Presentation first given to a roundtable talk at the Sim Kee Boon Institute at Singapore Management University (http://http://skbi.smu.edu.sg/) on March 5, 2015. Additional notes, references and citations are in the comments of each slide. I would like to thank Arthur Breitman, Andrew Geyl (Organ of Corti), Yakov Kofner, Raja Ramachandran and John Whelan for their feedback and comments on several slides.