Hint: It wasn’t plants:

Early Americans settlers were “indifferent” farmers, according to many accounts. They were fairly lazy in their efforts at both animal husbandry and agriculture, with “the grain fields, the meadows, the forests, the cattle, etc, treated with equal carelessness,” as one 18th-century Swedish visitor described—and there was little point in farming since meat was so readily available.

Settlers recorded the extraordinary abundance of wild turkeys, ducks, grouse, pheasant, and more. Migrating flocks of birds would darken the skies for days. The tasty Eskimo curlew was apparently so fat that it would burst upon falling to the earth, covering the ground with a sort of fatty meat paste. (New Englanders called this now-extinct species the “doughbird.”)

In the woods, there were bears (prized for their fat), raccoons, bobo­links, opossums, hares, and virtual thickets of deer—so much that the colo­nists didn’t even bother hunting elk, moose, or bison, since hauling and conserving so much meat was considered too great an effort. A European traveler describing his visit to a Southern plantation noted that the food included beef, veal, mutton, venison, turkeys, and geese, but he does not mention a single vegetable.

Infants were fed beef even before their teeth had grown in. The English novelist Anthony Trollope reported, during a trip to the United States in 1861, that Americans ate twice as much beef as did Englishmen. Charles Dickens, when he visited, wrote that “no breakfast was breakfast” without a T-bone steak. Apparently, starting a day on puffed wheat and low-fat milk—our “Breakfast of Champions!”—would not have been considered adequate even for a servant.

Indeed, for the first 250 years of American history, even the poor in the United States could afford meat or fish for every meal. The fact that the workers had so much access to meat was precisely why observers regarded the diet of the New World to be superior to that of the Old.

Lobster used to be fed to prisoners, because it was considered inferior to other meats. The notion that we ate plants is all part of the junk science of nutrition.