I'm actually going to disagree with the above posters (and it seems the conventional logic of SDN). No, major does not matter directly. Ceteris paribus, a lit major is the same as a bio major. BUT that is a very unlikely position because I think science majors get a big leg-up on some of the other parts of an application. For example, almost all medical schools require a letter of recommendation from one or more than one science professor(s). If you have just taken the premed pre-reqs how are you going to get a LOR? Are you going to get a LOR from your general chemistry prof who taught a class of 600? For me all of my letters of recommendation came from profs I had small upper level seminars with. I suppose its possible, but I think the science majors have a leg-up.
Also for medical school, research is a big help to your application, it is much easier to get involved in science research if you are a science major. At interviews, I have been interviewed by many PhDs, and sometimes the conversation has swayed into a scientific topic. Having comfortability with discussing a higher-then-MCAT-level science topic can definitely help you score points with an interviewer. But this is a discourse someone who had experieinced upper-level science electives that involve reading journal articles and talking about research will be more skilled in.
Lastly, BCPM GPA counts, and for me, it was very hard to do well in the pre-req classes because of curves and other pre-meds. I only slowly rebuilt my BCPM GPA in upper level courses that although they were hard, were not impossible to get decent grades in because the classes emphasized knowledge over competition.
Now, I know many humanities majors who got into medical school and go to medical school and rock it without ever taking a single BCPM class over the pre-reqs. But I think it is innacurrate to say there is NO advantage in being a science major in the premed game.
-Roy