Like many great scientists, Alan Turing found beauty in simple explanations for nature’s complexity. He often found simple explanations for very complex problems. The same mind that cracked Germany’s Enigma code during WWII (inspiring Winston Churchill to say Turing made the biggest single contribution to the allied victory) wondered how a human emerges from a homogeneous blob of cells. While trying to answer that question, he created a model that generated spots and stripes. This model turned out to explain how patterns emerge on animal fur. Turing answered the old questions: How do tigers, zebras, and many others, get their stripes? How do leopards get their spots?
Working in the 1940s, Turing didn’t have the great computers you and I have (To crack the Enigma code he created a huge computer), but he laid out the basic model that you can now run over the web (you can access this toy model on this page). One reason this model generating spots and stripes was so revolutionary was that it showed how the patterns need not be genetically determined, like a blueprint. Rather the patterns emerge dynamically from positive and negative feedback. Only a few chemical processes of feedback are needed, not an elaborate genetic coding of entire patterns. This is an elegant and general model that, as scientists discovered after Turing’s death, can explain a wide range of patterning, even sand dune stripes. Surface complexity emerges from simple rules of interaction. Turing wasn’t able to take the model further due to his untimely death. He was arrested for having a relationship with a man, and forced to either go to prison or take feminizing hormones. He soon committed suicide.