ago. No living man witnessed the American Civil War, only 140 years ago. You would have to go back at least four generations (120 years) from the oldest living man to find someone who lived through the Napoleonic Wars. You'd have to go back another forty generations (1200 years) to find anyone who saw a Roman army in battle. That Roman would have to go back twice as far from his time to find an ancestor who might have seen the Great Pyramid being built. And all of that is just the span of recorded human history -- 5,000 years, more or less.

Well, geologic time is measured in millions of years, not mere thousands. We think of the dinosaurs as one great group, Tyrannosaurus rex and Apatosaurus and Coelophysis in the same breath. Yet the reality is that T. rex lived closer to our time (65,000,000 years ago) than it did to that of Apatosaurus (150,000,000 years ago), and it's as far back again to the time of the first dinosaurs (around 220,000,000 years ago). And even before that, it's another 300,000,000 years to the Cambrian "explosion" of multicelled animal life.

Now, against that concept of "Deep Time," set this: we've seen micro-evolutionary changes take place in as little as one year in insects, five or ten years in fish, ten or twenty years in large animals. Even such huge and slow-breeding animals as elephants have demonstrated evolutionary changes within a single human lifetime. The fossil record doesn't show us why or exactly how major evolutionary changes took place, but it can certainly tell us how long they took. Major changes such as the fish-to-amphibian transition or dinosaur-to-bird took several millions of years. Think about that -- millions of years. Try to visualize the amount of time that Egypt has existed as a distinct land and people: five thousand years. That's enough time for a single human to have more than two hundred and fifty generations of descendants. Enough time for multiple cultures and civilizations to grow and die, one atop another. Now imagine a span of time two thousand times as long as that. That's how long it took for dinosaurs to evolve into birds.

Do you still think there "hasn't been enough time" for evolution to occur?

Counter-argument: brief explanation of difference between 'gradualist' and 'punc-eq' models of evolution.

The same mechanism is used by both models: variation and selection. The only difference is how fast the change occurs. For example, consider two species A and B, where A is the ancestor and B the descendant. Perhaps we expect to find three significant transitional forms: A1, A2, and A3. The old gradual theory says that the process of A evolving into B looks like this (time in 1000s of years):

The problem with this model is that we don't have many cases where we find A1-A3. We find specimens of A, and we find specimens of B, but we don't find the ones in between. But we should, because if A1, A2, and A3 each existed for a hundred thousand years, then at least a few of them should have been fossilized.

So, several guys put their heads together and came up with punctuated equilibrium, or punk-eek for short. Punk-eek says that the process looks more like this:

Under this model, A1, A2, and A3 exist for only a few thousand years each, so the chance of finding fossils of them is much, much lower. The two models start in the same place, end in the same place, include the same number of intermediate forms, and take the same total amount of time. The only difference is that in the gradual model the change is spread over the whole timespan, while in the punctuated model the change all takes place in less than a quarter of the whole timespan.

Counter-argument: The breeds of domestic cat called the American Wirehair and the Scottish Fold.

The American Wirehair cat has unusual, curled, wiry coat hairs. The Scottish Fold has ears that fold forward about halfway up, like some breeds of dog. Both of these distinctive traits are dominant, meaning that if a kitten gets one gene for the unusual trait from either parent, the kitten will have that trait. Both of these traits are also known to be of very recent origin. All American Wirehair cats trace back to a male red-and-white barn cat named Adam, born March 5th, 1966 on a farm near Verona, New York. All Scottish Folds trace their ancestry to a white female farm cat named Susie, which was born near Cowpar Angus in east-central Scotland in 1961. Since the unique traits that mark these breeds are of recent origin, and the traits are dominant, they must be from new mutations. And they are clearly not harmful, since they don't hinder the animal's ability to survive.

Counter-argument: Several phyla have appeared in the fossil record since the Cambrian. Others have no fossil record at all, so we have no idea when they appeared.

Based on known fossil data, the following phyla appeared on Earth after the Cambrian 'explosion':

(Sources: EARTH AND LIFE THROUGH TIME, 2nd Edition, 1989; THE EVOLUTIONARY BIOLOGY OF PLANTS, Karl Niklas, c. 1997)

There are no certain chordates known from the Early Cambrian. There are two probable chordates from the Burgess Shale, but no certain ones.

In addition, as best I can tell from my available references, the following animal phyla don't seem to have any fossil record at all: Mesozoa, Phoronida, Pentastomida, Tardigrada. All are very small or microscopic organisms, unlikely to be fossilized.

Counter-argument: From ape to human in eight easy steps.

Now, let's fill in the names:

If you put the fossils and other remnants (ie, tools) of these eight species in a row, sorted by time, the sequence they form is obvious. In chronology and in morphology they are an excellent evolutionary series.

Genetic evidence agrees with this sequence. Genetic comparisons tell us that the last common ancestor of human and chimpanzee lived approximately five to seven million years ago. Ardipithecus ramidus appears in precisely the right place and time, and has precisely the right morphology, to be a close descendant of that last common chimp/man ancestor. The rest of the series follows ramidus exactly as we would expect from evolutionary theory.

Counter-argument: Jack Horner's ceratopsid dinosaur finds of the late 1980s and early 1990s.

Over the period 1985-95, dinosaur paleontologist Jack Horner made a series of very impressive discoveries in northwestern Montana. Among many other things, he and his crew found fossils of four ceratopsid (horned) dinosaurs in the Two Medicine and Hell Creek formations, several meters apart vertically in the strata and several million years apart in time. Skulls from these four dinosaurs are illustrated on p. 194 of his book DINOSAUR LIVES and described in the accompanying text.

To make a long story short, the four skulls look nearly identical except for the horns and frills. The oldest skull in the sequence has no formal name but is very similar to Styracosaurus, with a single long nose horn and a large frill with two long spikes extending back from the frill's trailing edge. The second skull, from a species named Einiosaurus procurvicornis, is similar to the first except frill spikes are curved more to the sides, and the long nose horn has a 90-degree forward bend just above the base so that it's "drooped" forward over the nose, and bumps above both eyes. In skull #3, from Achelosaurus horneri, the nose horn is drooped so far forward that it actually fuses with the bones of the snout. The top of the nose horn is very rough-textured, and similar rough patches appear above both eyes. Skull #4 is from a species called Pachyrhinosaurus, which had no nose horn at all, but did have rough, rugose bone covering the entire top of the head from the eyes forward.

Horner shows left-profile and dorsal views of all four of these skulls. When I look at the four dorsal views, I'm struck by three things: first, large openings in the frills on all four look like huge eyes; second, the actual face is arranged so from the top it combines with the frill to form an image of a much larger face; and third, in each successive species the overall effect is much more "facelike," from the unnamed first species where the effect is mild to Pachyrhinosaurus, where the "face" image is unmistakable.

When the four skulls are placed in chronological sequence, it looks exactly like the sort of evolutionary change one might expect from sexual selection, if males who had more "facelike" arrangements of their frills and horns did better at reproducing than males with less "facelike" arrangements.

Counter-argument: First, let's get terminology straight: A "circular argument" in logic is a situation where you construct a proof of statement A using a line of argument that assumes A is true to start with. Geologists didn't do that when they were constructing the geologic column, so the column isn't circular. Here's how the geologic column was built:

• During the 1700s and 1800s, a lot of geologists rambled all over Europe, and also all over the Americas, collecting fossils and making careful notes of what fossils they found in which rock layers.
• After they'd been doing this, and comparing notes, for a few dozen years, geologists began to notice that certain fossils were narrowly limited in the fossil record, appearing in only one or two layers. Others appeared in many layers. Further comparison of observations showed that in many places the fossils changed in consistent ways as you went up or down through the rock layers.
• After more years of looking at fossils and comparing their notes, geologists learned that certain fossils could be reliably used to identify certain strata, like page numbers in a book. More comparisons showed them that in many cases these "index" fossils could be used to correlate different strata, even half a world apart.
• With the introduction of the notion of geologic time, which was already being noised about by 1700, it was easy to make the next jump, which was that these index fossils represented correlations in time -- that two formations which shared the same index fossils had been deposited at about the same time.
• Through the 1800s, the system of indexing strata by their fossils was extended worldwide, and no one ever found a flaw in it. Still, it only provided relative dates to the strata: older, younger, the same age as.
• After 1900, it became possible to assign absolute dates to sedimentary strata indirectly, by 'sandwiching' the sedimentary rocks between igneous rocks that could be dated radiometrically. Then you could use those index fossils and correlation tables, exhaustively built up over generations, to link your dated sedimentary stratum to others around the world. That way, those other strata got absolute ages too.

So, geologists never assumed anything about the rock record. They made observations, and they thought about those observations. Then they drew rational conclusions about those observations. Then they used the conclusions as bases for further reasoning. No assumptions, so no circularity. Geologists started by assigning ages to rocks based on their fossils. It was only after a LOT of confirming work had been done that they felt safe flipping it around, and dating fossils by the rocks they were found in.

It's worth noting that the two methods of dating rocks, relative by fossils and absolute by radio-dating, agree consistently throughout the geologic record, everywhere it's been tried. Wherever two different rock formations were linked based on fossil correlation, radio-dating has confirmed that they are indeed about the same age.

Counter-argument: This argument is really quite absurd, for a very simple reason: The basic concept of the geologic column pre-dates Darwin's theory of evolution by more than fifty years. The geologic column was a viable concept before 1800, and existed in more or less its present form by 1850. On the Origin of Species wasn't published until 1859. Most of the geologists who worked on assembling the geologic column were creationists.

Counter-argument: Nebraska Man was not a fraud. It was a mistake. The Piltdown Man fraud actually represents a shining victory for evolutionary theory. Here's why: For most of its accepted existence, "Piltdown Man" didn't fit the theory. The most man-like of the living apes lived in Africa. Pre-human hominid fossils were being found in Africa and Southwest Asia. Those hominid fossils all showed intermediate features between ape and human, more or less as expected. But "Piltdown Man" broke that entire picture. He was found in England, thousands of miles away from Africa. He had a completely human skull and a completely apelike jaw. In the words of prominent anthropologist Sherwood Washburn, "You could make sense of human evolution if you didn't try to put Piltdown into it." When Piltdown was exposed as a fraud, the entire field of paleoanthropology breathed a sigh of relief.

In other words, as long as Piltdown Man was considered genuine, it was a problem for evolutionary theory. The theory said that Piltdown shouldn't exist. When Piltdown was exposed as a fraud, it was a victory for evolutionary theory!