Languages disfavor word forms containing sequences of similar or identical consonants, due to the biomechanical and cognitive difficulties posed by patterns of this sort. However, the specific evolutionary processes responsible for this phenomenon are not fully understood. Words containing sequences of identical consonants may be more likely to arise than those without; processes of word form mutation may be more likely to remove than create sequences of identical consonants in word forms; finally, words containing identical consonants may die out more frequently than those without. Phylogenetic analyses of the evolution of homologous word forms indicate that words with identical consonants arise less frequently than those without, and processes which mutate word forms are more likely to remove sequences of identical consonants than introduce them. However, words with identical consonants do not die out more frequently than those without. Further analyses reveal that forms with identical consonants are replaced in basic meaning functions more frequently than words without. Taken together, results suggest that the under representation of sequences of identical consonants is overwhelmingly a byproduct of constraints on word form coinage, though processes related to word usage also serve to ensure that such patterns are infrequent in more salient vocabulary items. These findings clarify previously unknown aspects of processes of lexical evolution and competition that take place during language change, optimizing communicative systems.

翻译：语言倾向于避免包含相似或相同辅音序列的词形，这是由于这类模式带来的生物力学和认知困难。然而，导致这一现象的具体进化过程尚未完全明了。含有相同辅音序列的词汇可能比不含这类序列的词汇更易产生；词形变异过程可能更倾向于移除而非创建词形中的相同辅音序列；最后，含有相同辅音的词汇可能比不含这类辅音的词汇更频繁地消亡。对同源词形进化的系统发育分析表明，含有相同辅音的词汇产生频率低于不含这类辅音的词汇，且变异词形的过程更可能移除而非引入相同辅音序列。然而，含有相同辅音的词汇并不比不含此类辅音的词汇更易消亡。进一步分析显示，在基本意义功能中，含有相同辅音的词形比不含这类辅音的词汇更频繁地被替换。综合来看，结果表明相同辅音序列的欠表达主要是词形创造约束的副产品，尽管与词汇使用相关的过程也确保了这类模式在更显著词汇项中罕见。这些发现阐明了语言变化过程中此前未知的词汇进化与竞争过程方面，优化了交际系统。