Recently there was yet another attempt to force Creationism into the science classrooms of America as if it was a valid scientific concept on par with the theory of evolution. The theory of biological evolution is basically that species originate as a result of heritable changes in a population passed down over many generations. (Here is another good version of a simple definition of biological evolution.)
These latest attempts to insert Creationism into the science classroom are being made in Florida, but they happen frequently all over America. They are usually the work of conservative Christians who believe or wish to believe that God created all species more or less in accordance with a literalistic reading of the creation stories in the Old Testament, in other words, more or less instantly, like magic.
These Creationist attempts to inject religion into the classroom, are essentially political actions, and a manifestation of the religious right. Another version of Creationism is "Intelligent Design" Creationism, the non-scientific belief that that some unverifiable "agent"--perhaps God--set the evolution of species in motion, perhaps guides it, and perhaps initiated it with a common ancestor for all life of Earth. An even more watered down version of Creationism is that God is evolution's ultimate initiator, even if not its ongoing guide.
It is mendacious to insinuate or claim that Creationism or the other versions of it, like Intelligent Design, are scientific. The language of the recent Florida proposal displays ignorance about evolution, describing evolution as something concerning "how the universe was formed," and referring to it as one of "several theories." It didn't starkly proclaim evolution as one of "several scientific theories," but it is implied.
The truth is, quite simply, that the only scientific theory we have for the origin of species is evolution, and it is extremely well-founded.
Like the theories of gravity, germs, and plate tectonics, evolution is a formal scientific theory. By theory it is meant that it is well-established and overarching--it has both breadth and depth in terms of evidence and relevance.
When science uses the term "theory" formally, the term does not mean an idea based on idle or slightly-informed conjecture. That is how the term is used most frequently in casual conversationally--basically meaning, "a guess."
In science, formal theory status is a grand achievement, indicating that the theory consists of multiple, interrelated lines of repeatedly verified evidence, that the theory has been to a critical degree (and will continue to be) honed through the falsification or validation of predictions based upon it, thereby leading to better understanding of the theory. As always, these predictions will be rejected or accepted based on evidence that is open to peer review--that is, other scientists will challenge the evidence or interpretations of it.
Creationists (and many other people) routinely misunderstand how science works, and mistakenly interpret disagreements among scientists regarding evolution as an indication that evolution itself is a weak theory or that anything like a significant number of scientists don't hold to it. The opposite is true. Disagreements among scientists about evolution do not indicate a weakness in the theory of evolution; rather they are demonstrations of the scientific process in action: debate, examination of evidence, and competition among scientists as they attempt to falsify or verify propositions.
This happens in physics all of the time and no one bellows or hollers that, for instance, gravity isn't true, or that "other theories" besides gravity should be taught in science class as explanations for why objects fall or why you don't fly off the Earth as it spins. For instance, the theory of gravity is and has been perfected and revised based on evidence. When Albert Einstein in the early 1900's enhanced our understanding of gravity with his General Theory of Relativity, he presented something radical in light of to what Isaac Newton had discovered before him about gravity, but that did not mean that suddenly gravity ceased to exist! Newton's equations--which were generations-old by the time Einstein learned them--still worked even after Einstein enhanced our understanding of gravitation with his own scientific discoveries.
In much the same way as Einstein's scientific work built on Newton's, forced us to reconsider it and look at it in a new way, but did not invalidate the basics of either Newton's discoveries or the basic understanding of the laws of attraction that we call gravity, our understanding of the theory of evolution can improve when evidence--data--comes onto the scene and is considered in light of previous evidence. If new evidence seems to contradict old evidence, it may mean scientists got something wrong within the theory, but not that the theory overall is no longer the best scientific understanding for the origin of species.
An example of this is how scientists once hypothesized (or we could say, "theorized," using the term more casually) that humans descended from Neanderthals. Now, the preponderance of evidence, including genetic evidence, is that we are not descended from Neanderthals, but rather that Neanderthals and humans are descended from a common, earlier ancestor. But either way, the theory of evolution stands.
Our understanding of evolution can be improved not just by one set of evidence competing against another set of evidence, but also by new evidence adding to prior evidence, even in unexpected ways. For instance, Charles Darwin, who is credited with first coherently formulating the basics of the theory of evolution in 1855 in his book, On the Origin of Species by Means of Natural Selection, knew nothing of genes. The scientific field of study known as genetics did not even exist in Darwin's day. Genetics greatly enhances our understanding of evolution by explaining how heredity works--by explaining how parents pass on traits to their offspring. (They do it by passing on molecules called DNA.) Darwin knew heredity happened. He could see that traits were passed down from parents to offspring. But he had no real idea how it all happened, and freely admitted that the missing "how" was very important to better understanding evolution.
Genetics explained the "how" of heredity, thereby adding hugely to our understanding of evolution, and by the early 1900's adding an entire new field of study--genetics--that both supports and refines the theory of evolution, just as geology--the study of rocks and soil--supports the theory of evolution by demonstrating that the Earth is very old indeed, and that the evidence of the thousands of millions of years of Earth's existence is all around us.
This is why it's ignorant to do as Creationists do and gleefully misinterpret disagreements between scientists about aspects of evolution as reason to doubt the overall theory. Science is about disagreements over evidence; and is about new interpretations challenging or enhancing old ones.
Imagine if two medical doctors disagreed over the best sort of treatment for an infection. One doctor proposes a radical new treatment that is based on the surprising findings of experiments he or she has completed. The other doctor prefers the old treatments. This situation doesn't mean that suddenly germs don't exist! Or that Louis Pasteur's germ theory is fundamentally not true! If two doctors disagree with each other about how to treat infections are you going to stop cooking your meat before you eat it or stop washing your hands if they are dirty because you assume (or hope) that it means that germs don't actually exist! You wouldn't say, "Oh, there is a new drug out for fighting staph infections, I guess instead I should follow 'another theory' about all this, such as one that says infections come from the will of God. If I just pray and please God, I'll never again have to cook my chicken breasts before I eat them." That might sounds silly, but remember, in the past people have believed all sorts of unscientific things--that depression was caused by demons, that plagues were spread by poor ventilation or creeping swamp gas, and that gold could be created from lead.
This is why it is so worrying that organized anti-science groups routinely spend so much money and time every year to convince parents, administrators, and occasionally ill-trained educators to put non-scientific ideas about the origins of species into the science classrooms of American public schools. (And there are such groups in other nations, too, including the United Kingdom and Canada; and in some Muslim countries teaching evolution is extremely rare.)
Imagine a group arguing that medical schools must let witch doctors and astrologists teach courses on how voodoo and horoscopes are vital to understanding surgical medicine. Would you want your surgeon to have gone to such a medical school before he operates on you? Would you rather that your doctor revealed to you before he operated on you, "I picked the best time for this surgery based on past medical experience and recent evidence-based studies published in medical journals;" or, "I picked the best time for this surgery based on my star chart. I'm a Gemini, by the way."
If you won't allow such gobbledygook non-science from your surgeon, then certainly don't allow such gobbledygook non-science--almost always religion- and politics-driven--into the science classroom as
*evolution is "only a theory," or
*there are "numerous theories" about the origin of species, or
*scientific evidence exists for an "intelligent designer" at the root of evolution, or
*something divine or supernatural is the only explanation for the complexity of an organism or of life, or
*disagreements among scientists mean that the underlying reality of evolution is shaky.
To allow such as the above is to allow non-science into education.
Now, some people may believe such supernatural non-science very deeply. They might even claim that you are being offensive to them or may even argue that you're being closed-minded (even "unscientific") because you don't want their beliefs to be introduced into the science classroom. If they are offended, then suggest that they ask themselves why they are offended, and leave it at that. You should not need to apologize for supporting quality science education for the children of the United States.
Here is a free documentary--in 12 short and easy-to-view segments--that you can watch on your computer. The documentary, Judgment Day, is just one chapter (with a happy ending) in the ongoing story (still unfinished) of how religion and politics embolden anti-science crusaders to push Creationism into the science classroom.
You can learn more about evolution from these free online lectures or from the online project, Understanding Evolution, particularly the Evolution 101 section originally designed for teachers. If you would like to support the work of defenders of quality education about evolution in America's classrooms, please join the non-partisan not-for-profit organization, the National Center for Science Education (NCSE).