It's more than simply a claim (and I'm not the one who made it). It's actual peer-reviewed and published research; y'know, sciency stuff. I actually couldn't care less what the function of that 97% is. In fact, let's raise that to 100%. I am not myself an evolutionary biologist - my personal field is astronomy - however I can read and I do in fact enjoy learning from people whose knowledge outstrips mine (which is sort of the point, really). Try doing what I did; dig around some of the research papers. Hell, there's videos of this stuff being presented at lectures.
At the age of five, Skagra decided emphatically that God did not exist. This revelation tends to make most people in the universe who have it react in one of two ways - with relief or with despair. Only Skagra responded to it by thinking, 'Wait a second. That means there's a situation vacant.'