An alternative, favored by those of a religious persuasion, was that A’Tuin was crawling from the Birthplace to the Time of Mating, as were all the stars in the sky which were, obviously, also carried by giant turtles. When they arrived they would briefly and passionately mate, for the first and only time, and from that fiery union new turtles would be born to carry a new pattern of worlds. This was known as the Big Bang Hypothesis.
Terry Pratchett, The Colour of Magic