A year ago, I posted “Ten Questions To Ask Your Biology Teacher About Evolution.” On November 28, 2001, The National Center for Science Education (NCSE) posted its answers to my questions.
According to the NCSE, many of the claims in my questions “are incorrect or misleading,” and they are “intended only to create unwarranted doubts in students’ minds about the validity of evolution as good science.” It is actually the NCSE’s answers, however, that are incorrect or misleading. My original questions (in italics) are posted below; each question is followed by the NCSE’s answer (in bold), a brief outline of my response, and then my detailed response. Numbers in parentheses refer to research notes at the end.
Please feel free to copy and distribute this document to teachers, students, parents, and other interested parties.
My Question: ORIGIN OF LIFE.
Why do textbooks claim that the 1953 Miller-Urey experiment shows how life’s building blocks may have formed on the early Earth — when conditions on the early Earth were probably nothing like those used in the experiment, and the origin of life remains a mystery?
NCSE’s Answer: Because evolutionary theory works with any model of the origin of life on Earth, how life originated is not a question about evolution. Textbooks discuss the 1953 studies because they were the first successful attempt to show how organic molecules might have been produced on the early Earth. When modern scientists changed the experimental conditions to reflect better knowledge of the Earth’s early atmosphere, they were able to produce most of the same building blocks. Origin-of-life remains a vigorous area of research.
My Response in Outline
- Most biology textbooks include the origin of life–and the Miller-Urey experiment–in their treatments of evolution. If the NCSE feels that the origin of life is really “not a question about evolution,” the organization should launch a campaign to correct biology textbooks.
- Because the Miller-Urey experiment used a simulated atmosphere that geochemists now agree was incorrect, it was not the “first successful attempt to show how organic molecules might have been produced on the early Earth.” When conditions are changed to reflect better knowledge of the Earth’s early atmosphere, the experiment doesn’t work.
- If the origin of life “remains a vigorous area of research,” it is only because origin-of-life researchers are dedicated to their work, not because they have discovered anything that demonstrates how life originated.
My Response in Detail
- The NCSE’s claim that the origin of life is “not a question about evolution” ignores the fact that most biology textbooks include it — along with the Miller-Urey experiment — in their treatments of evolution. For example, Campbell, Reece and Mitchell’s Biology (5th Edition, 1999), one of the most widely used introductory textbooks for college undergraduates, discusses the Miller-Urey experiment in “Unit Five: The Evolutionary History of Biological Diversity.” Similarly, Mader’s Biology (6th Edition, 1998), Starr and Taggart’s Biology: The Unity and Diversity of Life (8th Edition, 1998), Schraer and Stoltze’s Biology: The Study of Life (7th Edition, 1999), Guttman’s Biology (1999), Audesirk, Audesirk and Byers’s Life On Earth (2nd Edition, 2000), and Purves, Sadava, Orians and Heller’s Life: The Science of Biology (6th Edition, 2001) all feature the Miller-Urey experiment in their sections dealing with evolution. Alberts, Bray, Lewis, Raff, Roberts and Watson’s upper-division textbook for biology majors, Molecular Biology of the Cell (3rd Edition, 1994), discusses it in a chapter titled “Evolution of the Cell.” The Miller-Urey experiment is also standard fare in upper division and graduate-level textbooks devoted entirely to evolution, such as Futuyma’s Evolutionary Biology (3rd Edition, 1998) and Freeman and Herron’s Evolutionary Analysis (2nd Edition, 2001). If the NCSE feels that the origin of life is really “not a question about evolution,” the organization should launch a campaign to correct biology textbooks.1
- The 1953 Miller-Urey experiment used a simulated hydrogen-rich atmosphere of methane, ammonia, hydrogen and water vapor. By 1970, however, geochemists were nearly unanimous in agreeing that the Earth’s primitive atmosphere was nothing like this. Excess hydrogen is quickly lost to space because the Earth’s gravity is too weak to hold it, so the early atmosphere would almost certainly have consisted of gasses emitted from volcanoes–mainly carbon dioxide, nitrogen and water vapor. When this more realistic mixture is put into a Miller-Urey-type apparatus, the experiment doesn’t work. Stanley Miller himself reported in 1983 that the most he could produce in the absence of methane was glycine, the simplest amino acid, and then only if free hydrogen were present. But free hydrogen is precisely what geochemists now agree was essentially ABSENT. So the Miller-Urey experiment was unsuccessful, and NCSE’s claim that it was the “first successful attempt to show how organic molecules might have been produced on the early Earth” is false. The NCSE’s claim that “when modern scientists changed the experimental conditions to reflect better knowledge of the Earth’s early atmosphere, they were able to produce most of the same building blocks” is also false.2
- If the origin of life “remains a vigorous area of research,” it is only because origin-of-life researchers are dedicated to their work, not because they have discovered anything that demonstrates how life originated. As New York Times science reporter Nicholas Wade wrote in 2000: “Everything about the origin of life on Earth is a mystery, and it seems the more that is known, the more acute the puzzles get.”3
My Question: DARWIN’S TREE OF LIFE.
Why don’t textbooks discuss the “Cambrian explosion,” in which all major animal groups appear together in the fossil record fully formed instead of branching from a common ancestor–thus contradicting the evolutionary tree of life?
NCSE’s Answer: Wells is wrong: fish, amphibians, reptiles, birds, and mammals all are post-Cambrian–aren’t these “major groups”? We would recognize very few of the Cambrian organisms as “modern”; they are in fact at the roots of the tree of life, showing the earliest appearances of some key features of groups of animals–but not all features and not all groups. Researchers are linking these Cambrian groups using not only fossils but also data from developmental biology.
My Response in Outline
- The NCSE is wrong: Fish DID make their first appearance in the Cambrian explosion.
- The “major groups” to which my question refers are the animal phyla. Fish, amphibians, reptiles, birds and mammals are sub-groups (classes) of a single phylum. The NCSE is using semantics to give the illusion that the Cambrian explosion never happened.
- It is through assumption and extrapolation, not “fossils” and “data from developmental biology,” that Darwinists are supposedly “linking” the Cambrian groups.
My Response in Detail:
- The fossil record shows that fish were among the animals that made their first appearance in the Cambrian explosion.4
- Fish, amphibians, reptiles, birds and mammals are not the “major groups” to which my question refers. As every biologist knows, animals are classified into a hierarchy of groups: species, genera, families, orders, classes, and phyla. The phyla are the several dozen major categories that distinguish mollusks, arthropods, echinoderms, annelids and chordates, among others. (Modern representatives of the five phyla listed include snails, insects, starfish, earthworms and mammals, respectively.) Fish, amphibians, reptiles, birds and mammals are sub-groups (classes) of the chordate phylum. Since fish first appeared in the early Cambrian, this phylum was present in the Cambrian explosion, even though not all of its sub-groups were. Representatives of the five phyla listed here, and most of the other phyla as well–the “major groups” of animals recognized by all biologists–appear in the Cambrian explosion, with no fossil evidence that they evolved from a common ancestor. Berkeley paleontologist James Valentine and his colleagues wrote in 1991 that the Cambrian explosion “was even more abrupt and extensive than previously envisioned” and gives the impression that animal evolution “has by and large proceeded from the ‘top down’.” This does not fit Darwin’s theory that major differences should have evolved over millions of years from minor differences in a single ancestral species–that is, from the “bottom up.” By labeling vertebrate classes “major groups,” the NCSE uses a semantic trick to give the illusion that the Cambrian explosion never happened, and that the conflict with Darwin’s theory doesn’t exist. Similarly, most biology textbooks avoid any mention of the Cambrian explosion, and the few that do mention it try to dismiss it. The NCSE, like the textbooks, is concealing a problem with the fossil record so significant that Darwin himself considered it a “valid argument” against his theory.5
- The NCSE’s claim that “researchers are linking these Cambrian groups using not only fossils but also data from developmental biology” is profoundly misleading. First, the principal lesson of the Cambrian explosion is that the fossils needed for “linking” the phyla to a common ancestor are nonexistent. Second, with a few rare exceptions developmental data are available only from living animals. Although embryological similarities and differences can help us to classify living animals into phyla, we can only speculate how most extinct animals developed. Darwinian researchers ASSUME the existence of a common ancestor, and then extrapolate modern similarities and differences hundreds of millions of years into the past to guess what the hypothetical ancestor might have been or how it might have developed. Thus it is through assumption and extrapolation, not “fossils” and “data from developmental biology,” that Darwinists are “linking” the Cambrian groups.
My Question: HOMOLOGY.
Why do textbooks define homology as similarity due to common ancestry, then claim that it is evidence for common ancestry — a circular argument masquerading as scientific evidence?
NCSE’s Answer: The same anatomical structure (such as a leg or an antenna) in two species may be similar because it was inherited from a common ancestor (homology) or because of similar adaptive pressure (convergence). Homology of structures across species is not assumed, but tested by the repeated comparison of numerous features that do or do not sort into successive clusters. Homology is used to test hypotheses of degrees of relatedness. Homology is not “evidence” for common ancestry: common ancestry is inferred based on many sources of information, and reinforced by the patterns of similarity and dissimilarity of anatomical structures.
My Response in Outline
- I thank the NCSE for conceding my main point: Homology (defined by modern Darwinists as similarity due to common ancestry) is not evidence of common ancestry.
- Yet many biology textbooks tell students that it is. When the NCSE launches its campaign to correct textbooks that treat the origin of life as part of evolution, it should also correct textbooks that treat homology as evidence for common ancestry.
- At the level of the animal phyla, common ancestry is not inferred from “sources of information” such as fossils, molecules or embryos; instead, it is assumed on theoretical grounds.
My Response in Detail
- As the NCSE acknowledges, homology (defined by modern Darwinists as similarity due to common ancestry) is not evidence of common ancestry.
- Why, then, do many biology textbooks tell students that homology is evidence of common ancestry? For example, Starr and Taggart’s Biology: The Unity and Diversity of Life (8th Edition, 1998), states that the “pattern of macroevolution – that is, change from the form of a common ancestor – is called morphological divergence… Homology [is] a similarity in one or more body parts in different organisms that share a common ancestor…. Homologous structures provide very strong evidence of morphological divergence.” In a section on “The Evidence for Evolution” in the teacher’s edition of Johnson’s Biology: Visualizing Life (1998), students are told that “homologous structures are structures that share a common ancestor,” and an accompanying note tells the teacher that “such structures point to a common ancestry.” According to Campbell, Reece and Mitchell’s Biology (5th Edition, 1999), “similarity in characteristics resulting from common ancestry is known as homology, and such anatomical signs of evolution are called homologous structures. Comparative anatomy is consistent with all other evidence in testifying [to] evolution.” Raven and Johnson’s Biology (5th Edition, 1999), in a section titled “The evidence for macroevolution is extensive,” includes the following: “Homology: Many organisms exhibit organs that are similar in structure to those in a recent common ancestor. This is evidence of evolutionary relatedness.” A few pages later, the same textbook explicitly defines homologous structures as “structures with different appearances and functions that all derived from the same body part in a common ancestor.” Audesirk, Audesirk and Byers’s Life On Earth (2nd Edition, 2000) calls homology “evidence of relatedness” in a section titled “Comparative Anatomy Provides Structural Evidence of Evolution.” The textbook tells students: “Internally similar structures are called homologous structures, meaning that they have the same evolutionary origin despite possible differences in function. Studies of comparative anatomy have long been used to determine the relationships among organisms, on the grounds that the more similar the internal structures of two species, the more closely related the species must be, that is, the more recently they must have diverged from a common ancestor.” When the NCSE launches its campaign to correct textbooks that treat the origin of life as part of evolution, it should also correct textbooks that treat homology as evidence for common ancestry.6
- According to the NCSE, “common ancestry is inferred based on many sources of evidence.” As we have seen, however, at the level of the animal phyla the fossil record does not support such an inference. Neither does the molecular evidence. As biologist Michael Lynch wrote in 1999: “Clarification of the phylogenetic [i.e., evolutionary] relationships of the major animal phyla has been an elusive problem, with analyses based on different genes and even different analyses based on the same genes yielding a diversity of phylogenetic trees.” And as the next question demonstrates, the embryological evidence does not support common ancestry even at the level of the vertebrate classes, much less at the phylum level. At these levels, common ancestry is assumed on theoretical grounds, not inferred from evidence.7
My Question: VERTEBRATE EMBRYOS.
Why do textbooks use drawings of similarities in vertebrate embryos as evidence for their common ancestry — even though biologists have known for over a century that vertebrate embryos are not most similar in their early stages, and the drawings are faked?
NCSE’s Answer: Twentieth-century and current embryological research confirms that early stages (if not the earliest) of vertebrate embryos are more similar than later ones; the more recently species shared a common ancestor, the more similar their embryological development. Thus cows and rabbits — mammals — are more similar in their embryological development than either is to alligators. Cows and antelopes are more similar in their embryology than either is to rabbits, and so on. The union of evolution and developmental biology — “evo-devo” — is one of the most rapidly growing biological fields. “Faked” drawings are not relied upon: there has been plenty of research in developmental biology since Haeckel–and in fact, hardly any textbooks feature Haeckel’s drawings, as claimed.
My Response in Outline
- Far from confirming the NCSE’s claim that the early stages of vertebrate embryos are more similar than later ones, embryological research confirms that the claim is false.
- The NCSE’s claim that “the more recently species shared a common ancestor, the more similar their embryological development” is also false.
- Textbooks claim that the various CLASSES of vertebrates resemble each other in their early stages. By focusing on taxonomic levels below classes, the NCSE is attempting to evade the issue.
- Although the NCSE claims that “faked” drawings “are not relied upon,” a simple examination of biology textbooks shows that the NCSE is wrong.
My Response in Detail
- Contrary to the NCSE’s claim, the early stages of vertebrate embryos are generally NOT more similar than later ones. Early vertebrate embryos actually look very different from each other, then they converge somewhat in appearance midway through development before diverging again–a pattern known to embryologists as the “developmental hourglass.” Birds and mammals, for example, have fundamentally different patterns of early cell divisions (called “cleavage”), yet the two classes look somewhat similar for a short time midway through development. In the 1860’s, German Darwinist Ernst Haeckel produced drawings of vertebrate embryos that not only exaggerated their similarities at the midpoint of development, but also omitted the strikingly different stages that preceded the midpoint. The drawings gave the impression that vertebrate embryos are most similar in their early stages, suggesting common ancestry; but the drawings were faked, and the impression is false. In 1976, embryologist William Ballard wrote that it is “only by semantic tricks and subjective selection of evidence,” by “bending the facts of nature,” that one can argue that the cleavage and gastrulation stages of vertebrates “are more alike than their adults.” (Gastrulation refers to the cell movements that follow the cleavage stage.) In 1987, developmental biologist Richard Elinson noted that the early embryos of frogs, chicks and mice “are radically different in such fundamental properties as egg size, fertilization mechanisms, cleavage patterns, and [gastrulation] movements.” Thus “twentieth-century and current embryological research” confirms that the NCSE is wrong.8
- The NCSE further claims that “the more recently species shared a common ancestor, the more similar their embryological development.” As a general description of vertebrate embryos, however, this is also false. For example, the pattern of development in some frog species looks very much like that in birds, but no one thinks those frogs are more closely related to birds than to other frogs.9
- The standard textbook claim is that the various CLASSES of vertebrates resemble each other in their early stages. Yet in its answer, the NCSE compares representatives of only one class, mammals. No one doubts that the embryos of mammals tend to resemble each other more than they resemble the embryos of reptiles, but Haeckel’s drawings fraudulently portrayed the embryos of ALL vertebrate classes as though they were alike. Just as the NCSE evaded my question about the “tree of life” by focusing on classes instead of phyla, here the NCSE evades my question about vertebrate embryos by focusing on taxonomic levels below classes. The NCSE thereby resorts to exactly the sort of “semantic tricks and subjective selection of evidence” criticized by Ballard in 1976.
- According to the NCSE, “faked” drawings “are not relied upon,” and “hardly any textbooks feature Haeckel’s drawings.” Yet two college textbooks, Starr and Taggart’s Biology: The Unity and Diversity of Life (8th Edition, 1998) and Guttman’s Biology (1999) feature slightly redrawn versions of Haeckel’s faked originals. Three high-school textbooks, Biggs, Kapicka and Lundgren’s Biology: The Dynamics of Life (1998), Schraer and Stoltze’s Biology: The Study of Life (7th Edition, 1999), and Miller and Levine’s Biology (5th Edition, 2000), contain stylized drawings that improve only slightly on Haeckel, and perpetuate Haeckel’s misrepresentation of the midpoint of development as the first stage. Worse yet, two advanced textbooks for college biology majors feature Haeckel’s original drawings: Alberts, Bray, Lewis, Raff, Roberts and Watson’s Molecular Biology of the Cell (3rd Edition, 1994), and Futuyma’s Evolutionary Biology (3rd Edition, 1998). It was textbooks like these that prompted Harvard evolutionary biologist Stephen Jay Gould to write in 2000: “We do, I think, have the right to be both astonished and ashamed by the century of mindless recycling that has led to the persistence of these drawings in a large number, if not a majority, of modern textbooks.”10
My Question: ARCHAEOPTERYX.
Why do textbooks portray this fossil as the missing link between dinosaurs and modern birds — even though modern birds are probably not descended from it, and its supposed ancestors do not appear until millions of years after it?
NCSE’s Answer: The notion of a “missing link” is an out-of-date misconception about how evolution works. Archaeopteryx (and other feathered fossils) shows how a branch of reptiles gradually acquired both the unique anatomy and flying adaptations found in all modern birds. It is a transitional fossil in that it shows both reptile ancestry and bird specializations. Wells’s claim that “supposed ancestors” are younger than Archaeopteryx is false. These fossils are not ancestors but relatives of Archaeopteryx and, as everyone knows, your uncle can be younger than you!
My Response in Outline
- If the notion of a “missing link” is out of date, why do biology textbooks continue to use it? When the NCSE launches its long-overdue campaign against misconceptions in biology textbooks (such as calling the origin of life part of evolution, or using homology as evidence for common ancestry), it can add “missing link” to its list.
- If Darwin’s theory is true, there must have been organisms in the past that were transitional links between ancestors and descendants–yet most of them are missing from the fossil record. So the notion of “missing link” is no more “out-of-date” than evolutionary theory itself.
- Archaeopteryx is not preceded by fossils showing how reptiles “gradually acquired” bird-like features. Furthermore, without fossils of the appropriate age, the NCSE has no grounds for saying “Wells’s claim that “supposed ancestors” are younger than Archaeopteryx is false.”
- Bird-like dinosaurs are not just younger than their supposed relative, but millions of generations younger, so it makes no sense to call them “uncles” of Archaeopteryx.
My Response in Detail
- Many biology textbooks call Archaeopteryx a “link” that once was missing but now is found. Starr and Taggart’s Biology: The Unity and Diversity of Life (8th Edition, 1998) calls Archaeopteryx “the first of the “missing links”. Mader’s Biology (6th Edition, 1998), describes this fossil as “a transitional link between reptiles and modern birds.” Schraer and Stoltze’s Biology: The Study of Life (7th Edition, 1999) calls it “an evolutionary link between reptiles and birds.” And according to Raven and Johnson’s Biology (5th Edition, 1999), Archaeopteryx is an example of a fossil “linking” major groups. If the NCSE ever launches a campaign against misconceptions in biology textbooks (such as calling the origin of life part of evolution, or using homology as evidence for common ancestry), it can add “missing link” to its list.11
- In any case, the NCSE’s claim that “missing link” is a misconception is odd, since if Darwin’s theory is true there MUST have been organisms in the past that were transitional links between ancestors and descendants. Transitional links are a logical consequence of evolutionary theory, yet most of them are missing from the fossil record. Archaeopteryx is famous precisely because it is one of the few supposed links that have been found. So the notion of “missing link” cannot possibly be any more “out-of-date” than evolutionary theory itself. Of course, whether any PARTICULAR fossil can be determined to be a transitional link is open to serious doubt. According to Henry Gee, chief science writer for Nature, “the intervals of time that separate fossils are so huge that we cannot say anything definite about their possible connection through ancestry and descent.” But if the NCSE is suggesting, like Gee, that NO fossil can be identified as transitional between its ancestors and descendants, why does it call Archaeopteryx a “transitional fossil” that shows “reptilian ancestry” as well as bird-like features?12
- Archaeopteryx is the oldest bird in the fossil record. It appears fully formed, and it is not preceded by fossils showing gradual transitions from reptiles to birds. So the NCSE’s claim that it shows “how a branch of reptiles gradually acquired” bird-like features is false. If the NCSE is suggesting that this gradual transition is seen in bird-like dinosaurs (a view passionately — and controversially — defended by NCSE’s president, Kevin Padian), the problem is that these supposed ancestors do not appear in the fossil record until tens of millions of years AFTER Archaeopteryx. Without fossils of the appropriate age, the NCSE has no grounds for saying “Wells’s claim that “supposed ancestors” are younger than Archaeopteryx is false.”13
- Calling bird-like dinosaurs “uncles” instead of “ancestors” of Archaeopteryx merely obscures the problem: Although an uncle isn’t the ancestor of his nephew, and the former can be younger than the latter, the two — by definition — are no more than a generation apart, and they are members of the same species. Yet according to the fossil record, Archaeopteryx is millions of generations older than the bird-like dinosaurs. Furthermore, the two are not in the same species — in fact, they’re not even in the same genus, family, order or class! It makes no sense to call David Ben-Gurion the “uncle” of Abraham — much less to call bird-like dinosaurs the “uncles” of Archaeopteryx.
My Question: PEPPERED MOTHS.
Why do textbooks use pictures of peppered moths camouflaged on tree trunks as evidence for natural selection — when biologists have known since the 1980s that the moths don’t normally rest on tree trunks, and all the pictures have been staged?
NCSE’s Answer: These pictures are illustrations used to demonstrate a point–the advantage of protective coloration to reduce the danger of predation. The pictures are not the scientific evidence used to prove the point in the first place. Compare this illustration to the well-known re-enactments of the Battle of Gettysburg. Does the fact that these re-enactments are staged prove that the battle never happened? The peppered moth photos are the same sort of illustration, not scientific evidence for natural selection.
My Response in Outline
- The NCSE’s first point is technically correct: The textbook pictures are illustrations, not actual evidence.
- The NCSE is using this technical point, however, to obscure the real issue: The textbook pictures misrepresent the natural resting-place of peppered moths and conceal serious flaws in the standard story.
- Staged peppered moth photos are not comparable to re-enactments of the Battle of Gettysburg, because the former misrepresent the truth.
- If using staged photos and re-telling a flawed story “demonstrate a point,” as the NCSE claims, the point is that students cannot trust what they read in their biology textbooks.
My Response in Detail
- True, the textbook pictures are illustrations, not actual evidence. It would have been more accurate for me to write “examples of” or “illustrations of” instead of “evidence for.”
- The NCSE uses this technical point, however, to obscure the fact that textbook pictures misrepresent the evidence and conceal serious flaws in the peppered moth story. Two hundred years ago, almost all peppered moths in the U.K. were light-colored. During the industrial revolution, dark-colored moths became much more common–especially in the polluted woodlands around major cities. According to theory, the shift occurred because dark-colored moths were better camouflaged against pollution-darkened tree trunks, and thus less likely to be eaten by predatory birds. In the 1950s, Bernard Kettlewell released light and dark-colored moths onto nearby tree trunks in polluted and unpolluted woodlands, and watched as birds ate the more visible ones. The story, and Kettlewell’s experiments, became the classic textbook example of natural selection. When pollution-control legislation resulted in cleaner air after the 1950s, light-colored moths became more common again, as the theory predicted. Contrary to the theory, however, this occurred BEFORE tree trunks reverted to their former light color. In the 1980s, biologists discovered that peppered moths don’t normally rest on tree trunks, and many began to question the classic story about camouflage and bird predation. In 1998, Theodore Sargent, Craig Millar and David Lambert wrote in Evolutionary Biology: “There is little persuasive evidence…to support this explanation at the present time.” And as University of Chicago evolutionary biologist Jerry Coyne wrote in Nature, the fact that peppered moths do not normally rest on tree trunks “alone invalidates Kettlewell’s experiments, as moths were released by placing them directly onto tree trunks.”14
- The NCSE’s comparison of staged peppered moth photos with re-enactments of the Battle of Gettysburg is inappropriate, because the former misrepresent the facts. The appropriate comparison would be with FALSE re-enactments of the Battle of Gettysburg–such as re-enactments staged in Chancellorsville (where the other side won). Scientific illustrations, like historical re-enactments, should portray the truth.
- Instead of telling students the truth about peppered moths, most biology textbooks repeat the classic story and illustrate it with staged pictures–many of them made by pinning or gluing dead moths to tree trunks. For example, Johnson’s Biology: Visualizing Life (1998), Guttman’s Biology (1999), Schraer and Stoltze’s Biology: The Study of Life (7th Edition, 1999), and Miller and Levine’s Biology (5th Edition, 2000) all use staged photos and summaries of Kettlewell’s experiments to convince students that peppered moths are a classic demonstration of natural selection in action. Mader’s Biology (6th Edition, 1998) goes even further, using Kettlewell’s experiments as the paramount example of how to do science: “The scientific method consists of forming a hypothesis, testing it, and coming to an conclusion…In order to examine the scientific method in more detail, we will consider research performed by British scientist H.B.D. Kettlewell.” If these illustrations “demonstrate a point,” as the NCSE claims, the point is that students cannot trust what they read in their biology textbooks.15
My Question: DARWIN’S FINCHES.
Why do textbooks claim that beak changes in Galapagos finches during a severe drought can explain the origin of species by natural selection — even though the changes were reversed after the drought ended, and no net evolution occurred?
NCSE’s Answer: Textbooks present the finch data to illustrate natural selection: that populations change their physical features in response to changes in the environment. The finch studies carefully–exquisitely–documented how the physical features of an organism can affect its success in reproduction and survival, and that such changes can take place more quickly than was realized. That new species did not arise within the duration of the study hardly challenges evolution!
My Response in Outline
- The NCSE is evading the question, which is not whether the finch data demonstrate natural selection (they do), but whether those data explain the origin of new species (they don’t).
- To the extent that scientific theories are supposed to rely on evidence, the finch study DOES challenge Darwin’s theory of the origin of species by natural selection. No one doubts that natural selection occurs, but every time it has been observed (as in the finches) it has occurred only within existing species.
My Response in Detail
- The question is not whether the finch data demonstrate natural selection, but whether those data explain the origin of new species. In the 1970s, biologists Peter and Rosemary Grant watched as a severe drought killed 85% of a particular finch species on one island in the Galapagos archipelago. The survivors had (on average) slightly larger beaks, enabling them to crack the hard seeds that had weathered the drought; but average beak size returned to normal after the rains returned. There was no net change, and no new species emerged. In fact, several species of Galapagos finches now appear to be merging through hybridization–the exact opposite of producing new species. Yet some textbooks — and a publication of the U. S. National Academy of Sciences (NAS) — make it sound as though the finch studies showed how new species can originate. Miller and Levine’s Biology: The Living Science (1998) tells students: “It might take only between 12 and 20 droughts to change one species of finch into another!” According to Science and Creationism: A View from the National Academy of Sciences (1999), the Grants’ observations showed that “if droughts occur about once every ten years on the islands, a new species of finch might arise in only about 200 years,” making the Galapagos finches “a particularly compelling example of speciation [a technical term for the origin of new species].” Both the Miller-Levine textbook and the NAS booklet neglect to mention that the data actually points to oscillating selection with no net change, and not to the merging of species through hybridization. The question is not whether the Grants observed natural selection — they did — but why the evidence is exaggerated to make it appear to show much more. The NCSE fails to answer this question.16
- The fact that no new species arose in the course of the Grants’ study does not refute the theory of evolution. It certainly “challenges” it, however, because scientific theories need to be supported by evidence. Darwin’s theory, as expressed in the title of his 1859 book, was The Origin of Species by Means of Natural Selection, and the Galapagos finches are held up by our nation’s premier science organization as a “particularly compelling example” of this. Yet the finch data do not show cumulative changes in beak size, much less the origin of species through natural selection. No one doubts that natural selection occurs, but every time it has been observed (as in the finches) it has occurred within existing species. For example, natural selection has often been observed in bacteria. Because of their rapid generation times, bacteria ought to be the easiest organisms in which to observe the origin of species through natural selection. Yet as British bacteriologist Alan H. Linton wrote in 2001: “Throughout 150 years of the science of bacteriology, there is no evidence that one species of bacteria has changed into another.” Faced with this lack of evidence for a key element of Darwin’s theory, some defenders of the theory — even in the prestigious NAS–have taken to exaggerating the finch data. Although this does not refute the theory, it hardly inspires confidence in it. As Berkeley law professor and Darwin critic Phillip E. Johnson wrote in 1999: “When our leading scientists have to resort to the sort of distortion that would land a stock promoter in jail, you know they are in trouble.”17
My Question: MUTANT FRUIT FLIES.
Why do textbooks use fruit flies with an extra pair of wings as evidence that DNA mutations can supply raw materials for evolution — even though the extra wings have no muscles and these disabled mutants cannot survive outside the laboratory?
NCSE’s Answer: In the very few textbooks that discuss four-winged fruit flies, they are used as an illustration of how genes can reprogram parts of the body to produce novel structures, thus indeed providing “raw material” for evolution. This type of mutation produces new structures that become available for further experimentation and potential new uses. Even if not every mutation leads to a new evolutionary pathway, the flies are a vivid example of one way mutation can provide variation for natural selection to work on.
My Response in Outline
- The four-winged fruit fly is found in a lot more than “very few” textbooks.
- The mutations that produce the four-winged fruit fly lead to the LOSS of important structures–and to their replacement by duplicates of structures already present elsewhere in the fly–not to “new structures that become available for further experimentation.”
- Mutations must be advantageous to the organism in order to provide raw materials for evolution–otherwise, natural selection will tend to eliminate them. Yet the four-winged fruit fly is seriously disabled, so it is not “a vivid example of one way mutation can provide variation for natural selection to work on.”
My Response in Detail
- More than a few textbooks use the four-winged fruit fly. Mader’s Biology (6th Edition, 1998), Raven and Johnson’s Biology (5th Edition, 1999), Guttman’s Biology (1999) and Purves, Sadava, Orians and Heller’s Life: The Science of Biology (6th Edition, 2001) all use pictures of four-winged fruit flies to illustrate how mutations can affect development–after telling students that gene mutations are the raw materials of evolution. Two advanced textbooks for biology majors, Futuyma’s Evolutionary Biology (3rd Edition, 1998) and Freeman and Herron’s Evolutionary Analysis (2nd Edition, 2001), include pictures of four-winged fruit flies in their discussions of how mutations supposedly provide raw materials for evolution.18
- Contrary to the NCSE’s claim, the extra wings in the four-winged fruit fly are not “novel structures,” but pathological duplications of body parts already present elsewhere in the fly. The mutations that produce the four-winged fly damage a gene that normally enables the fly to develop “balancers”–tiny structures behind the wings that help to stabilize the insect in flight. Unable to form balancers, the mutant fly sprouts a second pair of normal-looking (though not normal-functioning) wings by default. In other words, the mutations lead to a LOSS of important structures, not to “new structures that become available for further experimentation.”19
- In order for a mutation to provide raw materials for evolution, it must be advantageous to the organism–otherwise, natural selection will tend to eliminate it. Although most mutations are harmful, a mutation occasionally benefits an organism by increasing its resistance to an antibiotic or a pesticide–usually by damaging a molecule that would otherwise react with the antibiotic or pesticide. Such mutations, however, affect only single molecules, while Darwinian evolution requires changes in anatomy as well as biochemistry. But advantageous anatomical mutations are never observed. The four-winged fruit fly is a case in point: The second set of wings lacks flight muscles, so the useless appendages interfere with flying and mating, and the mutant fly cannot survive long outside the laboratory. Similar mutations in other genes also produce various anatomical deformations, but they are harmful, too. In 1963, Harvard evolutionary biologist Ernst Mayr wrote that the resulting mutants “are such evident freaks that these monsters can be designated only as “hopeless.” They are so utterly unbalanced that they would not have the slightest chance of escaping elimination” through natural selection. So the NCSE’s claim that four-winged fruit flies “are a vivid example of one way mutation can provide variation for natural selection to work on” is false.20
My Question: HUMAN ORIGINS.
Why are artists’ drawings of ape-like humans used to justify materialistic claims that we are just animals and our existence is a mere accident — when fossil experts cannot even agree on who our supposed ancestors were or what they looked like?
NCSE’s Answer: Drawings of humans and our ancestors illustrate the general outline of human ancestry, about which there is considerable agreement, even if new discoveries continually add to the complexity of the account. The notion that such drawings are used to “justify materialistic claims” is ludicrous and not borne out by an examination of textbook treatments of human evolution.
My Response in Outline
- The field of human origins is actually one of the most contentious in biology, because individual researchers interpret the relatively meager evidence on the basis of different biases and preconceptions.
- Darwin’s followers — like Darwin himself — agree that humans evolved from ape-like animals. This theoretical consensus, however, owes less to the evidence than to materialistic philosophy.
- One consequence of this philosophy is the claim that there has been no purpose or direction in the history of life. Many biology textbooks promote this view and use drawings of ape-like humans to convince students that we are no exception to it.
My Response in Detail
- Contrary the NCSE’s claim of “considerable agreement,” the field of human origins (paleoanthropology) is actually one of the most contentious in biology. According to experts in the field, this is because of subjective interpretations of the relatively meager evidence. Berkeley evolutionary biologist F. Clark Howell wrote in 1996: “There is no encompassing theory of [human] evolution… Alas, there never really has been.” According to Howell, the field is characterized by “narrative treatments” based on little evidence, so “it is probably true that an encompassing scenario” of human evolution “is beyond our grasp, now if not forever.” Arizona State University paleoanthropologist Geoffrey Clark was equally pessimistic in 1997: “Scientists have been trying to arrive at a consensus about modern human origins for more than a century. Why haven’t they been successful?” Clark is convinced it is because paleoanthropologists proceed from different “biases, preconceptions and assumptions.” And in 1999 Henry Gee, chief science writer for Nature, pointed out that all the evidence for human evolution “between about 10 and 5 million years ago–several thousand generations of living creatures–can be fitted into a small box.” According to Gee, the conventional picture of human evolution as lines of ancestry and descent is “a completely human invention created after the fact, shaped to accord with human prejudices.”21
- Of course, Darwin’s followers–like Darwin himself–agree that humans evolved from ape-like animals. This agreement, however, represents a theoretical consensus. It does not emerge from the evidence–not the meager evidence for human origins, nor (as we have seen) the evidence from four-winged fruit flies, Darwin’s finches, peppered moths, vertebrate embryos, comparative anatomy, or the fossil record of the animal phyla. On what, then, is this theoretical consensus based?
- It seems to me that it is based largely on a philosophical commitment–specifically, a commitment to materialism, the philosophical doctrine that the physical universe is the only reality; God, spirit and mind are illusions. One consequence of this doctrine is the claim that there has been no purpose or direction in the history of life. According to the NCSE, the notion that textbooks use drawings of supposed human ancestors to justify this claim is “ludicrous.” Yet Guttman’s, Biology (1999) tells students that living things have developed “just by chance,” by a roll of the “cosmic dice,” through “the action of random evolutionary forces.” Miller and Levine’s Biology (5th Edition, 2000) asserts that “evolution works without plan or purpose,” so “evolution is random and undirected.” Purves, Sadava, Orians and Heller’s Life: The Science of Biology (6th Edition, 2001) states that “evolution is not directed toward a final goal or state.” And all three of these textbooks include fanciful drawings of ape-like humans that help to convince students we are no exception to the rule of purposelessness.
- Some biology textbooks use other kinds of illustrations as well as interviews with famous Darwinists to persuade students that human beings are merely accidental by-products of purposeless natural processes. Raven and Johnson’s Biology (5th Edition, 1999) depicts a speculative reconstruction of the famous “Lucy” fossil after treating students to an interview with Harvard professor Stephen Jay Gould, who tells them: “Humans represent just one tiny, largely fortuitous, and late-arising twig on the enormously arborescent bush of life.” Campbell, Reece and Mitchell’s Biology (5th Edition, 1999) uses drawings of reconstructed fossil skulls rather than whole animals, and features an interview with Oxford professor Richard Dawkins, who declares: “Natural selection is a bewilderingly simple idea. And yet what it explains is the whole of life, the diversity of life, the complexity of life, the apparent design of life”–including human beings, who “are fundamentally not exceptional because we came from the same evolutionary source as every other species.” Our existence was not planned, however, because natural selection is “totally blind to the future”–the “blind watchmaker.” For further reading, students are referred to Dawkins’s book of that name, in which he writes: “Darwin made it possible to be an intellectually fulfilled atheist.”22
My Question: EVOLUTION A FACT?
Why are we told that Darwin’s theory of evolution is a scientific fact–even though many of its claims are based on misrepresentations of the facts?
NCSE’s Answer: What does Wells mean by “Darwin’s theory of evolution”? In the last century, some of what Darwin originally proposed has been augmented by more modern scientific understanding of inheritance (genetics), development, and other processes that affect evolution. What remains unchanged is that similarities and differences among living things on Earth over time and space display a pattern that is best explained by evolutionary theory. Wells’s “10 Questions” fails to demonstrate a pattern of evolutionary biologists’ “misrepresenting the facts.”
My Response in Outline
- Darwin called his theory “descent with modification.” Defenders of the theory often refer to descent from a common ancestor as a “fact,” and reserve the term “theory” for ideas about the mechanisms of modification. This distinction is found in most biology textbooks that deal with evolution.
- Yet some of the best evidence for the “fact” of evolution comes from the fossil record, homology, and embryology–and as we have seen, there are serious problems with all three. The claim that evolution is a fact, like the claim that humans evolved from ape-like ancestors, owes more to materialistic philosophy than to empirical science.
- If anything demonstrates “a pattern of evolutionary biologists’ “misrepresenting the facts,” it is the NCSE’s evasive and false answers to my Ten Questions.
My Response in Detail
- Darwin called his theory “descent with modification.” He wrote in 1859: “I view all beings not as special creations, but as the lineal descendants of some few beings” which lived in the remote past, and he considered natural selection “the main but not exclusive means of modification.” Thus from the very beginning the theory of biological evolution has had two elements: the pattern of descent from a common ancestor, and the processes by which descendants have been modified. As the NCSE points out, ideas about the processes of evolution have been augmented by modern research, but the idea of an underlying pattern of descent from a universal common ancestor has remained unchanged since Darwin’s time. Defenders of Darwin’s theory often refer to universal common ancestry as a “fact,” reserving the term “theory” for ideas about process.23
- This distinction is found in most biology textbooks that deal with evolution. For example, Futuyma’s Evolutionary Biology (3rd Edition, 1998) tells students: “Descent with modification from common ancestors is a scientific fact, that is, a hypothesis so well supported by evidence that we take it to be true. The theory of evolution, on the other hand, is a complex body of statements, well supported but still incomplete, about the causes of evolution.” Guttman’s Biology (1999) makes the same distinction: “The concept of evolution actually has two faces – one fact, one theory. If we ask how all the organisms on Earth have reached their present forms, the answer is that they have evolved. This answer is based on such an enormous, coherent body of evidence that we must take it as a fact. By contrast, the other face of evolution, the complex body of ideas about how evolution occurs, is a theory.” According to Audesirk, Audesirk and Byers’s Life On Earth (2nd Edition, 2000), evolution means that “modern organisms descended, with modification, from pre-existing life-forms.” The book then asserts: “Virtually all biologists consider evolution to be a fact. Although debates still rage over the mechanisms of evolutionary change, exceedingly few biologists dispute that evolution occurs. Why? Because an overwhelming body of evidence permits no other conclusion.” Yet the textbooks claim that some of the best evidence for the “fact” of evolution comes from the fossil record, homology, and embryology–and as we have seen, there are serious problems with all three. Why, then, are we still told that evolution is a fact?24
- It seems to me that this claim, like the claim that humans evolved from ape-like ancestors, owes more to materialistic philosophy than to empirical science. Audesirk, Audesirk and Byers’s Life On Earth (2nd Edition, 2000) tells students: “Over the course of human history, two approaches have been taken to the study of life and other natural phenomena. The first assumes that some events happen through the intervention of supernatural forces…In contrast, science adheres to the principle of natural causality: All events can be traced to natural causes.” The claim that “all events can be traced to natural causes” is not a methodological statement limiting science to the study of natural phenomena, but a sweeping metaphysical statement about the whole of reality: It is an affirmation of materialism. Guttman’s Biology (1999), as we saw above, promotes materialism in its statements that evolution is purposeless and undirected. And Futuyma’s Evolutionary Biology (3rd Edition, 1998) tells upper division and graduate students: “By coupling undirected, purposeless variation to the blind, uncaring process of natural selection, Darwin made theological or spiritual explanations of the life processes superfluous.” Futuyma concludes that it was Darwin’s theory of evolution, together with Marx’s view of history and Freud’s view of human nature “that provided a crucial plank to the platform of mechanism and materialism” that “has since been the stage of most Western thought.”25
- According to the NCSE, my Ten Questions fail to “demonstrate a pattern of evolutionary biologists’ “misrepresenting the facts”.” Yet the NCSE’s evasive and false answers to my questions clearly demonstrate such a pattern. The NCSE’s evasions include: using “major groups” to denote vertebrate classes rather than animal phyla, thus side-stepping the challenge to Darwin’s theory posed by the Cambrian explosion; listing embryos from only one vertebrate class to give the illusion that similarities among the embryos of ALL classes provide evidence for common ancestry; and comparing staged photos of peppered moths that misrepresent the truth to historical re-enactments of events that actually happened. Furthermore, the NCSE makes numerous false claims about the scientific evidence, such as the following: the Miller-Urey experiment succeeded in showing how organic molecules might have been produced on the early Earth (it didn’t); when the experiment is repeated using a more realistic mixture of gasses, it still produces most of the same building blocks (it doesn’t); fish do not appear in the Cambrian explosion (they do); the early stages of vertebrate embryos are generally more similar than later stages (they’re not); and anatomical mutations in fruit flies produce novel structures that provide raw materials for evolution (they don’t). The NCSE also makes statements about biology textbooks that are demonstrably false, for example: textbooks do not rely on faked embryo drawings; very few textbooks feature the four-winged fruit fly; and textbooks do not use drawings of ape-like humans in the context of promoting materialistic philosophy. Simple examination shows that many textbooks do these very things. To see a pattern of evolutionary biologists’ misrepresenting the facts, one needs only to read the NCSE’s answers to my “Ten Questions To Ask Your Biology Teacher About Evolution.”
The NCSE introduces its answers to my Ten Questions by calling many of my claims “incorrect or misleading,” and by maintaining that they are “intended only to create unwarranted doubts in students’ minds about the validity of evolution as good science.” The evasions and falsehoods listed above, however, make it clear that it is the NCSE’s answers that are incorrect or misleading. If students have doubts about the scientific validity of evolution, their doubts are amply warranted not only by the systematic pattern of misrepresentations in biology textbooks, but also by the false and evasive statements the NCSE makes in defense of those misrepresentations.
Good science is the search for truth, and it searches for truth by comparing theories with the evidence. A good science education should present the evidence truthfully — especially the evidence for and against a theory as influential as Darwin’s. Yet biology textbooks invariably present this evidence with a pro-Darwin spin, indoctrinating students rather than educating them. It seems that the National Center for Science Education, despite its title, wants students to inherit the spin.
Note: More detailed information on all ten questions is available in my book, Icons of Evolution (Washington, DC: Regnery, 2000; paperback edition 2002).