Living systems are not the only sources of recursion in nature. Branching crystals called dendrites, branching river basins, and spiral structures in turbulence all form through "self-organization" (try different options in the "Seed" dropdown menu above). This is often the result of a positive feedback loop. A few atoms cluster together, but new ones tend to stick on the outer most, the next stick on the outermost of those, eventually making a dendrite. A little water clears a path through soil, and that allows more water to flow, making more paths. As flowing fluid starts to push thorough standing fluid it creates little swirls that accumulate into greater swirls.