Introductory Paragraphs
The intro paragraphs are good, but they could be a lot better.  I think that right now there's too much of a technical sound to it, as opposed to something more educational and inviting to people trying to learn about the subject.  I'd just like you to compare/contrast with the following paragraph, which is how evolution is introduced in a Bio101 textbook:

(Fair use excerpts follows)
Evolution originated with Darwin's publication of the Origin of Species...He argued from evidence that the species of organisms inhabiting Earth today descended from ancestral species.  Second, he proposed a mechanism for evolution which he termed natural selection, the idea that organisms can change over the generations if individuals having certain heritable traits leave more offspring than other individuals.  ..In modern terms, we would say that the genetic composition of the population had changed over time, and that is one way of defining evolution.  But we can also use the termin evolution on a much grander scale to mean all of the biological history, from the earliest microbes to the enormous diversity of modern organisms.

An understanding of evolution informs every field of biology, and applications of evolutionary biology are transforming medicine, agriculture, biotechnology and conservation...Evolution integrates all of biology.
(above is for example purposes onlywe can't use this in the article.)

We can't use the above since it would be fair-use, but do you see what I mean about making the article more accessible?

Another thing I'd note about the above example is that it also makes Evolution sound more exciting.  Just because we are an encyclopedia doesn't mean we can't put the subject in the exciting, important context that it deserves.

We could use something closer to the above, and then dive into a description of how the Theory of Evolution (what you might call a description of the fact of evolution that's described above) has developed from Darwin's original theory to modern-day explanations (and at the same time state how the question of whether evolution occurs has been a relatively incontroversial fact amongst biologists for the better part of a century).