Even though 'Lost' ended on Sunday night, more mysteries were introduced in those final 2½ hours. One of these was: who originally put that stopper in the ground to plug the hole, so that the Well of Golden Light could fill up again? And who carved all those symbols on that stopper? That's an easy one to answer, actually. It was the race of planet-builders known as the Magratheans, who were building the planet Earth to the specifications of the super-computer Deep Thought (as seen in 'The Hitch-Hiker's Guide To The Galaxy'). The Earth was going to be a super-computer as well, more powerful than Deep Thought, who would supply the question to the ultimate answer of Life, the Universe, and Everything - which was "42". When Desmond pulled the stopper out of the ground, the super-computer basically shut down. Jack had to replace the rock stopper in order to reboot the system. And for the Creationists out there, I've got you covered. God created the original Earth, its twin planet Mondas (as seen in 'Doctor Who'.)
For those who might point out that the planet Earth was destroyed in the first episode of 'The Hitch-Hiker's Guide To The Galaxy', you must remember that Arthur Dent and Ford Prefect were thrown back in Time to the age of the cavemen. And their interference in the planet's original programming - along with all of the other programming viruses like alien invasions - tweaked the Toobworld timeline so that eventually the Vogons never received any orders to destory the planet in order to make room for a hyperspace bypass.