In addition to sitting on a few classes- can he ask someone in the history department (departmental secretary or chair) to set him up for a lunch with a senior who is majoring in history?
Get the “skinny” from someone with similar interests. At some LAC’s, History and the like are where the brainiacs congregate, but at others-- not so much. Find out from the senior how many of his/her friends are writing honors theses, how many have gotten internships at museums, historical societies, auction houses. Find out how many of his/her friends have applied for fellowships, and how much faculty support they’ve gotten for their applications.
He will either walk away from this with a “oh god, not four years of this” or “Wow, I can see myself here” which will answer your question.