Phylogenetic signal in phonotactics

Phylogenetic methods have broad potential in linguistics beyond tree inference. Here, we show how a phylogenetic approach opens the possibility of gaining historical insights from entirely new kinds of linguistic data – in this instance, statistical phonotactics. We extract phonotactic data from 112 Pama-Nyungan vocabularies and apply tests for phylogenetic signal, quantifying the degree to which the data reflect phylogenetic history. We test three datasets: (1) binary variables recording the presence or absence of biphones (two-segment sequences) in a lexicon (2) frequencies of transitions between segments, and (3) frequencies of transitions between natural sound classes. Australian languages have been characterized as having a high degree of phonotactic homogeneity. Nevertheless, we detect phylogenetic signal in all datasets. Phylogenetic signal is greater in finer-grained frequency data than in binary data, and greatest in natural-class-based data. These results demonstrate the viability of employing a new source of readily extractable data in historical and comparative linguistics.1. Introduction 1.1 Motivations 1.2 Phonotactics as a source of historical signal 2. Phylogenetic signal 3. Materials 3.1 Language sample 3.2 Wordlists 3.3 Reference phylogeny 4. Phylogenetic signal in binary phonotactic data 4.1 Results for binary phonotactic data 4.2 Robustness checks 5. Phylogenetic signal in continuous phonotactic data 5.1 Robustness checks 5.2 Forward transitions versus backward transitions 5.3 Normalization of character values 6. Phylogenetic signal in natural-class-based characters 6.1 Natural-class-based characters versus biphones 7. Discussion 7.1 Overall robustness 7.2 Limitations 8. Conclusio

The deep history of the number words

We have previously shown that the ‘low limit’ number words (from one to five) have exceptionally slow rates of lexical replacement when measured across the Indo-European (IE) languages. Here, we replicate this finding within the Bantu and Austronesian language families, and with new data for the IE languages. Number words can remain stable for 10 000 to over 100 000 years, or around 3.5–20 times longer than average rates of lexical replacement among the Swadesh list of ‘fundamental vocabulary’ items. Ordinal evidence suggests that number words also have slow rates of lexical replacement in the Pama– Nyungan language family of Australia. We offer three hypotheses to explain these slow rates of replacement: (i) that the abstract linguistic-symbolic processing of ‘number’ links to evolutionarily conserved brain regions associated with numerosity; (ii) that number words are unambiguous and therefore have lower ‘mutation rates’; and (iii) that the number words occupy a region of the phonetic space that is relatively full and therefore resist change because alternatives are unlikely to be as ‘good’ as the original word. This article is part of a discussion meeting issue ‘The origins of numerical abilities’

The evolution and ecology of land ownership

Land ownership norms play a central role in social-ecological systems, and have been studied extensively as a component of ethnographies. Yet only recently has the distribution of land ownership norms across cultures been examined from evolutionary and ecological perspectives. Here we incorporate evolutionary and macroecological modelling to test associations between land ownership norms and environmental, subsistence, and cultural contact predictors for societies in the Bantu language family. We find that Bantu land ownership norms likely evolved on a unilinear trajectory, but not necessarily one requiring consistent increase in exclusivity as suggested by prior theory. Our macroecological analyses suggest that Bantu societies are more likely to have some form of ownership when their neighbors also do. We also find an effect of environmental productivity, supporting resource defensibility theory, which posits that land ownership is more likely where productivity is predictable. We find less support for a proposed link between agricultural intensification and land ownership. Overall, we demonstrate the value of combining analytical approaches from evolution and ecology to test diverse hypotheses on land ownership across a range of disciplines.1. Introduction 2. Materials and methods 2.1 Data 2.2 Phylogenetic analyses of evolution of land ownership 2.3 Multi-model inference of drivers of spatial patterns in land ownership 3. Results 3.1 Evolutionary trajectories of land ownership 3.2 Drivers of spatial variation in land ownership 4. Discussio

Demographic shifts, inter-group contact, and environmental conditions drive language extinction and diversification

Humans currently collectively use thousands of languages1,2. The number of languages in a given region (i.e. language “richness”) varies widely3–7. Understanding the processes of diversification and homogenization that produce these patterns has been a fundamental aim of linguistics and anthropology. Empirical research to date has identified various social, environmental, geographic, and demographic factors associated with language richness3. However, our understanding of causal mechanisms and variation in their effects over space has been limited by prior analyses focusing on correlation and assuming stationarity3,8. Here we use process-based, spatially-explicit stochastic models to simulate the emergence, expansion, contraction, fragmentation, and extinction of language ranges. We varied combinations of parameter settings in these computer-simulated experiments to evaluate the extent to which different processes reproduce observed patterns of pre-colonial language richness in North America. We find that the majority of spatial variation in language richness can be explained by models in which environmental and social constraints determine population density, random shocks alter population sizes more frequently at higher population densities, and population shocks are more frequently negative than positive. Language diversification occurs when populations split after reaching size limits, and when ranges fragment due to population contractions following negative shocks or due to contact with other groups that are expanding following positive shocks. These findings support diverse theoretical perspectives arguing that language richness is shaped by environmental and social conditions, constraints on group sizes, outcomes of contact among groups, and shifting demographics driven by positive innovations, such as new subsistence strategies, or negative events, such as war or disease

Drivers of geographical patterns of North American language diversity

Although many hypotheses have been proposed to explain why humans speak so many languages and why languages are unevenly distributed across the globe, the factors that shape geographical patterns of cultural and linguistic diversity remain poorly understood. Prior research has tended to focus on identifying universal predictors of language diversity, without accounting for how local factors and multiple predictors interact. Here, we use a unique combination of path analysis, mechanistic simulation modelling, and geographically weighted regression to investigate the broadly described, but poorly understood, spatial pattern of language diversity in North America. We show that the ecological drivers of language diversity are not universal or entirely direct. The strongest associations imply a role for previously developed hypothesized drivers such as population density, resource diversity, and carrying capacity with group size limits. The predictive power of this web of factors varies over space from regions where our model predicts approximately 86% of the variation in diversity, to areas where less than 40% is explained

Towards a mechanistic understanding of linguistic diversity

Our species displays remarkable linguistic diversity. While the uneven distribution of this diversity demands explanation, the drivers of these patterns have not been conclusively determined. We address this issue in two steps. First, we review previous empirical studies that have suggested environmental, geographical, and socio-cultural drivers of linguistic diversification. However, contradictory results and methodological variation make it difficult to draw general conclusions. Second, we outline a program for future research. We suggest that future analyses should account for interactions among causal factors, lack of spatial and phylogenetic independence of data, and transitory patterns. Recent analytical advances in biogeography and evolutionary biology, such as simulation modeling of diversity patterns, hold promise for testing four key mechanisms of language diversification proposed here: neutral change, population movement, contact, and selection. Future modeling approaches should also evaluate how the outcomes of these processes are influenced by demography, environmental heterogeneity, and time

Post-marital residence patterns show lineage-specific evolution

Where a newly-married couple lives, termed post-marital residence, varies cross-culturally and changes over time. While many factors have been proposed as drivers of this change, among them general features of human societies like warfare, migration and gendered division of subsistence labour, little is known about whether changes in residence patterns exhibit global regularities. Here, we study ethnographic observations of post-marital residence in societies from five large language families (Austronesian, Bantu, Indo-European, Pama-Nyungan and Uto-Aztecan), encompassing 371 ethnolinguistic groups ranging widely in local ecologies and lifeways, and covering over half the worlds population and geographical area. We apply Bayesian comparative methods to test the hypothesis that post-marital residence patterns have evolved in similar ways across different geographical regions. By reconstructing past post-marital residence states, we compare transition rates and models of evolution across groups, while integrating the historical descent relationships of human societies. We find that each language family possesses its own best fitting model, demonstrating that the mode and pace of post-marital residence evolution is lineage-specific rather than global.We thank Laura Fortunato (Institute of Cognitive and Evolutionary Anthropology, University of Oxford, UK) and Kit Opie (Department of Anthropology, University College London, UK) for access to analyses from their published work; Lyle Campbell (Department of Linguistics, University of Hawai’i Manoa, USA) and Jane Hill (School of Anthropology, University of Arizona, USA) for cognancy coding in the Uto-Aztecan dataset; and Eilis Donnelly (Victoria University of Wellington) for assistance with summarizing the ethnographic literature of Uto-Aztecan and Pama-Nyungan speakers. This research was supported by the Royal Society of New Zealand through a Rutherford Fellowship (RDF-10-MAU-001) to M.P.C., by an Allan Wilson Centre for Molecular Ecology and Evolution grant to M.P.C. and R.G., and by an Alexander von Humboldt Stiftung fellowship to M.P.C. The Max Planck Institute for the Science of Human History funded J.C.M. to attend its 2016 Spring School on quantitative methods for studying linguistic and cultural evolution. S.M. and M.P.C. are partially supported by the New Zealand Centre of Research Excellence Te Pūnaha Matatini. R.M.R. was supported by a grant from the European Union Horizon 2020 Research and Innovation Programme (grant agreement No 644055 [ALIGNED, http://aligned-project.eu]). F.M.J. received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No 639291, Starting Grant VARIKIN), and was supported by a Leverhulme Research Fellowship (47690)

Does Lateral Transmission Obscure Inheritance in Hunter-Gatherer Languages?

In recent years, linguists have begun to increasingly rely on quantitative phylogenetic approaches to examine language evolution. Some linguists have questioned the suitability of phylogenetic approaches on the grounds that linguistic evolution is largely reticulate due to extensive lateral transmission, or borrowing, among languages. The problem may be particularly pronounced in hunter-gatherer languages, where the conventional wisdom among many linguists is that lexical borrowing rates are so high that tree building approaches cannot provide meaningful insights into evolutionary processes. However, this claim has never been systematically evaluated, in large part because suitable data were unavailable. In addition, little is known about the subsistence, demographic, ecological, and social factors that might mediate variation in rates of borrowing among languages. Here, we evaluate these claims with a large sample of hunter-gatherer languages from three regions around the world. In this study, a list of 204 basic vocabulary items was collected for 122 hunter-gatherer and small-scale cultivator languages from three ecologically diverse case study areas: northern Australia, northwest Amazonia, and California and the Great Basin. Words were rigorously coded for etymological (inheritance) status, and loan rates were calculated. Loan rate variability was examined with respect to language area, subsistence mode, and population size, density, and mobility; these results were then compared to the sample of 41 primarily agriculturalist languages in [1]. Though loan levels varied both within and among regions, they were generally low in all regions (mean 5.06%, median 2.49%, and SD 7.56), despite substantial demographic, ecological, and social variation. Amazonian levels were uniformly very low, with no language exhibiting more than 4%. Rates were low but more variable in the other two study regions, in part because of several outlier languages where rates of borrowing were especially high. High mobility, prestige asymmetries, and language shift may contribute to the high rates in these outliers. No support was found for claims that hunter-gatherer languages borrow more than agriculturalist languages. These results debunk the myth of high borrowing in hunter-gatherer languages and suggest that the evolution of these languages is governed by the same type of rules as those operating in large-scale agriculturalist speech communities. The results also show that local factors are likely to be more critical than general processes in determining high (or low) loan rates

The global geography of human subsistence

How humans obtain food has dramatically reshaped ecosystems and altered both the trajectory of human history and the characteristics of human societies. Our species' subsistence varies widely, from predominantly foraging strategies, to plant-based agriculture and animal husbandry. The extent to which environmental, social and historical factors have driven such variation is currently unclear. Prior attempts to resolve long-standing debates on this topic have been hampered by an over-reliance on narrative arguments, small and geographically narrow samples, and by contradictory findings. Here we overcome these methodological limitations by applying multi-model inference tools developed in biogeography to a global dataset (818 societies). Although some have argued that unique conditions and events determine each society's particular subsistence strategy, we find strong support for a general global pattern in which a limited set of environmental, social and historical factors predicts an essential characteristic of all human groups: how we obtain our food

The ethics of inherent trust in care robots for the elderly

The way elderly care is delivered is changing. Attempts are being made to accommodate the increasing number of elderly, and the decline in the number of people available to care for them, with care robots. This change introduces ethical issues into robotics and healthcare. The two-part study (heuristic evaluation and survey) reported here examines a phenomenon which is a result of that change. The phenomenon rises out of a contradiction. All but 2 (who were undecided) of the 12 elderly survey respondents, out of the total of 102 respondents, wanted to be able to change how the presented care robot made decisions and 7 of those 12 elderly wanted to be able to examine its decision making process so as to ensure the care provided is personalized. However, at the same time, 34% of the elderly participants said they were willing to trust the care robot inherently, compared to only 16% of the participants who were under fifty. Additionally, 66% of the elderly respondents said they were very likely or likely to accept and use such a care robot in their everyday lives. The contradiction of inherent trust and simultaneous wariness about control gives rise to the phenomenon: elderly in need want control over their care to ensure it is personalized, but many may desperately take any help they can get. The possible causes, and ethical implications, of this phenomenon are the focus of this paper