My first ex-husband got a BA in Social Anthropology at a competitive college and went directly to the Business School connected to his college. He was in the minority; most of the (then men) had worked or been in the military.
Here are the requirements; the same as they were in 1957:
http://www.hbs.edu/mba/admissions/admissioncriteria.html
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H*****d B School is a demanding, fast-paced, and highly-verbal environment. We look for individuals who will thrive on sophisticated ideas and lively discussion. Our case-based method of learning depends upon the active participation of prepared students who can assess, analyze, and act upon complex information within often-ambiguous contexts. The MBA Admissions Board will review your prior academic performance, the results of the GMAT, and, if applicable, TOEFL and/or IELTS, and the nature of your work experience. There is no particular previous course of study required to apply; you must, however, demonstrate the ability to master analytical and quantitative concepts.