I'm not sure my response was the best one for this, for I replied that I believed in creative evolution. I didn't get much of a chance to explain after that, as he seemed shocked and walked away.
Basically, the Catholic Church says that all of creation is being held into being by a Creator God. God chose to create the entire universe out of nothing, set all the physical laws into place, is intimately connected with the continuation of creation at every moment and will choose at one point in the future to bring it all to a close.
Science is the study of how creation works, all the laws which God has put into place to make the universe and ordered and non-chaotic place. Evolution is the theory for how our universe went from a primordial (life-less) soup to a place that is host to a world teeming with such diverse forms of life. I've not heard of another scientific theory that explains how this change has come about and until I do I have no qualms with supporting it.
So there are two questions you can ask, "how does creation work?" and "what is the purpose of creation?" Science answers the first and religion the second. They don't contradict because they ask different questions. The only time they appear to contradict is when one field tries to answer the wrong question. When science tries to answer questions on the purpose of creation or when religion tries to answer questions on the how of creation, then you run into problems.
The apparent contradiction comes about from just this problem, where both sides stepped outside of their field of expertise. Some scientists have said that evolution removes the need for a creator, when that is simply not the case. To say that is like saying that because you understand art theory and know all the techniques used in creating a painting there is no need for a painter.
Some religions have also made the same mistake when they tried to turn the Bible into a science textbook. The Bible is the story of salvation and while it is possible that it contains scientific truth, that is not it's primary purpose nor should it be used that way. The purpose of Genesis is to let us know that God created everything out of nothing and to tell us why (so that all of creation may be in union with God and share in divine love).
Properly understood though they build upon each other and enlighten the other. As JPII said, "Science can purify religion from error and superstition. Religion can purify science from idolatry and false absolutes"
Further resources to learn more about the relationship between the Catholic Church and Science can be found at these websites:
My primary evangelization partner from last semester came back to into town this past weekend, so we of course went out to share our faith. With three days of questions I have plenty of content and I've promised followup on a couple of these, so look forward to new blog posts!
Pray he has a safe trip back home and that in this new location he'll continue to share his faith!