Assuming that life did not parachute in, fully formed, from elsewhere, a number of authors12,13,14,15 have argued that the transition from non-life to life took place in the context of geochemical energy, with the ability to harness sunlight evolving later (Fig. 1). Consistent with this, both phylogenetic16 and biochemical13,17 evidence suggest that the earliest life forms were chemoautotrophs, perhaps living by reacting hydrogen with carbon dioxide and giving off acetate, methane and water13,16. Mounting evidence18,19,20,21,22 suggests that the transition from non-life to life may have taken place before 3.7 Ga—a time from which few rocks remain23.
central_va: "I am not saying I have the answers but this is gobbledygook.
I know BS when I see it."
Not total BS, but admittedly speculation, hypotheses based on very detailed observations and some experiments.
So when might natural organic chemistry have "complexified" into biology -- was it 3.7 billion years ago?
Maybe, but that all depends on your definition of "life".