Good questions about what is traditional. Apparently, if you go back far enough, nothing. Nonetheless, eating more than the Roman one-meal-a-day in the last century seems to have led to 1) healthier babies 2) taller people. Healthier babies = less infant mortality. That could be more related to what we eat rather than when. Growing up in Montreal in the middle of the last century, the schools then gave us an hour and a half for lunch which we called dinner. Evening meal was smaller and called supper.