After noticing that there are no cross-cultural phylogenetic studies of grandparent terminologies, the authors use the record from 134 Pama-Nyungan languages to explore the evolution of this kinship category and to evaluate the effects of social structures in this evolution. The authors suggest that there used to be four different terms for grandparents in the proto-Pama-Nyungan language family, which was supported by the data. The results show no evidence of co-evolution between these grandparent systems with neither community marriage organization nor post-marital residence. There is not a significant correlation between grandparent and cross-cousin terms; however, there is some evidence that grand-child terms are correlated to grandparent systems.

Previous research has found that words are replaced faster in language vocabularies the less the word is used, whereas words that are used more frequently endure longer. Drawing from this theory, the authors of this article propose two questions: 1) Is the rate of replacement for Indo-European kinship terms correlated with their usage frequency? 2) How does this relationship differ between kinship terms and core vocabulary? Using phylogenetic comparative methods to analyze 10 kinship categories from 47 Indo-European languages, the authors find that more frequently used kinship terms tend to be replaced at a much slower rate than less frequently used words. Furthermore, this relationship between word replacement rate and usage frequency is stronger for kinship terms than it is for core vocabulary terms.

Kinbank is a global database of 210,903 kinship terms derived from 1,229 spoken and signed languages. The authors created Kinbank as a tool to help explain recurring patterns across cultures through kinship terminology. They illustrate its usefulness by addressing two questions as an example: 1) Is there gender bias in the phonological structure of parent terms? and 2) Did bifurcate-merging terminology and cross-cousin marriage co-evolve in Bantu languages? Using a Bayesian phylogenetic approach, the authors find support for the first question, but none for the latter.