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
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
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
Around these simple ideas they developed a theory of
- 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
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.
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
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
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
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
National Center for Science Education -- here you will discover a variety of
resources designed to help you teach evolution in the public schools.
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
-- 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
excellent resource for the study of Darwin and evolution. Best, however, if you
have a high-speed internet connection.
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
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,
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.