Low fertility doesn&#x27;t lead to extinction in a few hundred years. Let&#x27;s say the average is one child per woman (even places like Japan are above this), then it still takes 23 generations to reduce the global population to a thousand people, and a further ten generations to reduce to one.<p>Use Japan&#x27;s fertility rate and you can roughly double those numbers.<p>I also don&#x27;t see why disagreement has bizarre implications. World fertility rate is still somewhat above replacement, so all you really need is for the populations currently having lots of babies to keep on doing so. And even if the trend continues way downwards, reversal doesn&#x27;t require weird scenarios where all children suddenly decide to have twice as many children as their parents. If fertility rates go from 1.5 to 2.5 over the course of ten generations, that would do it too.<p>Nobody really understands <i>why</i> fertility rates drop with wealth, so it&#x27;s not weird to think that further changes could cause them to increase again, especially in a world with a much lower population than today.