This talk by David Jubb, in particular part 5 here, points to humans being originally vegetarian, whatever we later have needed to do for survival; very high glycemic fruits can present a problem for some people, again not part of our original biological diet although fruit was; beans and grains not our natural biological foodstuffs; the long and ancient history of human diet is long and sometimes seems complex but maybe distils down into something simpler and reflected by the experiences we have today.
