Scientists hypothesize that an ancient westward-flowing river carved the large valley, tens of millions of years before the Nile River existed.
(the Nile River; existed; ) (Scientists; hypothesize; that an ancient westward-flowing river carved the large valley, tens of millions of years before the Nile River existed) Context(Scientists hypothesize,List([0, 22))):(an ancient westward-flowing river; carved; the large valley)
Scientists hypothesize,List([0, 22))
the Nile River Scientists an ancient westward-flowing river
existed hypothesize carved
that an ancient westward-flowing river carved the large valley, tens of millions of years before the Nile River existed
the large valley