长难句翻译:obviously we must do soe serious rethinking of our pri

长难句翻译:obviously we must do soe serious rethinking of our priorities, least linguistics go down in history as the only science that presided obviously over the disappearance f 90 percen of the very field to which it is dedicate .

lest什么意思？？ very feild 强调的是哪个feild？