Is it possible something can appear from cold, empty nullity or thin air? If you think of numbers and try counting backwards, eventually you'll reach zero. Start with now and take things backwards counting day by day. Continue to count and at some point, make no mistake, you'll get to "day zero."
Now consider "day zero." What is "day zero" and could things exist that day somehow? Something occured day zero unleashing matter, and time, right? Consider that day and take things one step backwards. Why backwards? No small lead up would have been possible considering nullity implies no environment existed--no time and no matter, right?
Consider how you simply can't have something born from nothing. Or can you? But if something big happened, you must have had a precursor, and something previous, and again previous. Would that imply making backward moves basically from time zero? Could events have possibly occurred prior to day zero?
Now extrapolate to man. If something sparked life, something must have sparked that. Now count event by event back to "day and event zero."