There must be a creator because life is too complex to have created itself.
But if something can create life then it must be more complex than life?
So where is the creator's creator? and where is the creator's creator's creator and where is the creator's creator's creator's creator and where is the creator's creator's creator's creator's creator . . . . . . . . . . . . . . .
The only possible explanation is that things started simple and became more complex automatically.