Why are many Mayan languages mutually unintelligible?

The Mayan languages are a large family comprising 31 living and two extinct languages, and their mutual unintelligibility is a result of the family's extensive historical diversification.12

Over time, the ancestral Mayan language split into distinct branches, each further subdividing into individual languages. The diversification process began with the separation of the Huastecan branch, followed by the Yucatecan branch. The remaining languages, often referred to as Core Mayan, subsequently branched into three major groups: Greater Tzeltalan (which split into Ch’olan and Tzeltalan), Greater Q’anjob’alan (comprising Q’anjob’alan and Chujean), and Eastern Mayan (comprising K’ichean and Mamean).1

Because these languages diverged from a common ancestor long ago and developed independently within their respective branches, they have evolved significant linguistic differences that prevent speakers of one language from understanding speakers of another. While they share structural traits due to their existence within the Mesoamerican linguistic area, these shared features—such as vigesimal numeral systems and specific word orders—do not equate to mutual intelligibility.13