The document provides an overview of early civilizations from 8000 BCE to 600 CE. It describes the transition from hunter-gatherer societies to agricultural societies beginning around 8000 BCE, marking the start of the Neolithic era. Early civilizations developed independently in river valleys including Mesopotamia, Egypt, Indus River Valley, China, and Mesoamerica. These civilizations were characterized by cities, centralized governments, social classes, job specialization, writing systems, trade networks, and religious and philosophical belief systems. Major classical empires that arose during this period include Greece, Rome, various Chinese dynasties, India's Mauryan Empire, and the Maya in Mesoamerica.