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RCAlyra,
Creationists take issue with common descent. That's pretty much it. The rest is window dressing.
A while back it was discovered that a brand of lab mice had become contaminated by mutants, and had been for a while. Lab mice aren't just random albino mice from a pet store. They are ridiculously pedigreed like purebred dogs. By having these purebred uniform mice you can do controlled biological research. Otherwise, how would you know if your result is due to what you want to study and not due to some biological difference between your control and test populations? Simple, by having genetically uniform mice in respect to the trait you're studying. Thus, ridiculously pedigreed lab mice. Different brands suited to different purposes.
So what happens when you discover that some of your purebred mice aren't suitable for their advertized purpose, and that the mutant mice may have skewed the results of years of research?
Well, you dig up those preserved specimens, you dig up that ridiculous pedigree, and work out which litter contained your original mutant. Then you track the mutation all the way through your pedigree, and provide the necessary information to allow the data to be corrected for the presence of the mutants. Also, you seperate out your current inventory and relabel the mutants as a new product. Neat stuff.
Here's the really neat thing. This is only possible because the "family tree" generated by genome analysis is identical to the recorded pedigree. The sequence comparison algorithms used in genome analysis have a proven track record in the real world. It's also possible to simulate sequence evolution on a computer for millions of generations. The algorithms prove themselves there, as well. So, not only do we know that the algorithms work, we can quantify how well they work. They can report their own confidence in the "family trees" they generate.
So. What does it mean when we can take genetic sequence data from all sorts of life on earth, run it through these verified and tested algorithms, and have them spit back out a high confidence "family tree"? Correlation is not causation, true, but we have tools that will tell you how slim the chances are that it's not.
Should all that be necessary for highschool biology? Of course not. But all that and more is available underpinning the statement in highschool biology classes that life on earth shares common ancestry. Theories should be questioned, but the questions asked by creationists have already been answered... there is no debate where the creationists wish to debate.
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Simple Machines in Higher Dimensions
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