If you're building fictional worlds and want language families that actually feel like they evolved rather than sprung from nothing, this handles the historical linguistics side. It covers sound change patterns, grammatical drift, contact effects, and how geography plus social structure creates divergence. The tables mapping morphological types to word order patterns and the evolution sequences like tonal development or case system collapse are solid references. Works across fantasy, sci-fi, and post-apocalyptic settings with specific guidance for each. Think of it as the piece that gets you from proto-language to believable dialect continuum without handwaving the phonological changes.
npx skills add https://github.com/jwynia/agent-skills --skill language-evolution