You mean could God have created natiral forces and used them to form the earth? Then yes, it certainly is possible. All things are possible with God. God COULD have done it in six days, He COULD have done it in six SECONDS, or He COULD have done it in six million years. We dont know exactly what 'days' mean in creation terms. Time was different then. I think 'survival of the fitest' was a process that arose after the sin of mankind because there was no death before that. So, no i dont think God specifically used that but i do think He allowed it to occure, as He allows all the consequences of human sin to be. And i do believe the world continued to 'evolve' physically after the Flood (via Gods processes, many warped by inherent sin), unlike many uber-traditionalists who believe the earth is currently exactly as it was after the Flood with no changes in many thousands of years.