Data from: New evidence from linguistic phylogenetics identifies limits to punctuational change

Since the early 1970s, biologists have debated whether evolution is punctuated by speciation events with bursts of cladogenetic changes, or whether evolution tends to be of a more gradual, anagenetic nature. A similar discussion among linguists has barely begun, but the present results suggest that there is also room for controversy over this issue in linguistics. The only previous study correlated the number of nodes in linguistic phylogenies with branch lengths and found support for punctuated equilibrium. We replicate this result for branch lengths, but find no support for punctuated equilibrium using a different, automated measure of linguistic divergence and a much larger data set. With the automated measure, segments of trees containing more nodes show no greater divergence from an outgroup than segments containing fewer nodes.

自20世纪70年代初起，生物学界便一直围绕演化究竟是会被物种形成事件引发的分支演化（cladogenetic）剧变所间断，还是演化整体更偏向渐进式的线系演化（anagenetic）本质这一核心议题展开辩论。语言学界针对类似议题的讨论才刚刚起步，但本次研究结果表明，语言学领域中该议题同样存在争议空间。此前仅有的一项研究将语言系统发育树（linguistic phylogenies）中的节点数量与分支长度进行关联分析，并为间断平衡（punctuated equilibrium）假说提供了支持证据。我们针对分支长度重复了该研究的分析结果，但采用了另一种自动化语言演化分歧度度量方法，且使用规模远超此前研究的数据集，却并未发现能够支持间断平衡假说的证据。通过该自动化度量方法，节点数量更多的树片段与外群（outgroup）之间的演化分歧度，并不比节点数量更少的树片段更高。