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from The Textbook Letter, March-April 1993

Reviewing a middle-school book in the Prentice Hall Science Series

Evolution: Change Over Time
1993. 112 pages. ISBN of the teacher's edition: 0-13-986563-2.

Science in Boxes

Kevin Padian

At a time when scientists and science educators are calling for textbook reform and for instructional materials that will use unifying ideas and overarching theories to integrate the various scientific disciplines, Prentice Hall is going the other way. This company is chopping science into pieces and putting the pieces into separate boxes. Macmillan/McGraw-Hill, Scholastic, Encyclopaedia Britannica and Scott, Foresman (to name only a few) appear to be doing the same thing.

In Prentice Hall's case, the boxes are nineteen books with titles such as Heat Energy; Matter; Cells; Exploring Earth's Weather; Dynamic Earth; Chemistry of Matter; Sound and Light; Evolution; Exploring the Universe; Heredity; and Electricity and Magnetism. In the teacher's edition of each book, Prentice Hall says that this collection provides "flexibility" and will allow the teacher to choose only "those topics you want to teach."

Whether this approach represents a marketing strategy or a misguided attempt to make things convenient for teachers, its effect (intended or unintended) is to turn "science" into a fragmented, disconnected enterprise. To be sure, publishers were already doing a darned good job of isolating science from ideas, and from other disciplines, even before this science-in-boxes approach was invented. But now teachers will have to work twice as hard to show the integration and coherence of science.

I am one of the people who wrote and edited California's current Science Framework, published in 1990. I also served on the panel that evaluated textbooks during California's most recent adoption of curriculum materials for science courses, conducted in 1992. In the Framework we declared that science should not be presented as an enterprise disconnected from society or from other endeavors, and we said that instructional materials should emphasize how the many branches of science are unified. In the materials that were submitted for the 1992 adoption, most publishers bent over backwards to present "Science, Technology, and Society" tie-ins, along with a host of activities that tried to link science with language arts. But the most important effort that we made in writing the Framework -- our attempt to ensure that the science curriculum would show the interconnectedness of scientific fields and scientific methods -- was completely frustrated by the science-in-boxes gimmick.

The California Framework stresses that instructional materials should not give the impression that chunks of scientific knowledge can be taught in any order, or that large chunks can be omitted at the teacher's option. Instead, textbooks and other materials must help students understand that there is a logic to science and that there are "big ideas" (or theories) overarching the simpler, factual information. This requirement reflects a philosophy that is shared, as far as I can tell, by all the scientific organizations that are concerned about the presentation of science to young students. But science-in-boxes thwarts this philosophy by physically fragmenting and randomizing scientific topics. What's worse, some publishers are explicitly telling teachers that they can teach the fragments in any order that they like, and that they can even omit some fragments altogether. (Recall Prentice Hall's "flexibility" claim, noted above.) Does this sound like an integrated, logical science program?

The science-in-boxes format virtually ensures that students will not see the links among topics and fields, will not be able to discern which topics are more important than others, and will not be able to follow the ramifications of an overarching theory as they encounter new concepts and disciplines. In my judgment, the science-in-boxes approach is even worse than what we had before. It is insidious and perverse. In my opinion, students and educators are being misled and shortchanged, both intellectually and financially.

Now a question that brings us back to the Prentice Hall series and to the book under review. In a science-in-boxes series, does the science within each book have to be poor? Judging from Evolution, the answer seems to be that it doesn't have to be any worse than a typical part of any typical textbook. In other words, the answer seems to be yes. But some parts are more successful than others.

The writers of Evolution have generally taken an open, frank approach to evolutionary biology, and they have generally avoided the weasel-wording and issue-ducking that we have seen in some other middle-school books. The concepts that they cover range through many lines of evidence, with a good logical flow. But the text seems schizophrenic: It gives me the impression that its various sections have been written by different people, only a few of whom know what they are talking about.

The three chapters -- "Earth's History in Fossils," "Changes in Living Things Over Time" and "The Path to Modern Humans" -- vary noticeably in style and in the quality of their content. The first two perpetuate some bad habits, and they could have benefited from review by a geologist, a paleontologist and an evolutionary biologist. (More than 30 "content reviewers" are listed in the front of the book, but needless to say, the list doesn't appear to include anyone who reasonably could have been expected to have scientific expertise.) The third chapter is particularly strong, though it falters when it tries to tell why scientists differ in their interpretations of human evolution. In terms of writing style, the text generally consists of the usual, patronizing pabulum that is common in middle-school books. Mercifully, however, the writers don't feel obliged to begin every sections with a bogus "relevance" passage that will "motivate" students. The illustrations are generally effective and are tied to the text, though the paintings of prehistoric scenes are a bit garish for my taste.

The prose in the first two chapters is distinctly different from that in the third. The writers of chapters 1 and 2 evidently do not know the difference between the terms evolve and develop, so they use them interchangeably. In chapter 1, a chart of the history of life (pages 30 and 31) manages never to use the word evolve, though plenty of organisms "appear" or "develop." In the same chapter, a long narrative of the history of life (on pages 29 through 41) uses evolve only once. And the writers of the first two chapters continually say that scientists "believe" this or that, as if scientific work depended on leaps of faith, instead of on the examination of evidence.

The writing changes dramatically in chapter 3, in which I have found only one use of "believe." As far as presentation is concerned, this chapter is exemplary -- a model of how to use language in presenting science to students. Whoever wrote it should be made an editor and should ride herd on the rest of Prentice Hall's people.

Now, what about scientific content? In choosing the sequence and scope of topics to be treated in Evolution, the writers seem to have meant well. In chapter 1, they consider the rock record and show how fossil evidence creates a need to explain large-scale change over time. About half of the chapter is given to the aforementioned narrative of the history of life, a narrative that is choppy but readable. Unfortunately, the list of "Outside Teacher Resources" given in the teacher's edition is execrable and worthless. The writers have wasted an opportunity to help teachers and students alike.

Chapter 2 moves from the fossil record to the concept of evolution and then to Lamarck, whose ideas are presented here more clearly, and at greater length, than in most comparable books. But the writers don't do an adequate job of showing how Lamarck's thoughts about inheritance and about use and disuse were rooted in the scientific knowledge of his time, and they don't adequately distinguish Lamarck's views from those of Darwin and other scientists. (Note to the editors of middle-school science books: Isn't it time to ditch Lamarck entirely? Nobody really gets him right, and much has happened in evolutionary biology since his day.)

The text moves on to homology, but the writers are confused: They evidently don't know that homologies are defined on the basis of ancestry but are recognized on the basis of criteria such as position, ontogeny and histology. So they say (on page 52) that homologous structures "evolve from the same ancestral body parts" -- fins giving rise to arms, presumably. The glossary simply repeats this mistake. (About a third of the glossary's 27 definitions are incorrect or misleading.)

Embryology is poorly explained, in text that concludes by saying that "many living things share a common ancestor" (emphasis added). Next come passages that make a bogus separation between "Chemical Evidence of Change" (which involves DNA) and "Molecular Evidence of Change" (which involves unspecified proteins.) The passage about "chemical evidence" is typical wheel-spinning. A better explanation might have been possible if the editors had not given space to an irrelevant painting (page 56).

There are dozens of other mistakes in the first two chapters. The writers apparently don't understand hybridization, and they seem particularly confused about what they call "hybrid species." (See the "Science, Technology, and Society" note on pages 46 and 47 of the teacher's edition.) They profess that Darwin used adaptation to demonstrate evolution. (He didn't.) They ignore the fact that the same argument was used by advocates of special creation. They say that Darwin and Wallace proposed "the theory of evolution" (page 58). They misunderstand the significance of the peppered moth (page 61), confuse the terms niche and adaptive zone (page 62), and misrepresent the issues and evidence involved in the question of whether the ancient dinosaurs were "warmblooded" (page 63).

The diagram of vertebrate phylogeny (page 66) is outdated and wrong, and the writers seem not to have heard of the advances that have been made by cladistic analysis of phylogenies, though this is an exciting subject and a wonderful thing to present to students. On page 67 students read that "birds evolved from the most famous of the dinosaurs, Tyrannosaurus rex," and on the same page the teacher finds a pedagogic note that associates the bird lineage with "the same dinosaur line that eventually gave rise to Apatosaurus and its kin." Both claims are false. The writers' description of punctuated equilibrium, involving bursts of adaptive radiation during short periods of time, is completely wrong (page 70). In the teacher's edition, though, the same page has a pedagogic note about a mysterious "second theory developed by Stephen Gould and Niles Eldridge." The second man's name is really Eldredge, but the note accurately describes punctuated equilibrium.

And so on, with all the typical silliness that we have come to associate with the textbook industry.

My advice to Prentice Hall is to get some expert help, especially with topics in the first two chapters. My advice to educators is to avoid materials that use the science-in-boxes approach. You'll just have to hire a curriculum specialist to reintegrate the concepts that the science-in-boxes writers have dispersed and hidden in their collections of crates and bells and whistles.


Kevin Padian is a professor in the Department of Integrative Biology at the University of California at Berkeley, a curator in that institution's Museum of Paleontology, and a fellow of the California Academy of Sciences. His scientific specialties include studies of the ancient dinosaurs.

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