Fundamentally, at some point, some elements combined to form molecules that have different properties than their individual atoms. And those molecules attracted more elements and molecules based on new and newer properties, to form even more complex molecules. Eventually that molecule may separate due to instability when it gets to a certain size/length. And then starts the process over again, this time 2x.
This is something that should happen by pure chance, given how many atoms there are on the Earth and the infinite combinations provided. We all know how certain atoms naturally combine to form more complex molecules with different properties, like water. It does not need to happen everywhere spontaneously. Just in one spot with one teeny tiny molecule that will split and replicate itself again, and then split again, etc... This may be happening constantly to this day. As it spreads, it will create a need for more atomic resources as it uses the neighboring ones. When the resources start to dwindle, mutations in some of these molecules will allow one of them to start using more diverse resources to help them continue to combine and replicate. And so on, and so on, and so on. Until we get to a very complex molecule like RNA/DNA. This is evolution and natural selection.
Whether you consider replicating molecules to be "life", is up to you and your beliefs. If you do, then it should happen naturally given enough opportunity, and we are already making great strides on replicating the process. And AI will eventually create a brand new version of life in that sense. If you don't consider replicating molecules as life, then you have a definition of life that is based on something else, possibly more supernatural. If so, what is your prerequisite for the definition of "life"?
Short Sharp Science: Biologists create self-replicating RNA molecule