My understanding is that McMaster wants as diverse an applicant pool as possible, and I think that by not requiring students to have taken too many science courses before applying, they're trying to encourarge more non-science students to apply. And while science students' science class scores can sometimes correlate with med school success, that's not to say they're absolutely necessary. The first year of med school focuses heavily on physiology, and at no point will you be taught about galvanic cells, friction, or the plant kingdom. Their reasoning, it seems, is that a strong poli-sci, music, or history student should be able to learn about physiology as well as a strong science student. Science undergrads will have a leg up on some of the non-science undergrads, particularily if they've taken physiology/biochem courses, I'd imagine -- but not having taken physics and chemistry in your undergrad by no means means you'll do poorly in med school. You just might have to do a bit more studying in the first year or so.
