Thirty years ago, Sir Mix-a-Lot sang “Baby Got Back.” But the fascination with the derriere is as old as time itself. Heather Radke is an essayist and contributing editor and reporter at Radiolab. She joins host Krys Boyd to discuss our understanding of the backside – from evolutionary biology to its sexualization – and why power points in its direction. Her book is “Butts: A Backstory.”