The Neolithic Revolution began around 12,000 BCE as some humans transitioned from nomadic hunter-gatherer lifestyles to more sedentary agricultural societies, settling in permanent villages. This was driven by climate change, food scarcity, and increasing populations. Early sites included the Zagros Mountains where animals like cows, pigs, sheep, and goats were domesticated. Farming allowed for surplus food and more complex, hierarchical societies to emerge with specialized workers, social classes, governments, religions, and other institutions, leading to early civilizations in places like Mesopotamia, Egypt, India, and China along major river valleys.