comparative method shared sound changes alice faber sound posting brings important point indvidual sound changes especially known common languages world basis subclassification need either sets unrelated changes english diphthongized long high vowels high german eis ice haus house sound rather similar share changes chronology sound changes respect changes e g diphthongization english presumably preceded loss x c change high german hand find northern uto aztecan languages share changes intervocalic l n n velar nasal c one would mean little three together fact l n feed n ng change make reasonably certain really shared innovations northern uto aztecan genuine classificatory unit valid node uto aztecan tree something recently generally doubted