Department of Anthropology, University of Zurich, Zurich, Switzerland.
Department of Archaeology, University of Cambridge, Cambridge, United Kingdom.
PLoS One. 2020 Dec 1;15(12):e0243171. doi: 10.1371/journal.pone.0243171. eCollection 2020.
The origins of linguistic diversity remain controversial. Studies disagree on whether group features such as population size or social structure accelerate or decelerate linguistic differentiation. While some analyses of between-group factors highlight the role of geographical isolation and reduced linguistic exchange in differentiation, others suggest that linguistic divergence is driven primarily by warfare among neighbouring groups and the use of language as marker of group identity. Here we provide the first integrated test of the effects of five historical sociodemographic and geographic variables on three measures of linguistic diversification among 50 Austronesian languages: rates of word gain, loss and overall lexical turnover. We control for their shared evolutionary histories through a time-calibrated phylogenetic sister-pairs approach. Results show that languages spoken in larger communities create new words at a faster pace. Within-group conflict promotes linguistic differentiation by increasing word loss, while warfare hinders linguistic differentiation by decreasing both rates of word gain and loss. Finally, we show that geographical isolation is a strong driver of lexical evolution mainly due to a considerable drift-driven acceleration in rates of word loss. We conclude that the motor of extreme linguistic diversity in Austronesia may have been the dispersal of populations across relatively isolated islands, favouring strong cultural ties amongst societies instead of warfare and cultural group marking.
语言多样性的起源仍然存在争议。关于群体特征（如人口规模或社会结构）是加速还是减缓语言分化，研究结果存在分歧。虽然一些关于群体间因素的分析强调了地理隔离和语言交流减少在分化中的作用，但另一些分析则表明，语言的分歧主要是由邻近群体之间的战争以及语言作为群体身份标志的使用所驱动的。在这里，我们首次综合测试了五个历史社会人口学和地理变量对 50 种南岛语系语言的三种语言多样化测度的影响：词汇增益、词汇损失和整体词汇周转率。我们通过时间校准的系统发育姊妹对方法来控制它们的共同进化历史。结果表明，在更大的社区中使用的语言以更快的速度创造新词汇。群体内冲突通过增加词汇损失来促进语言分化，而战争则通过降低词汇增益和损失的速度来阻碍语言分化。最后，我们表明，地理隔离是词汇进化的一个强大驱动力，主要是由于词汇损失速度的明显漂移驱动加速。我们的结论是，南岛语系中极端语言多样性的动力可能是人口在相对孤立的岛屿上的扩散，这有利于社会之间的强烈文化联系，而不是战争和文化群体标记。
