This week in federal district court, a group of parents is challenging the Dover, Pa. school board’s decision to require the teaching of “intelligent design” in science classes, on the grounds that this policy violates the principle of separation of church and state. The case is just the latest in a long series of court battles between advocates and opponents of the teaching of evolution in the schools. Opinion polls over the past two decades have found the public deeply divided in its beliefs about the origins and development of life on earth, while broadly supportive of schools teaching evolution as well as alternative theories on how life began.

There is a great deal of consistency across polls in what the public believes about the origins of life and how the issue should be taught in the schools. Polling has regularly found that the public favors the teaching of multiple perspectives on the issue in the schools. While solid majorities believe that evolution should be taught in science classes, roughly two-thirds of Americans favor adding creationism to the school curriculum.

Surveys are also fairly consistent in their estimates of how many Americans believe in evolution or creationism. Approximately 40%-50% of the public accepts a biblical creationist account of the origins of life, while comparable numbers accept the idea that humans evolved over time. The wording of survey questions generally makes little systematic difference in this division of opinion.

Opinions on the theory of “intelligent design,” however, are far more complex, making it difficult to determine how many Americans subscribe to this view of life’s origins. In part, this reflects the public’s lack of familiarity with the concept of intelligent design, which holds that Darwin’s theory of natural selection is inadequate in explaining the development of complex life forms. A Gallup survey in August found that only about half of Americans are familiar with the term. Moreover, because the concept involves sensitive matters of faith and science, questions that attempt to indirectly measure support for intelligent design produce divergent results.

Consider for example the approaches taken by Pew and Gallup (see table below). The two organizations find similar numbers in favor of a creationist position ­ 42% for Pew, 45% for Gallup ­ although each describes the concept in decidedly different terms. But Pew finds far more people believing in natural selection (26% vs. 13% for Gallup) while Gallup finds more subscribing to the view that God or a supreme being guided the evolutionary process (38% vs. 18% for Pew).

These differences result from the way the options are presented. Gallup asks respondents to choose among three views, two of which suggest a belief in God (“God created human beings pretty much in the present form” and “God guided [the evolutionary] process”), and one that rejects God’s involvement altogether (“God had no part in this process”). It seems likely that for many respondents, agreeing with this last statement could imply a denial of belief in God. The resulting percentage choosing this option (13%) is about the size of the segment of the public that does not believe in God at all.

Pew’s approach, on the other hand, asks people initially if they believe life “evolved over time” or existed in its “present form since the beginning of time”; the question makes no mention of God. Those who said that life evolved were then asked if life “evolved due to natural processes such as natural selection” or whether “a supreme being guided the evolution of living things for the purpose of creating humans and other life in the form it exists today.” The Pew formulation provides a significantly more positive and inclusive description of the scientific position by characterizing natural selection as “a natural process” rather than something “God had no part in.” This implicitly allows people who believe that God or a supreme being set the evolutionary process in motion, or even shaped it in some way, to still opt for “natural selection” as the main engine of evolution.1

Confusing Concepts

Most Americans say they are familiar with creationism and evolution, but there is some confusion about the terms’ meaning. In an August 2005 Gallup poll, 58% of the public said that creationism was definitely or probably true as an explanation for the origin and development of life, but 55% also said this about evolution. Since creationism and evolution are incompatible as explanations, some portion of the public is clearly confused about the meaning of the terms.

A 1999 Fox News poll of registered voters offered respondents the explicit option to say that both Darwin’s theory of evolution and the biblical account of creation were true: 26% said both were. Similarly, Pew’s July 2005 poll found that about nearly three-in-ten of those who oppose the teaching of creationism nonetheless personally accept creationist accounts of life’s origins, and 14% of those who accept natural selection favor teaching creationism instead of evolution.

The term “intelligent design” is still unknown to much of the public. In the August 2005 Gallup survey, 52% said they were either “not too familiar” or “not at all familiar” with the phrase. By comparison, only 17% and 24% were not familiar with “evolution” and “creationism,” respectively. Given the low level of public recognition of the term, “intelligent design” is rarely mentioned in polling on the origins of life.

Scientists and Evolution

A narrow majority of the public (54% in a recent Pew poll) believes that scientists are generally in agreement about evolution. But fewer believe there is strong scientific evidence in support of evolution. A December 2004 Newsweek survey found just 45% saying evolution was both widely accepted in the scientific community and well supported by evidence, and the same number in a 2005 Harris Interactive survey agreed that “Darwin’s theory of evolution is proven by fossil discoveries” (48% disagree). A 2004 Gallup poll registered even fewer (35%) saying Darwin’s theory of evolution has been “well-supported by evidence.” This question also offered respondents the choice of saying they don’t know enough about the issue, an option that 30% selected.

Teach Evolution, Other Approaches

Despite the fact that fewer than half of Americans personally believe in evolution, a solid majority over the past 20 years has supported the teaching of alternative accounts of the origins of life, including evolution. Poll questions have typically asked if creationism should be taught along with evolution, and majorities ranging from 57% to 68% say that it should. Questions have been asked about removing evolution from the curriculum, but only a minority of the public favors this step. And questions that ask if creationism should be taught instead of evolution have found only 33%-40% in favor.

Relatively few questions have asked if respondents believe that evolution should be taught, perhaps because it is the status quo today. A recent Gallup poll found 61% favoring the teaching of evolution in public school science classes, while 54% said creationism should be taught and 43% said that intelligent design should be taught.

A survey conducted by Fox News in 1999 found nearly identical majorities of people favoring the teaching of evolution and opposing its removal from the curriculum. In one version of the question, respondents were told that the Kansas State Board of Education adopted new standards that would remove evolution from the mandatory curriculum; a 57% majority of registered voters disagreed with the board’s actions, while 33% agreed with the removal. The other version stated that “the National Academy of Sciences recommended that evolution be taught to all public school students as the most convincing theory for how human beings developed” and then asked if respondents agreed or disagreed that evolution should be taught in all public schools: 56% agreed with teaching evolution and 35% disagreed with it. Thus, despite the invocation of two very different kinds of authority on opposite sides of the issue, the public opinion result was the same.

None of the polls probes deeply into what respondents are thinking when they say a particular approach should be taught. Should standardized science tests now include sections on both evolution and creationism? Does support for teaching evolution (or creationism) mean mandatory or optional instruction? On the latter question, a 1999 Gallup survey found that when offered the choice between having evolution as required instruction or having it offered as an elective but not required, just 28% said it should be required; 49% supported offering it as an option, and 21% opposed offering it at all. The same alternatives were offered for creationism and responses were very similar.

1. For a complete discussion of the Pew poll, see “Religion a Strength and Weakness for Both Parties,” released Aug. 30, 2005. Note that prior to being asked about evolution, respondents in the Pew poll were given a chance to express their belief in God or a higher power and that God (or a higher power) created life on earth.