Population size is generally assumed to play a pivotal role in the evolution of languages and cultures, but the expected patterns and potential mechanisms of change are unsettled. Theoretical models are limited by this uncertainty because they require making prior assumptions about language evolution. Using a sample of 20 Polynesian languages, authors test the effect of population size on the gain, loss, and total change of basic vocabulary words.

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.

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.

Researchers looked at the meaning of various emotion concepts, 'emotion semantics' in an attempt to determine the patterns and processes behind meaning cross-culturally. They used maps of colexification patterns (where semantically related concepts are named with the same word), adjusted Rand indices (ARIs) which indicated the similarities of two community's network structures, and various psychophysiological dimensions to test relationships and patterns of variability /structure in emotion semantics. These methods shed light on the underlying mechanisms behind emotions, both their words and their meanings in languages across the world. Their findings show substantial difference in language families and relationships between geographic proximity of language families and subsequent variation in emotion colexification tied to an evolutionary relationship, while also finding cultural universals in emotion colexification networks with languages primarily differentiating emotions on the basis of valence and activation.

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.

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.

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.

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).

Researchers examine post-marital residence patterns across five language phylogenies encompassing 371 ethnolinguistic groups. These language families are the Austronesian (Island Southeast Asia and the Pacific), Bantu (Sub-Saharan Africa), Indo-European (Eurasia), Pama-Nyungan (Australia), and Uto-Aztecan (Western USA and Mesoamerica). Contrary to the study's predictions, post-marital residence patterns did not evolve in similar ways across geographical regions but at a pace specific to its lineage.

Using ethnography, historical linguistics, paleoanthropology, and speech biomechanics, the present study examines the relationship between labiodentals and the post-Neolithic period with the introduction of agriculture and softer diets. The results offer support for the linguist, Charles Hockett's, hypothesis that the shift in bite configuration in the post-Neolithic period, as well as the persistence of overbite and overjet, facilitates and makes the articulation of labiodentals more prevalent. Using cross-cultural comparison, findings also reveal that societies that produce their food are more likely to evolve and keep labiodentals than those that are not food-producing. Contact with other societies is also a mode by which societies gain labiodentals. Lastly, the expansion of agricultural and food processing technology over time has been imperative to labiodental articulations.