In the wake of the Bubonic Plague, labor shortages were left all across Europe; with nearly 30% of the population wiped out by the Death, manpower was in extreme demand, with little supply to meet the need (Middle Ages - Definition, Timeline & Facts). However, it was also during this time that the waterwheel was evolved to meet the situation at hand; and as a result, the first instance of inanimate power was born. The waterwheel functioned simply: when it was placed in moving water, a rushing stream would rotate a wheel, deriving mechanical energy from the natural flow of water. This mechanical energy was then transferred through a series of machinations, allowing for the function of complex machines capable of performing a range of tasks; most notably, the milling of grain (InDepthArticles.com). 

Efforts were made as well to develop a horizontal waterwheel; it is important to distinguish it from its vertical counterpart. The vertical waterwheel was far more energy efficient than the horizontal wheel, as the directional flow of water also led to the cancelation of forces acting upon one body (Hansen, WaterHistory.org). As a result, milled grain could be far more easily produced and distributed, leading to a rise in that specific industry (Markets and Economic Growth: The Grain Market of Medieval England, Clark, Gregory). This trend of automatization would persist into the modern era, prevalent in an era of AI. Furthermore, the implementation of mechanical energy would be adopted and advanced by all major civilizations after the Europeans; evolved forms of the waterwheel are still used today in nuclear power plants to generate steam.