Comment by abeppu
Is there an agricultural analog of portfolio theory? Permaculture always seems to be pitched in terms of the ecological perspective, but I wonder if there's some way to firm up the idea that if your fields/portfolio are diversified across a range of crops/assets whose yields are not closely correlated, you'll have fewer bad years.
Well I'd say the ecology perspective is exactly that! It's not just about partitioning the resources efficiently or creating synergistic relationships... A diverse interconnected ecosystem is a damped system capable of absorbing shocks.
But I get your point. This was of course obvious to any subsistence farmer in history. Without long-distance trade and perfectly reliable preservation, you had better be harvesting food as close to year-round and possible, which means lots of different crops (in different microclimates if possible, to spread out their season.)
There were layers and layers of fallbacks, down to "famine foods" like wild roots or acorns. They also invested in social relationships by banqueting each other in productive times.