The basic tenets of the theory of evolution are ...
Those are my words. On this page, I'll give you science's definition of evolution, and then we'll look at a couple details that are important to the creation vs. evolution debate.
The most basic definition of evolution is change over time. To be more specific:
Alleles are genes that vary from individual to individual. For example, among humans I might (and apparently do) have a gene for brown eyes while my wife has a gene for green eyes. The two genes both code for the same trait—eye color—but produce different results.
So the most basic definition of evolution is not controversial. Evolution is the change in the frequency of alleles in a population. So if Americans became 90% blue-eyed, then evolution would have occurred.
No one has a problem with that. The question is, do changes in frequency of alleles in a population accumulate over hundreds of millions of years to the point that humans can descend from bacteria?
Ah, now that's a question.
The answer, unfortunately, has to be relegated to other pages. We're not going to answer that on one page.
Here's a couple more quotes just to show that the most basic definition of evolution is change of any sort.
Again, no one disagrees that evolution happens. The question is, has evolution been going on, bit by bit and small step by small step, from bacteria to modern life?
Arguments against the theory of evolution regularly point to the remote possibilities of certain structures arising by chance. Evolution does not rely on chance.
Another term for the theory of evolution is natural selection. Selection is the opposite of chance. Selection is choice. The theory of evolution teaches that nature selects certain individuals by the struggle to survive in much the same way a farmer selects cows that produce the most milk.
The theory of evolution involves two steps:
The first of those steps really is chance. Mutations occur in every generation, and so they provide abundant raw material upon which selection can work.
The second of those steps is not chance at all. Mutations that increase the possibility of reproduction are preserved. Such mutations will accumulate over successive generations leading to large changes over time.
That is the theory of evolution.
It is the rest of this site that is devoted to determining whether it is true.