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.

New Caledonian Crows Use Mental Representations to Solve Metatool Problems

One of the mysteries of animal problem-solving is the extent to which animals mentally represent problems in their minds. Humans can imagine both the solution to a problem and the stages along the way [1, 2, 3], such as when we plan one or two moves ahead in chess. The extent to which other animals can do the same is far less clear [4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25]. Here, we presented New Caledonian crows with a series of metatool problems where each stage was out of sight of the others and the crows had to avoid either a distractor apparatus containing a non-functional tool or a non-functional apparatus containing a functional tool. Crows were able to mentally represent the sub-goals and goals of metatool problems: crows kept in mind the location and identities of out-of-sight tools and apparatuses while planning and performing a sequence of tool behaviors. This provides the first conclusive evidence that birds can plan several moves ahead while using tools.

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Crows solved metatool problems where each stage was out of sight of the others

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Crows avoided distractor apparatuses during problem-solving

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This shows crows mentally represent the goals and sub-goals of metatool problems

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Crows can preplan three behaviors into the future while using tools

Cross-Linguistic Data Formats, advancing data sharing and re-use in comparative linguistics

The amount of available digital data for the languages of the world is constantly increasing. Unfortunately, most of the digital data are provided in a large variety of formats and therefore not amenable for comparison and re-use. The Cross-Linguistic Data Formats initiative proposes new standards for two basic types of data in historical and typological language comparison (word lists, structural datasets) and a framework to incorporate more data types (e.g. parallel texts, and dictionaries). The new specification for cross-linguistic data formats comes along with a software package for validation and manipulation, a basic ontology which links to more general frameworks, and usage examples of best practices.

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.

Mental template matching is a potential cultural transmission mechanism for New Caledonian crow tool manufacturing traditions

Cumulative cultural evolution occurs when social traditions accumulate improvements over time. In humans cumulative cultural evolution is thought to depend on a unique suite of cognitive abilities, including teaching, language and imitation. Tool-making New Caledonian crows show some hallmarks of cumulative culture; but this claim is contentious, in part because these birds do not appear to imitate. One alternative hypothesis is that crows’ tool designs could be culturally transmitted through a process of mental template matching. That is, individuals could use or observe conspecifics’ tools, form a mental template of a particular tool design, and then reproduce this in their own manufacture – a process analogous to birdsong learning. Here, we provide the first evidence supporting this hypothesis, by demonstrating that New Caledonian crows have the cognitive capacity for mental template matching. Using a novel manufacture paradigm, crows were first trained to drop paper into a vending machine to retrieve rewards. They later learnt that only items of a particular size (large or small templates) were rewarded. At test, despite being rewarded at random, and with no physical templates present, crows manufactured items that were more similar in size to previously rewarded, than unrewarded, templates. Our results provide the first evidence that this cognitive ability may underpin the transmission of New Caledonian crows’ natural tool designs.

Language continuity despite population replacement in Remote Oceania

Recent genomic analyses show that the earliest peoples reaching Remote Oceania-associated with Austronesian-speaking Lapita culture-were almost completely East Asian, without detectable Papuan ancestry. However, Papuan-related genetic ancestry is found across present-day Pacific populations, indicating that peoples from Near Oceania have played a significant, but largely unknown, ancestral role. Here, new genome-wide data from 19 ancient South Pacific individuals provide direct evidence of a so-far undescribed Papuan expansion into Remote Oceania starting ~2,500 yr BP, far earlier than previously estimated and supporting a model from historical linguistics. New genome-wide data from 27 contemporary ni-Vanuatu demonstrate a subsequent and almost complete replacement of Lapita-Austronesian by Near Oceanian ancestry. Despite this massive demographic change, incoming Papuan languages did not replace Austronesian languages. Population replacement with language continuity is extremely rare-if not unprecedented-in human history. Our analyses show that rather than one large-scale event, the process was incremental and complex, with repeated migrations and sex-biased admixture with peoples from the Bismarck Archipelago.

A Bayesian phylogenetic study of the Dravidian language family

The Dravidian language family consists of about 80 varieties (Hammarström H. 2016 Glottolog 2.7) spoken by 220 million people across southern and central India and surrounding countries (Steever SB. 1998 In The Dravidian languages (ed. SB Steever), pp. 1-39: 1). Neither the geographical origin of the Dravidian language homeland nor its exact dispersal through time are known. The history of these languages is crucial for understanding prehistory in Eurasia, because despite their current restricted range, these languages played a significant role in influencing other language groups including Indo-Aryan (Indo-European) and Munda (Austroasiatic) speakers. Here, we report the results of a Bayesian phylogenetic analysis of cognate-coded lexical data, elicited first hand from native speakers, to investigate the subgrouping of the Dravidian language family, and provide dates for the major points of diversification. Our results indicate that the Dravidian language family is approximately 4500 years old, a finding that corresponds well with earlier linguistic and archaeological studies. The main branches of the Dravidian language family (North, Central, South I, South II) are recovered, although the placement of languages within these main branches diverges from previous classifications. We find considerable uncertainty with regard to the relationships between the main branches.

PENGUINS, PETRELS, AND PARSIMONY: DOES CLADISTIC ANALYSIS OF BEHAVIOR REFLECT SEABIRD PHYLOGENY?

Whether or not behavior accurately reflects evolutionary relationships (phylogeny) has been hotly debated by ethologists and comparative psychologists. Previous studies attempting to resolve this question have generally lacked a quantitative, phylogenetic approach. In this study we used behavior and life-history (BLH) information (72 characters) to generate phylogenetic trees for 18 seabird species (albatrosses, petrels, and penguins). We compared these trees with trees obtained from isozyme electrophoretic analysis of blood proteins (15 loci and 98 electromorphs) and partial mitochondrial 12S ribosomal DNA sequences (381 base pairs). Cladistic analysis of the BLH data set generated three MP trees (tree length = 243, CI = 0.52, RI = 0.57) with significant cladistic structure. The BLH characters were classified into four types (foraging, agonistic, reproductive, and life history) and levels of homoplasy for each type were measured. No significant differences were found among these categories. The BLH trees were shown to be significantly more congruent with the electrophoretic and 12S sequence trees than expected by chance. This indicates that seabird BLH data contains phylogenetic signal. Areas of incongruence between BLH trees and a phylogeny generated by combining the data sets were predicted to result from ecological constraints that did not covary with phylogeny. These predictions were supported by the results of a concentrated changes test. This study found that this BLH data set was no more homoplasious than molecular data and that BLH trees were significantly congruent with molecular trees.

Kea show no evidence of inequity aversion

It has been suggested that inequity aversion is a mechanism that evolved in humans to maximize the pay-offs from engaging in cooperative tasks and to foster long-term cooperative relationships between unrelated individuals. In support of this, evidence of inequity aversion in nonhuman animals has typically been found in species that, like humans, live in complex social groups and demonstrate cooperative behaviours. We examined inequity aversion in the kea (Nestor notabilis), which lives in social groups but does not appear to demonstrate wild cooperative behaviours, using a classic token exchange paradigm. We compared the number of successful exchanges and the number of abandoned trials in each condition and found no evidence of an aversion to inequitable outcomes when there was a difference between reward quality or working effort required between actor and partner. We also found no evidence of inequity aversion when the subject received no reward while their partner received a low-value reward.

Keas Perform Similarly to Chimpanzees and Elephants when Solving Collaborative Tasks

Cooperation between individuals is one of the defining features of our species. While other animals, such as chimpanzees, elephants, coral trout and rooks also exhibit cooperative behaviours, it is not clear if they think about cooperation in the same way as humans do. In this study we presented the kea, a parrot endemic to New Zealand, with a series of tasks designed to assess cooperative cognition. We found that keas were capable of working together, even when they had to wait for their partner for up to 65 seconds. The keas also waited for a partner only when a partner was actually needed to gain food. This is the first demonstration that any non-human animal can wait for over a minute for a cooperative partner, and the first conclusive evidence that any bird species can successful track when a cooperative partner is required, and when not. The keas did not attend to whether their partner could actually access the apparatus themselves, which may have been due to issues with task demands, but one kea did show a clear preference for working together with other individuals, rather than alone. This preference has been shown to be present in humans but absent in chimpanzees. Together these results provide the first evidence that a bird species can perform at a similar level to chimpanzees and elephants across a range of collaborative tasks. This raises the possibility that aspects of the cooperative cognition seen in the primate lineage have evolved convergently in birds.

The Potential of Automatic Word Comparison for Historical Linguistics

The amount of data from languages spoken all over the world is rapidly increasing. Traditional manual methods in historical linguistics need to face the challenges brought by this influx of data. Automatic approaches to word comparison could provide invaluable help to pre-analyze data which can be later enhanced by experts. In this way, computational approaches can take care of the repetitive and schematic tasks leaving experts to concentrate on answering interesting questions. Here we test the potential of automatic methods to detect etymologically related words (cognates) in cross-linguistic data. Using a newly compiled database of expert cognate judgments across five different language families, we compare how well different automatic approaches distinguish related from unrelated words. Our results show that automatic methods can identify cognates with a very high degree of accuracy, reaching 89% for the best-performing method Infomap. We identify the specific strengths and weaknesses of these different methods and point to major challenges for future approaches. Current automatic approaches for cognate detection-although not perfect-could become an important component of future research in historical linguistics.

New Caledonian crows show behavioural flexibility when manufacturing their tools

New Caledonian crows have demonstrated flexible behaviour when using tools and solving novel problems. However, we do not know whether this flexibility extends to tool manufacture. Here, we show that these crows respond to different tool-using problems by altering the length of the tools that they manufacture; on average, crows made shorter tools for tasks requiring short tools and longer tools for tasks requiring long tools. They continued to do so when they could not simultaneously see the tool-manufacturing material and the apparatus requiring the use of a tool. Despite altering the length of their tools, the crows frequently did not make tools short or long enough to reliably extract the bait, though this may have been due to shortcomings in the task presented to them. Our results demonstrate that these crows have a degree of behavioural flexibility when making tools, which may be used in the wild during foraging.

Performance in Object-Choice Aesop's Fable Tasks Are Influenced by Object Biases in New Caledonian Crows but not in Human Children

The ability to reason about causality underlies key aspects of human cognition, but the extent to which non-humans understand causality is still largely unknown. The Aesop's Fable paradigm, where objects are inserted into water-filled tubes to obtain out-of-reach rewards, has been used to test casual reasoning in birds and children. However, success on these tasks may be influenced by other factors, specifically, object preferences present prior to testing or arising during pre-test stone-dropping training. Here, we assessed this 'object-bias' hypothesis by giving New Caledonian crows and 5-10 year old children two object-choice Aesop's Fable experiments: sinking vs. floating objects, and solid vs. hollow objects. Before each test, we assessed subjects' object preferences and/or trained them to prefer the alternative object. Both crows and children showed pre-test object preferences, suggesting that birds in previous Aesop's Fable studies may also have had initial preferences for objects that proved to be functional on test. After training to prefer the non-functional object, crows, but not children, performed more poorly on these two object-choice Aesop's Fable tasks than subjects in previous studies. Crows dropped the non-functional objects into the tube on their first trials, indicating that, unlike many children, they do not appear to have an a priori understanding of water displacement. Alternatively, issues with inhibition could explain their performance. The crows did, however, learn to solve the tasks over time. We tested crows further to determine whether their eventual success was based on learning about the functional properties of the objects, or associating dropping the functional object with reward. Crows inserted significantly more rewarded, non-functional objects than non-rewarded, functional objects. These findings suggest that the ability of New Caledonian crows to produce performances rivaling those of young children on object-choice Aesop's Fable tasks is partly due to pre-existing object preferences.

Does absolute brain size really predict self-control? Hand-tracking training improves performance on the A-not-B task

Large-scale, comparative cognition studies are set to revolutionize the way we investigate and understand the evolution of intelligence. However, the conclusions reached by such work have a key limitation: the cognitive tests themselves. If factors other than cognition can systematically affect the performance of a subset of animals on these tests, we risk drawing the wrong conclusions about how intelligence evolves. Here, we examined whether this is the case for the A-not-B task, recently used by MacLean and co-workers to study self-control among 36 different species. Non-primates performed poorly on this task; possibly because they have difficulty tracking the movements of a human demonstrator, and not because they lack self-control. To test this, we assessed the performance of New Caledonian crows on the A-not-B task before and after two types of training. New Caledonian crows trained to track rewards moved by a human demonstrator were more likely to pass the A-not-B test than birds trained on an unrelated choice task involving inhibitory control. Our findings demonstrate that overlooked task demands can affect performance on a cognitive task, and so bring into question MacLean's conclusion that absolute brain size best predicts self-control.

D-PLACE: A Global Database of Cultural, Linguistic and Environmental Diversity

From the foods we eat and the houses we construct, to our religious practices and political organization, to who we can marry and the types of games we teach our children, the diversity of cultural practices in the world is astounding. Yet, our ability to visualize and understand this diversity is limited by the ways it has been documented and shared: on a culture-by-culture basis, in locally-told stories or difficult-to-access repositories. In this paper we introduce D-PLACE, the Database of Places, Language, Culture, and Environment. This expandable and open-access database (accessible at https://d-place.org) brings together a dispersed corpus of information on the geography, language, culture, and environment of over 1400 human societies. We aim to enable researchers to investigate the extent to which patterns in cultural diversity are shaped by different forces, including shared history, demographics, migration/diffusion, cultural innovations, and environmental and ecological conditions. We detail how D-PLACE helps to overcome four common barriers to understanding these forces: i) location of relevant cultural data, (ii) linking data from distinct sources using diverse ethnonyms, (iii) variable time and place foci for data, and (iv) spatial and historical dependencies among cultural groups that present challenges for analysis. D-PLACE facilitates the visualisation of relationships among cultural groups and between people and their environments, with results downloadable as tables, on a map, or on a linguistic tree. We also describe how D-PLACE can be used for exploratory, predictive, and evolutionary analyses of cultural diversity by a range of users, from members of the worldwide public interested in contrasting their own cultural practices with those of other societies, to researchers using large-scale computational phylogenetic analyses to study cultural evolution. In summary, we hope that D-PLACE will enable new lines of investigation into the major drivers of cultural change and global patterns of cultural diversity.

Broad supernatural punishment but not moralizing high gods precede the evolution of political complexity in Austronesia

Supernatural belief presents an explanatory challenge to evolutionary theorists-it is both costly and prevalent. One influential functional explanation claims that the imagined threat of supernatural punishment can suppress selfishness and enhance cooperation. Specifically, morally concerned supreme deities or 'moralizing high gods' have been argued to reduce free-riding in large social groups, enabling believers to build the kind of complex societies that define modern humanity. Previous cross-cultural studies claiming to support the MHG hypothesis rely on correlational analyses only and do not correct for the statistical non-independence of sampled cultures. Here we use a Bayesian phylogenetic approach with a sample of 96 Austronesian cultures to test the MHG hypothesis as well as an alternative supernatural punishment hypothesis that allows punishment by a broad range of moralizing agents. We find evidence that broad supernatural punishment drives political complexity, whereas MHGs follow political complexity. We suggest that the concept of MHGs diffused as part of a suite of traits arising from cultural exchange between complex societies. Our results show the power of phylogenetic methods to address long-standing debates about the origins and functions of religion in human society.

Pulotu: Database of Austronesian Supernatural Beliefs and Practices

Scholars have debated naturalistic theories of religion for thousands of years, but only recently have scientists begun to test predictions empirically. Existing databases contain few variables on religion, and are subject to Galton's Problem because they do not sufficiently account for the non-independence of cultures or systematically differentiate the traditional states of cultures from their contemporary states. Here we present Pulotu: the first quantitative cross-cultural database purpose-built to test evolutionary hypotheses of supernatural beliefs and practices. The Pulotu database documents the remarkable diversity of the Austronesian family of cultures, which originated in Taiwan, spread west to Madagascar and east to Easter Island-a region covering over half the world's longitude. The focus of Austronesian beliefs range from localised ancestral spirits to powerful creator gods. A wide range of practices also exist, such as headhunting, elaborate tattooing, and the construction of impressive monuments. Pulotu is freely available, currently contains 116 cultures, and has 80 variables describing supernatural beliefs and practices, as well as social and physical environments. One major advantage of Pulotu is that it has separate sections on the traditional states of cultures, the post-contact history of cultures, and the contemporary states of cultures. A second major advantage is that cultures are linked to a language-based family tree, enabling the use phylogenetic methods, which can be used to address Galton's Problem by accounting for common ancestry, to infer deep prehistory, and to model patterns of trait evolution over time. We illustrate the power of phylogenetic methods by performing an ancestral state reconstruction on the Pulotu variable "headhunting", finding evidence that headhunting was practiced in proto-Austronesian culture. Quantitative cross-cultural databases explicitly linking cultures to a phylogeny have the potential to revolutionise the field of comparative religious studies in the same way that genetic databases have revolutionised the field of evolutionary biology.

Investigating animal cognition with the Aesop's Fable paradigm: Current understanding and future directions

The Aesop's Fable paradigm – in which subjects drop stones into tubes of water to obtain floating out-of-reach rewards – has been used to assess causal understanding in rooks, crows, jays and human children. To date, the performance of corvids suggests that they can recognize the functional properties of a variety of objects including size, weight and solidity, and they seem to be more capable of learning from causal information than arbitrary information. However, 2 alternative explanations for their performance have yet to be ruled out. The perceptual-motor feedback hypothesis suggests that subjects may attend solely to the movement of the reward, repeating actions which bring the reward closer, while the object-bias hypothesis suggests that subjects could pass certain tasks by preferring to handle objects that resemble natural stones. Here we review our current understanding of performance on the Aesop's Fable tasks, and suggest that studies controlling for feedback and object preferences will help us determine exactly what animals understand about the cause and effect of water displacement.

New Caledonian crows rapidly solve a collaborative problem without cooperative cognition

There is growing comparative evidence that the cognitive bases of cooperation are not unique to humans. However, the selective pressures that lead to the evolution of these mechanisms remain unclear. Here we show that while tool-making New Caledonian crows can produce collaborative behavior, they do not understand the causality of cooperation nor show sensitivity to inequity. Instead, the collaborative behavior produced appears to have been underpinned by the transfer of prior experience. These results suggest that a number of possible selective pressures, including tool manufacture and mobbing behaviours, have not led to the evolution of cooperative cognition in this species. They show that causal cognition can evolve in a domain specific manner–understanding the properties and flexible uses of physical tools does not necessarily enable animals to grasp that a conspecific can be used as a social tool.

Reasoning by exclusion in New Caledonian crows (Corvus moneduloides) cannot be explained by avoidance of empty containers

Whether animals can reason or merely learn associatively is a long-standing debate. Researchers have approached this question by investigating whether dogs, birds, and primates can reason by exclusion (choosing by logically excluding all other alternatives). However, these studies have not resolved whether animals are capable of inferring which option is rewarded or are merely avoiding options known to be incorrect. Here, we used a forced-choice tubes task, where strategies of "reasoning by exclusion" and "avoidance of empty containers" predicted different responses. Two tubes (1 straight, 1 bent) were presented in 5 types of orientation, varying whether the rewarded location could be inferred. We compared predictions from both strategies with the observed performance of 8 wild-caught New Caledonian crows. Two of the 8 birds' choices were entirely consistent with reasoning by exclusion only. A further 4 birds followed a mixed strategy, where both reasoning and avoidance could have influenced their decisions. Thus, although avoidance plays a role, it cannot fully explain the crows' choices. Confirming how animals naturally solve problems is increasingly important in animal cognition; we demonstrate that NC crows can inferentially reason without explicit training, but, like humans, most do not rely solely on reasoning to make decisions.

New Caledonian crows (Corvus moneduloides) attend to barb presence during pandanus tool manufacture and use

New Caledonian crows craft wooden hook tools and incorporate naturally occurring barbs into the leaf tools that they manufacture. This raises the question as to whether, or to what degree, these birds are sensitive to the hooks on their hooked and barbed tools. Past research in this area has provided equivocal results. We tested whether New Caledonian crows attend to the presence and orientation of barbs on pandanus leaves and tools during tool manufacture and selection tasks. Our results show that New Caledonian crows attend to barb presence during both pandanus tool manufacture and use, but do not attend to barb direction during pandanus tool use. We conclude that task context, the time and energetic costs of attending to barbs, relative foraging efficiency, and different experimental designs may influence whether, and to what degree, NC crows attend to pandanus barbs.