Neolithic (Agricultural) Revolution
It is the beginning of the evolution of human societies which cumulated in the one we inhibit today. Before the Neolithic Revolution humans, which had evolved into what they are over millions of years, were hunter gatherers. But domestication of crops and livestock allowed for the establishment of settlements and subsequently all sorts of developments and innovations.
Before the Neolithic Revolution the human population of the planet was pretty much stable for thousands of years, hovering around the 4 to 5 million mark. After the Neolithic Revolution, in a period of a couple of thousand years, the population increased something like a thousandfold. To sum it[1] up: