Each concept here is mapped to its prerequisites — the ideas you'd need first to understand it — all the way down to four foundations: Space, Time, Energy, Pattern. Click any prerequisite to drill down, or scroll for the chain graph.
A period in human history characterized by the widespread use of iron tools and technology, emerging as a significant transformation within a distinct era of human development.
External reference — all senses of the word “iron age” on Wiktionary. This atlas concept maps to only the slice of meaning relevant to the prerequisite graph.