We are obliged to them because some of these languages have since vanished, as the peoples who spoke them died out or became assimilated and lost their native languages.（2004，62）

短语：be obliged to sb 感激某人

　　　 die out 灭绝

           assimilate 动词使同化

大致翻译： 我们感激他们(上文中提到的人)因为这些语言中方有一些已经消失了，这是因为说这些语言的民族都灭绝或者被同化并且失去了他们的母语。