"For the last ten or fifteen years, I've been trying to understand situations in nature in which the genes within a single individual are in disagreement—or put differently, in which genes within an individual are selected in conflicting directions. It's an enormous topic, which 20 years ago looked like a shadow on the horizon, just as about a hundred years ago what later became relativity theory was just two little shadows on the horizon of physics, and blew up to become major developments. In genetics it's fair to say that about 20 years ago a cloud on the horizon was our knowledge that there were so-called selfish genetic elements in various species that propagated themselves at the expense of the larger organism. What was then just a cloud on the horizon is now a full-force storm with gale winds blowing."