Jumping to pre-agricultural humans, 50,000 years ago or so, we took in energy as food, plants and animals, and we used it by doing stuff: chopping wood, going for a walk.
Pasemos a los seres humanos preagrícolas, hace 50 000 años o más, tomamos energía como alimento, plantas y animales, la usamos haciendo cosas: cortando madera, yendo a caminar.