The Scribe’s Advantage

Companion Fig. M-1

The Cave Map

A cave is a population cluster above about ten thousand people, held together in one place long enough to be sorted. Drag the slider or press Play. The first caves appear on four river valleys; the frontier moves outward as each new technology makes more ground habitable, until the modern map lights up like a circuit board. Each cave takes the ink of the dragon holding its gate, and its ring shows that dragon’s age. Tap any cave for its people, its source, its dragon and the chapter that tells its story.

Loading the caves…
About this map: data, method and the defaults applied

The data

  • City populations, 3700 BCE to 1975: Chandler, Four Thousand Years of Urban Growth (1987), and Modelski, World Cities: -3000 to 2000 (2003), as digitized and geocoded by Reba, Reitsma and Seto, “Spatializing 6,000 years of global urbanization,” Scientific Data 3:160034 (2016), figshare, CC BY 4.0.
  • City populations, 1975 to 2025: United Nations, DESA, Population Division, World Urbanization Prospects 2025, File 21 (cities by the Degree of Urbanisation). Where a city appears in both, the UN series replaces Chandler from 1975.
  • Territories: Cliopatria, a dated polygon database of world polities from 3400 BCE to 2024 (Bennett et al., Seshat Global History Databank, 2025, CC BY 4.0). A polity’s polygon is drawn as a dragon’s territory when a cave the book names sat inside it while that dragon held the gate.
  • The caves the book names: the cave and dragon occupation master (45 caves, their gate-holders in order, the age of each dragon at move-in, and how each cave was gained and lost), with curated census figures for twelve of them.
  • Dragon ages: the four-age lock in dragon-stages.json for eleven dragons; ages proposed from the manuscript for the rest, drawn dotted until Will approves them; unstaged where the book gives no age.
  • The river: river-flow.json, the book’s ledger of world population and literacy by era.
  • Land: Natural Earth 1:110m, public domain.

The method

Two thresholds. A named cave forms when its cluster reaches about ten thousand and stays on the map from then on, drawn hollow whenever it is smaller than the date’s display threshold. Unnamed background caves are drawn only above that threshold, which rises from about ten thousand in 3500 BCE to about fifty thousand from the classical age to 1700, then climbs to about five hundred thousand today, so that the ancient map is sparse and the modern one dense. Populations between two recorded figures are interpolated on a log scale; a city drops off the map where the tables fall silent for long stretches.

The compiled tables are a floor, not a census of every cluster. Before 1800 they list only the larger cities, so the map undercounts early caves; it draws what the digitized tables can place.

Defaults applied (Will can overrule any of them)

  1. Two thresholds, a fixed marker of about ten thousand for named caves and a sliding display threshold for the rest.
  2. A bubble is a population cluster (a city or agglomeration), not a polity; the territory is drawn as a wash.
  3. The display threshold is the density-matched option, chosen because it met the most of Will’s density targets on the real data.
  4. Dragons not in the four-age lock keep their proposed ages, drawn dotted; where the book is silent they are unstaged.
  5. A colonial cave appears when its cluster reaches the marker, in the colonizer’s ink, and pulses in the year the book dates its own dragon (Singapore 1965, Seoul 1953).
  6. Tasmania, Comancheria and the Maori are hollow points captioned “no cave formed.”
  7. Contested ages follow dragon-stages.json and say so in the popup; the map does not settle the disagreement.