Harald Hammarström & Tom Güldemann

Broad not Tall!: Climatic conditions drive the east-west spread of language families

Harald Hammarström (Uppsala University) and Tom Güldemann (Humboldt-Universität zu Berlin & MPI Leipzig)

A theory popularized by Diamond (1997) holds that historical interaction and dynamics of human populations are facilitated along latitudes because of more similar climate- and human subsistence conditions. If this “geographical-axis” theory is correct we expect that the geospatial shapes of language families should tend to have a latitudinal orientation, provided they are sufficiently large. In other words, we expect the geospatial shape of large language families to be broad rather than tall. While the global mean of the axis ratios for all families turns out to be near neutral, a latitude bias emerges with growing geographical size. A comparison with randomly generated families shows that the shape of inhabitable landmasses do not account for the observed correlation. The latitude bias of language families is then arguably a reflex of how environmental patterns shape general geographical profiles of human populations and the features associated with them.