Most people assume that world history is just an endless series of facts, isolated to certain regions and time periods. Focusing on the details sometimes prevents us from seeing the big picture. World history is really about change. It is about the evolution of civilizations. It is about expansion and decline and about actions and reactions. World history examines the factors of change including geography, economics, government, culture, science, technology, society, and religion. World history is also about connections and the themes that connect civilizations over time and space.
With the advent of the Neolithic revolution, humans acquire the building blocks of civilization. From there civilizations spring up around the fertile river valleys of the Tigris and Euphrates Rivers, as well as the Nile, Indus, and Huang Ho Rivers. Many different rulers rise and fall as the civilizations become more and more complex culturally and technologically.
With the increased complexity come many developments. First is the rise of the classical empires. Classical Greece, Rome, India, and China all make their stamp on the history of the world for thousands of years to come. The complexity of the classical period also produced new sophisticated religions and philosophies that have impacted the history of the world in immeasurable ways.
The classic regional empires that flourished had all fallen partly due to nomadic invaders. With their fall, the stability enjoyed by the regions under their influence was lost. People began to rely on decentralized political structures. The limited trade between the classic regional empires continued along the Silk Road and developed into the first interregional trade network. This interregional network spread ideas and religion of the classical period. Invasions began this period and they also end it. Another nomadic group, the Mongolians, staged several invasions following the interregional trade network. Although these invasions were disruptive, they were only a temporary condition. Civilizations continued to centralize and develop. The march of progress would not be stopped.