Where do these life forms come from?
Why do (or did) people like Carl Sagan, Richard Dawkins, Stephen Jay Gould, et al, spend a great amount of time discussing that very issue?
Why does every Discovery Channel show talking about evolution begin with the Big Bang and the Origin of life?
There is only one other alternative - Special Creation by a Divine Creator.
I'll also ask you - why just one creator? Why not two or ten thousand?
Why is creation "special" and what dictates that a creator must be "divine" (whatever that means)? It reeks of irrational biases in your premises and does no credit to your argument.