Global hotspots of linguistic diversity: mapping richness and endemism

Abstract Understanding the uneven distribution of linguistic diversity over the globe is one of the central issues in linguistics, and the subject of a steadily growing body of studies. However, the majority of these studies focus on just one aspect of linguistic diversity: language richness, the number of languages spoken in a given area. While language richness might be suitable for answering some questions about the origins and drivers of linguistic diversity, for others it might not be the most appropriate measure. Here, we introduce a new approach to quantifying patterns of diversity: linguistic endemism. This measure quantifies an overlooked aspect of linguistic diversity: the degree of uniqueness of a given geographical unit in terms of its languages, genealogies or structural features, opening up the way to new questions relating to the origins and distribution of linguistic diversity. We illustrate our approach by identifying global hotspot regions where high linguistic diversity values are significantly clustered. We map these hotspots for richness and endemism for languages, genealogies and structural features, and assess their spatial congruence. We discuss endemism-richness combinations, and suggest how overlapping and disjoint hotspot regions may be indicative of the human past.