This can give rise to the situation in which two dialects (defined according to this paradigm) with a somewhat distant genetic relationship are mutually more readily comprehensible than more closely related dialects. In one opinion, this pattern is clearly present among the modern Romance languages, with Italian and Spanish having a high degree of mutual comprehensibility, which neither language shares with French, despite some claiming that both languages are genetically closer to French than to each other:[citation needed] In fact, French-Italian and French-Spanish relative mutual incomprehensibility is due to French having undergone more rapid and more pervasive phonological change than have Spanish and Italian, not to real or imagined distance in genetic relationship. In fact, Italian and French share many more root words in common that do not even appear in Spanish.
What is French-Spanish and Spanish-Italian mutual incomprehensibility due to?