Linguistic Diversity and Traffic Accidents: Lessons from Statistical Studies of Cultural Traits

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142

Worldwide patterns of genetic variation are driven by human demographic history. Here, we test whether this demographic history has left similar signatures on phonemes-sound units that distinguish meaning between words in languages-to those it has left on genes. We analyze, jointly and in parallel, phoneme inventories from 2,082 worldwide languages and microsatellite polymorphisms from 246 worldwide populations. On a global scale, both genetic distance and phonemic distance between populations are significantly correlated with geographic distance. Geographically close language pairs share significantly more phonemes than distant language pairs, whether or not the languages are closely related. The regional geographic axes of greatest phonemic differentiation correspond to axes of genetic differentiation, suggesting that there is a relationship between human dispersal and linguistic variation. However, the geographic distribution of phoneme inventory sizes does not follow the predictions of a serial founder effect during human expansion out of Africa. Furthermore, although geographically isolated populations lose genetic diversity via genetic drift, phonemes are not subject to drift in the same way: within a given geographic radius, languages that are relatively isolated exhibit more variance in number of phonemes than languages with many neighbors. This finding suggests that relatively isolated languages are more susceptible to phonemic change than languages with many neighbors. Within a language family, phoneme evolution along genetic, geographic, or cognate-based linguistic trees predicts similar ancestral phoneme states to those predicted from ancient sources. More genetic sampling could further elucidate the relative roles of vertical and horizontal transmission in phoneme evolution. cultural evolution | human migration | languages | population genetics

Section: Discussionsupporting

confidence: 78%

A comparison of worldwide phonemic and genetic variation in human populations

Creanza¹,

Ruhlen

Pemberton

et al. 2015

124

142

“…10 for the correlation between ejective use and reduced ambient air pressure, those explanations have yet to be supported by experimental evidence. The uncovered patterns could be epiphenomenal, and in general, the cross-linguistic statistical studies in question have not been buttressed by experimental support (11).…”

mentioning

confidence: 98%

Climate, vocal folds, and tonal languages: Connecting the physiological and geographic dots

Everett

Blasí

Roberts

2015

148

110

We summarize a number of findings in laryngology demonstrating that perturbations of phonation, including increased jitter and shimmer, are associated with desiccated ambient air. We predict that, given the relative imprecision of vocal fold vibration in desiccated versus humid contexts, arid and cold ecologies should be less amenable, when contrasted to warm and humid ecologies, to the development of languages with phonemic tone, especially complex tone. This prediction is supported by data from two large independently coded databases representing 3,700+ languages. Languages with complex tonality have generally not developed in very cold or otherwise desiccated climates, in accordance with the physiologically based predictions. The predicted global geographic-linguistic association is shown to operate within continents, within major language families, and across language isolates. Our results offer evidence that human sound systems are influenced by environmental factors.climate | language | adaptation | tone A standard assumption in linguistics is that sound systems are immune to ecological effects (1). This presumption has been called into question by several recent studies providing evidence for a correlation between aspects of phonology (such as sonority) and climatic and geographic factors (such as temperature, plant cover, or terrain), as well as behaviors associated with such factors (2-9). Most recently, a correlation was uncovered between ejective sounds and regions of high elevation in a sample of nearly 600 languages (10). Although two plausible physiological motivations are offered in ref. 10 for the correlation between ejective use and reduced ambient air pressure, those explanations have yet to be supported by experimental evidence. The uncovered patterns could be epiphenomenal, and in general, the cross-linguistic statistical studies in question have not been buttressed by experimental support (11).In this study, we offer evidence for a negative correlation between linguistic tone and characteristic rates of desiccation in ambient air. In contradistinction to the aforementioned studies offering geographic/phonetic correlations, however, we suggest this correlation is predicted by extensive experimental research on the properties of the human larynx. This research, which has been conducted by numerous laryngologists over the last decade and a half, has not been previously tied to the distribution of the world's tonal languages. We submit that the research predicts that the relatively precise manipulation of the vocal folds associated with tone, especially complex tone, should be more difficult to achieve in arid climates-particularly very cold ones-when contrasted to warmer and more humid climates. We offer global, continental, and intralinguistic-family data consistent with the expected geographic/tonemic association. Our results cannot facilely be ascribed to well-known phylogenetic and areal relatedness. We conclude by suggesting that the most reasonable interpretation of the data is that the a...

“…In particular, similarities and differences across languages cannot be compared as if they were statistically independent data points, because closely related languages are expected to be similar in many aspects. This hierarchical pattern of similarities can confound attempts to find causal correlations between aspects of human language and culture by creating spurious correlations, a methodological challenge sometimes referred to as Galton's problem (23,24). The comparison of rates of evolutionary change in different lineages presents additional challenges because we need to be able to infer the number of evolutionary changes that have occurred along each lineage (25,26).…”

mentioning

confidence: 99%

Rate of language evolution is affected by population size

Bromham

Hua

Fitzpatrick

et al. 2015

101

The effect of population size on patterns and rates of language evolution is controversial. Do languages with larger speaker populations change faster due to a greater capacity for innovation, or do smaller populations change faster due to more efficient diffusion of innovations? Do smaller populations suffer greater loss of language elements through founder effects or drift, or do languages with more speakers lose features due to a process of simplification? Revealing the influence of population size on the tempo and mode of language evolution not only will clarify underlying mechanisms of language change but also has practical implications for the way that language data are used to reconstruct the history of human cultures. Here, we provide, to our knowledge, the first empirical, statistically robust test of the influence of population size on rates of language evolution, controlling for the evolutionary history of the populations and formally comparing the fit of different models of language evolution. We compare rates of gain and loss of cognate words for basic vocabulary in Polynesian languages, an ideal test case with a well-defined history. We demonstrate that larger populations have higher rates of gain of new words whereas smaller populations have higher rates of word loss. These results show that demographic factors can influence rates of language evolution and that rates of gain and loss are affected differently. These findings are strikingly consistent with general predictions of evolutionary models. language evolution | sister-pair comparison | Austronesian | lexical change | Poisson regression P opulation size can play a crucial role in the evolution of languages and cultures (1). However, opinions differ on both the possible mechanisms and the expected patterns (2-7). It has been suggested that larger populations will generate more innovations and are less prone to random loss of cultural elements (8-10), but may have less efficient diffusion of innovations than smaller populations (4). Alternatively, languages spoken by small isolated populations of speakers may have lower rates of loss if they maintain tighter cultural norms that improve transmission and resist change (11). Rates of change might be accelerated by founder effects when a new population is started from a small number of colonists, which could result in loss of elements from the ancestral language (11-13). Population size might also influence language complexity if small populations can develop greater linguistic complexity (11), whereas large, widespread languages that are often learned by adults may become simplified (14). Conversely, it has been suggested that the average rate of word turnover is essentially the same in all languages (15-17), or that it is determined primarily by other factors such as language contact (6, 18).Uncovering systematic patterns of rates of language change may reveal underlying mechanisms of language evolution (13,19). In particular, investigating rates of language change can demonstrate whether langua...