Ursula K. Le Guin
The Birthday of the World: and Other Stories

She told him that he was born to the service of his people and had one responsibility, to sire children when he got old enough; and one duty, to be strong, brave man, stronger and braver than other men, so that women would choose him to sire their children. She said he had to live in the Castle because men could not live among women. At this, Ittu asked her, “Why can’t they?”
”You did?” I said, awed by his courage, for Vev Ushiggi was a formidable old woman.
”Yes. And she didn’t really answer. She took a long time. She looked at me and then she looked off somewhere and then she stared at me for a long time and then she finally said, ‘Because we would destroy them.’ “