We can sometimes see traces of their landscapes, parts of the land they would have known can now only be glimpsed in the intertidal zone or through innovative programmes of seabed mapping.
Erbyn hyn dim ond yn y parth rhynglanwol neu drwy raglenni arloesol i fapio gwely'r môr y gallwn gael cipolwg ar rannau o'r tir y byddent wedi'i adnabod.