As usual a long post, but you have a chance to learn some cool science!
I'm a middle school Science teacher. I teach 6-8th grade Science, namely Earth Science, Biology, and Physical Science in that order. Part of the Biology curriculum is evolution. This is no surprise: modern Biology makes no sense whatsoever without Darwin's Theory of Evolution and Natural Selection. Literally, it would all be a gigantic illogical nightmare if evolution is left out of the equation. How would you classify animals? How would we be able to explain interactions between species in their natural environment? How could we make sense of the inner workings of our bodies and compare that to other animals? If species just popped into and out of existence, we can just hang up our coats and go home.
Of course every biology teacher has to face off against Creationists. What surprised me in this case was how many Creationists I would have to spar with. One of my very own colleagues was a creationist! First off, I do not back off from scientific fact. There is no "It's not my place to present information that challenges people's beliefs." That's not science. My job is to teach science, as it is, and to teach kids that they can cultivate within themselves a scientific mindset that is valuable for their everyday lives. Knowing things about science is just plain beneficial.
My style is more confrontational than other teachers might be used to, but you cannot back down from what you know to be true. The children come first, and if they do not learn to question what they think, you're only helping to bring about a generation of sheep. So, here's what happened, I know you're dying to find out.
I was discussing evolution in my 7th grade biology class after our unit on DNA. My science class is probably more technical than most. I did this fun lab where I had the kids use LEGO pieces to decode an RNA strand to figure out what amino acids it would code for. For those not in the know, the way DNA works is that it is a series of letters, a code of sorts. Each letter corresponds to one of four chemicals: Adenine, Guanine, Cytosine, and Thymine, aka base pairs. In RNA, Thymine is replaced by Uracil (a much less stable version of a nearly identical molecule, must be too much reality TV). Your DNA splits in half, and an RNA strand comes along and is formed based on the original DNA strand. This is called "messenger RNA." The RNA leaves the nucleus of your cell and heads to a nearby ribosome. Think of ribosomes like scanners you feed paper through. The mRNA is fed into the ribosome. Transfer RNA (tRNA) links up to one end of the ribosome. Transfer RNA has two parts: one side is an amino acid and the other side is one of the four chemicals we talked about earlier: Adenine, Guanine, Cytosine, and Uracil.
So we look at the first group of three base pairs, namely AUG in this case. AUG is called the "start codon," meaning the reaction won't start until the start codon is fed into the ribosome. So, the AUG on the mRNA strand will bond with a tRNA strand that has the opposite base pairs, namely: UAC. Remember the amino acids I talked about? Well, the tRNA comes equipped with them. So that means that the AUG on the mRNA strand will attract a tRNA with the amino acid known by the sexy name of "Methionine." Next, the ribosome will read "CGC" and this will bond to a tRNA strand with the opposite base pairs, namely "GCG." Then, we will take the lovely Methionine we already have present, and link it up to a shiny new molecule of Argenine. You can use a handy dandy RNA codon table to figure out which amino acid goes with which codon.
This process goes on and on and on until you reach a "stop" codon, where the reaction stops. You get a peptide chain, and through some very complicated processes, you'll eventually have a protein. The proteins made by this process are used for pretty much everything your body could ever need. There are proteins that digest food, color your hair and eyes, keep your blood vessels nice and firm, and help you sense danger in case a bear attacks. Different sequences of amino acids make different kinds of proteins; the list is endless!
Changes in your DNA code due to mutations could have a big impact on the proteins that your body makes! Many mutations in the DNA code are "silent mutations," meaning mutations that don't do anything. For example, if your DNA code changed from CCU to CCC, it wouldn't make a difference, because your body would still make Proline. Even if your body uses a different amino acid in the chain, some amino acids are so similar, it doesn't make a difference if you use one or the other.
However, sometimes, mutations can cause BIG changes. Sickle cell anemia is an example of how a change in just ONE SINGLE BASE PAIR can make your cells go from a healthy looking round cells on the left, to bent, sickle shaped cells on the right.
Now, granted, my explanation is simplified and I am just giving you a breadth first overview, so for those that have deep knowledge of this subject, please forgive me :) If you're still awake, I went through this long explanation to make a single point: There is no magic in the way our cells work and the way our bodies work. There is no magic at all. DNA is not a mystic code handed to us by neo-Moses. It is explicable.
Btw, in case you're wondering, 7th graders can indeed understand this if you spend enough time and make sure you're as obvious as possible. Back to creationism.
So, we started talking about human evolution and natural selection. I showed the standard pictures of Austrolopethicus Afarensis, Lucy, Homo Habilis, etc. etc. and explained human ancestry. One of the creationists in my class looked a a photo I was showing, and then gleefully raised his hand to say that there was a "missing link" between the forms. My diagram was purposefully incomplete because I didn't want to include every single transitional form. Remember, 7th graders, not people with the greatest attention spans. I let him go to the front of the class, handed him my marker, and let him happily point to where he thought there was a gap. "If this is a monkey and this is a monkey, then where's the link between this and a human?" I then asked him a question...
"This one, this one right here! You need something here."
"No I don't."
"Yes you do, you need something here."
"Because if you don't have it then this doesn't make sense."
The kid was dumbfounded by the fact I just wasn't impressed. He laughed and was excited. His father is a pastor, so I know that his father passed this idiocy onto him, and he was making dad proud. It was kind of sick in a way. I then rolled up the overhead projector, and did a quick sketch of a jigsaw puzzle.
"Well, according to the logic of our classmate here, there is no puzzle."
"Wait, there's a puzzle right there..."
"But we're missing pieces! And because we're missing pieces, there is clearly is no puzzle."
One bright young girl raised her hand and said "Well we can figure out what pieces should be there because we know the shape 'n stuff."
The creationist kid was flustered. He hadn't thought of that. His dad hadn't put it into his mind and he didn't have a cookie cutter response. I decided to go on in an even manner.
"If you don't believe in evolution, then you don't believe in DNA . If you don't believe the planets were made from the accretion of dust and large particles in a nebula, you don't believe in gravity. If you don't believe in radiometric dating, then you don't believe in atoms."
Now I know, some of you will say I'm being mean and using my authority, blah blah blah, but honestly, you can't have it both ways. Mutations in genes happen and we can predict their frequency with a bit of calculus and some observation. Mutations can cause big changes in an organism. We don't need to have Homo Erectus just morph into Homo Habilis one day, we just need 10-15 mutations to occur within separate individuals of Homo Erectus and for those mutations to be beneficial, and for them to spread out through the population over the course of millions of years. Some mutations can occur once every 1,000 years. The earth is 4.5 billion, so really, that's just a drop in the bucket.
We know that our ancestors in the fossil record are linked because we can examine their DNA and use techniques, like a molecular clock, to tell us when two species diverged from one another. DNA doesn't lie. There is no magic. You get DNA from ancestors, and that is the only way you get it. If I can compare the DNA of one fossil, to another, I can even predict that there should be a transitional form, AND even tell you what it should look like and where you can find it. We have plenty of transitional forms for humans which you can peruse here:
If you don't believe in evolution, then you don't believe in DNA, or you believe DNA is magic.
Some of the students didn't care about what was going on because they were more concerned with trying to impress members of the opposite sex. The boy in question was stunned to say the least, but I did not single him out. He simply came to me with a misunderstanding, and I corrected him as a teacher should. The great thing, was that many of the kids in the room had a light bulb go off. Science was logic. Science was reason. Science had evidence. Science left no room for magic. This was a lesson I hoped they would take with them for the rest of their lives.
In case you're wondering, I went up to the creationist kid afterwards and simply thanked him for participating in class and helping with our discussion, and that it will be reflected kindly in his participation grade. He smiled.