bio

Reaction–diffusion

Alan Turing's 1952 mechanism: two chemicals that both react with each other and diffuse at different rates can spontaneously break uniformity and generate periodic spatial patterns — stripes, spots, regular spacing. The key condition is that the inhibitor must spread faster than the self-activator ("short-range activation, long-range inhibition"). This is how skin stripes, hair-follicle spacing, and digit condensation emerge from a featureless start with no blueprint.