I want to take a moment to remind you of where we have come from. For the first three million years of human history, we lived according to circumstance. Our lives were ruled by the happenstances of ecology. We existed, as all animals do, in fear of hunger, predation, weather and disease. For the following few thousand years, after we had grasped the rudiments of agriculture and crop storage, we enjoyed greater food security, and soon destroyed most of our non-human predators. But our lives were ruled by the sword, the axe and the spear. The primary struggle was for land.