The important number is not what percentage of admitted students are from various fields so much as the percentage of applicants from particular majors that are accepted. If you go through the AMCAS research section, you will see that there is no correlation between undergraduate major and later med school performance. The admission rate is similar across most majors, but, supposedly, history has one of the highest admit rates and biology has one of the lowest, although the difference is like a 55% admit rate for history applicants and 45% for biology applicants, so it's nothing very substantial and there are many confounding factors. As mentioned, as long as you get strong grades and a good MCAT, have the story to back up your career choice, do whatever you will find interesting (and, of course, take all the premed prereqs).