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 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).

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.

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.

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.

This article examines the relationship between grammatical forms and a society’s economic activity, particularly whether property-based societies are more likely to develop the possessive verbs. Analysis supports an association.

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.

How is the evolution of language shaped by speaker population size? Through comparative data analyses of 153 language pairs from the Austronesian, Indo-European, and Niger-Congo language families, the authors find that the influence of population size on language evolution is not the same in the three language families. Only in Indo-European languages did a smaller population size of language-speakers significantly predict more word loss.

This article explores the possible relationship between the cultural evolution of language, music, and genetic variation beyond the level of language families. Due to their linguistic diversity, the authors use a sample of 14 Northeast Asian societies with matching information on their music, genetics, and linguistic patterns. The variables measuring language are lexicon, phonology, and grammar. Then, the authors compare each variable's relationship to music and genetic variation. The results only show a significant correlation between grammar and genetic variation.

Reputations are an important aspect of human social interactions and cooperation, but much of the research on reputations has focused on a narrow range of domains such as prosociality and aggressiveness. This study aims to provide an empirical view of reputation domains across different cultures by analyzing ethnographic texts on reputations from 153 cultures. The findings suggest that reputational domains vary across cultures, with reputations for cultural conformity, prosociality, social status, and neural capital being widespread. Reputation domains are more variable for males than females, and certain reputation domains are interrelated. The study highlights the need for future research on the evolution of cooperation and human sociality to consider a wider range of reputation domains and their variability across different social and ecological contexts and genders.