Our knack for collective learning — preserving information, sharing it with one another, and passing it to the next generation — helps us create entirely new forms of complexity.

But they also survived the ice ages. Tools for survival included the controlled use of fire and better clothing technology. They also met others, told stories, and exchanged knowledge through the development of symbolic language and art, such as drawings on cave walls. Change was slow, but change was on the move.

Writing likely originated as a system of accounting as elites and power brokers who were accumulating more and more resources tried to keep track of their wealth. Eventually, the symbols used for accounting evolved to convey all the nuances of everyday languages and generate literature, history, and proper writing.

Using their learned knowledge from the environment, humans began to experiment with agriculture, which became a revolution. Farming produced a surplus of food, allowing others to take up new work. Societies became diverse, populations exploded, and collective learning thrived.

As cities grew, they increasingly reached out to each other. Commerce and conflict exposed once-isolated populations to a diversity of culture, religion, philosophy, language, and technology, as well as disease. And major trade routes such as the Silk Road paved the way for massive growth throughout Afro-Eurasia.