Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Proof for Evolution?
Name: Danielle Wilson
Status: N/A
Age: N/A
Location: N/A
Country: N/A
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 over.

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!

Jim Murray

Click here to return to the Biology Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (, or at Argonne's Educational Programs

Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory