Critique: Exploring "Explore Evolution"
The Introduction is laden with errors about biology, evolution, and what science is and how it is practiced. Beginning with the definitions of evolution, Explore Evolution misstates theoretical and factual components of evolutionary biology, omits other key evolutionary mechanisms, and misrepresents professional scientists. As is common in creationist literature, to present a veneer of scientific respectability for the views presented, Explore Evolution cites for student reference technical research requiring scientific and mathematical background that high school students simply will not have. It also misrepresents the nature of science in many ways, contending (among other errors) that evolutionary sciences are qualitatively different in their scientific approach. The book further distorts students' understanding of science by pretending that the classroom is where scientific debates ought to be resolved.
p. 3: "[I]n the historical sciences, neither side can directly verify its claims."
Philosophers of science dispute Explore Evolution’s claimed distinction between two kinds of science, and do not hold historical claims to be any less testable than others. But marginalizing evolution as an allegedly different kind of science allows the authors to cast doubt on its validity &mdash an approach commonly encountered in creationist sources.
p. 5: "The best explanation will be the one that explains more of the evidence than any other."
This is an incomplete and misleading view of science. To be scientifically useful, a hypothesis must be more than explanatory or verifiable, it must make predictions which lead us to new observations. In addition, Explore Evolution omits the means by which scientists actually evaluate scientific explanations. The focus on good science as explaining "more of the evidence" is commonly promoted in the intelligent design (ID) literature, where emphasis is on the "weaknesses" of evolution &mdash i.e., what evolution allegedly does not explain. From the perspective of an ID supporter, the lack of an evolutionary explanation for a phenomenon is evidence for God's involvement.
p. 8: "…three major uses of 'evolution.'"
Antievolutionists have a problem. It would be absurd to deny the phenomenon of natural selection, which is well-supported by much evidence, and they don't. Similarly, observations demonstrate that populations of organisms can change from generation to generation, and over many generations. Natural selection and change over time, then, have to be acknowledged as real entities &mdash yet such ideas are part of modern evolutionary biology. The solution: separate these "acceptable" ideas from the component of evolution they find most troublesome: the idea that living things share common ancestry (rather than having been specially created in their present form). The authors thus carve up evolution into three artificial components: "change over time", "universal common descent", and "the creative ower of natural selection", in order to single out the idea of common descent, even though all three ideas are related.
Alas, even here, they create a caricature, referring to "universal common descent" (i.e., a single organism at the base of the tree of life). The validity of common ancestry does not stand or fall on whether there is a single organism to which all living things can be traced. Whether all mammals share a common ancestor, for example, does not depend on whether mammals and all other organisms descended with modification from a single common ancestor. But claiming that this universal ancestor is essential allows the authors later in the book to cite some scientists who propose a more complex root of the tree as providing "evidence against evolution". The goal here, as always in this book, is to cast doubt about the validity of evolution. The unstated but obvious alternative, of course, is special creation.
p. 8: "Some people use the term evolution to refer to a cause or mechanism of change. When evolution is used in this way, it usually refers to the mechanism of natural selection."
The authors would do students a service by correcting rather than reinforcing the errors of "some people" (unidentified, but not likely to be scientists). The statement is simply wrong. A mechanism is not the same as the phenomenon that it affects. Evolution is the inference of common ancestry of living things, whereas natural selection is a powerful mechanism that produces adaptation, and therefore contributes to differences as seen in the tree of life. But even if "some people" use evolution to refer to natural selection as a mechanism of change, this is a greatly reduced and inadequate understanding of how evolution is brought about. Students cannot "explore evolution" without discussing mechanisms like neutral drift, gene flow, mutation, and recombination. Explore Evolution never presents a full range of mechanisms, a lapse which blocks inquiry and exploration.
p. 8: "…all modern life forms emerged and developed from the first one-celled organism."
Again, the number of organisms at the base of the tree of life is not critical to the concept of common ancestry. Scientists cited by Explore Evolution are not questioning the idea of common ancestry, but propose that there was a period when early life swapped genes so frequently as to form a common ancestral population of cells, from which all modern lineages split. Thus it would be impossible to recreate the exact common ancestor of all living things (other scientists disagree). In any event, there is evidence that much gene swapping took place early in the history of life (see illustration at the left) making the base of the tree of life spaghetti-like. This is irrelevant to whether and when humans and chimpanzees shared a common ancestor, or what the common ancestor of plants and animals looked like.
p. 9: "[Scientists disagree whether] natural selection [can] produce fundamentally new organisms."
Indeed, evolutionary biologists debate the strength of natural selection in producing new structures and body plans &mdash but the debates are over whether natural selection alone or combined with other mechanisms produces such changes. No one is debating whether such changes occur, but Explore Evolution wishes to leave the student with the belief that 1) natural selection is the be-all and end-all of evolutionary mechanisms, and 2) without natural selection as a mechanism, common ancestry fails as a theory. The book ignores the many additional mechanisms and processes affecting evolution, to the detriment of the students' understanding.
p. 10: "According to these scientists, the history of life should not be presented as a single tree, but as a series of parallel lines representing an orchard of distinct trees."
"These scientists" are found only on the pages of creationist journals. Creationists have long proposed that God specially created the "kinds", which then adapted and branched "within the kind". Although Explore Evolution does not use biblical terminology, the trees in the orchard (see illustration, left) are created "kinds", as described in the Bible. Mainstream science knows nothing of this orchard; standard science proposes a single tree of life of related organisms, and sees no evidence for separate entities.
Nature of Science: High school biology classes form the foundation of a student's understanding of how science works, not just of how the living world works. Explore Evolution badly misrepresents the way science is practiced.
Evolution: It is unacceptable that Explore Evolution misdefines evolution, and unacceptable that basic evolutionary mechanisms are ignored entirely. This mishandling of the central concept that the book claims to explore should disqualify it from use in any classroom.