While global patterns of human genetic diversity are increasingly well characterized, the diversity of human languages remains less systematically described. Here, we outline the Grambank database. With over 400,000 data points and 2400 languages, Grambank is the largest comparative grammatical database available. The comprehensiveness of Grambank allows us to quantify the relative effects of genealogical inheritance and geographic proximity on the structural diversity of the world’s languages, evaluate constraints on linguistic diversity, and identify the world’s most unusual languages. An analysis of the consequences of language loss reveals that the reduction in diversity will be strikingly uneven across the major linguistic regions of the world. Without sustained efforts to document and revitalize endangered languages, our linguistic window into human history, cognition, and culture will be seriously fragmented.

Sign languages can be categorized as shared sign languages or deaf community sign languages, depending on the context in which they emerge. It has been suggested that shared sign languages exhibit more variation in the expression of everyday concepts than deaf community sign languages (Meir, Israel, Sandler, Padden, & Aronoff, 2012). For deaf community sign languages, it has been shown that various sociolinguistic factors condition this variation. This study presents one of the first in-depth investigations of how sociolinguistic factors (deaf status, age, clan, gender and having a deaf family member) affect lexical variation in a shared sign language, using a picture description task in Kata Kolok. To study lexical variation in Kata Kolok, two methodologies are devised: the identification of signs by underlying iconic motivation and mapping, and a way to compare individual repertoires of signs by calculating the lexical distances between participants. Alongside presenting novel methodologies to study this type of sign language, we present preliminary evidence of sociolinguistic factors that may influence variation in the Kata Kolok lexicon.

Sign language lexicons incorporate phonological specifications. Evidence from emerging sign languages suggests that phonological structure emerges gradually in a new language. In this study, we investigate variation in the form of signs across 20 deaf adult signers of Kata Kolok, a sign language that emerged spontaneously in a Balinese village community. Combining methods previously used for sign comparisons, we introduce a new numeric measure of variation. Our nuanced yet comprehensive approach to form variation integrates three levels (iconic motivation, surface realisation, feature differences) and allows for refinement through weighting the variation score by token and signer frequency. We demonstrate that variation in the form of signs appears in different degrees at different levels. Token frequency in a given dataset greatly affects how much variation can surface, suggesting caution in interpreting previous findings. Different sign variants have different scopes of use among the signing population, with some more widely used than others. Both frequency weightings (token and signer) identify dominant sign variants, i.e., sign forms that are produced frequently or by many signers. We argue that variation does not equal the absence of conventionalisation. Indeed, especially in micro-community sign languages, variation may be key to understanding patterns of language emergence.

While global patterns of human genetic diversity are increasingly well characterized, the diversity of human languages remains less systematically described. Here we outline the Grambank database. With over 400,000 data points and 2,400 languages, Grambank is the largest comparative grammatical database available. The comprehensiveness of Grambank allows us to quantify the relative effects of genealogical inheritance and geographic proximity on the structural diversity of the world's languages, evaluate constraints on linguistic diversity, and identify the world's most unusual languages. An analysis of the consequences of language loss reveals that the reduction in diversity will be strikingly uneven across the major linguistic regions of the world. Without sustained efforts to document and revitalize endangered languages, our linguistic window into human history, cognition and culture will be seriously fragmented.