Usually when someone is trying to debate religion or creationism with you, they have no way to back up their arguments. It is in my opinion that these people generally are not even worth the time to debate such things with. Chances are they are not an expert in an even remotely related field (experts tend to be able to provide actual evidence) but more of an "armchair scientist" who says they enjoy "intelligent conversation" but usually just end up stubbornly refusing to see past their own views. These are not the type of people I care to refer to in this post, it honestly makes no difference what they think on the particular issue.
Every once in awhile you stumble upon someone who can actually provide some kind of "evidence" for what they believe. This is intriguing because at first you think, "maybe I will learn something new". More often than not however, they end up referring to an article from a church's website that was written up by the Pastor with no science education past the High School level, or a book written by some hack with a phony "doctorate" from a diploma mill bible beating "college" (See: no science education past the High School level). What these cretins do not seem to realize is that just because something is published, does not automatically make it valid or even substantial in any way.
At this point you may want to (attempt to) educate this person on the process and importance of peer reviewed scientific evidence and conclusions. One scientist working alone in his lab can come to any conclusion he wishes, to suit his own needs, but science does not work that way! Science is a collective of all the evidence which we know to be true because it is universally tested with the same results no matter what. Disproving a well known scientific theory by getting a different result as everyone else can be more of a scientific breakthrough than discovering something completely new! Emphasize the importance of peer review and how it works exactly, and you may end up leaving the other party a bit more informed and more skeptical of so-called "evidence" they are given.