The most promising candidate for a “natural engine” is proton flows across thermal vents that theoretically could generate high-energy molecules.
The piece is highly technical and mathematical, but the basic argument can be quickly summarized with only a marginal loss of technical accuracy.
Undirected natural selection can’t lift itself by its own bootstraps — accidents can’t happen in nature except in a sea of design.
Spontaneous natural processes always tend toward states of greater entropy, lower energy, or both.
A helpful formulation comes from podcaster Scott Adams, of “Dilbert” fame, who comments entertainingly on the political scene.