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Teach 'strengths and weaknesses' of evolution?

See that bet and raise it


June 21, 2008

As you may have read in The New York Times, the Texas State Board of Education this summer will consider whether to require teaching the "strengths and weaknesses" of evolutionary theory in the biology curriculum. The science-education community rightly sees the "strength and weaknesses" language as the latest ploy by creationists to undermine the teaching of evolution, the foundation of modern biology.

The creationists have no legitimate scientific cards to play. The "weaknesses" they hope to bring into the classroom amount to the two of diamonds and the three of clubs, amateurishly daubed with white paint and grease pencil in the hope they might pass for a pair of aces. Alas, a lot of people are easily fooled.

But the bad counterfeits are not the only cards in the game. There's plenty of drama in the honest hands. I think it would be both possible and beneficial to integrate that drama more fully into the science curriculum by going "strengths and weaknesses" one better.

Before delving into that notion, I should explain why the "strengths and weaknesses" rule would be bad policy. In practical effect, if it is adopted, any biology classroom could be held hostage by a smart-alecky brainwashed kid regurgitating alleged weaknesses that have been thoroughly refuted by real science. Granted, a well-prepared teacher could turn these interruptions into opportunities to advance students' ability to think critically: Some alleged weaknesses sound plausible to the uninformed, and by patiently, meticulously refuting them a teacher can help students appreciate that what seems plausible on the surface does not necessarily hold up on deeper study. But not all biology teachers are prepared (or inclined) to neutralize the torrent of creationist snake oil that the "strengths and weaknesses" rule would release. For those who are prepared, the time wasted swatting at Nerf balls could greatly hinder the teaching of a coherent biology curriculum.

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Worse, the whole process could leave many students with the impression that science is just a matter of opinion: Some people say the Sun revolves around the Earth; others say the Earth revolves around the Sun; whatever you decide is fine. What would be next? Allowing history classes to be hijacked by Holocaust deniers?

Despite all that, I think that the prevalence of misunderstanding about evolution underscores a need in the science curriculum -- and maybe in other curricula as well -- for a teaching approach that might be sellable as "strengths and weaknesses-plus." 

The underlying problem is this: Although the United States does a terrific job of producing scientists, we do a lousy job of producing scientifically literate non-scientists. Obviously we haven't done an adequate job of inoculating non-scientists against creationist pseudo-science, but neither have we prepared them to properly weigh and interpret news reports about the findings of legitimate science.

The biology classroom, like the physics and chemistry and mathematics classroom, is mostly preoccupied with imparting factual knowledge and skills. That's as it should be. There's a lot of basic knowledge that kids have to learn if they're going to be prepared for college science courses. The danger in this approach is that science can seem like a collection of settled knowledge rather than what it really is -- the disciplined pursuit of knowledge through a thicket of conceptual and practical difficulties. For students who are not already infected with the thrill of the chase, the standard way of teaching can make science seem like a bore.

Looking back at my own dismal experiences in high school biology, chemistry and physics, I wish another way had been available to me and others who were not aiming to become scientists but who would need to have some degree of science literacy and grounding in the scientific outlook in order to be full participants in modern culture.

As a supplement to the standard core science curriculum, I'd like to see a historical approach, a required course or a major unit within each standard laboratory course that immerses students in the ferment and questions and doubts and disagreements and dead ends and breakthroughs that led to a few key scientific developments. Such a curriculum would not aim for breadth, but for depth. It would not try to fill young heads with the greatest possible number of facts, but with the greatest possible understanding of science as a historical process and an intellectual pursuit.

Everything that is now known was once unknown. Every theory that is now canonical was once controversial. Every concept that today seems obvious was once counterintuitive. Much that once seemed obvious or plausible turned out to be wrong. Many questions remain unanswered.

What is the physical phenomenon that we perceive as light? If we know that sound is a wave that is transmitted through the medium of air, then light, by plausible analogy, must be a wave that is transmitted through a physical medium. That medium, dubbed the "luminiferous aether," is hard to detect but it must be there. Except that the experiments of Michelson and Morley demonstrated that it isn't. So maybe light is not a wave, but a particle. Obviously it has to be one or the other. Except that the two-slit experiment showed that light behaves like a particle if it passes through a single slit, but like a wave if it passes through two slits. How can we wrap our heads around that?

Teaching science as a developing narrative that never quite comes to a definitive end can be more interesting to students and more revealing of the culture of science than an approach that treats science as a static body of present knowledge.

Even a one-semester course ought to be able to take students through three or four major episodes, drawn from several fields. One episode certainly should come from biology, beginning with the observations that forced the conclusion that evolution happened, continuing with Darwin's theory of natural selection propounding in broad terms the framework of evolution, taking a detour into Mendel's genetics and the growth of knowledge of the mechanisms of descent with modification at the subcellular level, bringing those two strands together in what is called the Modern Synthesis, and concluding with the present state of knowledge, including some debates and lingering questions -- about the conditions that are favorable to speciation, for example. The claims of creationism and "intelligent design" would have a role in a this curriculum -- as examples of specious arguments and willful ignorance.

This story can be told in a way that conveys the general plot lines and flavor of the narrative, reserving for traditional lab courses the mass of detailed knowledge and skills. For students who are not headed for careers in science, the big picture is more important to know, and more likely to be remembered, than the detailed facts, which are likely to be forgotten immediately after the final exam, if not before. To the extent that the details are included in a historically oriented science curriculum -- and a fair number would have to be -- they're more likely to be retained if they're presented in a narrative context that gives them meaning.

The body of scientific knowledge has grown enormously and bewilderingly through specialization. In the 19th century, physics was a fairly compact field, the major landmarks and general contours of which were accessible to educated lay people. Today, the American Physical Society has 14 major divisions -- polymer physics, condensed matter physics, physics of beams, etc. -- and 10 "topical groups," including "shock compression of condensed matter" and "few-body systems."

At the same time that the body of knowledge has grown beyond general comprehension, science has become increasingly important in public policy and politics. "Common sense" is a highly unreliable guide to the decisions that policy makers and voters have to make regarding climate change, energy, transportation, water, food production, health insurance -- or the teaching of evolution in the schools. (Albert Einstein defined common sense as "the collection of prejudices acquired by age 18.")

Somehow, citizens have to be drawn into a fuller understanding of the culture and practices of science so that they can be better prepared to navigate these issues and whatever others might someday arise, and to be less vulnerable to charlatans and ideologues.

The body of scientific knowledge is rather like the rapidly spreading and increasingly confusing map of a sprawling city. Only a few need to memorize the location of every street. But everyone needs to internalize a perceptual map of the major arteries and neighborhoods and landmarks, and learn to read the street signs.

Mike Greenberg

A cultural aside:


One byproduct of American democratic, egalitarian values is intellectual populism, a tendency to distrust specialized knowledge, especially if it challenges prejudice, and to resent the prestige and resources of specialized priesthoods and their temples -- the elite universities, research laboratories, think tanks, foundations. Populism accords moral superiority -- and often even intellectual superiority -- to the common sense of the common man over the specialists' fancy ideas and subtle thinking.

Sometimes distrust and resentment are fully justified by the facts, but discovering the legitimate grounds for distrust of specialists is nearly always the work of other specialists.

The science priesthood clearly is one object of populist resentment, but I think another is the body of scholarly biblical research that demolished all intellectually respectable support for biblical literalism or inerrancy. Seminaries and universities associated with the mainstream, European-born Christian denominations harbored that research and were influenced by it. That portion of Christianity does not generally view the first chapter of Genesis as literal fact and thus has no brief against evolutionary thinking. In the United States, the old European denominations have something of a high-end, elite reputation relative to their American-born or bred populist counterparts -- largely non-denominational, but also including denomination such as the Southen Baptists -- which tend to take the bible as literal truth. I have long suspected that when Christian populists attack evolution, their real target is the Christian intellectual tradition itself.