Will Smith conceived this story when he was watching the television show I Shouldn’t Be Alive with his brother-in-law Caleeb Pinkett. It was originally not a science fiction story but about a father and son crashing their car in the mountains or some remote region, with the son having to go out and get rescue for his father. Will Smith then decided to change the setting to 1000 years in the future, which imposed a higher budget. Smith had his production company Overbrook contact Gary Whitta (who was then known for his script for The Book of Eli) with a simple log line for a movie: a father and son crash landed on Earth 1000 years after it had been abandoned by humankind. Impressed with his idea and excited about the opportunity to work with him, Whitta fleshed out Smith’s idea and pitched it to him, subsequently becoming the first employee on the project.
You can watch it here: