Being dead for sixty years hasn’t stopped Alan Turing’s giant contributions to science. While Turing is primarily famous for laying the foundations for computing (and cracking the Enigma Code) this work refers to a different sort of digit – an explanation of how fingers and toes form.
Aside from his work on computing, artificial intelligence and code breaking, Turing also proposed a theory for how identical embryonic cells could self-organize into the complex shapes and patterning we see in nature.
Turing demonstrated that remarkable features could be the product of just two chemicals, which he called morphogens. In Turing’s model one morphogen acted as an activator, the other as an inhibitor. Both diffuse away from the cell. On a leopard's fur, concentrations reduce with distance, but they do not do so evenly. While the inhibitor shows a linear decline, the activator declines exponentially from a higher starting point. Where the concentration of activator is higher than inhibitor cells can change color, creating dark spots on a light background.
The elegance of Turing's theory saw it win near universal support as an explanation for not just spots but other colouring such as zebra stripes and many plant features. Earlier this year experimental evidence for Turing’s explanation was published for the first time using synthetic cell-like structures.
