Sometime in the next few years, scientists may reprogramme a human egg or sperm cell, make a change in the genetic instructions carried by that cell, a change that will be passed on down into eternity. The scientific expertise exists to do this, as does the motivation: to erase the chance of inheriting a disease, to improve the intelligence or the stamina or the beauty of a child. On the brink of an era that may be defined by genetic engineering, McKibben asks: should this happen? He argues that genetic engineering and the technologies that lie beyond it will launch us free of our past, of our humanity, of meaning. We are sleepwalking towards a future that will take us far away from all we have known: Enough is our wake-up call.