More complex societies have more complex kinship lexicons

Increasing evidence suggests that language complexity is sensitive to sociopolitical factors. While most quantitative research has focused on morphology and syntax, the complexity of the lexicons of the world languages can be expected to be sensitive to extralinguistic factors too. In this paper, we have implemented a mathematical method for calculating the complexity of kinship term systems. We have furthermore conducted principal component analyses aimed to determine whether this complexity is impacted by core features characterizing sociopolitical complexity, including the status of the language within its society, the size of the language family that a language belongs to, the number of jurisdictional levels above the local community, the size of local communities, population size and density, fixity of residence, and distance moved each year. For this, we have drawn upon independently constructed databases of sociopolitical and linguistic complexity (WALS, D-Place, Ethnologue, Glottolog, and KinBank). We found that social complexity positively correlates with the complexity of kinship terms. We interpret this finding as suggesting that the languages spoken by complex societies develop greater expressive power in order to share decontextualized knowledge and know-hows with strangers. We expect that our algorithm can capture the complexity of other domains of the lexicons of the world’s languages.