Hi Chelsea et alia,
Evolution is more than a hypothesis. And the biologists didn't even need JPII to tell them that. Evolution is in fact the underlying framework of biology, without which nothing makes very much sense. Biologists have observed the evolution of new species (on a minor scale), and of course microevolution, which even the creationist crowd accepts. What's the difference between microevolution and macroevolution? A longer period of time during which more and more changes can take place. So why does evolution occur at all? There are several fundamental reasons. First, anyone who has taken more than a modicum of organic chemistry at the college level knows that organic reactions are "messy". When doing an experiment to create a given organic compound, you usually got the compound you were seeking, along with a whole cluster of "impurities". These impurities are the result of, in part, a carbon atom's ability to link to another carbon atom, which in turn links to other carbon atoms, forming at times large polymers (DNA is a polymer). Even after controlling for all possible variables in the laboratory, reactions typically don't go exactly the same way twice. Another reason is the latent radioactivity of not only the metals potassium and rubidium, but carbon itself. Potassium is an essential trace metal for all plants and animals. Rubidium is a fairly common radioactive metal which is closely related to potassium (they are both alkali metals). A person weighing 100 kg has about a gram of rubidium in his body. And then there is carbon itself. Carbon 14 drifts down from the upper atmosphere where living beings ingest it. Eventually, they die, and the carbon-14 importation stops. This is why carbon-14 dating works (up to about 50,000 years). All this natural radioactivity can easily cause genetic mutation.
Is evolution "certainly true"? This is a tricky question, but the answer is "no". It is no more certainly true than Newtonian mechanics (which fails for things that are very small or going very fast), or any other field in science. It's happened before that today's Wonderful Theory turns out to be tomorrow's junk. But for a 150 year theory, evolution is stronger than ever. This should not be construed to mean evolution is perfect. Evolution, like every other current branch of science, has its share of unanswered questions. And it is quite possible that they will remain forever unanswered (this has nothing to do with biology and everything to do with a peculiar result arising from Godel's Incompleteness Theorem. I had some details here somewhere, if I can find them I will post them).
A couple more comments, and then I'm off. No biologist considers evolution to be "dogma". Science (and scientists) do not work that way. Finally, "proof" exists only in mathematics and alcohol (I got that from someone arguing with the Catholic apologist Robert Sungenis).
This can be settled as to whether "evolution" as you use it is a hypothesis or not by simply providing a definition for the concept you hold (not that it will necessarily be the same as the concept taught in grade school, secondary school, college or university)...and offer the objectively verifiable support for the concept.