One can argue that this is uncontroversial on the ground that life's precursors came from elsewhere. The only debate is what level of complexity is meant by "came from elsewhere".

> And only the life forms that can quickly reproduce and spread to other planets get to live on.

There's another, more likely explanation -- that life in some form naturally arises if the conditions are right, and there doesn't need to be a connection with another life-supporting environment. This isn't proven yet, it's just likely.