Americans’ Scientific Knowledge and Beliefs about Human Evolution in the Year of Darwin

The year 2009 marked the 150th anniversary of the publication of Darwin’s On the Origin of Species by Means of Natural Selection. Over eighty years ago, the Scopes "monkey trial" in Dayton, Tennessee, marked the beginning of a long battle for the soul of American public opinion, pitting biblical creationism against the teaching of human evolution in public schools. But how well do we understand what Americans know and believe about human evolution? National surveys by Gallup have certainly told us much about trends in Americans’ core beliefs about human origins: a relatively stable, sizable plurality (45%), for example, appears to believe in a creationist version of human origins; nearly 40% endorse the theistic supernatural idea that "man has developed over millions of years from less advanced forms of life, but God guided this process, including man’s creation"; and only a very small percentage (12–14%) has accepted the naturalistic position that "man has developed over millions of years from less advanced forms of life. God had no part in this process"(http://www.gallup.com/poll/21814/Evolution-Creationism-Intelligent-Desi…). We have also learned a good deal about the socio-demographic characteristics of those who hold such beliefs (http://pewforum.org/docs/?DocID=392). But we know much less about the nuances and structure of these beliefs and the scientific knowledge or ignorance that underlie them. Data from a recent national Harris survey (2008) addresses these deficiencies by measuring multiple dimensions of Americans’ beliefs about evolution, their familiarity with scientific concepts in evolutionary biology (for example, adaptation), and their scientific knowledge in general (for example, the age of the earth and of the universe) — all social-psychological facts that the American scientific and educational communities must confront in dealing with the obstacles to full acceptance of the theory of human evolution in the 21st century.

Our first analysis of these data has revealed a remarkable diversity of religiously driven and scientifically informed (and uninformed) beliefs about human evolution, much of it seemingly contradictory (see summary table on page 17). To begin with, sizable chunks of the American adult public evidently believe a whole host of creationist articles of faith to be true, among them such claims as:

Archaeological findings have confirmed the authenticity of the people and incidents recorded in the Old Testament of the Bible (65%).

All people are descendants of one man and one woman — Adam and Eve (60%).

The theory of evolution proposes missing links and speculates about how humans developed but does not have strong factual evidence to support it (52%).

The Bible describes the creation of life exactly as it occurred in six days (50%).

The only reliable way to know for certain about what happened in the past is to have a reliable historic record written by someone who was an eyewitness (50%).

Human fossils have been found mixed in with dinosaur fossils showing that humans existed at the same time that dinosaurs existed (43%).

God created the universe, the earth, the sun, moon, stars, plants, animals, and the first two people within the past 10 000 years (39%).

There was a flood within the past 10 000 years that covered all of the earth and was responsible for most of the rock layers and fossils that are seen across the world (60%).

Yet hardly a fifth (18%) actually believes the statement "The earth is less than 10 000 years old." And this is one of many such cognitive-psychological incongruities in the public’s belief system.

At the same time, much of the American public appears to endorse as true propositions about the origins of life that are strikingly theistic and in sync with a range of appeals from the "Intelligent Design" movement, namely such claims as:

God created the fundamental laws of physics and chemistry in just the right way, so that life, particularly human life, would be possible (69%).

All living things exhibit evidence of having been purposefully designed which means there must be an Intelligent Force or a God (64%).

Humans are so complex, advanced, and unique that we cannot have arisen due to chance events (60%).

God started the evolutionary process and directed it over millions of years (56%).

God has intervened in the evolutionary process to create millions of species at various times over millions of years (54%).

There is no such thing as random genetic mutations causing changes in a species — all genetic changes result from the decisions of a God or an Intelligent Force (35%).

There’s no such thing as a genetic defect — all genetic changes result from the decisions of a God or an Intelligent Force (24%).

Layers of rock containing fossils cover the earth's surface and date back hundreds of millions of years (78%).

Humans share reflexes with other primates that are not shared with other animals (75%).

Dinosaurs became extinct about 65 million years ago (69%).

All life forms are descended from common ancestors that developed over millions of years (65%).

Birds appear to have evolved from dinosaurs (55%).

Living organisms on earth have evolved over a billion years ago from nonliving chemicals (44%).

Our exploratory factor analysis of sixty such items turned up four fundamental dimensions that underlie most beliefs about human evolution, which we call: (1) Purposeful Complexity–Intelligent Design, (2) God as Biblical Creator of the Universe & Human Life (3) Reality of Genetic Relatedness & Change in Life, and (4) Truth of Scientific Claims on Evolution (details are not included here, but are available on request from the authors). So Americans’ beliefs about evolution are a lot more nuanced and multidimensional than heretofore suspected. Not only that, we found a number of anomalous response patterns when we looked at the relationship between responses to our belief items and responses to the Gallup question about human origins.

For example, over a third (35%) of respondents who chose Gallup’s creationist category (God created human beings in their present form at one time in the last 10 000 years or so) did not believe the creationist tenet "Dinosaurs lived at the same time as people." In fact, over half (56%) of these respondents also agreed with the statement "Dinosaurs became extinct about 65 million years ago." Even better, a solid majority of them (54%) agreed that "All animals share common ancestors that gave rise to all the different types of animals that are alive today." These and other anomalous patterns (not shown here) tell us that the widely cited Gallup question may significantly overestimate the percentage of orthodox creationists in the American public.

We also discovered that, underneath all these inconsistent and perplexing belief patterns, Americans’ knowledge of basic scientific and evolutionary facts looks rather poorly grounded. Less than half (43%) knew (or guessed in a multiple-choice format) that the earth is billions of years old and only 30% knew that the universe was also billions of years old. Barely more than four out of ten Americans (42%) was aware that the last dinosaur existed on earth millions of years ago; roughly a fourth (26%) thought it was a hundred thousand years ago or less. Just a fifth or so (22%) could correctly answer that modern humans emerged hundreds of thousands of years ago, and not unexpectedly, less than one third (28%) could accurately identify when human beings began to migrate across the world from the continent where they originally emerged: 10 000–100 000 years ago (see "Atlas of the Human Journey" at ). In fact, 39% believed it was actually less than 10 000 years ago .

Furthermore, Americans’ self-reported acquaintance or familiarity with key evolutionary concepts looks equally abysmal:

So, with evolutionary literacy so rudimentary and fundamentalist, theistic, and "intelligent design" — driven beliefs so widespread, it should not be terribly surprising that public resistance to the theory of evolution in American society remains remarkably high, as compared to what has been documented in international surveys of citizens from other economically and scientifically developed nations by Jon Miller, Eugenie C Scott, and Shinji Okamoto (in their "Public acceptance of evolution," Science 2006; 313 [11]: 765–6) — all this, mind you, in the Year of Darwin, 150 years after the publication of the Origin of Species. Surely the graybeard must be turning in his grave.

Note: This article is a revised and updated version of a paper presented at the 64th Annual Conference of the American Association for Public Opinion Research, Hollywood, Florida, May 14–17, 2009. The data were originally collected by Harris Interactive with 4626 respondents in two waves of data collection from July to October, 2009. Respondents were drawn from Harris Interactive’s on-line panel and weighted based on age, sex, region of country, income, education, and ethnicity to resemble the overall US based on US Census proportions.