eLife Assessment
This study presents a useful theoretical model of molecular evolution of multi-copy gene systems by extending the classic Haldane model and applies the model to explain the surprisingly rapid evolution of rRNA genes. Although the conceptual model is intuitive and provides a new perspective for contextualizing this problem, the model presented does not adequately consider plausible biological constraints on the molecular and genetic processes. The lack of such constraints in the model, along with technical issues in the data analysis, provide incomplete support for the conclusion that the genetic variation patterns of rRNA genes in mouse is compatible with neutral evolution.