I'm sure someone will tell us who knows, but it's likely Italians ate barley and other old grains, flatbreads, dumplings, root vegetables, fruits, eggplants and squash, fish, shellfish, nuts, meats, eggs and cheeses.
It surely varies by latitude and culture, but I had the general impression that migratory humans ate game, stews, mushrooms, wild fruit, dried meat, nuts, fruit, and fish. As agriculture developed, they ate grains, beer, and gradually better diet with more diversity.
We put too much on tomato sauce, as many sauces improve pasta, not to mention yoghurt, milk, cream, butter, and cheese.