I know how to complete a 2x2 grid (past, future) x (yes, no).
First let's be clear we're talking about prepubescents. Take a girl of age 9.
Of course in the past there have been societies where adults have had sex with kids. But not the kind of sex people at GC hold up as their ideal.
Kids in the past have had sex because they were prostituted in one form or another, in order to gain some advantage along the lines of mentoring, or simply because they were powerless to stop it. And in a world with 50% child mortality, preventing sexual abuse isn't necessarily anyone's highest priority.
But what people at GC imagine -- what they propose in their best (albeit futile) effort to make this acceptable to the world -- is a girl who has genuine affection for a man, as he has for her, and decides she wants to do intimate sexual things because it's what she wants to do for her own sake as part of the affection she feels. I know of no place on earth, here or in the past, that has had that as a feature for prepubescents.