What does IQ have to do with human worth? Why are we deciding who to keep and who to kill based on a rough and unreliable measurement of intelligence?

I'm going to take a shot in the dark: You judge your own worth based on your intelligence. You think that because you're smarter than everyone else that you deserve to live more than them.

In an apocalypse scenario, I'd recruit from the ghetto before I picked your egghead ass. You'd be calculating the trajectory of a bullet before it passes through your brain and wipes out all your progress.