Recently the State of Oklahoma considered a Disclaimer, originally drafted by the Alabama Board of Education in 1996, to be placed in science textbooks that mention evolution and are used by public schools in the State.

Unfortunately, the disclaimer is laden with scientific inaccuracies and distortions that will confuse students about the nature of science and the science of evolution. Such statements place an unwelcome burden on teachers, who must correct this misinformation for their students. They also set the dangerous precedent of placing official statements by public officials at odds with scientific accuracy and good educational practice.

What follows is a line-by-line analysis of the scientific accuracy of the disclaimer:

This statement is a deliberate attempt to mislead young readers as to the scientific standing of evolutionary biology. Within the scientific community, evolution is anything but a controversial theory. Rather, as the National Academy of Sciences states, evolution is "the most important concept in modern biology." Saying that "some" scientists present evolution as the explanation for the origin of species is equally misleading. It's a bit like saying that "some scientists believe" that matter is composed of small units they call atoms. That statement would also be true, but would convey a false sense of uncertainty regarding atomic theory. A more accurate statement would tell students that evolution is accepted by the vast majority of life scientists around the world, including every leading scientific organization in the United States as well as the National Academy of Sciences, as the best available explanation for the origin of species.

Absolutely correct.

This statement shows a serious misunderstanding of the scientific usage of the terms "theory" and "fact." A theory in science is an explanation of a natural phenomenon, and a fact is a confirmed observation. A example of a fact would be that there is great consistency in the sequence of fossils in the fossil record, with no major branch of the tree of life being out of order (fossils of mammals are not found in the Devonian age of fishes, for example). Another fact is that living species tend to be found where their fossil ancestors are also found. We explain these and many other confirmed observations, or "facts," with the explanation that living things share common ancestors, from which they have diverged. This explanation is the "theory" of evolution, an extremely strong and well-supported theory. The disclaimer will confuse students about these important elements of science. Theories explain facts, and unlike the impression given in the disclaimer, this means that theories are more important than facts.

The disclaimer also will confuse students about the nature of science by implying that science can be done only if one can directly observe phenomena. Actually, many scientific discoveries are made about phenomena that are not directly observable, such as those that are too far away (astronomy), or too small (particle physics) as well as those that occurred in the past (geology and evolutionary biology.) Just because "no one was there to see it" does not mean something cannot be studied scientifically, or that we cannot have confidence in our explanations.

Ironically, this means that well-written science textbooks place even less confidence in current ideas about how life may have originated than the disclaimer does. Typically, ideas about the origin of life are regarded as hypotheses, placing them a rung lower on the scientific hierarchy of ideas than the textbook committee was willing to do. The disclaimer makes a serious error by elevating current hypotheses about the origin of life to the status of theories (which would mean that they are generally accepted by the scientific community).

Once again, the writers of the disclaimer do not use the scientific meaning of terms. Evolutionary biologists use "microevolution" to refer to the processes (most of them having to do with genetics) that produce evolutionary changes in populations of species: natural selection, mutation, migration, genetic drift, and other mechanisms. Writers of the disclaimer apparently share this definition, and are correct in noting that we can observe these processes at work.

Evolutionary biologists use "macroevolution" to refer to a range of issues having to do with the pattern of evolutionary change: how groups are related to one another above the level of the species, and issues such as rates of change, the behavior of lineages over time, and so forth. But in the disclaimer, the term "macroevolution" means merely the general principle of evolution: that living things have descended with modification from common ancestors. This is not what macroevolution means in science, and it misleads and confuses students to use the term as a synonym for evolution.

Clearly, the writers of the disclaimer want students to reject the idea that living things share common ancestry, and they are in the bind of having to accept well understood and widely-demonstrated processes of evolutionary change, which over time, would result in evolution. The reason for this is at bottom a sectarian religious belief known as "special creation": that all living things were created in their present form and did not descend with modification from common ancestors. Special creation is not supported by science — regardless of how the disclaimer authors attempt to redefine scientific terms.

Evolution is not rigidly divided into two types of change, "microevolution" and "macroevolution," as the disclaimer states. Macroevolution, for example, may be used to refer to the process of speciation, to major evolutionary transformations, or both. Most importantly, it is commonly accepted among evolutionary biologists that "microevolutionary" changes (whether caused by natural selection or by genetic drift) can accumulate in such a manner that they ultimately cause reproductive isolation, and hence lead to speciation or "macroevolution." Has macroevolution "never been observed?" A 1997 study by Reznick et al in the journal SCIENCE (Volume 275, 28 Mar 1997, pp. 1934 - 1937) evaluated the observed rates of evolutionary change in populations of guppies (Poecilia reticulata) in the wild. These researchers observed rates of evolutionary change "up to seven orders of magnitude greater than rates inferred from the paleontological record." In other words, field studies of natural selection show rates of change that are more than large enough to account for the "macroevolutionary" changes documented in the fossil record. This is just one of many studies that cast serious doubt on the assertion that macroevolution has "never been observed."

This statement is false on two accounts. Evolution is not a "random" process, and to characterize it as such seriously misleads students. Natural selection, the most important force driving evolutionary change, is not random at all, but an observable, verifiable process that fine-tunes variation in populations of a species to the demands of the environment in which they live. It is true, of course, that variation in a species arises from sources such as mutation and sexual recombination, which are inherently unpredictable. Therefore evolution, like any historical process, can be influenced by random forces.

But a larger problem with this statement is the attribution to evolution of an idea outside of science. Whether evolution is "undirected" or "directed" is a matter of theology or philosophy, not of science. Writers of the disclaimer wish students, most of whom are religious, to believe that acceptance of evolution is incompatible with faith. This is demonstrably false: far too many scientists (and clergy) accept both evolution and a God who creates through evolution. Students should not be taught the evolution equates with atheism, and, incredibly, that is exactly what this portion of the disclaimer says.

It is absolutely true that there are "many unanswered questions about the origin of life," and most biology textbooks point this out in far greater (and more accurate) detail than the disclaimer. Indeed, there are unanswered questions in each and every area of biology, making biology an exciting and vigorous discipline. The disclaimer, however, does not seek to draw student attention to unanswered questions in biochemistry, ecology, or physiology, but singles out evolution for special attention, as if it had special difficulties that other fields do not.

Scientifically, this is not correct, and the next few sentences of the disclaimer show just how badly-informed its authors were:

This statement is false, and seriously misleads students as to the actual natural history of this planet. The term "major group" is without scientific meaning. Many students, for example, might regard the mammals as a "major group." Mammals, however, did not appear during the Cambrian explosion, but rather in the Triassic, nearly 300 million years later. The same can be said of birds, insects, reptiles, and amphibians, each of which are "major groups" in the ordinary meaning of that term, and none of which appeared in the Cambrian period. Clearly, the authors of the statement could have prevented such confusion by referring only to the animal phyla instead of "major groups."

Unfortunately, even if they had done so, the statement would still be false. All animal phyla did not originate during the Cambrian. Compounding this serious mistake, the authors of the disclaimer seem to be unaware that the first multicellular animals appeared on earth during the Ediacaran period, and many predate the Cambrian by more than 100 million years.

This curious statement requires students to determine what is meant by a "major group" and also what is meant by "a long time." Neither term, of course, has any scientific meaning. One might regard 100 years as a "long time," and it is indeed true that no new phyla have originated in the last 100 years. However, by standards of geologic time, one of the most important "major groups of living things" did indeed originate recently. Flowering plants (the Anthophyta) appeared for the first time in the Cretaceous, roughly 125 million years ago. Against the 4.5 billion year timescale for this planet, flowering plants appeared only in the last 3% of geologic history, which certainly qualifies as recent. Therefore, this statement, which overlooks the recent evolutionary appearance of flowering plants, is wrong.

This statement is false. The fossil record is, in fact, replete with splendid examples of transitional forms, as the National Academy of Sciences has taken pains to point out:

This is an excellent question, and students would be well-advised to keep it in mind as they study biology. They may wonder why, for example, the "complex set of instructions" referred to by this sentence includes the genetic remnants of an ancient infection by an HIV-like virus. The curious fact about these genetic remnants is that they are found not only in humans, but in our closest primate relatives, indicating that these viral DNA sequences entered the genome roughly 30 million years ago. As the investigators who made this discovery pointed out, the existence of identical sequences in closely related species is "very good evidence" that we share a common ancestry with these other primates. As the National Academy has written: "compelling lines of evidence demonstrate beyond any reasonable doubt that evolution occurred as a historical process and continues today."

At last, some excellent advice!

 

---

Summary

By any standard, this disclaimer fails even a modest test of scientific accuracy. Twelve statements are included in the disclaimer. Of these, only five are free of major errors. Three are seriously misleading, and four are downright false. If a biology teacher were asked to mark a written project that contained only five correct statements out of twelve, he would, at best, calculate a score of 42% – a failing grade.

Our students deserve better.

To be sure, the disclaimer's admonition that students study hard and keep an open mind fits the best traditions of scientific study. But keeping an open mind does not mean that students should intentionally be taught nonsense, nor does it mean that we should pretend to know less than we do about the natural history of this planet and the origins of living species, including our own. Healthy skepticism is at the core of a scientific education, but elevating falsehoods and half-truths to the status of scientific theory most definitely is not.

I would argue that any textbook, indeed, any course in the biological sciences should tell students the plain and simple truth, as described in 1999 by the National Academy of Sciences. That is, to put it in a single sentence, that "Biological evolution is the best scientific explanation we have for the enormous range of observations about the living world."

 

Kenneth R. Miller
Professor of Biology
Brown University
Providence, RI 02912