People insist on more generations because we believe we are on balance good and that our lives are worth living. Only a small minority regrets having been born. We know that if we produce another generation, they too will generally consider themselves good and not regret having been born. Through a temporal veil of ignorance, it is good to produce as many happy future generations as possible.
If there is no future for mankind, then the restraints of moral obligation begin to erode. Not everyone will immediately abandon their values and start looting and wanton descent into libertinism and such, but the “to hell with it” factor becomes more and more compelling over time. The world becomes an increasingly negative-sum game: who gets to enjoy themselves the most before the end? The old no longer have a real obligation to the young.
Creeping back to the original point of the thread…
Performing a very small number of evil deeds to ensure that the only known intelligent life in the universe doesn’t disappear along with all its accumulated knowledge and culture… I’m pro-choice right up to there, and then I say “tough luck.”
Human beings typically (but not always) place a high value on children (even those that aren’t our own), it’s pretty well hard-wired into us. We automatically feel protective anxiety when we hear a child crying, which is why it can be the most annoying thing in the world to hear a child cry and not be in a position to do anything about it.
There may be a small percentage of people who do not feel that anxiety: hard-core sociopaths and temporarily insane people. And the vast majority of sociopaths could probably even be bargained with: people would no doubt offer mountains of riches to make the last fertile woman their baby mama or (eventually) part of their extended family. But there might be a tiny number who simply will not want to be pregnant for any amount of honor, love, power or material reward.
If the last remaining fertile woman (or a small number of women) happen to be in that super-misanthropic minority, the rest of the human race is going to have its way with her (to put it brutally).
Rationalizations for this behavior that would in normal times be considered barbaric: [ul][li] Only a small minority of people regret having been born. The happiness of all those future people is not merely a “potential” but a choice: do we coerce one empathy-challenged person now so that many can live?[/li][li] A small number of evil acts is the vice that all future virtue requires. Mankind has always been willing to engage in temporary evils to secure a better future.[/li][*] Desperate times call for desperate measures. Our descendants will be able to live better lives, free from these awful choices, if we make those choices. After all, our ancestors thousands of years ago were barbaric almost by default, and we’ve created beautiful wondrous things in such a short period of time… we have developed so far that we can imagine curing poverty, hunger and illness for all if we get just a little more time to do it. Just because our ancestors were barbaric doesn’t mean we don’t deserve to live. And that tells us that just because we have to be barbaric in this unique circumstance doesn’t mean they’ll inherit our sins, but you can bet they’ll inherit our virtues.[/ul] This doesn’t lead down a slippery slope to rape and forced pregnancy as policy in normal times. In normal times, a rape or (if you subscribe to pro-choice logic)forced pregnancy very likely degrades society in addition to harming the immediate victim, and there are plenty of children born into supportive families who can go on being happy and having their own children. But in a misanthrope-fertile-woman Children of Men scenario, those things are necessary to preserve and eventually improve society.