Four of seven independently originated civilizations fall within 200 km of a single great circle (pole: 59.68°N, 138.65°W). Among 100,000 random great circles, only 42 achieve the same (p = 0.00042). An inhomogeneous Poisson point process model confirms site-level concentration after controlling for elevation, coastline, rivers, and latitude. A log-Gaussian Cox process preserves the effect (p < 10⁻¹¹); a Thomas cluster process absorbs it. The civilization-level collinearity is robust across distance thresholds, civilization list variants, and Benjamini-Hochberg correction. The circle traces a quantifiable concentration of tectonic-climatic circumscription zones: 29 arid-fertile lithological transitions vs. 4.5 for random circles (p < 0.0001), and significantly elevated tectonic plate boundary crossings (p = 0.011). Three alternative mechanism tests (agricultural productivity, groundwater, building stone) are null. The geometric concentration of Carneiro's (1970) circumscription environments along a single arc is quantified for the first time.
Elliot Allan (Thu,) studied this question.