The prevailing wisdom is that even if you’re a newborn baby, you don’t have to worry about your as-yet-unborn progeny traveling back in time to murder you. Killing you would result in them never being born because, with you dead, the killer’s parents, one of which is your future spawn, would never have been born, and neither, in turn, would your would-be assassin. Ergo, your genetic downline can’t come back through time to kill you. One less thing to worry about, right?

Wrong.