> For Smil, the history of human civilization is nothing more and nothing less than the history of attempts to balance a single equation: joules of energy input

> For Smil, the history of human civilization is nothing more and nothing less than the history of attempts to balance a single equation: joules of energy input, in the form of food and fuel, versus joules of energy output, in the form of metabolic demands, muscle power to perform labor, and heating. https://en.wikipedia.org/wiki/Energy_slave https://en.wikipedia.org/wiki/Energy_slave