"...those ancients were beloved of God, and [lately] made by God himself: and because their food was then fitter for the prolongation of life, might well live so great a number of years. And besides, God afforded them a longer time of life on account of their virtue, and the good use they made of it in astronomical and geometrical discoveries: which would not have afforded the time for foretelling [the periods of the stars] unless they had lived six hundred years; for the Great Year is completed in that interval."
-- Flavius Josephus of the Antiquities of the Jews, Book I, Chpt. 3 verse 9