We have lots of evidence of how the processes of life are chemically driven: Photosynthesis captures energy from sunlight, metabolism of sugars produces ATP which is then used in a variety of ways by the cell's proteins, the DNA->RNA->Protein pipeline builds proteins from the sequences of base pairs stored in a cell's DNA, and DNA copying enzymes pass that information from generation to generation. Since you probably already know about that stuff, I guess I must be misunderstanding what kind of proof you are looking for. What sort of discovery would count as "proof" to you?