Once upon a time, all humans got their nutrition from foraging, or as it is called when the food can see you coming and can run away, "hunting". Somewhere in between foraging and hunting lies "clamming", the art of digging a clam out of the mud before it realizes what you are up to. Some of them move pretty fast, and easy gathering turns into active hunting. If you are not a very good clam hunter, then maybe it is better to go collect mussels; they don't move and can also be used to make a tasty chowder for dinner.
Domesticated animals make 'hunting' a lot easier, and domesticated plants take the effort out of foraging. In the days leading up to actual planned agriculture, the care and domestication of wild plants must have occupied the attention of tribal leaders of the day. Living near a grove of fig trees took a lot of the effort out of mid-summer foraging with maybe a three month season of ripening fruit. Winter in sub-tropical climates brought out the slow growing greens, chicories and mustards and cresses and lettuces that could be clipped again and again. In a good foraging environment, there is always something ready to eat, whether it is actively growing like a chicory or whether it is dormant and waiting for the next growing season, like a cluster of sumac berries.
Through selective encouragement of various plantings then, it should be possible to plan the foraging throughout the year. This is the idea behind the "food forest", a new term for a very old idea. Rather than have a vast expanse of one plant, something like the typical 80 acre grove of navel oranges, why not mix up the plants in order to have fresh fruit every month of the year? Citrus can stay on the tree six months or more, so maybe I have not started off with the best example, but what do you do for the other six months? Plums and cherries for early summer, figs for mid-summer, apples and pears for late summer into fall, and finally persimmons and pomegranates to finish out the year until the citrus are once again in season.
The idea is easy to explain and easy to implement with fruit trees, but leafy and root vegetables require attention, they need to be picked at just the right moment for the right flavor. Or do they? Instead of growing carrots as a row crop and having a big harvest where they are gathered and stored, how about just continually throw out carrot seed into the garden beds? Have your carrots in all stages of their life cycle, from little sprout to the "baby carrot" stage to soup pot size and then to old and slightly woody and gone to seed. My garden has all those stages of carrot, and consequently I never need to buy carrots from someone else's larder (the grocery store) and I can pick whatever I need the day I need it. By putting attention in on the front end, i.e., continuous plantings of carrot seed, I don't have to put a lot of attention into weeding, spraying, cultivating, etc. on the back end. I can do that with celery as well. By growing celeriac varieties, one plant can provide me with celery cuttings for a couple of years before it completes its life cycle.
When I go out and walk the rows between my hugelbeds, there is wide variety of food plants that can be clipped to put either into the salad bowl or the soup pot. By having a wide variety of plantings in my 200' of hugelbed, I have guaranteed food security right outside my back door. How much would it take to keep one person supplied? That's not really the right question to ask. If there is more there than I can eat, I can give it away/feed my animals/chop it for green manure/let the wildlife graze it, it's not going to "go to waste". This concept of "go to waste" is the product of an economic system that puts a price on everything and know the value of nothing except the almighty dollar.
If you are going to plant a garden for food security, then you can't evaluate it by the economic value of the produce harvested from it. The way to evaluate it is by asking the question "can I pick enough to satisfy my hunger?".