Agriculture, the conversion of sunlight to chemical energy and fibres for human use, and Industry, the manipulation of matter to create artefacts, form the foundation of any economy while also being dependent on one another. Agriculture, even in its most primitive form, cannot function without tools (try digging soil with your bare hands), which are products of industry. However, industry, especially handcraft industry, requires the energy provided by agriculture to both create artefacts and extract the raw materials necessary. Neither of these elements stands apart but rather meshes in an intertwining whole. This follows naturally from humanities evolution from only being tool-wielding hunter-gatherers to farmers who used tools with both agriculture and industry being formed together at the same time.
What are the practical aspects of this analysis? It basically allows us to start technological triage on the basic elements of our tech base in a system based holistic approach. We can define completely internal economic units e.g. an organic agriculture with horses, charcoal from a logging industry (half agriculture, half industry) and a blacksmith with bog iron is a self-sufficient unit that can be expanded/changed in various ways and join other units. Expanding the smithy to a machine shop, using bicycles, adding recycling technology, electricity and/or basic renewables (other than charcoal and food) are some of the ways the alter this basic unit.
Lets imagine this system, how it functions and how changes and linkages could occur. We’ll use a small village surrounded by farmland and forests, no major settlements are nearby (towns and cities) only other villages connected by roads. For the baseline village the only power sources are food (human), fodder (animal) and wood (charcoal, heating or cooking). Local resources are what can be grown and accessed from iron deposits (bog iron or minable) that a small village could utilise. The baseline tech/skill structure to provide the economy is founded on farming, logging and blacksmithing, each feeds the other in some vital way to produce all of the resources the others need to function. The farmers and loggers require tools from the blacksmith, the blacksmith needs charcoal made from wood and the loggers and blacksmith need food from the farmers (yes, they would grow/hunt their own in this situation but only a supplementary amount). Horses and oxen provide transport both within the village, from the farms and to other villages. This basic structure could last indefinitely (if the iron is recycled) without outside imports, unless some disaster hits. However, it doesn’t fulfil all the needs of the villagers; cloth needs to be spun to make clothes, shelters needs to be erected and medicine created for times of sickness. So these other tech units (fibre production, then spinning thread, making clothes and the tools necessary for the cloth industry) need to be added. In a peasant village these jobs wouldn’t be done by specialists, the wives would have spun cloth and made clothes, but as specialisation occurs new professions would have sprung up but the basic tech/skill structures are still there.
Now let’s change the basics. Instead of only having access to wood, food and fodder, these peasants use either windmills or waterwheels to provide motive power. For this you need a more advanced smithy and also carpentry. Therefore, to add the complexity of waterwheels or windmills we have to expand the skills of an already existing component. The same occurs if bicycles are added, along with new materials. What happens if we upgrade the single blacksmith to a small machine shop and foundry? Suddenly the range of tools and machines that can be made (and the quantity) has expanded and if we add electricity more things become possible still (like radio). To accommodate this would require more specialisation in the machinists and more resources, e.g. if the machines run of an electric motor or a heat engine then the energy would have to be provide via either the windmills, waterwheels, biofuels or wood. Every change affects all the relating techs and alters, even if only slightly, the dynamics of the system.
Ultimately, which basic forms of agriculture and industry are implemented in a given area will depend on both the local environment of resources, weather/climate plus wildlife and the community of technology in adjacent areas. From these two elements will a human-technology ecosystem form.