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A Brief -- and Simple -- Introduction

Simply put, evolution is descent with modification or change. Put another way, evolution is the change in the genetic makeup of a population from one generation to the next. It is, in reality, a very simple concept.

The "theory" part of evolution has to do with how these changes in genetic makeup occur, and what effect they have on the living population.

There is no question about whether evolution actually exists -- if there were no evolution, every generation would be exactly the same genetically as the one before it. And this we realize empirically is not the case.

In 1859 Charles Darwin (1809-1882) published On the Origin of Species, the product of many years of observation and recording by both Darwin and naturalist Alfred Russel Wallace (1823-1913). Both men observed the variation that exists within plant and animal species. Members are not identical, but show great variation in size, strength, health, fertility, longevity, behavior, and other characteristics. Darwin realized that humans, in particular, use this variation when they selectively bred plants and animals -- allowing only particular individuals possessing desired qualities or traits to interbreed.

Both men also built on the much earlier work of the English clergyman, T.R. Malthus, who revealed the reproductive potential of mankind far exceeds the natural resources available to nourish the expanding population. Darwin and Wallace recognized that what was true for human populations was equally true for other animals and even plants -- the reproductive potential of species vastly exceeds that necessary to maintain a constant population size. Those individuals that survive must be, in some way, better equipped to live in their environment than those that do not survive. They also realized that variations which increased an individual's ability to survive would be preserved, while those variations that decreased survival would most likely be eliminated.

Around these simple ideas they developed a theory of evolution:

  • Organisms produce more offspring than required to maintain their population size, yet the population size generally remains more or less constant over long periods of time. This suggests that there is a high rate of mortality among immature individuals.
  • Individuals in any population show much variation and those that survive probably do so, at least to some extent, because of their specific characteristics. Put another way, individuals with certain characteristics are better adapted to their particular environment
  • Since offspring resemble their parents closely -- but not exactly -- successive generations will maintain and improve on the degree of adaptation through gradual changes in each generation.

Darwin and Wallace provided a rational and convincing explanation for the diversity and changing nature of species. This process of variation and selection by the environment for better-adapted individuals is called natural selection and the change in the nature of the population that follows is the process of organic evolution. Substantially the same processes occur among both plants and animals -- including human beings.

The new way of looking at the world, however, required humans to develop a new set of attitudes toward the natural world and face an entirely novel view of human origins. Darwin's scientific study countered the prevailing belief that species were fixed for all time and were part of a "Grand Design." This agonizing reappraisal was only possible for those who were capable of rational thought.

Natural selection can be observed and even measured. The long-term studies of Rosemary and Peter Grant on Galápagos finches show the reality of evolutionary change within a human lifetime. Darwin argued -- and the scientific community continues to agree -- that natural selection is neutral -- it has no long-term goal.

Evolution was further advanced in the 1960s when the mechanisms of plate tectonics were recognized. Geology and paleoanthropology revealed that from the formation of the earth's crust and the appearance of early life almost 4 billion years ago, new species emerged, diverged, flourished, were replaced, and became extinct. Life forms change in rhythm with the changing earth. We can trace the evolution of life forms from the first vertebrates to the first mammals to the first appearance of our own primate relatives. All of these "products" of evolution have been shaped through a unique combination of natural selection, recombination of genes, mutation, genetic drift, and species migrations.

This chart shows the public acceptance of evolution in 34 countries based on a 2005 survey. Studies such as this taken since 1985 consistently show the United States ranks next to last in acceptance of evolution theory, with the number of Americans uncertain about evolution steadily increasing. This stands in marked contrast to both Europe and Japan, where adults generally accept the concept of evolution. The data comes from the article, “Public Acceptance of Evolution,” by Jon D. Miller, Eugenie C. Scott, and Shinji Okamoto published in the August 11, 2006 issue of Science.


Evolution Today

At the conclusion of the First World War there was a wave of nostalgia for more simple times and ideas. Fundamentalist religion expanded, particularly in the South and Midwest. Locked into a literal interpretation of the Christian Bible, the Fundamentalists saw Darwin and evolution as the enemy and they set out to eradicate it, beginning first with the educational system. By 1925 a number of Southern states, including Oklahoma, Florida, Mississippi, North Carolina, and Kentucky, had passed laws prohibiting the teaching of evolution in the classroom, insisting instead on the teaching of Biblical creationism. One of the most memorable attacks on the teaching of science was the "Scopes Monkey Trial." This link also has a PBS curriculum guide to help teach about the trial.

Although easily convicted of breaking the Tennessee law that prohibited the teaching in public school "any theory that denies the story of divine creation of man as taught in the Bible," the Supreme Court did direct Tennessee that it could not indict anyone else under the law.

In 1968 the U.S. Supreme Court ruled in Epperson v. Arkansas, that evolution can be taught in public schools because it is a science, but not creationism, because it constitutes religion. In 1987 the Supreme Court, in Edwards v. Aguilar, that the state-mandated teaching of evolution and creationism side-by-side in Louisiana was unconstitutional, again because teaching creationism meant the state was endorsing a particular religion.

Rebuffed time and time again, creationists have hit on a new idea -- "intelligent design." Billed as a "theory" that nature is so complex it could only have been created by design, it is actually just another attempt to force one particular religious belief into the public schools. Advocates of "intelligent design" clearly reveal their underlying goal -- one claims that the concept will liberate science from the grip of "atheistic naturalism," while in 1996 one of the primary backers, Phillip E. Johnson stated, "This isn't really, and never has been, a debate about science. It's about religion and philosophy." While those espousing "intelligent design" want to suggest their concepts are as science-based as evolution, they have no empirical research program and, consequently, have published no data in peer-reviewed journals (or elsewhere) to support their intelligent-design claims.

What "intelligent design" advocates do have is a loud and aggressive public relations program that one authority reveals "includes conferences that they or their supporters organize, popular books and articles, recruitment of students through university lectures sponsored by campus ministries, and cultivation of alliances with conservative Christians and influential political figures." Such efforts simply represent another attack on science and effort to force fundamentalist religion into the classroom in violation of the First Amendment.

Teaching Evolution to Create a Science-Literate Society

If you are a science or anthropology teacher and you want to ensure that your students are literate in science, there are a variety of web sites where you can get additional, sound, science-based information to help.

University of California Museum of Paleontology -- this site is the myth buster for evolution, helping students to better understand evolution, the evidence and its implications.

Michigan Citizens for Science -- this web site provides a variety of policy statements on the teaching of evolution (these are not Michigan specific) and provides excellent background information.

National Center for Science Education -- here you will discover a variety of resources designed to help you teach evolution in the public schools.

American Anthropological Association -- this link provides the statement of the Association on the teaching of evolution and a consensus of anthropological judgments regarding human evolution.

Botanical Society of America -- this link directs you to the Society's statement on evolution. This provides a very clear explanation of evolution as a scientific theory. It is contrasted with the ideas of creationism and "intelligent design." -- This page includes interviews, articles, and pdf lesson plans written by science educators and includes activity handouts and many approaches to the intellectual comparison of evolution, creationism, and "intelligent design."

BBC's Evolution Website -- An excellent resource for the study of Darwin and evolution. Best, however, if you have a high-speed internet connection.

Oklahomans for Excellence in Science Education -- This web site promotes the education of the public about the methods and values of science and advocates excellence in the science curriculum. It contains a variety of additional links and web sites of use to teachers.

Responding to In-Your-Face Creationists and Attacks on Science

If you need quick responses to creationists here are a few excellent websites:

Defender's Guide to Creationism and Science

Creation "Science" Debunked

National Academy of Sciences - Science and Creationism

You can also download this brochure, produced by the Skeptics Society, Top 10 Myths About Evolution. Quick, simple, booklet to debunk creationism. Hand it out to all who question and have an open mind.

There are also several excellent articles in the December 2005 issue of the American Anthropological Association's Anthropology News. These are available on-line and provide excellent critiques of "creationism," "intelligent design," and the general "anti-evolutionary" movement.

Andrew J. Petto, University of Wisconsin at Milwaukee, strips the scientific veneer off "intelligent design" and reveals that its proponents are still attempting to force God into the classroom. Read his article here.

Chris Toumy, University of South Carolina, takes on "intelligent design" and provides detailed arguments that derail the central arguments, exposing the concept as lacking in any vague credibility. Read his article here.

Religion and Evolution

While not really the topic of this page, some readers might be interested in learning how the Catholic Church has viewed the interaction of religion and evolution.

PBS also has an excellent program, Faith and Reason, that includes an evolution component.  


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