Proof for Evolution?
Name: Danielle Wilson
Date: Around 1993
What proof is there for Evolution?
First let me say that I am not a biologist, but a chemist. So I
do not have a very detailed answer to your question. I first want to say that
scientists have a very special meaning for the word "proof." In fact, it is
so difficult to "prove" a scientific theory that I can honestly say that there
are NO pieces of scientific knowledge that have actually been "proved."
Scientists come up with a theory, and then they test it in as many ways as
they can, looking for evidence or information which will either prove the
theory to be impossible, or maybe verify some of the theory's predictions, or
change the theory a little. Most theories start out because someone has done
a lot of experiments, or a lot of studies, to look at something, and then they
make a general guess as to how that thing works. This is called a "theory" in
science. However, if we guess how things are based on what someone else tells
us, or based on what we read, that is not a "theory" to a scientist but a
"guess." After all of that, I guess you would like to hear some EVIDENCE
supporting evolution. One piece of evidence is based on our DNA molecules.
Every single cell in our bodies contains DNA, a special molecule which
literally makes us what we are. Our DNA is almost EXACTLY the same as gorilla
DNA, and is even closer to DNA obtained from fossils of ancient ancestors of
human beings. There is much more evidence, but I will let the biologists take
Dr. R. Topper
Dr. Topper is right that it is hard to prove a theory beyond
doubt. This is particularly true in science because scientists can be very
skeptical. The approach many scientists take is to try to disprove a theory.
That way they know it is false. Evolution is a theory that has not yet been
disproved. It is always best to define one's terms before explaining
something. Evolution, in this context, is how life in general changes over
time. There is little doubt that life on earth has changed over time. It is
believed that 99% of all the species that have lived on earth, are now
extinct. Extinction of a species is one way in which life evolves. That
evolution occurs within populations of life forms on earth is well supported.
Scientists measure gene frequencies and protein structures in a group of
organisms, and then see how those frequencies and structures change over time.
Another term you might have heard is "natural selection." It is not the same
as evolution. Natural selection simply means that some individuals reproduce
more than others, and which leave the most offspring is due to forces at work
in nature. If a rabbit made a lot more noise than its neighbor, then it might
be more at risk of getting eaten by a lynx or an eagle. If it gets eaten, it
will not reproduce anymore. Natural selection has also been shown to occur in
nature in many instances. Charles Darwin proposed that this process of
natural selection might cause evolution in nature. And that this evolution by
natural selection could have been the major force that made so many species of
organisms. This was a controversial theory then because it was contrary to
what most people believed about how g-d created each species himself. Today,
most all people familiar with the evidence for evolution of life on earth,
accept it as the best explanation for the diversity of life. There are two
large lines of evidence to support this theory. The first is fossils. The
other is HOMOLOGY. All life on earth, according to evolutionary theory,
evolved from common ancestors. All life on earth is related to each other; we
are all of the same family. Modern whales have hip bones in their flesh that
they do not use because they do not walk. They probably evolved from mammals
that did walk. Paleontologists have found a fossil whale called Pakicetus
that has more developed rear legs. Older whales should look more like their
ancestors if evolution is correct. Without evolution, we could not understand
why whales have hip bones. I should also emphasize that homologous structures
do not have to be used for the same purpose. Whale flippers and human hands
are homologous, but are used in very different ways. Another interesting
fossil is Archaeopteryx. This was a dinosaur that had feathered wings, like
birds. Bird and dinosaurs have a common ancestry. This fossil has teeth,
although no bird has teeth. It has the skeleton of a dinosaur, but the
feathers of a bird. It shows that there was a time when the difference
between birds and dinosaurs was not obvious. Birds are the only remaining
species from the dinosaur line. Homology is a complicated concept. It means
that two structures are similar because they are related genetically. If two
structures are similar but not related then they are only analogous. The
wings of birds and insects are analogous. They both are used to fly, but in
different ways. They are not related animals. Many differences between their
structures make this apparent to the keen observer. But the wing of a bat and
the wing of a bird are homologous. They both contain the same bones. Both
have an upper arm bone (humerus), both have a radius and ulna (lower arm
bones), and both have wrist bones and metacarpals and digits. They were both
derived from the same genetic plan. Look up homology in a biology text for
more examples. There is a growing mountain of evidence that supports
evolution. It will never be proven true because we can not know for sure.
But by using the scientific method, we can make a good guess, based on careful
observations of the earth as it exists today. A long answer to a short
question. Because evolution is a complicated theory. Keep asking questions.
And do not take anybody's word for it, go out and see for yourself!
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Update: June 2012