Abstract: This study explores the determinants of ethnolinguistic diversity within as well as across countries, shedding light on its geographic origins. The empirical analysis conducted across countries, virtual countries, and pairs of contiguous regions establishes that geographic variability, captured by variation in regional land quality and elevation, is a fundamental determinant of contemporary linguistic diversity. The findings are consistent with the proposed hypothesis that differences in land endowments gave rise to location-specific human capital, leading to the formation of localized ethnicities. (JEL J15, J24, Z13)