The Soil Health Academy is a group of farmers from across the US that educates other farmers in regenerative farming practices. I was recently reading a blog post by one of their instructors, Allen Williams, about the role of phytochemicals (carotenoids, flavonoids, ellegic acid and allium compounds). We hear about the importance of vitamins and minerals in our diet, but I had never heard of phytochemicals before, and from what I can gather, the research on these compounds in relatively new.
The more one digs into soil health and human health, the more one realizes how incredibly complex both of those things are in and of themselves, and how complex is the relationship between the two. For example, we are just beginning to understand the relationship between soil fungi and plant roots: how they exchange carbon and nitrogen and the particular isotopes of carbon and nitrogen that are exchanged. Similarly, we are also learning more about the role that bacteria and fungi play in the human body. There are more bacteria and more fungi cells in a human body than cells with human DNA!
As far as I can see, there are two ways of responding to this complexity when deciding how to farm or what to eat. The first is what I would call the a priori approach. You use scientific investigation to figure out the functions of all the different parts of the system and then build a model of health around the organization of those parts. The second I would call the a posteriori approach. You look at flourishing systems (healthy soils and pastures and animals, and healthy populations) and assume those as your models. Then you begin to explore the parts of the system and see how they fit. With a priori approach the models of the overall system are open to constant revision. With the a posteriori approach, the models of the overall system are relatively fixed, though the understanding of the role of the parts can deepen and change.
To my mind, the a posteriori approach is more reasonable. I’m doubtful that, considering the complexity of biological systems, our knowledge will ever be comprehensive enough to build a great a priori model. More importantly our scientific knowledge is not the cause of biological systems working. The systems work whether we understand the details or not. By beginning with the macroscopic view (what farming practices create healthy soil? and what diets create healthy people?) we begin with what is more evident and move to what is less evident, never allowing our always-open-to-revision understanding of the details to override the givenness of the natural world.