The millennia have added energy from the flow of water and, later, air to the repertoire. But, important as water- and windmills were, they did little to change the overall energy picture. Global energy use broadly tracked the size of a population fed by farms and warmed by wood compared to more than 100,000 years whereby humans derived all their energy from what they hunted, gathered and grazed on or grew for themselves. Their own energy for moving things came from what they ate. Energy for light and heat came from burning the rest. What is needed to completely transform the energy systems ?