NOT FIRST PRINCIPLES. We always assume that evolution has developed the most highly adapted design for a particular function — think Darwin’s Finches — and how adapted they are to their particular foods. However, most of evolution seems to have been a series of workarounds from an outmoded design to a new use, rather than a design from first principles. The evolution of the human foot is a case in point. It derived from a quadrupedal and arboreal ancestor, trying to make it suitable for bipedal locomotion. Or, put differently, turning a square into a triangle.