Replication has many shades of gray. Does a fire self-replicate? How about a prion? Somewhere in between would be self-catalyzing chemical reactions. It's not

Replication has many shades of gray. Does a fire self-replicate? How about a prion? Somewhere in between would be self-catalyzing chemical reactions. It's not that hard to imagine how such things could eventually evolve into what we call "life", with no clear line between non-living and living.