Is grammatical complexity shaped by sociodemographic and sociolinguistic factors? The previously accepted "linguistic niche hypothesis" claims that with an increased number of nonnative speakers in a social group (high exotericity), grammatic complexity decreases; on the other hand, grammatical complexity increases amongst isolated linguistic communities (low exotericity). Through the use of spatiophylogenetic modelling of 1314 languages, the authors of this study do not find adequate evidence to support the linguistic niche hypothesis. Instead, they suggest that linguistic complexity is better predicted by phylogeny and geographic contiguity.

While not mechanically related, the transmission of genes and the transmission of languages are both mediated by culture. For example, in societies where marriage outside the language group is common, matrilocal residence practices may result in the preferential conservation of the mother’s language(s), as well as the development of distinct mtDNA haplogroups throughout a region. In this study, the authors use single nucleotide polymorphism (SNP) data from 130 culturally distinct populations to assess the correlation between genetic distance and linguistic distance, while controlling for various cultural and geographic factors (in other words: when populations are more genetically dissimilar, do they also tend to be further apart linguistically?). Results suggest that while the often-referenced idea of sex-based transmission of language is not universally predictable, linguistic distance almost always tends to correlate positively to both spatial and mitochondrial genetic variation.

This dissertation is a cross-cultural study of the relationship between cultural complexity and linguistic variables. The hypothesis is supported using a sample of fifty languages. Cultural complexity is theorized to instigate change in linguistic devices that are better tailored to express new areas of discourse.

This study posits that dowry is a recent historical development, and that cultural complexity is a necessary but not sufficient cause for its emergence. Comparisons of frequencies support these claims.

How do subsystems of language evolve over time? It is commonly assumed that grammatical changes of language are slower than vocabulary changes. Using a Dirichlet process mixture model to analyze rates of language evolution in 81 Austronesian languages, the authors find that to the contrary, the grammatical features of language tend to change at a faster rate than basic vocabulary. Furthermore, their results show that grammatical features have higher rates of homoplasy, more frequent contact-induced change, and less deliberate differentiation than basic vocabulary.

This article tests some conditions that may lead to the emergence of unilineal descent, focusing on unilocality and warfare. Unilineal descent is thought to be likely in a unilocal society without a centralized political system that is experiencing intra- or inter-societal warfare. The authors also posit that a "clan" system usually develops prior to a "lineage" system.

The authors statistically test existing theories and proposals regarding the existence and nature of the creole language profile. Results indicate that consistencies and variation between creole languages, as with non-creole languages, is a result of genealogical and contact processes. However, creole languages are unique from non-creole languages in that they have more than one language in their ancestry. Findings "call into question the existence of a pidgin stage in creole development and of creole-specific innovations." Support is found for the idea that language learning and transmission are strikingly resilient processes.

This article explores the relationship between language structure and social environment, positing that linguistic factors such as morphological complexity are associated with demographic/socio-historical factors such as number of speakers, geographic spread, and degree of language contact. Data support such an association. The authors further propose a Linguistic Niche Hypothesis suggesting that “the level of morphological specialization is a product of languages adapting to the learning constraints and the unique communicative needs of the speaker population” (7).

This study explores the relationship between level of legal evolution (measured on a Guttman scale that ranges from just mediation to counsel, police, and mediation) and level of societal complexity. Results suggest a significant association between level of legal evolution and level of societal complexity.

The "equi-complexity hypothesis" suggests that there is an equal complexity across languages, meaning that there are constant trade-offs between different domains. Using phylogenetic modelling in a sample of 244 languages, this study follows a diachronic perspective to explore if there is an inversed coevolution within the grammatical coding of nominal and verbal domains. The results show that while there appears to be a coevolutionary relationship between some features of these two domains, there is no evidence to support the idea that all languages maintain an overall equilibrium of grammatical complexity. Rather, the correlation nominal and verbal domains vary between lineages. Austronesian languages do not show a coevolution between the domains. Sino-Tibetan languages seem to have a positive correlation while Indo-European languages appear to have a negative correlation, meaning that this inverse coevolution can be lineage specific.