Abstract

Imagine landing in the largest city, the capital, of an alien planet. You are stunned to see that every humanoid is within a few centimeters of the same height, everyone has a nearly identical muscular body, and everyone’s facial features are quite similar—high cheekbones, small noses, and black eyes. Perhaps most surprising to you, everyone has purple skin. The ambassador accompanying you tells you the purple skin is a consequence of interacting skin pigment proteins, the double sun of that planetary system, and generation upon generation of voluntary random breeding. As you walk to your important meeting, the ambassador also informs you that every adult humanoid on the planet looks the same. She is no exception. Call this planet “Unity.”