Islands have played a prominent role in evolutionary and ecological theory, centring the theoretical framework for understanding biodiversity in terms of isolation and area and providing ‘laboratories’ of evolutionary change and adaptive radiation. However, a similar role for islands in understanding global language diversity has not been established, even though one-sixth of the world’s languages are spoken on islands which account for <1% of the inhabited land area. The striking diversity of island languages remains largely unexplained. We construct a global database which reveals that 10% of the world’s languages are endemic to islands (landmasses <11,000 km²) and we test several key theories of language evolution and diversity. We show that language diversity on islands increases with area but does not show a steady decrease with isolation, nor are island languages at elevated risk of loss. However, number of endemic languages per island increases with both area and isolation. We demonstrate that islands shape language evolution, with fewer phonemes (distinct sounds) in island endemic languages with increasing isolation. Our results suggest that islands generate language diversity by accelerating both language change and diversification.

岛屿在进化和生态理论中发挥了突出作用，从隔离和面积的角度理解生物多样性的理论框架的核心，并提供了进化变化和适应性辐射的“实验室”。然而，尽管世界上六分之一的语言是在占有人居住陆地面积 <1% 的岛屿上使用的，但岛屿在理解全球语言多样性方面也尚未确定。岛屿语言的惊人多样性在很大程度上仍未得到解释。我们构建了一个全球数据库，该数据库显示世界上 10% 的语言是岛屿（陆地 x3C11,000 km²）所特有的，并且我们测试了语言演变和多样性的几个关键理论。我们表明，岛屿上的语言多样性随着面积的增加而增加，但并没有随着孤立而稳定下降，岛屿语言的损失风险也没有增加。然而，每个岛屿的地方语言数量随着面积和孤立程度的增加而增加。我们证明岛屿塑造了语言的演变，随着孤立程度的增加，岛屿地方语言中的音素（不同的声音）越来越少。我们的结果表明，岛屿通过加速语言变化和多样化来产生语言多样性。