Teaching Evolution in the U.S.A.


From the Marshall Memo #443

In this thoughtful article in American Educator, Michael Berkman and Eric Plutzer of Pennsylvania State University say that despite a national consensus on the need to improve student learning in STEM subjects – science, technology, engineering, and mathematics – our schools have a long way to go. One of the worst areas – highlighted in the 2011 National Research Council’s Framework for K-12 Science Education as one of the four core ideas in the life sciences – is evolution. 

Scientists are very confident about the theory of evolution. In 2008, the National Academy of Sciences said, “there is no controversy in the scientific community about whether evolution has occurred. On the contrary, the evidence… is both overwhelming and compelling.” Berkman and Plutzer concur: “Although the details are subject to revision based on new and better evidence, the fundamental hypothesis of common ancestry has been verified so many times, by so many independent kinds of experiments spanning different scientific specialties, that there is no longer serious debate that evolution has occurred. This justifies confidence in the claim that, as much as any sound scientific statement, evolution is true.” 

But many Americans are skeptical. Isn’t evolution just a theory? Aren’t scientific theories tentative and open to challenge and revision in light of new facts? Shouldn’t schools be teaching both sides of the story? “[S]uch a view,” say Berkman and Plutzer, “fails to appreciate that when a theory survives decades of rigorous testing – as evolution has and its opposing assertions have not – scientists are justified in their high confidence in the theory. It is only after findings have been replicated many, many times that scientists begin to consider them ‘facts.’ Modern evolutionary science rests on a foundation of such facts.”

Charles Darwin was an exemplar of this kind of scientific research and thinking; his 1859 book, On the Origin of Species, was 22 years in the making. “Meticulous in its presentation of evidence,” say Berkman and Plutzer, “written in a style that remains accessible to nonexperts, and rich in its description of the natural world, Darwin’s compelling argument about common ancestry offered a theoretical understanding of what naturalists had long observed: dogs resemble wolves, housecats resemble tigers, and apes resemble human beings. To read On the Origin of Species is to be invited inside the mind of a scientist who questions everything, responds fully to actual and anticipated challenges to his conclusions, and understands that his argument will not stand or fall based on any individual finding.” 

Darwin’s theory is based on three well-established processes that lead to changes in populations of living things: 

  • Individuals within a population are genetically diverse and variations can be inherited. 
  • Population growth is limited by the food and environmental features in a particular habitat, and as a result, not all individuals survive. 
  • Those individuals with traits best suited to get food and cope with the environment are the most likely to survive and reproduce, passing along those advantageous traits to their offspring.

Darwin had the theory right but didn’t know exactly how traits are passed along. It was only after Gregor Mendel’s work on heredity, and the development of population genetics in the 20th century, that scientists filled in the details, explaining how mutations occur, how new genetic features spread through a population, and how, given time and isolation, entirely new species emerge. 

Evolutionary theory explains the extraordinary diversity of life on earth and provides “a cornucopia of testable hypotheses,” say Berkman and Plutzer. Schoolchildren can look at branching diagrams of species and see how bats are more similar to mice than to birds and mastodons are more similar to modern elephants than to modern rhinos. And these diagrams can be checked against DNA evidence and compared to the fossil record, confirming that primitive species (starfish, for example) did, in fact, live earlier than more advanced species (bony fish). Fossils also show us transitional features, for example, the wrists, elbows, and necks of Tiktaalik fish, which lived between 365 and 380 million years ago in an area with freshwater streams. Additional evidence comes from the field of developmental evolutionary biology, which has found striking similarities in vestigial embryonic features across species. 

So why did 40 percent of U.S. adults say in a 2010 Gallup Poll that human beings were created “pretty much in their present form at one time within the last 10,000 years or so”? Why did 39 percent say it’s not true that “Human beings, as we know them today, developed from earlier species of animals” (National Science Foundation Science Literacy survey, 2010)? Why did 45 percent reject the idea that “Evolution is the best explanation for the origins of human life on earth” (Pew Forum poll in 2007)? 

Clearly the scientists’ message isn’t getting through. In addition, a significant number of Americans don’t want the messengers (science teachers) to teach that evolution is true. A 2005 Pew Research Center poll found that 57 percent of Americans say evolution should be taught “along with” creationism, with only 22 percent supporting teaching only evolution. Even in Massachusetts, the most pro-evolution of all the states, only 50 percent support the exclusive teaching of evolution. “Given that public sentiment is at odds with the nation’s scientific organizations and in direct conflict with the rulings of the U.S. Supreme Court,” say Berkman and Plutzer, “it cannot be easy to be a high school biology teacher.” 

What are the origins of this widespread resistance to evolution? Berkman and Plutzer trace it back to the birth of fundamentalism in the mid-1800s, which asserted the literal truth of the Bible’s creation story and declared war on evolution. By the 1920s, fundamentalism had spread beyond its southern Evangelical roots to other denominations and to all parts of the nation, and the teaching of evolution in public schools was seen as a dangerous idea. Even though the clergy and leadership of mainline Protestant and Catholic churches accept the idea of evolution, 35-45 percent of their followers believe evolution is false. Among major American religious groups, only adherents of Judaism overwhelmingly accept evolution. 

Confronted with court rulings that creationism cannot be taught in public schools, anti-evolutionists have made a tactical shift to “intelligent design.” They argue that the odds are close to zero that natural selection and mutation alone could account for complex biological features (mainstream evolutionary biology disagrees). They present a three-part argument: 

(a) evolution is scientifically controversial; (b) evolution and religion are incompatible; and 

(c) to be fair, both sides must be taught. This argument has been widely accepted, including by many high-school biology teachers, even those who don’t consider themselves anti-evolution.

Berkman and Plutzer surveyed 900 ninth- and tenth-grade biology teachers in 49 states, asking about their classroom practices and experiences, personal beliefs, and pre-service education, and how they respond to student comments and questions on evolution. Based on the responses, teachers fell into one of three groups:

Evolution advocates (28 percent) – These teachers tell their students that scientists overwhelmingly say evolution is a fact (while saying that scientists disagree on specific mechanisms), don’t present it as a theory in crisis, treat it as a major unifying theme in biology, and believe it’s impossible to offer an excellent biology course without including Darwin and evolutionary theory. Many of these teachers use evolution to show how science and religion ask different questions, thereby countering the notion that evolution is in conflict with religion. 

Creationism advocates (13 percent) – These teachers minimize the teaching of evolution and spend at least an hour presenting creationism or intelligent design as a valid scientific alternative to evolution, stating that many reputable scientists agree. One Illinois teacher told students that neither evolution nor creationism can be proved or disproved since “man was not present at the beginning to satisfy his or her curiosity as to the nature of the situation.” 

The cautious middle (60 percent) – These teachers use a range of strategies. About 10 percent are closet creationists; they don’t advocate, but in response to a student’s question or comment, they’ll validate creationism as credible science. Eighty-five percent accept evolution but avoid controversy by implicitly accepting the three-pronged argument of creationists. They do this by (a) distinguishing between micro- and macroevolution (saying evolution only applies within species); (b) saying they are required to teach evolution and students must learn it because it will be on state tests (this dissociates everyone from the validity of the science); (c) “teaching the controversy” and encouraging students to use “critical thinking” to make up their own minds (this plays into creationists’ hands by putting creationism on the same playing field as evolution); and (d) scheduling biology units at the end of the semester so evolution is covered in a big rush. 

“Whether the teacher is trying to introduce creationism, hoping to avoid controversy, or simply manifesting great confidence in students’ ability to learn by exploration,” say Berkman and Plutzer, “the effect is the same. One teacher put it this way: ‘I encourage my students to gather as much information as possible and make their own conclusions.’ But it is simply not realistic to expect that, with only 10-15 class hours devoted to evolution, students are really equipped to assess and perhaps reject the thousands of peer-reviewed scientific papers that form the empirical foundation of evolutionary theory. This approach tells students that science is not a cumulative body of highly technical knowledge, but is instead something that has some element of personal preference, like whether Claude Monet created more beautiful paintings than Paul Cézanne.”

Berkman and Plutzer believe that teachers who inhabit the cautious middle play a bigger role in hindering scientific literacy than teachers who explicitly advocate creationism. The tactics they use to avoid controversy are exactly what creationists use to make their case. Their approach seems fair-minded, but they fail to explain evolution properly and don’t help students reconcile the differences between religion and science. 

Why don’t these teachers do a better job with evolution? “Our research suggests that many teachers do not feel like they have the expertise they need to confidently teach evolutionary biology in a rigorous and unapologetic manner,” say Berkman and Plutzer. As part of their survey, they asked teachers about their academic training in evolutionary theory. Not surprisingly, 56 percent of evolution advocates had completed a college-level course on evolution, compared to 37 percent of those in the cautious middle and 33 percent of creationism advocates. The difference between evolution advocates and the other two groups was even more striking when teachers were asked to rate their knowledge of the scientific evidence on evolution. The stronger their knowledge and training, the more likely teachers were to do a responsible job teaching evolution. 

“In the coming decade,” conclude Berkman and Plutzer, “the United States will have to make important choices about energy policy…, the environment…, the wisdom of increasing our production of genetically modified foods, and much more. Because the disciplines of evolutionary biology, paleontology, climate science, and astrophysics each share similar methods with all sciences, any undermining of children’s trust in science – intentional or not – will have important consequences. If students come to think that science is simply a matter of one’s opinion, and that those opinions come from our values and faith, then it will be impossible for science to provide trusted, unbiased information to citizens and policymakers.”

What is to be done? Berkman and Plutzer believe better pre-service education for science teachers will make a difference in the long term. The goal is a new generation of teachers who can teach controversial subjects with the same confidence and commitment to scientific accuracy as when they teach other topics in science. “We would never ask students to debate or make up their own minds about whether the atmosphere of Venus contains sulfuric acid, whether protons and electrons have opposite charges, or which gene on chromosome 11 is linked to sickle cell disease,” they say. “Rather, to the extent possible at each grade level, we expect students to learn both scientific facts and what constitutes scientific evidence.” 

“An Evolving Controversy: The Struggle to Teach Science in Science Classes” by Michael Berkman and Eric Plutzer in American Educator, Summer 2012 (Vol. 36, #2, p. 12-17, 20-23, 40), http://www.aft.org/pdfs/americaneducator/summer2012/berkman_plutzer... 


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