Teaching
About Evolution
Judy
Jones
The quizzical
expression of the monkey at the zoo comes from his wondering whether
he is his brother's keeper, or his keeper's brother.
Evan Esar
I am asked many
times about how I teach about Evolution. Fortunately, I teach in
a district where a large number of the parents are scientists and/or
professors who would be outraged if I did not teach the scientific
theory of evolution by natural selection – and teach it well!
However, I know that this is not true in many districts across the
United States. And I do get isolated students each year who make
it clear to me that they “do not believe in evolution.”
I am always a little amused by this statement but I approach it
seriously and I will share with you how I address this controversial
issue. The current idea that looms as a challenge to evolution is
the idea of “intelligent design.” And I will try to
briefly explain this idea as I discuss my approach to the teaching
of evolution.
During my discussions
and activities about evolution, I am always respectful of the diversity
of my students. I try to help them understand that there are multiple
ways to view and understand the world – through science, through
literature, through art, through religion – and many other
ways, also. I explain that I am not trying to change their faith.
I am merely trying to help them understand a scientific theory that
is at the core of understanding biology. I try to help them understand
the differences between the processes of science and the processes
of faith.
I begin by talking
about Science and the Nature of Science. I talk to the students
about hypotheses, theories, and laws and how they are derived in
science. I talk about ideas that are scientific and ideas that are
not scientific. I explain that the process of science is generally
this:
Observe =>
Ask questions => Propose hypotheses => Conduct Investigation
=> Alter hypotheses when repeated investigations do not support
the hypotheses => etc.
Whereas faith
is a belief; one does not alter one’s faith to fit observed
evidence.
I ask students
to learn the theory of evolution by natural selection; they don’t
have to “believe” in it. Science is about evidence to
support ideas, not about belief. I do not teach creationism nor
intelligent design because they are not science and I am a science
teacher. I will however, try and explain the controversies when
my students ask. But I encourage them to ask their parents or their
religious leaders as well.
The scientific
method is not esoteric. It is not used just by those with
scientific Ph.D.’s. Science methods are used in our daily
life. When we get ready to cross a street, we gather evidence concerning
traffic patterns, lights, and speeds, and we generate hypotheses
about the best time to cross and then we test the hypothesis. Certainly,
we attempt to gather the best evidence possible because we have
no desire to disprove this particular hypothesis and get hit by
a car!
Science is universal
and has been used throughout the history of humankind. Prehistoric
hunters certainly used science as they learned the behaviors and
tracks of their prey and generated the best theories about the time
to hunt, the type of weapons to use, and other things that would
help them survive. As said before, science is simply a way of viewing
and understanding the world. Scientists have simply formalized this
process.
Scientists gather
data to make initial observations, they develop hypotheses, they
test those hypotheses with controlled experiments and then if the
experiments negate the hypotheses, new ones are developed. And if
the hypotheses are supported, then the scientists will develop new
related hypotheses to test. The process is ongoing………
“In
many of our classes from kindergarten through college, we teachers
fail to communicate that excitement, wonder, and creativity. We
teach the scientific method, experimental design, statistical significance,
and multitudes of detailed facts. These are, of course, very important,
but they should develop later, once the joy of science is clearly
established. Many dedicated teachers do this already, and they should
be admired and rewarded for it.
A better
way, in my opinion, is to teach the process of science as a way
of living, a means to a good life. This should not be hard to do,
because everyone wants a better life. Teach that people must draw
conclusions everyday, and that the best conclusions for them personally
are those founded on strong evidence. Show them that certainty is
seldom attained and to accept uncertainty.”
Jere H. Lipps – UC Berkeley
So
what is a THEORY?
Most scientists think of a theory as a coherent explanation for
a large number of facts and observations. A theory should be consistent
and compatible with the evidence and have been tested against a
wide range of phenomena. A theory should be effective in problem-solving.
Theories are more certain than hypotheses. A theory explains how
something happens.
And
a LAW?
A law is a description of a natural phenomenon or principle that
holds true under specific conditions. For example, the law of gravity
describes what happens when we drop things. It is utterly predictable.
In a way, evolution is a law; organisms change over time –
and that is evolution. But the “how” of evolution is
a theory – the theory of natural selection. It is the most
tested and accepted explanation of how the change in organisms happens
over time.
So
what is the Theory of Evolution by Natural Selection?
Charles Darwin said:
- Populations
would grow exponentially if there were unlimited resources
- Environmental
factors limit reproductive capacity
- Organisms
compete for resources
- There is
variation within populations and those with useful adaptations
survive
- The survivors
reproduce and pass on their genes
- The new
generation will have a greater frequency of the adaptive traits
- Over a long
period of time, the differences are so great that the result could
be a new species
What
is the evidence that supports evolution by natural selection?
Evidence
from fossils
By studying fossil remains of organisms, scientists have made predictions
about what intermediate forms would look like and in fact, have
many times found samples of those intermediate forms. For example,
the hypothesis that birds evolved from reptiles rather than flying
insects has been supported by finding fossil birds that have the
features of both reptiles and modern birds.
Evidence
from genetics
Research has shown that the genomes of all organisms share the same
basic mechanism of heredity involving DNA and RNA and protein synthesis
based upon the same code and template. For example, mitochondrial
DNA evidence has been used to quantify relatedness in human evolution
that implies a branching tree radiating from a common ancestor.
This evidence supports and enhances that from fossil remains.
Evolution in action
Many bacterial pathogens have evolved resistance to antibiotics.
In the case of HIV, which causes AIDS, significant viral evolution
occurs within the course of infection of a single patient. Many
agricultural pests have evolved resistance to chemicals that farmers
have used for only a few decades. In addition, scientists can perform
experiments to study evolution in real time using bacteria and fruit
flies that reproduce quickly.
So what
is the “theory” of Intelligent Design?
The primary
arguments against evolution are proposed by Michael Behe at Lehigh
University. He states that some mechanisms found in organisms are
of such “irreducible complexity” that they could only
be explained if there was a creator.
An irreducibly
complex system cannot be produced directly by numerous, successive,
slight modifications of a precursor system, because any precursor
to an irreducibly complex system that is missing a part is by definition
nonfunctional. .... Since natural selection can only choose systems
that are already working, then if a biological system cannot be
produced gradually it would have to arise as an integrated unit,
in one fell swoop, for natural selection to have anything to act
on.
(Behe
1996)
There are other
arguments but they all involve the idea that organisms are so specific
and complex that they could not have arisen through multiple random
events.
What is one
response to Michael Behe’s argument about irreducible complexity?
One example
of irreducible complexity that Behe proposes is the bacterial flagellum.
The movement and function of the flagellum, which rotates at speeds
up to 100,000 rpm, is determined by a multitude of proteins that
have to work together like a fine engine in order for the flagellum
to move. Behe argues that if evolution is step-by-step then each
step has to have reproductive advantage for the flagellum to have
evolved by natural selection. He claims this is impossible.
Ken Miller of
Harvard University, says that the best response to Behe has come
through steady scientific work on genes and proteins. These studies
have shown that the bacterial flagellum is NOT irreducibly complex.
In fact a special secretion method used by bacteria to deliver molecules
to their host (involved in disease) uses some proteins that are
homologous to a portion of the proteins involved in the bacterial
flagellum mechanism. Studies such as these begin to “chip”
away at the irreducibly complex argument.
There are many
other examples that the reader can research if interested. One of
these involves the blood clotting mechanism of vertebrates.
It is important
to note that the arguments against evolution rarely propose alternate
ideas or explanations other than to say that “there must have
been an intelligent designer.” This is certainly not the way
of science but rather the way of faith.
In conclusion,
I like to share with my students a quote from Ken Miller, the author
of their textbook.
As Darwin
wrote, there is grandeur in an evolutionary view of life, a grandeur
that is there for all to see, regardless of their philosophical
views on the meaning and purpose of life. I do not believe, even
for an instant, that Darwin's vision has weakened or diminished
the sense of wonder and awe that one should feel in confronting
the magnificence and diversity of the living world. Rather, to a
person of faith it should enhance their sense of the Creator's majesty
and wisdom (Miller 1999). Against such a backdrop, the struggles
of the intelligent design movement are best understood as clamorous
and disappointing double failures – rejected by science because
they do not fit the facts, and having failed religion because they
think too little of God.
Please contact
me if you have questions or comments about this article.
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