" Long before we had writing or farms or post-digital strike helicopters, we had each other. We lived together and changed each other, and so we needed to say “this is who I am, this is what I do.”
So, in the same way that we attached sounds to meanings to make language, we began to attach clusters of behavior to signal social roles. Those clusters were rich, and quick-changing, and so just like language, we needed networks devoted to processing them. We needed a place in the brain to construct and to analyze gender. "