First meetings in the Enderverse by Orson Scott Card

generation.”
    She blinked. “Yes,” she said. “That’s right.” And then she blinked again. Apparently he had interrupted her lesson plan by getting to the answer immediately.
    “But what I wonder,” said John Paul, “is this: Since human communities depend on adaptability in order to thrive, then it isn’t just one set of traits that strengthen the community. So community life should promote variety, not a narrow range of traits.”
    “That would be true,” said Ms. Brown, “and indeed is true in the main, except that there are only a few types of human communities that actually survive long enough to improve the chances of individual survival.”
    She walked to the board and wiped out a swath of material that John Paul had just blown through by cutting to the chase. In its place, she wrote two headings: TRIBAL and CIVIL.
    “There are two models that all successful human communities follow,” she said. Then she turned to John Paul. “How would you define a ‘successful’ community, Mr. Wiggin?”
    “One that maximized the ability of its members to survive and reproduce,” he said.
    “Oh, if only that were true,” she said. “But it’s not true. Most human communities demand anti-survival behavior from large numbers of their members. The obvious example would be war, in which members of a community risk their own death-usually at the very age when they are about to begin family life. Many of them die. How can you possibly pass on the willingness to die before reproduction? Those who have this trait are the least likely to reproduce.”
    “But only males,” said John Paul.
    “There are women in the military, Mr. Wiggin.”
    “In very small numbers,” said John Paul, “because the traits that make good soldiers are far less common in women, and the willingness to go to war is rare in women.”
    “Women fight savagely and die willingly to protect their children,” said Ms. Brown.
    “Exactly-their children. Not the community as a whole,” said John Paul. He was making this up as he went along, but it made sense and was interesting-so he was quite willing to let her play the Socratic questioning game.
    “And yet women are the ones who form the tightest community bonds,” she said.
    “And the most rigid hierarchies,” said John Paul. “But they do it by social sanctions, not by violence.”
    “So you’re saying that violence in males but civility in women is promoted by community life.”
    “Not violence,” said John Paul. “But the willingness to sacrifice for a cause.”
    “In other words,” said Ms. Brown, “men believe the stories their communities tell them. Enough to die and kill. And women don’t?”
    “They believe them enough to…” John Paul paused a moment, thinking back on what he knew about learned and unlearned sex differences. “Women have to be willing to raise their sons in a community that might require them to die. So men and women all have to believe the story.”
    “And the story they believe,” said Ms. Brown, “is that males are expendable and females are not.”
    “To a degree, anyway.”
    “And why would this be a useful story for a community to believe?” She directed this question to the class at large.
    And the answers came quickly enough, because some of the students, at least, were following the conversation. “Because even if half the men die, all the women will still be able to reproduce.”
    “Because it provides an outlet for male aggressiveness.”
    “Because you have to be able to defend the community’s resources.”
    John Paul watched as Theresa Brown fielded each response and rifted on it.
    “Do communities that suffered terrible losses in war in fact abandon monogamy or do a large number of women live their lives without reproducing?” She had the example of France, Germany, and Britain after the bloodletting of World War I.
    “Does war come about because of male aggressiveness? Or is male aggressiveness a trait that