No doubt in the extreme social conditions proposed by some there would be marauders to contend with, but I think for the most part people would tend to band together - we are social animals, for the most part, and survive better as cooperating and trading groups than as wandering singletons, who, however fearsome their personal armory, must sleep sometime.

It certainly doesn't hurt to know your wild foods (and their nutritional value) - there is no time of year I couldn't find vegetation to eat in the woods and fields, couldn't find some creature to fish for, or small animals to snare or trap, or even fat grubs. Consider that bears survive on mostly berries and insects, with the occasional meat meal (although they do hibernate during the time of scarcest food).

A fine wild food example is the cattail: the root is starchy and edible, the young shoots are edible; when green, the seedhead is edible (boiled, tastes a bit like corn); when covered in pollen the pollen can be gathered and added to flour mixes. And when it has gone to fluff, it can be used as insulating material in quilts or clothing.