Societies of strangers do not speak less complex languages.

Many recent proposals claim that languages adapt to their environments. The linguistic niche hypothesis claims that languages with numerous native speakers and substantial proportions of nonnative speakers (societies of strangers) tend to lose grammatical distinctions. In contrast, languages in small, isolated communities should maintain or expand their grammatical markers. Here, we test these claims using a global dataset of grammatical structures, Grambank. We model the impact of the number of native speakers, the proportion of nonnative speakers, the number of linguistic neighbors, and the status of a language on grammatical complexity while controlling for spatial and phylogenetic autocorrelation. We deconstruct "grammatical complexity" into two separate dimensions: how much morphology a language has ("fusion") and the amount of information obligatorily encoded in the grammar ("informativity"). We find several instances of weak positive associations but no inverse correlations between grammatical complexity and sociodemographic factors. Our findings cast doubt on the widespread claim that grammatical complexity is shaped by the sociolinguistic environment.

Grammars are robustly transmitted even during the emergence of creole languages.

Most languages of the world are taken to result from a combination of a vertical transmission process from older to younger generations of speakers or signers and (mostly) gradual changes that accumulate over time. In contrast, creole languages emerge within a few generations out of highly multilingual societies in situations where no common first language is available for communication (as, for instance, in plantations related to the Atlantic slave trade). Strikingly, creoles share a number of linguistic features (the 'creole profile'), which is at odds with the striking linguistic diversity displayed by non-creole languages 1-4 . These common features have been explained as reflecting a hardwired default state of the possible grammars that can be learned by humans 1 , as straightforward solutions to cope with the pressure for efficient and successful communication 5 or as the byproduct of an impoverished transmission process 6 . Despite their differences, these proposals agree that creoles emerge from a very limited and basic communication system (a pidgin) that only later in time develops the characteristics of a natural language, potentially by innovating linguistic structure. Here we analyse 48 creole languages and 111 non-creole languages from all continents and conclude that the similarities (and differences) between creoles can be explained by genealogical and contact processes 7,8 , as with non-creole languages, with the difference that creoles have more than one language in their ancestry. While a creole profile can be detected statistically, this stems from an over-representation of Western European and West African languages in their context of emergence. Our findings call into question the existence of a pidgin stage in creole development and of creole-specific innovations. In general, given their extreme conditions of emergence, they lend support to the idea that language learning and transmission are remarkably resilient processes.