The details are unimportant. The world ended, and man's empire fell silent. Urban landscapes rested skeletal and brittle, the expanses of unbuilt land barren and red, while the ocean boiled green with heat and waste. The sky was blocked out by humanity's communications network and orbital fleets, left to drift aimlessly, becoming a blanket of junk.
But there were those who saw this coming, and deemed it unavoidable. They're final days on Earth were spent preparing, to give humanity a chance at redemption. That was Project Rebirth.
Hundred's of year's passed, and when the radiation ebbed away, the sea began to purge the waste upon the rocks, and greenery slowly but surely returned, reclaiming the broken buildings and blanketing the once dead vista's with grass.
Hundred's of years more passed, and in all of this time, the nameless computer watched from the few satellite's it had preserved. It watched as the land healed, as the plants grew, the toxicity left the air and the water, and as basic life returned... it had been reaching the end of it's life, and what was left of it's dwindling power was expended opening the stasis pod to Eve.
One naked woman, blissfully ignorant, yet with the basic knowledge of a human survivalist, stepped out into the new world. She was with child. Her kind was genetically pure... disease and birth defects would never occur, and they would live to be 600 year's old. She did not have memories, but she knew that she needed to repopulate the planet, and set out to create her home. Her child was born, and when he was old enough, they performed what they were created for, and raised a family.
This is a group roleplay, but it will start with only two player's. The story will regularly do time jumps, so after each love making scene, there will be a fast forward and a new player will enter as the now late teen son or daughter that was conceived.